Food additives are substances added to food, aimed to preserve flavor or improve taste and appearance of food. Preservatives food additives are anti-microbial preservatives, which inhibit the growth of bacteria and fungi, or antioxidants such as oxygen absorbers, which inhibit the oxidation of food constituents. Therefore, many manufacturers add preservatives into food to prolong products shelf life. However, there are strict regulations on addition of preservatives. In this article, we will talk about some other ways to prolong pet food shelf life in terms of pet food packaging.

1. Preservatives and Pet Food Shelf Life
By Yarina Gao
Labthink Instruments Co., Ltd, China
Trade5@labthink.cn
[Abstract] Food additives are substances added to food to preserve flavour or improve its taste
and appearance. Preservatives food additives are anti-microbial preservatives, which inhibit
the growth of bacteria and fungi, or antioxidants such as oxygen absorbers, which inhibit the
oxidation of food constituents. Therefore, many manufacturers add preservatives into food to
prolong the shelf life. However, it has strict regulations on addition of preservatives. In this
article, we will talk about some other ways to prolong pet food shelf life in terms of pet food
packaging.
[Keywords] Pet Food, Packages, Preservatives, Shelf Life
P et food has been one of keen competitive industries along with countless new pet foods
introduced into the market. There is a growing need for reliable methods of ensuring and
prolonging shelf life of pet food. Like human being foods, pet food must be ensured
qualified for pets’ lives and health. Therefore, pet food should maintain the necessary nutrition
and original flavor during the delivery, maintenance and shelf life.
Preservatives are used for centuries. They may be anti-microbial preservatives, which inhibit
the growth of bacteria and fungi, or antioxidants such as oxygen absorbers, which inhibit the
oxidation of food constituents. Common anti-microbial preservatives include calcium
propionate, sodium nitrate, sodium nitrite, sulfites (sulfur dioxide, sodium bisulfite, potassium
hydrogen sulfite, etc.) and disodium EDTA. Antioxidants include BHA and BHT.
Food preservatives are classified as: Natural Preservatives such as salt, sugar, vinegar, syrup,
spices, honey and edible oil; and Chemical Preservatives such as benzoates, sorbates, nitrites
and nitrates of sodium or potassium, sulfites, glutamates, glycerides and the like. Artificial
preservatives can be produced more economically, however, have worse side effects on pet food
than natural preservatives. More and more strict regulations have been issues on the classes
and quantity added in pet food. It is harder and harder for manufacturers to rely on
preservatives to ensure shelf life. In the real productions, usage of high barrier materials as pet
food packaging can also be very helpful in ensuring and prolonging pet food shelf life.
Tests
As we all know, growth of microorganisms need certain and proper environment. The most

2. three importance 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 pet food shelf life, oxygen and water vapor in the packages should maintain the prefilled
volumes. 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. 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 base on equal pressure method. Before testing, put 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 a upper chamber and lower
chamber by the specimen and then Fix and close the test chambers
 Pour high-purity oxygen into upper chamber, high-purity nitrogen in 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 the flowing Nitrogen
 We can get a oxygen concentration in lower chamber, and then calculate the
oxygen transmission rate through the specimen.
Water Vapor Transmission Rate Test Use Labthink W3/030 Water Vapor
Transmission Rate Tester and Based on 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
Detailed OTR and WVTR test results of these 7 packaging materials as follow:

3. 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/LDP
0.149 0.474
E
Aluminum-plastic 0.282 0.187
Table 1 Test Data of Pet Food Packaging Permeability
From the Analysis of test results of these 7 kinds of packaging materials, we can find that
materials laminated with differently 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. According to our research, pet food with these kinds of
packaging also usually has longer shelf life。

4. 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.
Testimonial
Referring to the tests, pet food manufacturers can use high barrier materials instead of more
additional of preservatives to prolong pet food shelf life. We recommend to 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.