The document discusses foam-mat drying, a technique for dehydrating heat-sensitive materials, which preserves their color, flavor, and nutrients. It operates in four steps: preparation, foam formation, drying, and product evaluation, highlighting various drier types and their mechanisms. Additionally, a case study on the foam mat drying of papaya pulp is presented, illustrating the optimal conditions and resulting product characteristics.

1. FOAM MAT DRYING
TECHNIQUE
NAME- MARIAH SADAF
UNIVERSITY ROLL NO – 0021
JADAVPUR UNIVERSITY
DEPARTMENT OF FOOD TECHNOLOGY & BIO-CHEMICAL ENGINEERING
(M.Tech 1ST YEAR)

2. INTRODUCTION
• Foam-mat drying is the method of drying in which a liquid concentrate along with a suitable
foaming agent is subjected to dehydration in the form of a mat of foam at relatively low
temperature.
• Foam drying is accomplished without substantial damage to colour, flavour, nutrient value, etc.
This method is suitable for any heat sensitive, sticky and viscous materials which cannot be dried
by spray drying.
• The dehydrated powder/ flakes are superior to drum and spray dried products because of its
honeycomb structure and better reconstitution properties.
• The dried product has desired properties such as rehydration, controlled density and retain
volatiles that would be lost during the conventional drying techniques.
• Foam drying is carried out in four steps :
1. Pre-treatment of material and preparation of liquid concentrate.
2. Preparation of stable foam and spreading it as a mat.
3. Drying.
4. Evaluation, treatment and packaging of the dried product.

3. SCHEMATIC FLOWSHEET OF FOAM MAT DRYING
Raw material
( Fruits, Vegetables
etc)
Preparation
( Washing, Peeling,
Deseeding, Cutting,
Crushing)
Puree / Pulp
Pasteurization
( as per the raw
material)
Foamed food
pulp/puree
Whipping
(for a given time)
Adding of Foaming
agent and Foam
stabilizers
Cooling
Drying
Powder Formation
(gentle and mild
grinding)
Foam Mat Dried
free-flowing
powders
Packaging and
Storage
#Source- Foam Mat Drying- Sabah Mounir

4. TYPES OF FOAM MAT DRIER
BELT TYPE FOAM DRIER –
 It consists of an endless steel belt or teflon coated belt
which alternatively passes over heating and cooling drums.
 The foam is spread over the belt which is moving in a
compartmentalized drying chamber, in which the
temperature of air flowing across the material through
ports is controlled and is kept in range from 65°C to 21 °C.
 The drying in such process takes roughly one hour.
 The main difficulty with such dryers is the removal of
product from belt in certain cases.
PRODUCT
SCHEMATIC DIAGRAM OF BELT TYPE FOAM DRIER
#Source-Foam Mat Drying-A.K Dodeja & S.C Sharma

5. TYPES OF FOAM MAT DRIER
TRAY FOAM DRIER –
 A layer of foam is spread over perforated metal trays.
 A controlled air blast is directed through the tray underneath by
nozzles of approximately 0. 8 mm size.
 These nozzles direct thin flat jets of air up through the tray
perforations to pierce the foam.
 As large surface is exposed to the air, most of water is removed
from the product in very short time. The drying time by this
method varies from 3 to 18 minutes.
 The dried product is scrapped off the tray and tray can be returned
to the cycle without washing.
 These dryers contain a single stack of tray in a close fitting vertical
duct. At a regular interval a tray of freshly created foam is fed into
the bottom of the stack.
 The entire stack moves upward and a tray containing dried product
is ejected out at the top of stack.
SCHEMATIC DIAGRAM OF TRAY FOAM DRIER
#Source-Foam Mat Drying-A.K Dodeja & S.C Sharma

6. FOAM FORMATION METHOD
1. SPARGING/BUBBLING
 A known amount of air bubble is bubbled
through an orifice into a known quantity of
liquid
 Liquid gets converted to foam if large amount
of gas is introduced
 The size of the bubble formed highly depends
on the viscosity of the liquid
 Bubble size is managed by adjusting the
diameter of the orifice
3. WHIPPING/ BEATING
 Incorporation of unlimited amount of air into known quantity of
liquid
 The size of the air bubble increases and breaks into small bubbles
because of the mechanical agitation.
 The final size of the bubble depends on
o the speed of the agitator
o the geometry of the apparatus
o the rheological properties of the liquid.
 More uniform dispersion of the gas/ air.
2. SHAKING
 Foam is obtained by agitating the liquid vigorously
 Comparatively a slower process
 The volume of the foam formed by shaking depends on
o the amplitude and frequency of shaking,
o shape of the container,
o the volume of the container
o protein content of the liquid taken.
o temperature of the liquid taken.

7. FOAM AND IT’S STRUCTURE
Foam is a colloidal dispersion in which gas is dispersed in a continuous liquid phase.
The dispersed phase is referred as the internal phase and continuous phase is
referred as the external phase.
Foams have thin, flat, liquid films or lamellae between bubbles. The lamellae meet
each other at a point called a plateau border. The mechanical strength of lamella
determines the stability of the foam along with their air/ water interface properties.
Viscous liquids used for foam making produce more stable foams due to the
increased elasticity of the lamella.
Based on the ratio of dispersed phase to continuous phase, foams can be classified into-
#Source-Foam Mat Drying Of Food Material-Sangamithra et.al
POLYHEDRIC FOAM DILUTE BUBBLY FOAM
Ratio of dispersed phase to continuous phase is
large
Ratio of dispersed phase to continuous phase is
small
Large number of bubbles forming a honeycomb
structure
Individual bubbles retain their spherical shape
Eg- egg white foam and beer foam Eg- choco mousse

8. FOAM AND IT’S STRUCTURE
Foam collapses by three principal mechanisms:
i. Bubble size reducing with
ii. Lamella rupture- bubbles coalesce quickly due to pushing and pulling forces causing holes
formation between two bubbles.
iii. Draining of water around the bubbles and form liquid layer removing proteins from the film
around the bubble which becomes too thin to support the bubble
KEY PARAMETRS-
 Stable gas-liquid foam
 Surface area exposed (directly proportional to the rate of moisture removal)
 Thickness of product spread
 Foaming agents and stablizers
 Temperature
 Whipping time

9. FOAMING AGENTS AND STABILIZERS
 Proteins gives a good foaming ability and high foam stability .Protein foaming agents should have the
following behaviours:
• Stabilize foams effectively and rapidly at low concentrations
• Perform effectively over the pH range, which exists in various foods
• Perform efficiently in the medium with foam inhibitors such as fat, alcohol or flavour substances
 Some common proteins used as Foaming Agents include -
EGG ALBUMIN WHEY PROTEIN
Stabilized foams usually collapse after 20 min of whipping Needs about 50 min of whipping time
Overrun decreases quickly with time Overrun of foam is maintained ever after continued whipping
o They can enhance the stability of foam proteins through a thickening or a gelling effect of the aqueous
solution
o They act by either increasing the viscosity of the continuous phase or by forming a 3D structured
network that retards the movement of components within the foam.
o Carboxy Methyl Cellulose (CMC) or cellulose gum is the most common foam stabilizer which is
added in food in the form of its sodium salt
FOAMING AGENTS
FOAMING STABILIZERS

10. FOAM CHARACTERISTICS
 Foam density (FD) - is calculated as the ratio of mass of foam to the volume of
foam :
FD =
Mf
Vf
 Foam expansion (FE) – is measured by (incase of pulp) :
FE =
Vf −V0
V0
 Foam stability (FS)- The mechanical strength of lamella determines the stability of
the foam along with their air/ water interface properties. The foam stability index
is expressed as :
FS =
V0
V
t Where,
Mf is the mass of foam in g
Vf is the final volume of formed material in cm3 .
V = change in volume of foam occurring during the time interval t
V0 = Initial volume of foam directly after whipping cm3

11. FOAM CHARACTERISTICS
 Drying rate can be influenced by
 Foam agent concentration
 Air drying temperature
 Air velocity
 Foam characteristics (FD FS AND FE)
 Layer thickness.
 Drying Characteristics
The rapid removal of water during the foam mat drying is due to three main reasons:
i. The formation of bubbles with air incorporation results in expanding the structure and increasing the product specific
surface area which allows rapid water removal from the product’s surface to the surrounding environment at the
beginning of drying reflecting high starting accessibility.
ii. The second stage of drying is carried out through water capillary action throughout the thin lamella walls of the foam
bubbles towards its external surface.
iii. The internal continuous evaporation of water is very weak due to the low permeation of vapour to cross the pore
walls.

12. QUALITY ATTRIBUTES OF FOAM-MAT DRIED FOOD MATERIALS
 NUTRITIVE VALUE
i. Sugar content- Sugar content of foam dried increases with increasing the concentration of foam agents. Along with that the
reducing sugars also shows similar increase
ii. Ascorbic Acid- A decrease in vitamin C (ascorbic acid) content is recorded in foam mat dried materials
 ANTIOXIDANT CAPACITY- A decrease in carotene is observed in foam mat dried food materials which is depends on
i. Drying conditions (temperature)
ii. Concentration of foaming agent
iii. Thickness of the layer of foamed material
 SENSORY CHARACTERISTICS
i. Flavor & Aroma – Retained
ii. Color- is darker other methods
 PHYSICAL PROPERTIES - The bulk and tapped densities of foamed powder are inferior to non-foamed powder
 RECONSTITUTION PROPERTIES - The foam mat dried powders could be reconstituted instantly with water at room temperature,
and its reconstitution properties are superior to the other methods. The wettability of powders obtained by the foam-freeze-dried
method was lower than the other methods and the water solubility index (WSI) for foam dried product was superior to
non-foamed product powder.

13. FOAM MAT DRYING
ADAVANTAGES
 Powder quality can be excellent due to the low drying temperature applied.
 Drying special products, such as malted-milk and cottage cheese whey is possible.
 Product formed has
 Low density
 Excellent flow properties
 Highly hygroscopic
 Rapid solubility
 Uniform particle size is obtained with foam spray drying.
 Three times faster than other drying methods
DISADVANTAGES
 High capital cost (but lower than vacuum drying)
 Slight decrease in retention of ascorbic acid and phenolic compounds
 Large surface area is required for high production rate

14. CASE STUDY – FOAM MAT DRYING OF PAPAYA PULP
 In the experimental study Papaya was chosen for
studying the drying process. As they are rich in several
phytochemical compounds such as polyphenols,
carotenoids, ascorbic acid etc, they are highly
perishable and has a fast ripening cycle, thus, papaya
fruit shelf life can be extended through this process.
 Two experimental designs were implemented :
i. OFAT preliminary experiments were applied where
Whipping time (WT), egg white percentage (EW%)
and xanthan gum percentage (XG%) were the factors
studied. Based on OFAT results, the study variables
producing the highest foam expansion percentage
(FE%)were determined, and were used throughout
the second part of the study.
ii. 2k full factorial design (FFD) was implemented to
reach maximum FE%, where k equals the number of
studied factors, which was 3 in this experimental
study.
NON-FOAMED
PAPAYA PULP
NON-FOAMED
PAPAYA PULP AT
THE END OF
DRYING PROCES
DRIED NON-
FOAMED PAPAYA
PULP AFTER
PULVERISATION
FOAMED
PAPAYA PULP
FOAMED
PAPAYA PULP AT
THE END OF
DRYING PROCES
DRIED FOAMED
PAPAYA PULP
AFTER
PULVERISATION
#Source- Foaming Process Optimization, Drying Kinetics And Quality Of Foam Mat Dried Papaya Pulp-A.M Ali et.al

15. PROCESS FLOWSHEET OF FOAM MAT DRIED PAPAYA PULP
RIPE PAPAYA
WASHING
PEELING
DE-SEEDING
PULP EXTRACTION
HOMOGENIZED PULP
TSS: 65% ± 5.8
pH: 4.36± 0.032
FOAMING AGENT-
EGG WHITE (5-20%)
XANTHAN GUM (0-0.5%)
WHIPPING FOR 2 mins
WHITE FOAM FORMATION
MIXING
AND
WHIPPING
FOR 5-20
mins
NON- FOAMED
PAPAYA PULP FOAMED
PAPAYA PULP
DRYING AT : 60°C and 80°C with
A THICKNESS OF 2,4,6 mm and
AIR VELOCITY OF 3 m/s
WEIGHT REDUCTION CHECKING
IN INTERVALS UNTIL CONSTANT
WEIGHT IS REACHED
NON FOAMED SAMPLE
FOAM DRIED SAMPLE
PULVERISING
STORING IN
GLASS JARS
AND
KEEPING IN
DESSICATOR
SEPARATING IN
THE FORM OF
LAYERS
SCRAPING
PRODUCT
ANALYSIS
#Source- Foaming Process Optimization, Drying Kinetics And Quality Of Foam Mat Dried Papaya Pulp-A.M Ali et.al

16. CASE STUDY – FOAM MAT DRYING OF PAPAYA PULP
#Source- Foaming Process Optimization, Drying Kinetics And Quality Of Foam Mat Dried Papaya Pulp-A.M Ali et.al
HIGHEST

17. CASE STUDY – FOAM MAT DRYING OF PAPAYA PULP
Fig 2. Response surface plots showing the influence of the studied factors and it’s interaction on FE%
#Source- Foaming Process Optimization, Drying Kinetics And Quality Of Foam Mat Dried Papaya Pulp-A.M Ali et.al
Highest FE% at
Higher EW% and Lower XG%
Highest FE% at
Higher WT and Higher XG%
Highest FE% at
Higher EW% and Higher WT

18. Fig 3. Drying Curve
CASE STUDY – FOAM MAT DRYING OF PAPAYA PULP
#Source- Foaming Process Optimization, Drying Kinetics And Quality Of Foam Mat Dried Papaya Pulp-A.M Ali et.al
For 60°C
For 60°C
For 80°C
For 80°C

19. SAMPLE TEMP (°C) THICKNESS
(mm)
COLOUR OF RECONSTITUTED SOLUTION
HYGROSCOPICITY
(g/100g)
ASCORBIC ACID
(mg/100g)
TOTAL
CAROTENOIDS
(µg/100g)
TOTAL
PHENOLIC CONTENT
(mg Gallic Acid
Equivalent/100g)
DISSOLUTION TIME
(s)
L* b* a*
FOAMED
PAPAYA
PULP
POWDER
60°C
2 40.74 ± 0.18 24.65 ± 1.54 -1.53 ± 0.29 21.01 ± 3.08 83.44 ± 3.08 10.93 ± 1.03 454.52 ± 2.11 50.00 ± 7.81
4 40.54 ± 1.04 28.23 ± 0.96 -1.20 ± 0.10 22.40 ± 1.08 96.58 ± 4.35 45.42 ± 0.81 451.50 ± 8.39 64.00 ± 4.36
6 39.49 ± 0.51 26.34 ± 1.14 -1.71 ± 0.15 21.41 ± 0.41 68.03 ± 3.16 29.41 ± 0.23 394.63 ± 2.11 106.33 ± 12.06
80°C
2 41.27 ± 1.34 26.85 ± 1.00 -1.68 ± 0.07 20.93 ± 0.42 89.49 ± 5.91 9.76 ± 0.39 450.42 ± 8.42 50.00 ± 5.57
4 41.65 ± 1.61 29.79 ± 0.94 -1.22 ± 0.02 21.14 ± 0.41 79.13 ± 3.49 43.85 ± 2.15 443.40 ± 8.76 53.33 ± 3.79
6 38.45 ± 0.23 27.16 ± 0.29 -1.95 ± 0.03 22.13 ± 0.93 83.44 ± 3.08 56.40 ± 1.13 456.03 ± 8.76 90.00 ± 10.00
NON-
FOAMED
PAPAYA
PULP
POWDER
60°C
2 40.20 ± 1.00 24.59 ± 0.13 -1.44 ± 0.02 25.40 ± 0.72 86.72 ± 5.00 41.92 ± 0.96 607.53 ± 1.24 955.00 ± 18.03
4 36.26 ± 0.25 22.41 ± 0.29 -1.51 ± 0.06 24.41 ± 0.23 66.25 ± 3.06 42.18 ± 0.98 495.15 ± 12.26 1127.00 ± 18.08
6 36.20 ± 0.28 23.40 ± 0.95 -1.54 ± 0.09 23.53 ± 0.61 66.31 ± 3.78 35.39 ± 2.24 520.86 ± 14.19 1320.66 ± 40.00
80°C
2 40.49 ± 0.52 24.56 ± 0.23 -1.23 ± 0.03 26.69 ± 0.20 100.41 ± 1.97 35.14 ± 0.85 646.25 ± 12.76 592.33 ± 7.51
4 39.93 ± 1.25 25.25 ± 0.57 -1.26 ± 0.06 25.55 ± 0.23 136.37 ± 1.14 45.62 ± 3.49 642.02 ± 41.65 789.00 ± 15.00
6 37.35 ± 0.17 23.04 ± 0.13 -1.38 ± 0.05 25.68 ± 0.42 110.44 ± 1.13 33.70 ± 0.70 639.02 ± 21.60 873.33 ± 10.41
CASE STUDY – FOAM MAT DRYING OF PAPAYA PULP
#Source- Foaming Process Optimization, Drying Kinetics And Quality Of Foam Mat Dried Papaya Pulp-A.M Ali et.al

20.  The optimal conditions for Foaming Papaya Pulp were-
 EW% of 15%,
 XG% of 0.3%
 WT of 15 min.
 At various drying conditions, the Foamed Papaya Pulp had
 The lowest drying times
 Highest drying rates
 Average drying rates were reached 2 times those of non-foamed ones
 The dissolution time and hygroscopicity values of Foamed Powders were
significantly lower than those of Non Foamed ones.
 The reconstituted Non-Foamed solutions exhibited more darkness (low L* values).
 The retention of Ascorbic Acid and Total Phenolic Compounds was significantly
decreased as drying time increased.
CASE STUDY - CONCLUSION
USE OF FOAM DRIED PAPAYA PULP POWDER
1. To prepare nectar
2. A flavouring agent for
i. Ice cream
ii. Fruited cereal products
iii. Whip cream
iv. Baked products

21. REFERENCES
 Foam Mat Drying- Sabah Mounir (2018)
 Source-foam Mat Drying- A.K Dodeja & S.C SharmaFoam Mat Drying Of Food Materials- Sangamithra. A
et.al(2014)
 Recent Development In Foam-mat Drying- Chandak, A.J. and Chivate, M.R. (1972)
 Drying Of Foamed Materials Opportunities And Challenges- Ratti C and Kudra T (2005)
 Optimization Of Process Parameters Of Foam Mat Drying Of Papaya Pulp - P. Kandasamy et.al (2012)
 Foaming Process Optimization, Drying Kinetics And Quality Of Foam Mat Dried Papaya Pulp-A.M Ali et.al
 Recent Developments In High-quality Drying Of Vegetables, Fruits, And Aquatic Products- Zhang M.
et.al(2017)
 Method For Evaluating Foams From Citrus Concentrates- Berry RE, Bissett OW, Lastinger JC. (1965)
 Recent Developments In Foam Mat Drying - Morgan AI, Graham RP, Ginnette LF and Williams GS (1961)
 Foams For Foam-Mat Drying. Food Technology- Hart MR, Graham RP, Ginnette LF and Morgan AI (1963)

22. THANK YOU