Same as human being food, pet food conforms to strict standards to ensure the safety of pets. Pet food must keep their original flavor and nutrition during maintenance, transportation and shelf life, which rely heavily on the pet food packages. In the keen competitions, prolonging pet food shelf life attracts more and more manufacturers and suppliers attentions. In this article, I will talk about the factors that affect pet food shelf life and related solutions to prolong shelf life in terms of pet food packaging.

1. Factors Affecting Pet Food Shelf Life
By Yarina Gao, China
[Abstract] Same as human being food, pet food conforms to strict standards to ensure the safety of
pets. Pet food must keep their original flavor and nutrition during maintenance, transportation and
shelf life, which rely heavily on the pet food packages. In the keen competitions, prolonging pet
food shelf life attracts more and more manufacturers and suppliers attentions. In this article, I will
talk about the factors that affect pet food shelf life and related solutions to prolong shelf life in
terms of pet food packaging.
[Keywords] Pet Food, Food Packaging, Shelf Life, Affecting Factors, Solutions
Pet food has been one of keen competitive industries along with countless new pet foods
introduced into the market. Same as human being food, pet food should conform to strict standards
to ensure pet safety and health. In America, pet food is supervised by AAFCO (Association of
American Feed Control Officials), USDA (United States Department of Agriculture) and FTC (Federal
Trade Community). AAFCO establishes the nutritional standards for complete and balanced pet
foods, and it is the pet food company's responsibility to formulate and maintain their products
according to the appropriate AAFCO standard. In many countries, like China, there aren’t special
regulations or standards related to pet food quality control, so they usually also apply to AAFCO
standards.
Like human being food, pet food also has a certain shelf life. Manufacturers and suppliers must
ensure the pet food won’t be stale or lost nutrition during the shelf life. To enhance and keep the
competitions, more and more manufacturers are trying to have a full consideration on factors
affecting shelf life, in order to prolong their products shelf life
Factors Affecting Shelf Life
Many factors affect pet food shelf life, like additives (preservatives), packages, maintenance
environment (temperature, lights). Maintenance environment, which is the conditions during the
pet food delivery and maintenance, is a human factor and can be controlled by us.
Preservatives can also affect pet food shelf life. Basically, pet food added with artificial preservatives
has as longer as months shelf life than those with natural preservatives. But artificial preservatives
can change the original taste of food and perhaps release some toxic substance. Therefore, there
are very strict restrictions on preservatives usage.
Complying with AAFCO, pet food must have primary nutrition including protein (more than 18%), fat
and additional nutrition like amino acids, mineral substance, crude fiber, calcium, iron, vitamins and
so on. All these nutrition aims to ensure the necessities of pet growth, living and make their fur
sleek. Meanwhile, it also provides a good medium for growth of microorganisms. These

2. microorganisms can reduce protein to organic amines and mercaptans, which stink and decay pet
food, reduce fat to smelly ketone and aldehyde and other spoilage substance. All these low
molecular will not only change the taste of pet food, but also make protein and fact lost their
nutrition. Therefore, it is essentially important to restrain microorganisms no matter on production
lines or shelves.
As we all know, growth and living of microorganisms need proper environment. The most three
important factors are temperature, oxygen and water. Oxygen is primary factor that cause food
decay. The less oxygen in food package, the less possibility food gets decay. While water also
provides a living environment for microorganisms, it can speed up the reduction of fat; shorten shelf
life of pet food. During shelf life, volumes of oxygen and water vapor in the packages mainly depend
on package integrity and permeability of packaging materials.
I. Package Integrity
Packages commonly used in pet food industry include plastic flexible packages, laminated
plastic packages, paper-plastic packages, aluminum-plastic packages and so on. No matter what
kind of package is used, package integrity is the first primary requirement for quality control.
Oxygen and water vapor will transmit into package through even a tiny opening. Basically,
package integrity issues always occur on the places of sealing and joint.
a) Package Entirety
Oxygen and water vapor in air will definitely transmit into food packages if the packages are
not sealed. Pet food will be easily decayed and nutrition will also lose.
b) Peel Strength and Seal Strength of Pet Food Packages
The most commonly used packages are stand up pouches with zipper and
Aluminum-plastic packages for pet food. These kinds of laminated packages can improve
the force resistance and permeability of the whole packages.
If the peel strength is too low, it means the layers of materials are not laminated well, and
then the packages cannot achieve the expected purpose on force resistance and
permeability. When packages drop from a height, it will be broken more easily.
Seal Strength also affects package integrity to a large degree. If the seal strength is not
strong enough, packages will split open at the seams, which may result in contents spilled
out or let oxygen and water vapor in air permeate into the packages.
c) Resistance of Puncture and Tearing
Puncture strength is generally strength that a material is ruptured by a probe or other type
of device. It is used in food processing industry to determine the texture of ripeness of
packaging. If puncture strength is not strong enough, pet food package can be broken down
during delivery and maintenance.
Tearing strength is force required to rupture a pre-slit packaging materials, like paper,

3. plastic films. It should not be too high, which results in worse consumer experiences or too
low, which results in packages opening during the transportation or maintenance.
II. Permeability of Packaging Materials
Permeability is a measure of the ability of a barrier material to allow gases (O2, N2, CO2 and
water vapor etc.) to permeate through it in a specific time. It usually depends on the type of
material, pressure, temperature and thickness of materials. During pet food shelf life, oxygen
and water vapor in the packages should maintain the prefilled volumes, which reply heavily on
pet food packages. In Labthink laboratory, we did oxygen transmission rate and water vapor
transmission rate testes, analysis and comparison of seven commonly used pet food packaging
PET, PET+CPP, Bopp/CPP, BOPET/PE, OPP/PE/CPP, BOPET/VMPET/LDPE. Higher oxygen
transmission rate, lower oxygen permeability of materials; high water vapor transmission rate,
lower water vapor permeability of materials.
Oxygen Transmission Testing Use Labthink OX2/230 Oxygen Transmission Rate Test
System and equal pressure testing method.
Before testing, place the specimen in a standard environment (23±2℃、50%RH) for 48h to
make a air balance of specimen surface.
 Select the smooth without wrinkle specimen and cut it into round shape
 Mount the conditioned specimen on OX2/230 Oxygen Transmission Rate Test System.
In this way, the test chamber is divided into an upper chamber and a lower chamber by
the specimen. Close and fix the test chamber
 Pour high-purity oxygen into upper chamber, high-purity nitrogen into lower chamber
 Because of concentration difference, oxygen will be in solution diffuses from upper
chamber to lower chamber, through the specimen, then these oxygen will be taken to
the oxygen sensor by flowing Nitrogen in lower chamber
 Oxygen concentration in lower chamber will be obtained using oxygen sensor, and
then oxygen transmission rate can be calculated through the specimen.
Water Vapor Transmission Rate Test Use Labthink W3/030 Water Vapor Transmission
Rate Tester and traditional cup method.
 Pre condition specimen as oxygen testing and cut the specimen into round shape
 Fill the test cup with certain quantity of double distilled water. Mount the specimen
into the test cup so that the test cup is divided into two part
 Set the test environment at 38 ℃ and 90%RH
 WVTR could be obtained through period-measuring the reductive weight of test cup
during the testing process

4. OTR and WVTR test results of these 7 packaging materials as follow:
Test Results
Specimen
OTR（ml/m2/day） WVTR (g/m2/24h)
PET/CPP 0.895 0.667
BOPP/CPP 601.725 3.061
PET 109.767 25.163
BOPET/PE 85.055 4.632
OPP/PE/CPP 716.226 2.214
BOPET/VMPET/LDPE 0.149 0.474
Aluminum-plastic 0.282 0.187
Table 1 Test Data of Pet Food Packaging Permeability
Analyzing the test results of these 7 kinds of packaging materials, we can find that materials
laminated with different layers can have a significant difference in oxygen permeability. From Table
1, aluminum-plastic materials, BOPET/VMPET/LDPE, PET/CPP has a relative lower oxygen
transmission rate (better oxygen barrier property). According to our research, pet food with these
kinds of packaging usually has longer shelf life。
Oxygen Transmission Rate
(ml/m2/day)
Aluminum-plastic 0.282
BOPET/VMPET/LDPE 0.149
OPP/PE/CPP 716.226
BOPET/PE 85.055
PET 109.767
BOPP/CPP 601.725
PET/CPP 0.895
0 100 200 300 400 500 600 700 800
Laminated films have a good performance in barrier of water vapor. Referring to the chart below,
PET has high water vapor transmission rate, which means it has a poor performance in barrier of
water vapor and not suitable for pet food packaging, as it will shorten the shelf life of pet food.

5. Water Vapor Transmission Rate
(g/m2/24h)
Aluminum-plastic 0.187
BOPET/VMPET/LDPE 0.474
OPP/PE/CPP 2.214
BOPET/PE 4.632
PET 25.163
BOPP/CPP 3.061
PET/CPP 0.667
0 5 10 15 20 25 30
Solutions
According to the tests we conducted in Labthink laboratory, choosing proper packaging for pet food
is helpful in prolonging pet food shelf life, decreasing the addition of preservatives, saving
production cost as well as pet health. Therefore, we have advices for manufacturers and suppliers of
pet food packaging as follows:
 Choose laminated plastic, aluminum-plastic materials and metal materials as pet food
packages, because all these materials have a good barrier properties to oxygen and water
vapor. Besides consideration of oxygen and water vapor permeation properties of materials,
we should know that the environment also have some impacts on these properties of
materials. Such as EVOH and PA, they are very sensitive about humidity. In Room
temperature and relative lower humidity, both of them have a good barrier to water vapor,
while in high humidity environment, their water vapor permeability would decrease. So if
there is high humidity environment during pet food delivery and maintenance, EVOH and
PA are not suitable for packaging.
 Choose materials with good peel strength, seal strength and puncture strength and other
physical properties. The mechanical properties of material can help to improve the integrity
of pet food packages, decrease the contacting of pet food and air, and prolong the shelf life
of pet food.