With 35+ years of experience across the food science and packaging spectrum, Dr Claire Sand, owner and founder of Packaging Technology & Research, helps clients achieve more sustainable packaging,  increase shelf life/prevent food waste, leverage food packaging innovations, address food package optimization and serves the food and packaging industry as a food packaging expert witness adjunct professor columnist for Food Technology and Packaging Digest   Want to know more about how this article affects your business? Reach out to Dr. Sand on LinkedIn - https://www.linkedin.com/in/clairekoelschsand   Want to keep learning from Dr. Sand? View more of her presentations and articles at https://www.packagingtechnologyandresearch.com/insights.html   Dr. Claire Sand | Owner, Packaging Technology & Research, LLC; Adjunct Professor, CalPoly and Michigan State University; Columnist for Food Technology Magazine and Packaging Digest http://www.packagingtechnologyandresearch.com/

1. Better Oxygen
and Grease/Oil
Barriers,
Longer Life
November 2023
Connect with me at 612-807-5341 or
claire@packagingtechnologyandresearch.com
Dr Claire
Sand’s article
in IFT’s Food
Technology
Magazine

3. between freezing and refrigerating temperatures
since no phase transition occurs. Generally, materi
als with a glass transition temperature (Tg) higher
than the intended use temperature and crystal-
line polymers provide superior oxygen barriers.
As a result, the Arrhenius relationship between
Tg, oxygen permeation, and temperature must be
understood to evaluate oxygen permeability.
Given the significance of the relationship between
temperature, humidity, and oxygen permeation, it is
worth noting that ASTM D3985, ASTM Fl927, ASTM
Fl307, and other oxygen transmission rate standards
are conducted at humidity and temperature conditions
that do not reflect frozen or refrigerated storage tem
peratures or humidity levels. ASTM D3985 standards
call for 73.4°F and 0% relative humidity, while ASTM
Fl927 standards call for 100.4°F and 90% relative
humidity. Notably, moisture has less effect on the oxy
gen permeability oflow-density polyethylene (LDPE)
and polyethylene terephthalate (PET) than on ethylene
vinyl alcohol (EVOH) and nylon. As a result, the oxy
gen permeability of prospective packaging must be
determined at three to five temperatures within the
intended storage temperature range. This ensures that
the Arrhenius relationship is known and can be used
to predict shelflife. Furthermore, the entire package
can be measured at different temperatures and humid
ities using modified methods and instruments such as
OxySense, a noninvasive oxygen measurement system.
It is possible to create a barrier with superior
properties by using material chemistry to reduce
the amount and rates of sorption and diffusion. The
primary alternatives are material science and tor
tuosity, followed by active packaging solutions.
In terms of chemistry, functional chemical
groups within polymers modify oxygen permea
bility. The oxygen barrier is tripled when a large
methyl group is substituted for a hydrogen atom
to form polypropylene instead of polyethylene.
Furthermore, substituting fluorine, chlorine, or
nitrogen groups for hydrogen improves oxygen per
meability by 30, 60, or 12,000 times, respectively.
Layers and coatings with naturally high oxy-
gen absorption resistance effectively reduce oxygen
solubility within packaging materials. Aluminum
metallization via plasma-enhanced chemical vapor
deposition, for example, and glass coating with sil
icon dioxide reduce oxygen sorption. This reduces
the amount of oxygen available for diffusion through
a structure. Metallization improves oxygen per
meability by 45 and 85 times in polypropylene and
polyethylene terephthalate, respectively. Similarly,
lowering the ethylene content ofEVOH from 44%
to 32% increases the oxygen barrier by a factor of 4,
Layers and
coatings wilh
naturally
high oxygen
absorption
resistance
elleclively
reduce
oxygen
SOiubiiity
Within
packaging
materials.
whereas the presence of naphthalate rather than tere
phthalate in polyethylene increases the barrier by a
factor of 10. By increasing the crystallinity of PET to
40%, the oxygen barrier is doubled. Increasing the ori
entation of polypropylene and polyethylene by 300%
doubles the oxygen barrier properties of film and blow
molding containers due to the increase in crystallinity.
Increased tortuosity is another way to change the
chemistry of a material. Using tortuosity to extend
the diffusion path in polymers such as Nylon-MXD6
increases the oxygen barrier by a factor of 10. The
aspect ratio and nanoparticle orientation deter-
mine a packaging material's oxygen diffusion rate.
Fillers, such as calcium carbonate or nanoparticles of
the same composition as the film base or imperme
able nanoscale glass or metal within a core material,
are other methods for improving the oxygen per
meability of packaging (Schuchardt et al. 2023).
Grease and Oil Resistance
Similarly, grease- and oil-resistant packaging is a
crucial development area to the paperboard and plas
tics industries. Grease is typically associated with
animal fat cooking byproducts, whereas oils are
derived from plants. Grease- and oil-resistant pack
aging is required for products such as cooked or fried
meats, fish, and poultry, French fries, chips, cook-
ies, crackers, salad dressing, and certain fried foods.
To determine grease resistance, ASTM D7334-08
is modified to determine grease-substrate con-
tact angle measurements. Material science and
coating chemistry govern the strategies used to
improve grease and oil resistance in packaging.
A viable solution to obtain more grease/oil resis
tance is to switch to a material with a better inherent
grease/oil resistance. Surface hydroxyl groups on
paperboard fibers "soak" in grease and oil during
direct contact, and common polyolefins such as poly
ethylene, polypropylene, and polystyrene are softened
or plasticized by grease and oil, which can result in
delamination or loss of packaging integrity. It is pos
sible to transition from polyolefin to metal, glass, or
a more chemically resistant polymer such as PET.
Another way to achieve grease/oil resis
tance is to increase the density of paperboard
and strengthen the internal bonds by controlling
the length and refinement of paper fibers. The
increased fiber content accounts for the higher
cost of higher-density paperboard. However, since
tensile and burst strength are improved, a thin
ner, less expensive paperboard is often viable.
Paper chemistry approaches such as the use of
strong acids to break existing bonds within the cel
lulose with wet paper fibers is also used. This results
www.ift.org I Food Technology 57

5. • Claire Sand is a Global Packaging Leader with 35+ years of broad
experience in the food and packaging science spectrum in industry -
from basic research to marketing - and in academia - tenured
professor and director.
• Sand's mission is to enable a more sustainable food system with
science and value chain innovations that more sustainably increases
food shelf life and prevents food waste.
• She solves packaging and food industry challenges using a blend of
packaging and food science and value-chain expertise.
• Dr. Sand holds a PhD in Food Science and Nutrition from the
University of Minnesota and MS and BS in Packaging from Michigan
State University.
Questions?
Let’s Connect!
Call 617-807-5341 or email
claire@packagingtechnologyandresearch.com
www.PackagingTechnologyandResearch.com