2. Food Chemistry 359 (2021) 129871
2
physicochemical and structural interactions between polysaccharides
and polyphenols (Liu, Le Bourvellec, & Renard, 2020; Zhu, 2015, 2018).
The results on the non-covalent as well as covalent (e.g., grafting) in
teractions between these two suggested their applications for the for
mulations of films and coatings with multiple functionalities (Liu, Wang,
Yong, Kan, & Jin, 2018; Hu & Luo, 2016). Information is scattered
regarding polyphenol fortified and polysaccharide based films and
coatings for food applications. The publications should be systematically
summarized and compared to provide a basis for better uses of these
films and coatings for food packaging.
2. Scope and approach
This review summarizes the fabrication and properties of poly
saccharide based films and coatings with the addition of polyphenols or
plant extracts rich in polyphenols (Supplementary Fig. 1). There are
many hundreds of papers published on this topic. Thus, papers pub
lished in recent 5 years or so are focused here. It is also impossible to
summarize all the papers from the recent years, and only selected papers
are summarized here. A few papers published over a decade ago are
cited here due to their importance for better understanding of the
context as well as for the coherence and balance of the content. Influence
of added polyphenol extracts on physical appearance and structure,
mechanical and barrier properties, biological functions including anti
oxidant and antimicrobial properties, and food applications are
described. They are also presented in the tables where only the patterns
of changes are described. Readers should refer to respective articles for
detailed description of the reported results. Nature of polyphenol-
polysaccharide interactions in the film systems is discussed. Structure-
property relationships of film components are highlighted. The review
tries to describe the general trends of the effects of added polyphenols
and extracts on film properties regardless of the types of polysaccharides
and polyphenols. There are different types of polysaccharides for film
formulations, thus the effect of polysaccharide type on film properties is
discussed. The potential uses of polyphenol fortified and polysaccharide
based films to stop stop the transmission of severe acute respiratory
syndrome coronavirus 2 (SARS-CoV-2) through food supply chain are
discussed. Research opportunities to improve polysaccharide based
films for food packaging are suggested.
The chemistry and properties of different types of polysaccharides
have been well documented in literature. The chemistry and biological
functions of different types of polyphenols and plant extracts rich in
polyphenols have been well studied and published in the forms of
journal articles and books during the last 2 decades or so. Previous re
views were focused on films made from polysaccharides (but not on
effect of polyphenols) as well as the effects of plasticizers and process
(Cazón et al., 2017; Nešić et al., 2020). Therefore, these contents are not
included/focused in the review. Readers are encouraged to refer to
previous publications on the fundamentals of polysaccharides and
polyphenols for background information necessary to better understand
the current review. The current review is focused on the effects of added
polyphenols and extracts on film functions. It may also be useful for new
researchers and students entering the field.
3. Fabrication of polysaccharide based films and coatings with
added polyphenols
Diverse polysaccharides and polyphenol extracts from different
sources were used to formulate films and coatings (Table 1) (Fig. 1 and
Fig. 2). Composite films were made from more than one type of poly
saccharides (e.g., pectin plus chitosan) or with the addition of non-
polysaccharide materials such as proteins and low-density poly
ethylene for improved performance (He, Wang, Song, Ou, & Zhu, 2020;
Panrong, Karbowiak, & Harnkarnsujarit, 2019; Yadav et al., 2020).
Polysaccharides that can be readily solubilized are dissolved in water
with the addition of polyphenols or plant extracts (Luo et al., 2019;
Mehdizadeh, Tajik, Langroodi, Molaei, & Mahmoudian, 2020; Rod
samran & Sothornvit, 2019; Sun et al., 2020a; Tong et al., 2020). For
some polysaccharides such as alginate, cross-linking agents such as Ca2+
and tannic acid are added to facilitate the film formation (Yuan et al.,
2019; Menzel, 2020). Some polysaccharides with crystallinity and low
water solubility such as starch in the form of granules should be cooked
in water to make them amorphous (Feng et al., 2018; Menzel et al.,
2019; Menzel, 2020). Polyphenols or extracts are mixed with poly
saccharides in solution before casting on plate and drying. The addition
levels of polyphenols or extracts varied greatly among different studies
(e.g., from 1 to 70%) (Fabra, Falcó, Randazzo, Sánchez, & López-Rubio,
2018; Mehdizadeh et al., 2020). In some studies, the formulations were
not clearly given. In some cases, the level of polyphenol extract addition
was given on volume basis. Such a lack and misrepresentation of in
formation on film formulations seriously undermine the usefulness of
the results from the reports. It is difficult to compare the results of these
reports with those of others. There tended to be an optimal level of
adding/grafting polyphenols for the desired properties such as suitable
mechanical properties of polysaccharide films; lower level or further
increase of addition level decreased the desired properties of the poly
saccharide films (Liu et al., 2017).
Plasticisers such as glycerol are added to improve the mechanical
properties (Mehdizadeh et al., 2020; Moreno et al., 2020; Sun et al.,
2020a). Polysaccharides grafted with polyphenols can be dissolved in
solution before casting (Liu et al., 2017). For food coating, products such
as fresh-cut fruits and vegetables can be immersed or dipped in film
forming solutions before drying (Moreno et al., 2020; Rojas-Bravo et al.,
2019; Romani et al., 2018). Blown extrusion process was also used to
fabricate films of thermoplastic starch with added green tea extracts
(Fig. 1a) (Panrong et al., 2019). This process has great potential for
commercial applications on industrial scale. Extrusion and compression
molding for starch film processing may induce molecular degradation of
amylose and amylopectin (Menzel et al., 2019; Menzel, 2020). However,
such degradation may not affect the quality of the resulting films if the
extents were controlled within certain limits. Microfluidic spinning pro
cess was also used to fabricate films of konjac glucomannan (KGM) for
tified with phenolics (Fig. 1b) (Lin et al., 2019). Manufacturing process of
microfluidic spinning can produce micro- and nanoscale biomaterials
with special properties for specific applications (Lin et al., 2019).
4. Mechanisms of interactions between polysaccharides and
polyphenols in films and coatings
Interactions between polysaccharides and polyphenols in films were
studied mechanistically using a range of different techniques including
Fourier-transform infrared spectroscopy (FTIR), scanning electron mi
croscopy (SEM), nuclear magnetic resonance (NMR), rheological and
thermal analysis and wide-angle X-ray scattering (WAXS) (Supplemen
tary Table 1). Polyphenols are structurally diverse. They can be very
different in physicochemical properties such as solubility and melting
points (Mota, Queimada, Pinho, & Macedo, 2008). For example, cur
cumin was not well dispersed in κ-carrageenan films and was partially
crystalline when exceeding a limit in concentration (Liu et al., 2018)
(Fig. 2a). Tea polyphenols were well dispersed within pectin-KGM films
(Lei et al., 2019). Unfortunately, most of the reports summarized here
did not take the physicochemical properties of polyphenols into con
siderations. Many studies used plant extracts obtained using organic
solvents such as ethanol. These extracts may not have good solubility/
dispersity when being formulated into films of polysaccharides.
When polyphenols were grafted onto polysaccharides, the in
teractions became covalent in nature (Liu et al., 2017). Added poly
phenols that can be well solubilized in water tend to have non-covalent
interactions with polysaccharides. The mode of the non-covalent in
teractions included hydrogen bonding, electrostatic and hydrophobic
interactions (Supplementary Fig. 2). For example, hydrogen bonding
was found between epigallocatechin gallate and KGM/carboxymethyl
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Table 1
Fabrication and physical characteristics of polysaccharide films fortified with phenolic extracts.
Polysaccharides and
components
Polyphenol type/extract Formulation Elaboration method Effect on physical characteristics Moisture content References
Alginate Green tea and grape seed
extracts
Sodium alginate: extract (1 :0.5/0.75) Alginate solution was mixed with lipid/
fatty acid esters/Tween80 before
homogenizing and emulsification. Solvent
casting was used for making films
Films were darker, more reddish and
less transparent
N.A. Fabra et al.,
2018
Alginate Tea polyphenols (purity
> 98%)
Tea polyphenols up to 5%, Ca2+
as cross-
linker
Plating Optical transmittance of films was
decreased (Fig. 1c) and thickness
increased; films showed dense
internal structure and smooth surface
Decreased Yuan et al.,
2019
Alginate Guava leaf extract Guava leaf water extract was added to
sodium alginate up to 20%, glycerol as
plasticizer
Casting on Petri dish Increasing extract concentration
made the films darker and browner.
The film thickness was decreased
Decreased Luo et al., 2019
Alginate, agar, or alginate/
agar (1:1) mix
Larrea nitida (aerial parts)
extract
Extract (50 mg), 1 g polysaccharide, 0.3 g
glycerol
Plating on Teflon plate The films became darker and more
orange-brownish with a somewhat
rougher surface
N.A. Moreno et al.,
2020
κ-Carrageenan Mulberry polyphenolic
extract
Extract up to 4%, glycerol (30%) Casting on Petri dish The film thickness was not affected,
and the films became bluer and
darker with rougher surface
Decreased from 39
down to 33%
Liu et al., 2019
κ-Carrageenan Pomegranate peel and
flesh extracts
Extract up to 4%, glycerol (30%) Casting on Petri dish The film thickness, darkness and
surface roughness were increased.
Films with peel extract were
yellowish, whereas those with flesh
extract were reddish
Decreased Liu et al., 2020
κ-Carrageenan Curcumin Curcumin up to 7%, heated at 90 o
C with
stirring
Casting on plate Films became yellow and darker.
Aggregation of curcumin in films was
obtained when the addition level
increased to over 3% (Fig. 2a)
Liu et al., 2018
κ- and ι-Carrageenans Lapacho tea extract Carrageenans (0.5 g in 45 mL water
containing up to 20% of the extract), 0.25
mL glycerol
Casting on Petri dish Film thickness was not affected and
the transmittance was decreased
Decreased Jancikova
et al., 2020
Carboxymethylcellulose Allium tuberosum (Chinese
chives) extract
Extract up to 5%, glycerol (30%) Casting on Petri dish The film thickness and the
transmittance were increased, the
opacity was decreased
Decreased Riaz et al.,
2020a
Carboxymethyl cellulose
/gelatin
Bamboo leaf polyphenol
extract
Carboxymethyl cellulose: gelatin: glycerol
(1:1:1), extract was added up to 0.4% of
solution
Casting on Petri dish The film became thicker and darker.
AFM analysis showed increased
surface roughness of the film
N.A. He et al., 2020
Carboxymethyl cellulose and
sodium alginate
Epigallocatechin gallate
(EGCG)
Alginate: carboxymethyl cellulose at 2g: 2g,
glycerol (2 mL), EGCG (up to 1.6g)
Casting on Petri dish Thickness of the films was not
affected. Films became darker and
yellower and a bit rougher on surface
N.A. Ruan et al.,
2019
Chitin Tannic acid Tannic acid (20 g/L) solution was added to
chitin film
Tannic acid was adsorbed onto chitin film
surface during shaking
Chitin films became darker. Lower
transmittance was obtained
N.A. Wang et al.,
2016
Chitosan Green and black tea
extracts
Green tea extracts up to 2% were added Casting on plate Increasing polyphenol content
increased film thickness from 72 up
to 132 μm; opacity was increased
Decreased from 29
down to 11%
Peng et al.,
2013
Chitosan Protocatechuic acid Protocatechuic acid was grafted onto
chitosan up to 280 mg/g
Casting on plate Thickness increased from 42 to 49
μm. The films became yellow with
protocatechuic acid grafted
Decreased from 15
(control) to 13%
Liu et al., 2017
Chitosan Thinned young apple
polyphenols
Polyphenols up to 1% (w/v) of the solution
containing chitosan and glycerol
Casting on Petri dish Increasing polyphenol content
increased film thickness (from 0.07 to
0.11 mm), density, swelling and
solubility
Increasing
polyphenol content
decreased the
moisture content
from 30− 17%
Sun et al.,
2017, 2018
Chitosan Pequi (Caryocar
brasiliense) peel extract
Chitosan:extract at 4:1 Casting on Petri dish N.A. N.A. Breda et al.,
2017
Chitosan Black soybean seed coat
extract
Extract up to 15% of chitosan weight Casting on plate The films became darker and more
reddish, thicker, more opaque; color
Decreased Wang et al.,
2019
(continued on next page)
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Table 1 (continued)
Polysaccharides and
components
Polyphenol type/extract Formulation Elaboration method Effect on physical characteristics Moisture content References
was pH dependent; the extract was
uniformly distributed within the films
Chitosan Extract of Chinese chive
(Allium tuberosum) root
Extract of up to 5% was formulated with
chitosan and glycerol as plasticiser
Casting on Petri dish The aggregates were formed in the
films. Thickness increased from 0.076
up to 0.113 mm. Transmittance was
decreased and opacity was increased.
The films became darker and
yellower
Decreased from 27
to to 18%
Riaz et al.,
2020b
Chitosan Thyme, cinnamon and
rosemary extracts
Polypropylene and polyethylene films were
coated with chitosan nanoparticles
embedded with the spice extracts
Polypropylene and polyethylene were
activated using UV and ozone before
coating with chitosan nanoparticles and
then with the spice extracts
Homogeneous distribution of
nanoparticles and extracts on the
surface of the films was obtained
N.A. Zemljič et al.,
2020
Curdlan, chitosan Tea polyphenols Curdlan and chitosan ratio at 4:1, glycerol,
tea polyphenols (98%) up to 3%
Plating N.A. Decreased from 30
to 14%
Zhou et al.,
2019
Furcellaran/gelatin
hydrolysate
Rosemary extract Furcellaran/gelatin hydrolysate (1:2),
extract up to 20% of the solution
Casting on Petri dish The films became greener, darker,
and thicker
Increased Jancikova
et al., 2019
Gellan Coffee parchment waste
extract
Glycerol (1.7%, v/v), extract (24.6%, v/v),
gellan solution (1% w/v)
Casting on plate The thickness and surface roughness
of the films were increased
Decreased Mirón-Mérida
et al., 2020
Konjac glucomannan Grape peel extract Carboxylated cellulose nanocrystals (up to
15% of KGM), extract (0.1% of KGM),
glycerol (0.1%)
Casting on Petri dish The nanocrystals and extract were
well dispersed in the films. The
roughness and transparency of the
films were increased
N.A. Tong et al.,
2020
Konjac glucomannan/polylac
tic acid (PLA)
trans-cinnamic acid KGM: PLA: cinnamic acid (1:1:0.5), Microfluidic spinning The diameter of a microfiber was ~5
μm (Fig. 1)
N.A. Lin et al., 2019
Konjac glucomannan and
polyvinylpyrrolidone
(PVP)
Epigallocatechin gallate
(EGCG)
KGM:PVP at 1:100, EGCG (50 mg/g of KGM) Microfluidic spinning Ni et al., 2019
Konjac glucomannan,
oxidized chitin
nanocrystals
Red cabbage anthocyanin
extract
KGM (0.95%, w/v), nanocrystals (0.05%, w/
v), extract (up to 0.09%, w/v)
Casting on Petri dish The nanocrystals and extracts were
well dispersed in the films. The films
became darker and bluer
Increased Wu et al., 2020
Konjac glucomannan,
carboxymethyl chitosan
Epigallocatechin gallate
(EGCG)
KGM: carboxymethyl chitosan (7:3),
epigallocatechin gallate (20% of KGM),
glycerol (0.1% of KGM + carboxymethyl
chitosan)
Casting on Petri dish EGCG up to 15% was well dispersed
in films, the films became darker and
browner, thickness was increased
from 88 to 95 μm
Decreased from 17
to 12%
Sun et al.,
2020a
Konjac glucomannan,
chitosan
Mulberry anthocyanin
extract
KGM: chitosan: nano-ZnO (3:7:1),extract up
to 90 mg/KGM+chitosan, glycerol (0.2%, v/
v)
Casting on Petri dish The films became darker, bluer and
thicker
N.A. Sun et al.,
2020b
Tara gum- polyvinyl alcohol Curcumin Gum: polyvinyl alcohol (7:3), curcumin (up
to 5% of total weight), glycerol (30%)
Casting on plexiglass glass plate Thickness of the films was little
affected. The films became yellow
N.A. Ma et al., 2017
Pectin (lime peel) Lime peel extract
containing polyphenols
Lime peel pectin (1g), lime peel extract (20
g), coconut water (19.8 g), glycerol (0.3 g)
Casting on Petri dish The thickness of films was not
affected, opacity was increased
Increased from 12
up to 26%
Rodsamran &
Sothornvit,
2019
Pectin, chitosan Tea polyphenols (purity
>98%)
Calcium chloride, chitosan and pectin at 1: 2
(w/w), tea polyphenols up to 15% of
chitosan weight
Blending and solution casting on dish The thickness of the films was
increased
N.A. Gao et al., 2019
Pectin-konjac glucomannan Tea polyphenols, (purity
≥ 98%)
Pectin (3.5 g), glucomannan (1.5 g), glycerol
(1.25 g), tea polyphenols up to 0.25 g
Plating The thickness of the films was
increased, the density was decreased.
Color became darker and yellower,
and light transmission lower
Decreased from 18
to 11%
Lei et al., 2019
Pomelo peel flours (33%
pectin and 49% of other
carbohydrates)
Tea polyphenols (purity
> 98%)
Polyphenols (20% of pomelo peel flour) Plating Increasing polyphenol content
increased film thickness from 60 to
104 μm, color turned to brownish,
transmittance was decreased
Decreased Wu et al., 2019
Starch (rice)/protein (fish) Pink pepper phenolic
extract
Starch: protein ratios ranged from 15:85 to
85:15. Pepper phenolic extracts up to 8%,
glycerol
Starch and protein mixtures were
solubilized in alkaline solution (pH 11) by
heating at 80 o
C. Then they were cooled and
Changing phenolic extract contents
had no effect on the color of the films.
Starch to protein ratio of 15:85 gave
N.A. Romani et al.,
2018
(continued on next page)
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Table 1 (continued)
Polysaccharides and
components
Polyphenol type/extract Formulation Elaboration method Effect on physical characteristics Moisture content References
the extracts were added before casting on
Petri dish
the most desirable strength and
flexibility
Starch (corn) Mango peel powder Starch (5%), peel powder (up to 4%),
sorbitol (2%)
Starch was solubilized in NaOH solution
(0.125 M) before adding sorbitol and
powder. The solution was neutralized
before casting on plate
The films became darker and orange
and yellow. The film surface became
more smooth (AFM analysis)
N.A. Rojas-Bravo
et al., 2019
Starch (cassava) Aqueous rosemary
extract
Starch (5 g), extract (up to 20 g), glycerol
(1.5 g), water (up to 93.5 g), total
polyphenol content of 13.6 mg per 1 g of film
The blends were heated (96 o
C) with
stirring before casting on plate and drying
(50 o
C)
Thickness of films was ~ 200 μm 15− 20% Piñeros-
Hernandez
et al., 2017
Starch (potato) Phenolic extracts (80%
methanol) from
sunflower hulls
Glycerol (0.25 g/g starch), the extract of up
to 6% of film weight
Heated and mixed at 160 ◦
C for melting.
The mix was cooled at 25 o
C for 7 days
before compression for film formation
Thickness was decreased from 210 to
180 μm, the films became yellow-
brownish color without change in the
transparency
Increased by 1% Menzel et al.,
2019; Menzel,
2020
Starch (cassava) (native and
hydrolyzed)
Yerba mate extract The extract was added to starch up to 20%,
glycerol was used as plasticizer
Extrusion and compression molding Increasing extract content up to 20%
led to the formation of rough and
factured surface. The films turned
yellow-orange-brown
Little affected Ceballos et al.,
2020
Starch (pea), chitosan Thyme extract Polymer: glycerol: tannic acid (cross-linker):
extract ratio at 1:0.2:0.04:0.15, the polymer
can be chitosan, starch, or chitosan/starch at
1:4
Casting on Petri dish The thickness of different films
ranged from 50 to 87 mm, films
became less transparent, more red,
and darker
Ranged from 12 to
22%
Talón et al.,
2017a, 2017b
Starch-chitosan Pomegranate peel
extract, essential oil
(Thymuskotschyanus)
Starch:chitosan (3.5:2), glycerol (30%),
Tween 80 (0.2%), peel extract (up to 1%),
essential oil (2%)
Casting on polytetrafluoroethylene plate Thickness was 0.046− 0.063 mm,
transparency increased with
increasing peel extract content
N.A. Mehdizadeh
et al., 2020
Acetylated starch/ LLDPE Green tea extract Starch: green tea extract: glycerol at 20:7:7
for blown extrusion to obtain
thermoplastics. The thermoplastics were
mixed with LLDPE at 7:3 or 6:4 before blown
extrusion
Extrusion blown process (Fig. 1a) Films turned darker and yellower N.A. Panrong et al.,
2019
Hydroxypropyl starch Tea polyphenol (purity >
98%)
Starch (18.0 g, dry base) and glycerol (4.5 g)
in water (300 mL) were cooked at 100 o
C
before cooling to 80 o
C, tea polyphenols (up
to 1.8 g) were added to the melt before
degassing and casting on polypropylene
plate and cooling
Plating Tea polyphenols were well dispersed
in starch matrix. The starch films had
smooth surface. The surface was not
affected. The white color changed to
be brownish
No effect Feng et al.,
2018
Tremella fuciformis (white
jelly mushroom)
Roasted peanut skin
extract
Glycerol (30% of polysaccharide), extract of
up to 1.0 g/100 mL
Casting on Teflon-coated glass plate The films became thicker, darker and
reddish, and rougher on the surface
N.A. Ju & Song,
2020
LLDPE, low-density polyethylene; SEM, scanning electron microscopy; AFM, atomic force microscopy; KGM, konjac glucomannan; N.A., not applicable
F.
Zhu
6. Food Chemistry 359 (2021) 129871
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chitosan (Sun et al., 2020a), κ-carrageenan films with well dispersed
curcumin (Liu et al., 2018), starch and tea polyphenols (Feng et al.,
2018), alginate (sodium) films with guava leaf extract (Luo, Liu, Yang,
Zeng, & Wu, 2019), KGM with carboxylated cellulose nanocrystals and
grape peel extracts (Tong et al., 2020), and pectin, KGM and tea poly
phenols (Lei et al., 2019). Cabbage anthocyanin extract and oxidized
chitin nanocrystals interacted electrostatically and by hydrogen bonding
(Wu et al., 2020). Hydrophobic interactions and hydrogen bonding be
tween tannic acid and chitin contributed to interfacial assembly of
tannic acid on the surface of chitin based films (Wang, Li, & Li, 2016).
Polar components of pequi (Caryocar brasiliense) extract and the amine
hydroxyl groups of chitosan interacted by hydrogen bonding and dipo
le–dipole forces (Breda, Morgado, Assis, & Duarte, 2017). Starch mol
ecules can form complexes with polyphenols through hydrogen bonding
as well as through the formation of V-type inclusion complexes (Zhu,
2015). In well-dispersed status, polysaccharides and polyphenols may
interact through hydrophobic interactions, hydrogen bonding and/or
electrostatic interactions (Supplementary Fig. 2) (Liu et al., 2020). The
extents and nature of polyphenol-polysaccharide interactions should be
studied in the content of specific polyphenol and polysaccharide com
bination. This is because of the diversity in the structure of polyphenols
and polysaccharides.
It should also be noted that plasticisers such as glycerol contributed
to the interactions. For example, the bonding between starch and glyc
erol was disrupted by the addition of aqueous rosemary extracts
(Piñeros-Hernandez et al., 2017). The interactions between poly
saccharides and polyphenols can also affect the physical status of the
components. For example, the non-covalent bonding between chitosan
and polyphenols of black soybean seed coat extracts decreased the
crystallinity degree of chitosan in the films (Wang et al., 2019). The
complexation between polyphenols and polysaccharides should be bet
ter studied (Dobson et al., 2019; Zhu, 2015, 2018; Liu et al., 2020). The
nature of the interactions depends on morphology (porosity and surface
area), chemical properties (solubility, composition of sugar and non-
sugar components), and molecular organization (esterification pattern,
molecular size distribution, conformation and functional groups) and
processing history (e.g., heating, ultrasound processing and mixing) of
both polysaccharides and polyphenols (Liu et al., 2020; Zhu, 2015,
2018). Unfortunately, many studies summarized here only indicated the
existence of such interactions between polyphenols and polysaccharides
in the films without being able to mechanistically identify the exact
nature of the interactions. This seriously hinders the development of
“designer films and coatings” for food applications.
5. Effect of polyphenols and extracts on moisture content,
appearance and structural properties of films and coatings
Moisture content of polysaccharide based films may be increased,
little affected or decreased by polyphenol extract addition (Azeredo &
Waldron, 2016; Ceballos, Ochoa-Yepes, Goyanes, Bernal, & Famá, 2020;
Jancikova et al., 2019; Mirón-Mérida et al., 2019; Rodsamran &
Sothornvit, 2019). The moisture contents were seen to depend on the
types and composition of polysaccharides and polyphenol extracts and
the presence of other components. For example, adding coffee parch
ment waste extract decreased the moisture content of gellan based films
(Mirón-Mérida et al., 2019). Adding rosemary extract increased the
moisture content of furcellaran/gelatin hydrolysate based films (Janci
kova et al., 2019). Polysaccharides and added plasticizers tend to be
very hydrophilic and can bind water efficiently. Adding polyphenol
extract limited the interactions of the polysaccharides and glycerol with
water, decreasing the moisture content of the resulting films (Liu et al.,
2020). On the other hand, interactions between film components and
polyphenols may lead to the releasing of water molecules, resulting in
increased moisture content of the films (Jancikova et al., 2019).
Thickness, color and microstructure of films are important quality
attributes. Addition of polyphenols or extracts increased, had little effect
or decreased the thickness of films, depending on the types and
composition of polysaccharides and polyphenol extracts (Table 1). For
example, adding the extract of roasted peanut skin increased the
thickness of the films made from Tremella fuciformis (white jelly mush
room) polysaccharides (Ju & Song, 2020). Adding mulberry poly
phenolic extract had no effect on the thickness of κ-carrageenan based
films (Liu et al., 2019). Adding guava leaf extract decreased the thick
ness of sodium alginate based films (Luo et al., 2019). Interstitial spacing
between polysaccharides and plasticizers relates to film thickness
(Jongjareonrak, Benjakul, Visessanguan, & Tanaka, 2006). Added
polyphenol extracts interacted with polysaccharides or plasticizers,
changing the film thickness. The thickness of films should be related to
consumer acceptance when the films are used for food packaging.
Addition of polyphenols and extracts tended to make polysaccharide
based films colored and darker (Table 1). Transmittance may become
lower and opacity of the films higher upon the addition in different films
Fig. 1a. “Bubble” films made from blown-extrusion process using different materials. LLDPE/LL, linear low-density polyethylene; NS, cassava native starch; AS,
acetylated starch with low (AS-L) and high (AS-H) substitution degrees (Panrong et al., 2019) (Reprinted with permission from Elsevier).
F. Zhu
7. Food Chemistry 359 (2021) 129871
7
with different extracts. The color of the films is largely dependent on the
composition and addition levels of the polyphenols and extracts as well
as the types of polysaccharides (Fig. 1c) (Jancikova et al., 2019; Ju &
Song, 2020; Liu et al., 2019; Wu et al., 2020; Yuan et al., 2019). For
example, in Fig. 1c, the addition of green tea polyphenols increased the
opacity and brownish color of calcium alginate based films (Yuan et al.,
2019). Adding mulberry polyphenolic extract made κ-carrageenan films
bluish (Liu et al., 2019). Tea polyphenol addition made the films of
pectin-KGM yellowish (Lei et al., 2019). The changes in the color of the
films became more obvious with increasing levels of polyphenol ex
tracts. The film color should be related to consumer acceptance when
the films are used for food packaging.
Color of films containing anthocyanins can be pH dependent when
coming into contact with food materials, and can be used for intelligent
packaging (Wang et al., 2019). For example, color of starch films con
taining yerba mate extract was pH sensitive (Ceballos et al., 2020).
Similarly, color of films made of KGM and oxidized chitin nanocrystals
with red cabbage anthocyanin extract was pH sensitive (Wu et al., 2020)
(Fig. 2b). Color of KGM and chitosan films containing nano-ZnO and
mulberry anthocyanin extract was pH sensitive (Sun et al., 2020b). The
pH sensitivity of the films containing certain types of polyphenols can be
used to indicate product freshness as described in section 9.
Polysaccharide based films tend to be smooth on surface with com
pacted structure (Fig. 2c) (Piñeros-Hernandez et al., 2017). Addition of
polyphenol extracts increased or decreased the roughness of the film
surface, depending on the composition of addition level of the extracts
(Han & Song, 2021; Ju & Song, 2020; J. Liu et al., 2018; Y. Liu et al.,
2019, 2020; Mirón-Mérida et al., 2019; Rojas-Bravo et al., 2019). For
example, adding mango peel powder to starch films made the surface
smoother (Rojas-Bravo et al., 2019). Adding coffee parchment waste
extract increased the surface roughness of gellan based films (Mirón-
Mérida et al., 2019). Suitable addition levels of polyphenol extracts led
to even distribution of polyphenols inside the films. However, the
addition of too high levels of polyphenol extracts can lead to rough
surface and cracks in films. For example, aggregation of curcumin in
κ-carrageenan based films was obtained when the addition level
increased to over 3% (Fig. 2a) (Liu et al., 2018). Increasing the amount
of rosemary extract led to the formation of cracks on the surface of
cassava starch films (Piñeros-Hernandez et al., 2017) (Fig. 2c). Excessive
amount of polyphenol extracts disrupted the polysaccharide-
polysaccharide interactions, weakening the network. In most of the
studies, the surface properties of the films were not quantified. Atomic
force microscopy (AFM) can be used to obtain quantitative data of the
film surface (Han & Song, 2021). The significance of surface roughness
remains to be related to functional properties of the films.
6. Effect of polyphenol extracts on mechanical properties and
stability of films and coatings
Tensile strength and elongation at break were obtained for poly
saccharide based films with added polyphenol extracts to describe me
chanical properties of films (Table 2). Addition of polyphenol extracts
either increased or decreased the tensile strength and elongation at
break of the films, depending on the composition and addition levels of
polysaccharides and polyphenol extracts as well as the plasticizers (Gao,
He, Sun, He, & Zeng, 2019; Han & Song, 2021; Ju & Song, 2020;
Kaczmarek, 2020; Lei et al., 2019; J. Liu et al., 2018; Y. Liu et al., 2019;
Luo et al., 2019; Ma, Ren, & Wang, 2017; Moreno et al., 2020; Ni et al.,
2019; Rodsamran & Sothornvit, 2019; Ruan et al., 2019; Sun et al.,
2020a,b; Tong et al., 2020; Wu et al., 2020; Yilmaz-Turan et al., 2020;
Yuan et al., 2019; Zhou et al., 2019). For example, adding roasted
peanut skin extract increased tensile strength and decreased elongation
at break of films based on polysaccharides of Tremella fuciformis (white
jelly mushroom) (Ju & Song, 2020). Adding lime peel extract containing
polyphenols decreased tensile strength and increased elongation at
break of films made from lime peel pectin (Rodsamran & Sothornvit,
2019). The tensile strength of KGM, chitosan and nano-ZnO based films
increased before decreasing with increasing addition levels of mulberry
anthocyanin extract (Sun et al., 2020b). Opposite trend was obtained for
the elongation at break (Sun et al., 2020b). Adding suitable amount of
epigallocatechin gallate (EGCG) improved the mechanical properties of
KGM and carboxymethyl chitosan films, whereas excessive EGCG
addition decreased those. EGCG may induce cross-linking of the poly
saccharide molecules, whereas excessive EGCG inhibited the cross-
linking by dispersing them (Sun et al., 2020a). Polyphenols may also
hinder the polysaccharide-polysaccharide interactions (Liu et al., 2019).
Adding phenolic extracts may lead to deterioration in the mechanical
properties of starch films (Menzel et al., 2019). Polyphenol extracts may
also have plasticizing effect on polysaccharide based films (Cerruti et al.,
2011). Therefore, the changes in mechanical properties induced from
adding polyphenol extracts were dependent on the types, addition levels
and composition of both the polysaccharides and polyphenol extracts.
Deterioration in mechanical properties of the films induced by adding
polyphenol extracts may be reduced using other components. For
example, a combination of adding cellulose fibers and using cross-
linkers (citric acid) can significantly improve the functional properties
Fig. 1b. Films of konjac glucomannan and polylactic acid with trans-cinnamic acid made using microfluidic spinning, A, digital photo; B, scanning electron mi
croscopy (SEM) photo (Lin et al., 2019) (Reprinted with permission from Elsevier).
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8. Food Chemistry 359 (2021) 129871
8
Fig. 1c. Alginate based films fortified with tea polyphenols at different levels of 0 (a), 1 (b), 2 (c) 3 (d), 4 (f), 5% (g) (Yuan et al., 2019) (Reprinted with permission
from Elsevier).
Fig. 2a. Scanning electron microscopy (SEM) photos of κ-carrageenan films with added curcumin up at different levels of A, 0; B, 1%; C, 3%; D, 5%; E, 7%; F, pure
curcumin crystals (Liu et al., 2018) (Reprinted with permission from Elsevier).
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9. Food Chemistry 359 (2021) 129871
9
of starch films by increasing resistance towards stress without affecting
extensibility (Menzel, 2020). The addition of the cellulose fibers
increased the Young’s modulus by 3 times. Citric acid induced cross-
linking by increasing the molecular size of starch (Menzel, 2020).
Glycerol can also be used to modulate the mechanical and thermal
properties of polysaccharide based films (Menzel et al., 2019; Menzel,
2020).
Thermal properties of films were mostly measured using thermog
ravimetric analysis (TGA) and differential scanning calorimetry (DSC)
(Breda et al., 2017; Liu et al., 2018; Menzel, 2020; Menzel, González-
Martínez, Chiralt, & Vilaplana, 2019; Piñeros-Hernandez, Medina-
Jaramillo, López-Córdoba, & Goyanes, 2017; J. Sun et al., 2020a; L.
Sun et al., 2017, 2018; Wang et al., 2019). Adding polyphenol extract
increased, had little effect or decreased the thermal stability of poly
saccharide based films (Table 2). The changes were seen to depend on
the types, composition and addition levels of polysaccharides and
polyphenol extracts. Mechanistically, the effect of adding polyphenol
extracts on the thermal properties is similar to that on the mechanical
properties through affecting polysaccharide interactions. For example,
only a suitable amount of curcumin addition (less than 4%) led to
improved tensile strength and thermal stability of κ-carrageenan films.
Excessive curcumin addition (over 4%) in κ-carrageenan films decreased
the tensile strength and thermal stability (Liu et al., 2018).
7. Effect of polyphenols and extracts on barrier properties of
films and coatings
Wettability of films can be described using contact angle (Breda
et al., 2017; Feng et al., 2018; Ju & Song, 2020; Lei et al., 2019; Piñeros-
Hernandez et al., 2017). Contact angle of polysaccharide based films
was increased or decreased by adding polyphenol extracts, depending
on the types, composition and addition levels of both polysaccharides
and extracts. For example, pequi (C. brasiliense) peel extract addition
decreased the surface hydrophilicity of chitosan film by increasing the
contact angle (Breda et al., 2017). Adding roasted peanut skin extract to
the films of Tremella fuciformis polysaccharide increased the contact
angle from 66 (control) to 83◦
(Ju & Song, 2020). Increasing the
addition level of aqueous rosemary extracts increased contact angle of
starch (cassava) films from 39 to 53◦
(Piñeros-Hernandez et al., 2017).
Tea polyphenol addition increased the water resistance of pectin-KGM
films by increasing contact angle (Lei et al., 2019). In contrast, tea
polyphenol addition at 10% decreased the contact angle from 92 to 66◦
(Feng et al., 2018). At certain addition level, hydroxyl functional groups
of polyphenols may bind with those of polysaccharides, decreasing the
availability of hydroxyl groups on film surface. This would lead to
decreased wettability of the films. When the amount of polyphenols
increased to over a limit, more functional groups of polyphenols would
replace those of polysaccharides to be present on the film surface. The
hydrophilicity of film surface would increase or decrease if polyphenol
extract is more or less hydrophilic than polysaccharides, respectively.
The surface roughness and morphology remain to be related to wetta
bility of polysaccharide based films.
The barrier properties of polysaccharide based films relate to
permeability of water vapor, oxygen, oil and ultraviolet (UV) light
(Table 2). Adding polyphenol extracts tended to increase the UV barrier
capacity of the films (He et al., 2020; Ju & Song, 2020; Liu et al., 2019,
2020; Piñeros-Hernandez et al., 2017; Riaz et al., 2020b; Sun et al.,
2020a,b; Tong et al., 2020; Wu et al., 2020). This can be readily
attributed to the chromatic nature of polyphenols. The permeability of
water vapor, oxygen and oil of polysaccharide based films was
increased, little affected or decreased by the addition of polyphenol
extracts, depending on the types, composition and addition levels of
both polysaccharides and extracts (Table 2). For example, alginate films
had low water barrier capacity (Farha et al., 2020). Adding green tea
and grape seed extracts and lipids significantly improved the water
barrier capacity of the films through emulsifications and molecular in
teractions (Farha et al., 2020). Adding extract of Chinese chive (Allium
tuberosum) root into chitosan films decreased the oil adsorption dose-
dependently (Riaz et al., 2020a). A suitable amount of curcumin addi
tion (less than 4%) led to improved water and oxygen barrier capacity of
κ-carrageenan films. Excessive curcumin addition (over 4%) in
κ-carrageenan films decreased the water and oxygen barrier capacity
(Liu et al., 2018). Adding thyme extract had no effect on water vapor
permeability of chitosan film, decreased that of films containing starch
Fig. 2b. Color changes of konjac glucomannan based films containing oxidized chitin nanocrystals and red cabbage anthocyanins after being immersed in different
buffer solutions (pH 2 to 12) (Wu et al., 2020) (Reprinted with permission from Elsevier).
F. Zhu
10. Food Chemistry 359 (2021) 129871
10
Fig. 2c. Scanning electron microscopy (SEM) photos of surfaces of thermoplastic cassava starch (TPS) based films fortified with rosemary extracts (RE) at different
levels up to 20%. The magnifications for the left and right columns are 2,000 and 10,000 respectively. Increasing the amount of the added extracts led to the
formation of cracks on the surface of the films (Piñeros-Hernandez et al., 2017) (Reprinted with permission from Elsevier).
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Table 2
Effect of polyphenol extracts on barrier and mechanical properties of polysaccharide based films.
Polysaccharide type Polyphenol type/
extract
Water barrier
(WVP)
Oxygen barrier Oil
penetration
UV barrier Mechanical properties and stability References
Tensile strength Elongation at break Thermal
stability
Solubility
Alginate Tea polyphenols
(purity > 98%)
Increased N.A. Increased only
at the highest
addition level
of polyphenols
N.A. Increased Increased with
Increasing
polyphenol
concentration
N.A. N.A. Yuan et al.,
2019
Alginate (sodium) Guava leaf extract Decreased N.A. N.A. N.A. Increased Decreased N.A. Increased Luo et al.,
2019
Alginate, agar, or
alginate/agar (1:1) mix
Larrea nitida (aerial
parts) extract
Decreased Decreased for
alginate based
films, increased
for agar and agar/
alginate based
films
N.A. N.A. Decreased Little affected N.A. N.A. Moreno et al.,
2020
Alginate Tannic acid up to
30% in content was
added to sodium
alginate
Increased Increased oxygen
permeability
N.A. N.A. Decreased Increased N.A. N.A. Kaczmarek,
2020
Arabinoxylan (AX) Feruloylated AX; AX
+ ferulic acid (8 mg/
g AX); sorbitol (30%)
as plasticizer
Adding free ferulic
acid and
feruloylation had
no effect on WVP
Adding free
ferulic acid and
feruloylation had
no effect
N.A. N.A. AX films with added
ferulic acid had higher
tensile strength than
those of feruloylated
AX
AX films with added
ferulic acid had
higher elongation at
break than those
from feruloylated
AX
Films of
feruloylated AX
or with added
ferulic acid
were more
stable
N.A. Yilmaz-Turan
et al., 2020
Carboxymethyl cellulose
+ sodium alginate
Epigallocatechin
gallate (EGCG)
N.A. N.A. N.A. Increased Increased Decreased N.A. N.A. Ruan et al.,
2019
κ-Carrageenan Curcumin (up to 7%) Curcumin (up to
3%) decreased
water penetration
Curcumin (up to
3%) increased O2
barrier capacity
N.A. N.A. Curcumin (up to 3%)
increased
Curcumin (up to
3%) decreased
Curcumin (up to
3%) increased
N.A. Liu et al.,
2018
κ-Carrageenan Mulberry
polyphenolic extract
Decreased N.A. N.A. Increased Increased Decreased Increased N.A. Liu et al.,
2019
κ-Carrageenan Pomegranate peel
andflesh extracts
Decreased N.A. N.A. Increased Increased Increased N.A. N.A. Liu et al.,
2020
κ- and ι-Carrageenans Lapacho tea extract N.A. N.A. N.A. N.A. Increased for κ-
carrageenans based
films and had no effect
on ι-carrageenans
based films
Increased for films
with the extracts of
less than 20%
N.A. All films had
solubility of
100%, little
affected
Jancikova
et al., 2020
Carboxymethyl cellulose
/gelatin
Bamboo leaf
polyphenol extract
Increased N.A. N.A. Increased Decreased Decreased Increased
(melting point)
N.A. He et al.,
2020
Carboxymethylcellulose Allium tuberosum
(Chinese chives)
extract
Decreased N.A. Decreased Increasing Decreased Decreased Decreased Swelling
and
solubility
decreased
Riaz et al.,
2020b
Chitin Tannic acid on
surface
Water vapour
permeability
decreased
N.A. N.A. Increasing Increased Little affected N.A. N.A. Wang et al.,
2016
Chitosan Black and green tea
extracts
Decreased N.A. N.A. N.A. Decreased Decreased N.A. Solubility
and swelling
power
increased
Peng et al.,
2013
Chitosan Pequi (Caryocar
brasiliense) peel
extract
Decreased N.A. N.A. N.A. Little affected Decreased Decreased N.A. Breda et al.,
2017
(continued on next page)
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Table 2 (continued)
Polysaccharide type Polyphenol type/
extract
Water barrier
(WVP)
Oxygen barrier Oil
penetration
UV barrier Mechanical properties and stability References
Tensile strength Elongation at break Thermal
stability
Solubility
Chitosan Protocatechuic acid
was grafted onto
chitosan
Decreased N.A. N.A. Increased
before
decreasing
with
increasing
grafting
Increased before
decreasing with
increasing grafting
degree
Increased before
decreasing with
increasing grafting
degree
Decreased Solubility
increased
Liu et al.,
2017
Chitosan Thinned young apple
polyphenols
Increased N.A. N.A. N.A. Increasing polyphenol
concentration
decreased tensile
strength
Increasing
polyphenol
concentration
decreased
elongation at break
Decreased with
increasing
polyphenol
content
N.A. Sun et al.,
2017, 2018
Chitosan Black soybean seed
coat extract
Water vapour
permeability
decreased
N.A. N.A. Increasing Increased Increased Increased Increased Wang et al.,
2019
Chitosan Extract of Chinese
chive (Allium
tuberosum) root
Water vapour
permeability
decreased
N.A. Decreased oil
penetration
N.A. Decreased Decreased Decreased with
increasing
extract content
(TGA and DSC)
Solubility
and swelling
power
decreased
Riaz et al.,
2020a
Chitosan, starch (pea),
starch/chitosan
Thyme extract No effect on
chitosan film,
decreased for films
containing starch
or starch/chitosan
Increased for
chitosan films,
had no effect on
starch film,
decreased for
starch/chitosan
films
N.A. N.A. Adding the extract
increased elasticity
modulus and tensile
strength of chitosan
containing films, and
decreased those of
starch films
Adding the extract
decreased
percentage of
elongation of
chitosan containing
films, but had no
effect on starch films
N.A. N.A. Talón et al.,
2017a
Curdlan, chitosan Tea polyphenols Decreased N.A. N.A. N.A. Decreased Decreased N.A. N.A. Zhou et al.,
2019
Furcellaran/gelatin
hydrolysate
Rosemary extract N.A. N.A. N.A. Increased Increased Increased N.A. N.A. Jancikova
et al., 2019
KGM and
polyvinylpyrrolidone
(PVP)
Epigallocatechin
gallate (EGCG)
N.A. N.A. N.A. N.A. Increased Increased N.A. N.A. Ni et al.,
2019
KGM and oxidized chitin
nanocrystals
Red cabbage
anthocyanin extract
Decreased N.A. N.A. Increased Decreased Decreased N.A. Increased Wu et al.,
2020
KGM, chitosan, nano-ZnO Mulberry
anthocyanin extract
Decreased before
increasing with
increasing extract
content
N.A. N.A. Increased Increased before
decreasing with
increasing extract
content
Decreased before
increasing with
increasing extract
content
Increased N.A. Sun et al.,
2020b
KGM, carboxymethyl
chitosan
Epigallocatechin
gallate (EGCG)
Decreased N.A. N.A. Increased Increased (up to at
15% of EGCG) before
decreasing at 20% of
EGCG
Decreased Increased N.A. Sun et al.,
2020a
KGM with carboxylated
cellulose nanocrystals
Grape peel extracts Adding extract
increased water
vapor permeability
of films made of
KGM with
nanocrystals (10
and 15%)
N.A. N.A. Increased Increased Increased Increased N.A. Tong et al.,
2020
Pectin-KGM Tea polyphenols Increased N.A. N.A. N.A. Increased when
polyphenol addition
was added at 2%
Decreased Little affected N.A. Lei et al.,
2019
Pectin, chitosan Tea polyphenols Increased N.A. N.A. N.A. Decreased by 17% Increased by 37% N.A. N.A. Gao et al.,
2019
(continued on next page)
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Table 2 (continued)
Polysaccharide type Polyphenol type/
extract
Water barrier
(WVP)
Oxygen barrier Oil
penetration
UV barrier Mechanical properties and stability References
Tensile strength Elongation at break Thermal
stability
Solubility
Pectin (lime peel) Lime peel extract
containing
polyphenols
Increased N.A. N.A. N.A. Decreased Increased N.A. N.A. Rodsamran &
Sothornvit,
2019
Pomelo peel flours (33%
pectin and 49% of other
carbohydrate)
Tea polyphenols
(purity > 98%)
Decreased before
increasing with
increasing
polyphenol
concentration
N.A. Very strong N.A. Decreased with
increasing polyphenol
addition
Decreased with
increasing
polyphenol addition
N.A. N.A. Wu et al.,
2019
Hydroxypropyl starch Tea polyphenol
(purity > 98%)
No effect N.A. N.A. N.A. Decreased from 20
down to 16 MPa
Decreased from 74
down to 65%
N.A. N.A. Feng et al.,
2018
Starch (corn) Mango peel powder
(up to 4%)
N.A. N.A. N.A. N.A. Increased Increased N.A. N.A. Rojas-Bravo
et al., 2019
Starch (cassava) Aqueous rosemary
extracts
Increased N.A. N.A. Increased Increased Decreased Decreased N.A. Piñeros-
Hernandez
et al., 2017
Starch (potato) Phenolic extracts
(80% methanol)
from sunflower hulls
Increased Decreased N.A. N.A. Increased Decreased Little affected N.A. Menzel et al.,
2019;
Menzel, 2020
Starch (cassava) (native
and hydrolyzed)
Yerba mate extract Increased N.A. N.A. N.A. Little affected Increased N.A. Little
affected
Ceballos
et al., 2020
Tara gum-polyvinyl
alcohol
Curcumin Increased N.A. N.A. N.A. Decreased Increased N.A. N.A. Ma et al.,
2017
Tremella fuciformis (white
jelly mushroom)
Roasted peanut skin
extract
Increased N.A. N.A. Increased Increased Decreased N.A. N.A. Ju & Song,
2020
WVP, water vapour permeability; KGM, konjac glucomannan; N.A., not available
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14. Food Chemistry 359 (2021) 129871
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or starch/chitosan (Talón et al., 2017a). When moisture content of films
is high, plasticization effect of water should also be taken into consid
eration together with the polyphenol effect (Talón et al., 2017a). The
interactions and associations between polyphenols and polysaccharides
may lead to more compacted structure of the films, resulting in
decreased permeability. When excessive polyphenol extracts are added,
they may aggregate into small particles, resulting in structural defects
within the films (Wu et al., 2019; Talón et al., 2017a).
Adding polyphenol extracts increased, little affected or decreased the
solubility of polysaccharide based films, depending on the types of
polyphenol extracts and polysaccharides (Ceballos et al., 2020; Janci
kova, Dordevic, Jamroz, Behalova, & Tremlova, 2020; Liu, Meng, Liu,
Kan, & Jin, 2017; Luo et al., 2019; Peng et al., 2013; Riaz et al., 2020b,a;
Wang et al., 2019; Wu et al., 2020). For example, adding red cabbage
anthocyanin extract increased solubility of KGM based films fortified
with oxidized chitin nanocrystals (Wu et al., 2020). Adding A. tuberosum
(Chinese chives) extract decreased the solubility of carboxymethyl cel
lulose based films (Riaz et al., 2020b). Interactions between certain
polyphenols and polysaccharides at a range of concentrations may lead
to decreased availability of hydroxyl groups on the film surface,
decreasing the water interactions and the solubility (Riaz et al., 2020b).
On the other hand, certain polyphenols such as anthocyanins would
increase the hydrophilicity of films, increasing the solubility (Wu et al.,
2020).
8. Releasing behaviors of polyphenols from films and coatings
with added polyphenols and extracts
Polyphenols are encapsulated in polysaccharide matrix when
formulated into films. Releasing properties of polyphenols from poly
saccharide based films in different food simulants were studied (Ben
bettaïeb et al., 2020; Ceballos et al., 2020; Gao et al., 2019; Gomaa,
Fawzy, Hifney, & Abdel-Gawad, 2018b; Gomaa, Hifney, Fawzy, &
Abdel-Gawad, 2018a; Lin, Ni, Liu, Yao, & Pang, 2019; Liu et al., 2018;
Ma et al., 2017; Moreno et al., 2020; Ruan et al., 2019; Talón, Trifkovic,
Vargas, Chiralt, & González-Martínez, 2017; Wu et al., 2020). Types of
food simulants (viscosity and water activity), phenolics and poly
saccharides as well as formulations significantly affected the releasing
property of phenolics from polysaccharide films (Gomaa et al., 2018a,
2018b; Benbettaïeb et al., 2020). For example, food simulants such as
glycerol may migrate into the films, creating plasticization effect. Gallic
acid interacted more with chitosan/gelatin based films than cinnamic
acid, affecting the diffusivity of the phenolics (Benbettaïeb et al., 2020).
Migration tests were done on cassava starch films with rosemary extracts
for 7 days (Piñeros-Hernandez et al., 2017). Most of the polyphenols
were migrated into water as food simulant, whereas little polyphenols
were released into ethanol solution (95%). Epigallocatechin gallate
(EGCG) contained in films of carboxymethyl cellulose plus sodium
alginate can be released slowly into fatty food systems (Ruan et al.,
2019). The type of polysaccharides largely affected the release property
of the polyphenols (Talón et al., 2017b). Pea starch films with thyme
extract had faster and higher releasing of polyphenols than chitosan
films. Chitosan films had the higher polyphenol releasing in acetic acid
solution than ethanol aqueous solution or water. Use of cross-linking
agent (tannic acid) in chitosan films reduced the releasing of poly
phenols (Talón et al., 2017b). Swelling capacity of KGM films contrib
uted to controlled release behaviors of cinnamic acid (Lin et al., 2019).
Controlled releasing of polyphenols from alginate/agar films containing
Larrea nitida extracts was obtained (Moreno et al., 2020). Increasing tea
polyphenol concentration increased the amount of the polyphenols
released from chitosan and pectin composite films (Gao et al., 2019)
(Supplementary Fig. 3). The releasing of polyphenols from different
films for different packed food materials with different chemical and
biological environments should be tested (Ceballos et al., 2020).
The releasing kinetics of polyphenols from different polysaccharide
based films was studied (Gomaa et al., 2018a, 2018b). The release of
polyphenols from alginate-chitosan-fucoidan of seaweed (Sargassum
latifolium) and fungus (Aspergillus niger) was described using Peleg’s
model. The effective diffusion coefficient of the release of polyphenols
from the films was expressed based on simplified Fick’s second law
(Gomaa et al., 2018a, 2018b). Releasing analysis of anthocyanins from
KGM and oxidized chitin nanocrystals with red cabbage extract followed
Fickian diffusion (Wu et al., 2020). Curcumin was released from Tara
gum/ polyvinyl alcohol films and can be described using Fickian law in
fat based simulants (Ma et al., 2017). Release of curcumin from
κ-carrageenan films mostly followed the Fickian diffusion (Liu et al.,
2018). Overall, the kinetics studies showed that the release of poly
phenols is sustained from polysaccharide based films. The encapsulation
systems also have potential to be used as delivery systems of poly
phenols. The releasing kinetics of polyphenols remains to be related to
food protection. There have been many studies on the use of different
types of polysaccharides in the encapsulation of food ingredients for the
controlled release applications (Akbari-Alavijeh, Shaddel, & Jafari,
2020; Zhu, 2017). The methods used may be extended to include the use
of polysaccharide based films as encapsulation systems of polyphenols
for food packaging applications.
9. Antioxidant, antimicrobial and antiviral properties of
polysaccharide based films and coatings with added polyphenol
extracts
9.1. Antioxidant and antimicrobial properties
It has been well established that polyphenols are natural antioxidants
with many biological effects (Pandey & Rizvi, 2009). Certain types of
polyphenols have antimicrobial activities (Daglia, 2012). It is expected
that adding polyphenols into films formulations increases antioxidant
and antimicrobial activities of the films. Many studies measured the in
vitro antioxidant activities of polysaccharide based films fortified with
polyphenol extracts (Table 3). Most of the studies measured the total
phenolic content (TPC) of polysaccharide based films. Chemical assays
for measuring antioxidant activities included ferric reducing antioxidant
power assay (FRAP) and scavenging activities against 2,2′
-azino-bis(3-
ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhy
drazyl (DPPH) and OH radicals. Invariably, addition of any types of
polyphenol extracts increased the in vitro antioxidant activities of the
films, mostly in a concentration-dependent manner (Feng et al., 2018;
Gao et al., 2019; Gomaa et al., 2018a; Jancikova et al., 2020; Liu et al.,
2020; Menzel, 2020, 2019; Rodsamran & Sothornvit, 2019; Zhou et al.,
2019; Farha et al., 2020; Jancikova et al., 2019; Lei et al., 2019; Luo
et al., 2019; Peng et al., 2013; Piñeros-Hernandez et al., 2017; Riaz et al.,
2020b,a, J. Sun et al., 2020a,b; L. Sun et al., 2018; X. Wang et al., 2019;
Y. Wang et al., 2016; C. Wu et al., 2020; H. Wu et al., 2019; Yadav et al.,
2020; Yuan et al., 2019). Grafting of protocatechuic acid onto chitosan
also increased the antioxidant activity of the films (Liu et al., 2017).
Many studies also showed that the TPC was positively correlated with
the in vitro antioxidant activities. There has been increasing concern
regarding the significance of these in vitro methods for measuring anti
oxidant activity and total phenolic content (Granato et al., 2018). The
biological significance of the results of antioxidant activities has been
challenged, though recent studies continue to use the in vitro chemical
assays. Cellular based assays may be used to measure the antioxidant
activities, though their validity remains to be studied.
Diverse bacteria, yeasts, molds and viruses used in the studies
included Escherichia coli, Salmonella spp., Listeria monocytogenes, Staph
ylococcus aureus, S. typhimurium, Bacillus cereus, murine norovirus,
hepatitis A virus, Saccharomyces cerevisiae and Candida tropicalis,
Botryosphaerial dothidea, Colletotrichum fructicola and Alternariatenuis
sima, Fusarium verticillioides, Colletotrichum gloeosporioides and Fusarium
sp. (Table 3) (Feng et al., 2018; Liu et al., 2020; Farha et al., 2020; Luo
et al., 2019; Mirón-Mérida et al., 2019; Riaz et al., 2020b; Sun et al.,
2018; Wang et al., 2016). Different films containing different
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15. Food Chemistry 359 (2021) 129871
15
polyphenol extracts inhibited these microorganisms to different extents
in vitro, depending on the types and composition of polysaccharides and
polyphenols. Increasing concentration of polyphenol extracts in the
formulations tended to increase the antimicrobial activity of films (Wu
et al., 2019, 2020; Lei et al., 2019; Sun et al., 2020a, 2020b) (Supple
mentary Fig. 4). The antimicrobial mechanisms of polyphenols and
polysaccharides have been well studied and illustrated at molecular and
cellular level (Daglia, 2012; Farha et al., 2020; Benhabiles et al., 2012).
Thus, these aspects are not included here. Certain polysaccharides such
as chitosan and some sulfated ones have antimicrobial activities (Kwon
et al., 2020). Synergistic antimicrobial effects may be obtained from
both polyphenols and polysaccharides of the films (Lin et al., 2019). For
example, hydrophilicity of KGM contributed to the antibacterial prop
erty of the KGM based films containing polyphenols (Lin et al., 2019).
Chitosan and young apple polyphenols both contributed to the antimi
crobial activities of chitosan based films fortified with the polyphenols
(Sun et al., 2017). Overall, selection of polyphenols and polysaccharides
with suitable formulations can lead to desired antimicrobial activities.
There are many previous studies on the antioxidant and antimicro
bial activities of different types of polyphenols as well as a range of
natural polysaccharides (Mirzadeh et al., 2020; Olszewska et al., 2020;
Wang et al., 2016; Dzah et al., 2020). The structure–function relation
ships of many polyphenols and polysaccharides have been studied in
detail. Such vast knowledge should be better utilized to guide the se
lection of polysaccharides and polyphenols for antioxidant and antimi
crobial applications of films and coatings.
9.2. Potential of polysaccharide based films and coatings with added
polyphenols to address food safety related to the COVID-19 through active
packaging
The ongoing COVID-19 pandemic is a major threat for human sur
vival (Rizou, Galanakis, Aldawoud, & Galanakis, 2020). Severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) has been found
through the food supply chain. A few positive cases of SARS-CoV-2 have
been related to stored food products (Dai et al., 2020; Chin et al., 2020).
For example, SARS-CoV-2 attached to salmon remained highly infec
tious for over 1 week (Dai et al., 2020). SARS-CoV-2 may be transmitted
onto food products, which in turn leads to human infection. Active food
packaging with antiviral activity against SARS-CoV-2 should be devel
oped to address this food safety issue. Different types of polyphenols
such as epigallocatechin gallate, curcumin and resveratrol showed in
vitro antiviral activity against SARS-CoV-2 (Paraiso et al., 2020;
Annunziata et al., 2020). Sulfated polysaccharides from marine source
also showed in vitro antiviral activity against SARS-CoV-2 (Song et al.,
2020; Kwon et al., 2020). It is proposed here that films developed from
these sulfated polysaccharides fortified with these polyphenols should
have antiviral activity against SARS-CoV-2. The transmission of the
coronavirus can be inhibited from using the active packaging along food
supply chain. Formulations of these films with desirable mechanical and
barrier properties remain to be developed.
10. Food packaging applications and health effects of
polysaccharide based films and coatings with added polyphenol
extracts
Different polysaccharide based films were used to pack different food
products (Table 4). The shelf life of these products was significantly
improved through active packaging. The protective properties of these
films can be readily attributed to their antioxidant and antimicrobial
capacities as well as their barrier properties described in sections 8 and
6, respectively.
10.1. Animal based and dairy products
Polysaccharide based films with added polyphenol extracts became
active packaging materials for animal based food products (Guo, Han,
Yu, & Lin, 2020; Liu et al., 2018; Mehdizadeh et al., 2020; Sun et al.,
2017, 2018; Xie et al., 2020; Zhou et al., 2019). Physicochemical and
compositional changes of these products during storage were signifi
cantly slowed using the films and coatings for packaging. For example,
wrapping grass carp fillets by chitosan films with polyphenols from
thinned young apples decreased protein and lipid oxidation, changes in
color and pH and content of amino acids, microbial proliferation, and
reduction of water holding capacity and functionalities of soluble
myofibrillar protein (Sun et al., 2017, 2018). The water retention,
antioxidant and antimicrobial capacities of the films with thinned young
apple polyphenols contributed to the positive packaging properties of
grass carp fillets (Sun et al., 2017, 2018). Similarly, increasing sea
buckthorn pomace extract content in esterified potato starch based films
largely decreased the quality loss of beef jerky products by decreasing
water loss, total volatile basic nitrogen content, thiobarbituric acid
reactive substances, while maintaining the color. The growth of bacteria
including E. coli, L. monocytogenes, Salmonella spp. and S. aureus were
significantly inhibited by the films containing the extracts. However, the
addition of the extract at 6% negatively affected the smell of the prod
ucts (Guo et al., 2020). Therefore, release of film components including
polyphenols and their migration into food products should be better
studied to ensure the sensory quality.
Polysaccharide based films containing certain types of polyphenols
such as anthocyanins and curcumin showed potential for intelligent
packing (Liu et al., 2018, 2019; Wu et al., 2020). Color of the films was
dependent on pH of the environment as described in section 4 (Fig. 2b).
This property can be used to indicate freshness of some animal based
food products (Liu et al., 2018, 2019). For example, κ-carrageenan based
films with added curcumin turned from yellow to red at alkaline pH
conditions (Liu et al., 2018). This was used as indicator of pork and
shrimp freshness. The color change of κ-carrageenan based films con
taining mulberry polyphenolic extract was related to pH changes of milk
during storage. The films can be put in milk to detect any spoilage (Liu
et al., 2019). The polyphenol type should be carefully selected, so that
color of the films is pH sensitive for intelligent packaging (Jancikova
et al., 2019).
The type of polyphenol extracts should be carefully chosen for spe
cific functionality of the films. For example, κ-carrageenan based films
with pomegranate peel extracts were more suitable for active packaging
due to high antioxidant and antimicrobial capacities; whereas those
with the pomegranate flesh extract were more suitable for intelligent
packaging (color was sensitive to pH changes). The former was rich in
tannin type polyphenols, whereas the latter contained high levels of
anthocyanins (Liu et al., 2020).
10.2. Plant based products
Polysaccharide based films with added polyphenol extracts became
active packaging systems for oils, fruits and vegetables (Moreno et al.,
2020; Riaz et al., 2020b,a; Rodsamran & Sothornvit, 2019; Rojas-Bravo
et al., 2019; Romani, Hernández, & Martins, 2018; Wu et al., 2019). It
was shown that polysaccharide films can have good barrier capacity
against oil penetration (section 6). Adding polyphenols into poly
saccharide based films significantly delayed oil oxidation by decreasing
the thiobarbituric acid reactive substances and weight loss (Rodsamran
& Sothornvit, 2019; Wu et al., 2019). Such effect could be readily
attributed to the antioxidant and radical scavenging capacities as
described in section 8. It was not clear if any components of the films
including polyphenols and plasticizers may migrate into the oils,
changing the sensory quality. Indeed, many polyphenols such as tannins
have bitter taste, which is undesirable for many consumers (Drewnowski
& Gomez-Carneros, 2000).
Starch based films containing polyphenol extracts decreased the
browning of freshly cut apples (Rojas-Bravo et al., 2019; Romani et al.,
2018). Such effect could be readily attributed to the antioxidant
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16. Food Chemistry 359 (2021) 129871
16
Table 3
Effect of polyphenol extracts on in vitro antioxidant and antimicrobial properties of polysaccharide based films.
Film formulations Antioxidant activity Antimicrobial activity References
In vitro assay Major results Microbial/virus type Major results
Alginate-lipid films with green tea and grape
seed extracts
ABTS Increased Murine norovirus, hepatitis A
virus
Adding the extracts
significantly inhibited the
viruses
Farha et al.,
2020
Alginate (sodium) with guava leaf extract DPPH Increased E. coli,
S. aureus
Increasing extract content
increased the antibacterial
property
Luo et al., 2019
Alginate with tea polyphenols DPPH, ABTS Increased N.A. N.A. Yuan et al.,
2019
Alginate-chitosan-fucoidan from seaweed
(Sargassum latifolium) and fungus
(Aspergillus niger)
FRAP, OH
scavenging, total
antioxidant
capacity
Adding fucoidan
decreased the
antioxidant activity
N.A. N.A. Gomaa et al.,
2018a
κ-Carrageenan with pomegranate peel or
flesh extracts
DPPH Films with peel extract
had higher antioxidant
activity than those with
flesh extract
E. coli, Salmonella spp.,
L. monocytogenes, S. aureus
Films with peel extract had
higher antimicrobial activity
than those with flesh extract
Liu et al., 2020
κ- or ι-Carrageenans with lapacho tea extract DPPH, FRAP Increased, polyphenol
concentration-
dependent
N.A. N.A. Jancikova
et al., 2020
Carboxymethylcellulose with Allium
tuberosum (Chinese chives) extract
DPPH, ABTS Increased, polyphenol
concentration-
dependent
E. coli, S. typhimurium,
S. aureus, B. cereus
Increasing extract content
increased the antibacterial
property, though the effects
were not as good as antibiotic
control (tetracycline)
Riaz et al.,
2020a
Chitin films with tannic acid on surface DPPH, ABTS Increased, polyphenol
concentration-
dependent
E. coli, S. aureus Tannic acid addition gave
chitin films antibacterial
capacity. Stronger inhibitory
effect on S. aureus than on
E. coli
Wang et al.,
2016
Chitosan with green and black tea extracts DPPH Increased, polyphenol
concentration-
dependent
N.A. N.A. Peng et al.,
2013
Chitosan with polyphenols from thinned
young apple
DPPH Increased, polyphenol
concentration-
dependent
L. monocytogenes, E. coli and
S. aureus), 3 yeasts (Baker’s
yeast, S. cerevisiae and Tropical
candida) and 3 moulds*
Dose-dependently inhibited
bacteria and moulds, had no
effect on yeasts
Sun et al.,
2017, 2018
Chitosan with black soybean seed coat
extract
DPPH Increased, polyphenol
concentration-
dependent
N.A. N.A. Wang et al.,
2019
Chitosan with Chinese chive (A. tuberosum)
root
DPPH, FRAP Increased E. coli, S. aureus, B. cereus,
S. typhimurium
Dose-dependently inhibited
bacteria
Riaz et al.,
2020b
Chitosan-gelatin-starch with quercetin DPPH, ABTS Increased B. substilis, E. coli Inhibited the bacteria,
especially effective against
E. coli
Yadav et al.,
2020
Furcellaran/gelatin hydrolysate rosemary
extract
DPPH, FRAP Increased N.A. N.A. Jancikova
et al., 2019
Konjac glucomannan, carboxymethyl
chitosan with epigallocatechin gallate
(EGCG); konjac glucomannan, chitosan
with mulberry anthocyanin extract; konjac
glucomannan and oxidized chitin
nanocrystals with red cabbage anthocyanin
extract
DPPH Increased, polyphenol
concentration-
dependent
S. aureus, E. coli Dose-dependently inhibited
bacteria
Sun et al.,
2020a, 2020b;
Wu et al., 2020
Pectin-konjac glucomannan with tea
polyphenols (purity ≥ 98%)
DPPH Increased, polyphenol
concentration-
dependent
E. coli, S. aureus Dose-dependently inhibited
bacteria
Lei et al., 2019
Pomelo peel flours (33% pectin and 49% of
other carbohydrates) with tea polyphenols
(purity >98%)
DPPH Increased, polyphenol
concentration-
dependent
E. coli, S. aureus Dose-dependently inhibited
bacteria (Fig. 5)
Wu et al., 2019
Pectin (lime peel) with peel extract
containing polyphenols
DPPH, ABTS Increased, polyphenol
concentration-
dependent
N.A. N.A. Rodsamran &
Sothornvit,
2019
Hydroxypropyl starch with tea polyphenols
(purity > 98%)
DPPH Increased, polyphenol
concentration-
dependent
S. aureus, E. coli Increasing extract content
increased the antibacterial
property
Feng et al.,
2018
Potato starch with phenolic extracts from
sunflower hulls
DPPH Increased, chlorogenic
acid is the major
antioxidant
N.A. N.A. Menzel et al.,
2019; Menzel,
2020
ABTS, 2,2′
-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid); DPPH, 2,2-diphenyl-1-picrylhydrazyl; FRAP, ferric reducing antioxidant power ; N.A., not available; *
the moulds included Botryosphaerial dothidea, Colletotrichum fructicola and Alternariatenuis sima
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17. Food Chemistry 359 (2021) 129871
17
activities of the polyphenols as well as oxygen barrier property of the
films described in sections 6 and 8. Agar based films containing Larrea
nitida (aerial parts) extract significantly controlled the level of murine
norovirus to be under detection limit in blueberries (Moreno et al.,
2020). Indeed, the antimicrobial and antiviral capacities of polyphenol
fortified films of polysaccharides were described in section 8 above. The
major issue of using these films for fruit and apple packaging is that the
sensory properties of the products have not been well studied. It is likely
that the components of the films may migrate onto the food products,
changing the eating quality. Such a lack of information compromises the
usefulness of this kind of active packaging.
Table 4
Food packaging applications of polysaccharide based films fortified with polyphenol extracts.
Polysaccharides and polyphenols Food systems and packaging conditions Major findings References
Animal based products
Chitosan with polyphenols from thinned young
apple
Grass carp (Ctenopharyngodon idellus)
fillets, wrapping for cold storage (4 ◦
C)
The film wrapping significantly reduced the following changes
of the fillets:
• Protein and lipid oxidation
• Changes in color and pH
• Microbial proliferation
• Reduction of water holding capacity
• Reduction in functionalities of soluble myofibrillar protein,
content of amino acids
• The loss of the appearance, texture and sensory properties
Sun et al., 2017,
2018
Furcellaran/gelatin hydrolysate with rosemary
extract
Carp fish fillet (Cyprinus carpio) • The films developed were not suitable as pH-indicator for
detecting the fish spoilage
Jancikova et al.,
2019
Curdlan, chitosan with tea polyphenols Fresh pork, wrapping for cold storage
(4 ◦
C, 9 days)
• Adding tea polyphenols significantly improved the storage of
the fresh pork as reflected by measuring the total volatile
basic nitrogen, thiobarbituric acid reactive substances,
number of bacterial colony, pH and color
• The shelf life of the fresh pork was significantly increased by
3 to 5 days
Zhou et al., 2019
Potato peels with curcumin and bacterial
cellulose
Fresh pork, wrapping for cold storage
(4 ◦
C, 7 days)
• The films with curcumin largely inhibited the lipid oxidation
in the fresh pork by reducing the content of malondialdehyde
(MDA) formed during storage
Xie et al., 2020
κ-Carrageenan films with curcumin Pork, shrimp (25 ◦
C, 75% RH) • κ-Carrageenan films with curcumin turned from yellow to red
at alkaline pH conditions
• The color changes of the films were highly correlated with
total volatile basic nitrogen of pork and shrimp
• The color change was used as indicator of pork and shrimp
freshness
Liu et al., 2018
Esterified potato starch with sea buckthorn
pomace extract; extract was added to starch up
to 6% with 20% glycerin
Beef jerky, wrapping, the products
were placed at supermarket
• Increasing sea buckthorn pomace extract content of the films
significantly decreased the quality loss by decreasing water
loss, total volatile basic nitrogen content, thiobarbituric acid
reactive substances, while maintaining color
• The growth of bacteria including E. coli, L. monocytogenes,
Salmonella spp. and S. aureus were significantly inhibited by
the films containing the extracts
• Addition of the extract at 6% negatively affected the smell of
the products
Guo et al., 2020
Chitosan-starch with pomegranate peel extract
and essential oil (Thymus kotschyanus)
Beef stored at 4 ◦
C for 21 days,
wrapping
• Different parameters of quality including color, odor,
thiobarbituric value, pH, lactic acid, Pseudomonas spp., and
L. monocytogenes contents of beef were measured
• The use of the films containing the peel extract and essential
oil significantly increased the storage property of the beef
Mehdizadeh
et al., 2020
κ-Carrageenan with mulberry polyphenolic
extract
Fresh milk was stored in beaker at 40
◦
C. Film was put inside the milk for
color monitoring
• The color change of the films was related to pH changes of the
milk during storage.
• The films can be used to detect milk spoilage using color
change
Liu et al., 2019
Plant based products
Carboxymethylcellulose with Allium tuberosum
(Chinese chives) extract
Soybean oil stored in glass tubes sealed
with films (50 ◦
C, 28 days)
• The films with extract addition significantly prolonged the
shelf life of the oil by decreasing the peroxide value
Riaz et al., 2020a
Pomelo peel flours (33% pectin and 49% of other
carbohydrate) with tea polyphenols (purity >
98%)
Soybean oil stored at 50 ◦
C for 30 days,
films were used as cap of glass tube
containing the oil
• The addition of tea polyphenols into the film delayed oil
oxidation by reducing peroxide value and weight loss during
the storage compared to the control film
Wu et al., 2019
Lime peel pectin with peel extract containing
polyphenols
Soybean oil in sealed films for 30 days
of storage at 27 ◦
C under fluorescent
light
• The films significantly delayed oil oxidation by decreasing
the amount of thiobarbituric acid reactive substances formed
during storage
Rodsamran &
Sothornvit, 2019
Chitosan films fortified with Chinese chive
(A. tuberosum) root extract
Soybean oil at 50 ◦
C for 4 weeks • Increasing the extract content decreased the oil absorption
capacity of the films, while decreasing the peroxide values of
the oil during storage
Riaz et al., 2020a
Alginate, agar, or alginate/agar (1:1) mix with
Larrea nitida (aerial parts) extract
Blueberries were dipped in film
forming solution before drying
• Blueberries were challenged with murine norovirus before
storage at 10 or 25 ◦
C for different times
• Agar based films containing the extracts significantly
controlled the level of murine norovirus to be under detection
limit
Moreno et al.,
2020
Starch films with mango peel powder Apple slices, dipped in film forming
solution
• The coating slowed the browning of apple slices, while
keeping the phenolics content and antioxidant activity
Rojas-Bravo
et al., 2019
Starch (rice)/protein (fish) with pink pepper
phenolic extract
Freshly-cut apples, dipped in film
forming solution
• The coating significantly slowed the browning of apple cuts Romani et al.,
2018
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18. Food Chemistry 359 (2021) 129871
18
10.3. Health effects of polysaccharide based edible films with added
polyphenol extracts
Polysaccharide based films fortified with polyphenol extracts can be
used as edible films and coatings. There are many health effects of
polysaccharides and polyphenols. They include, but not limited to,
antioxidation, anticancer, antidiebetic capacity, antiobesity, antiin
flammation, glycemic control, antimicrobial, cardiovascular diseases
(Lovegrove et al., 2017; Ma & Chen, 2020). They can positively modu
late gut microbiota to improve human health (Ma & Chen, 2020; Xu, Xu,
Ma, Tang, & Zhang, 2013). Overall, polysaccharide based films fortified
with polyphenol extracts have potential to be used to improve human
health. On the other hand, safety aspects of these edible films with
different plant extracts should be also considered (Pitkänen, Heinonen,
& Mikkonen, 2018). Sensory properties of these edible films and coat
ings should also be considered.
11. Biodegradation of films and coatings fortified with
polyphenols and extracts
Overall, polysaccharide films fortified with polyphenol extracts
showed good biodegradation through interactions with soil bacteria
(Ceballos et al., 2020; Ju & Song, 2020; Piñeros-Hernandez et al., 2017;
Riaz et al., 2020b). For example, in soil, T. fuciformis polysaccharide
based films with or without roasted peanut skin extract were completely
degraded after 50 days (Ju & Song, 2020). Starch films containing yerba
mate extract were decomposed within 10 weeks upon burial (Ceballos
et al., 2020). Therefore, these films are environmentally friendly and
sustainable.
Increasing content of polyphenol extracts increased biodegradation
of some polysaccharide based films (Piñeros-Hernandez et al., 2017;
Riaz et al., 2020a,b). Soil burial test showed that 47% of chitosan films
fortified with A. tuberosum root extract were degraded within 3 weeks
(Riaz et al., 2020a), whereas chitosan films without the extract had only
27% degradation. Adding the extract increased the biodegradation of
carboxymethyl cellulose films (Riaz et al., 2020b). In contrast,
increasing content of rosemary extracts decreased the biodegradation of
cassava starch films after 14 days of burial test (Piñeros-Hernandez
et al., 2017). The differences in the results from these studies could be
attributed to different formulations of these films. Adding polyphenol
extracts may lead to cracks on the films as described in section 4
(Fig. 2c). Such cracks facilitated the interactions of soil bacteria with the
films and the degradation. Adding polyphenol extracts may lead to the
formation of compacted film micro-structure (section 4), resulting in
retarded interactions and degradation. Different polyphenols had
different interactions with microbial communities in soil (Schmidt et al.,
2013). Such differences may lead to different degradation rates in soil.
Nevertheless, any polysaccharide based films with polyphenol extracts
are biodegradable.
12. Comparative studies on effect of polysaccharide type on film
and coating properties
The above sections showed that different types of polysaccharides
can be formulated into films with different polyphenol extracts. An
important question is how the type and form of polysaccharides can
affect the applications of the films with added extracts. Only a few
studies compared the effects of adding polyphenol extracts on properties
of different polysaccharide based films (Ceballos et al., 2020; Jancikova
et al., 2020; Moreno et al., 2020; Talón et al., 2017a). For example, films
of κ-carrageenan and ι-carrageenan with lapacho tea extract were
compared for properties (Jancikova et al., 2020). The 2 carrageenans
showed different film forming properties and different changes in the
film properties to the extract addition. The extract addition increased
the tensile strength of κ-carrageenans films but not that of the ι-carra
geenans films (Jancikova et al., 2020). Adding thyme extract increased
the tensile strength and elasticity modulus of chitosan based films, but
decreased those of pea starch films (Talón et al., 2017a). The addition
decreased water vapor permeability of films containing starch with
lower moisture content, but had no effect on that of chitosan films. The
differences could be due to different water contents of the films and
component interactions (e.g., interactions of polyphenols and chitosan
led to cross-linking) (Talón et al., 2017a). Adding Larrea nitida (aerial
parts) extract decreased oxygen barrier capacity of alginate based films,
but increased that of agar and agar/alginate based films (Moreno et al.,
2020). Films of native and hydrolyzed cassava starches showed different
changes in properties when fortified with yerba mate extract (Ceballos
et al., 2020). Therefore, the types of polysaccharide should be carefully
selected to formulate the films with polyphenols for desired properties.
Films based on single polysaccharide tend to have limitations in func
tionalities such as poor mechanical properties (Sun et al., 2020a).
Blending different types of polysaccharides to obtain desired properties
of films can be a strategy to overcome certain shortcomings for obtaining
desired functionalities (Fang et al., 2020). The importance of poly
saccharide type in relation to film applications with added polyphenols
has not been well addressed yet. A major challenge of commercialization
of these films has been the high production cost compared with petro
leum based plastic films. Polysaccharides that are cheap and abundant
such as cellulose and starch may have advantages for further industrial
developments.
13. Conclusions
Different polysaccharides and polyphenols or extracts at various
compositions were formulated into a range of films and coatings using
plate casting, microfluidic spinning, compression molding or extrusion
blowing. Depending on the polyphenol composition, the films and
coatings can be used for active and/or intelligent packaging. Functional
and physicochemical properties of the films depend on the types of
polyphenols/extracts and polysaccharides, formulations and processing
history. Suitable amounts of polyphenol extract addition lead to for
mation of films with improved barrier and mechanical performance,
whereas overloading the films with polyphenols tends to result in
negative outcomes such as formation of aggregations inside poly
saccharide matrix. The films and coatings with antioxidant and anti
microbial activities were used to pack different foods of plant and
animal origins with significant increases in the shelf life of these prod
ucts. Suitable selection of polysaccharides and polyphenols to film for
mulations may have potential to be used in preventing transmission of
viruses including SARS-CoV-2. Overall, polysaccharide based films for
tified with polyphenols are multiple-functional with potential for active
and intelligent packaging of foods.
14. Research outlook
The results summarized in this review showed that there tends to be
a lack of fundamental principles and the ability to make targeted design
of suitable films and coatings for applications without exhaustive ad hoc
testing. More fundamental understanding in this field is needed by
focusing on the nature of the interactions between polyphenols and
polysaccharides for film and coating applications. Structure-function
relationships of the film and coating components should be studied in
relation to the functional properties of the films and coatings. New
analytical methods such as artificial intelligence may be used to improve
the design of the films and coatings with desired properties.
There are research opportunities to better study and use the films and
coatings for food applications. The formulations of the composite film
were not clearly given in some studies. This lack of information made
the results not useful as the experiments were impossible to repeat.
Future studies should clearly express the ratio of polyphenol extracts to
polysaccharide by weight. Most of the studies published used extracts
which were mixtures and may contain non-polyphenol components.
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19. Food Chemistry 359 (2021) 129871
19
Pure phenolic compounds should be used to reveal structure–function
relationships of film components. There are many different types of
polyphenols and plant materials rich in polyphenols. Screening of po
tential plant materials for desired functional properties to formulate
films should be done. For example, tannins tend to have high antioxi
dant activity and may be tested for film formulations. Comparison be
tween phenolics or plant extracts rich in polyphenols and some easily
available industrial antioxidants for film and coating formulations
should be done for testing their commercial viability. Other poly
saccharides such as cereal bran polysaccharides and polyphenol grafted
polysaccharides can be used to formulate films. Nano-structure of sur
face morphology of the films should be better studied in relation to
functional performance. Comparative studies between different poly
saccharides for film formation and with commercial films and coating
should be done. Safety aspects of different plant materials/extracts
should be considered, and toxicity of biomaterials should be tested
before film formulations. Sensory quality of food products packed or
coated with these films should be analyzed in consideration of the
possible migration of components into food products. A major reason for
the lack of commercial applications of these films is the high cost
compared with the currently used petroleum based plastic films. Stra
tegies to lower the production cost of polysaccharide based films should
be developed in a polysaccharide- and polyphenol-specific manner.
Funding Declaration
None.
Declaration of Competing Interest
The author declares no known competing financial interests or per
sonal relationships that could have appeared to influence the work re
ported in this paper.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.foodchem.2021.129871.
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F. Zhu
