Pet 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 types and quantity added into pet food. It is harder and harder for manufacturers to rely on preservatives to ensure shelf life. Using 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 needs proper environment. The most three important factors are temperature, oxygen and water. Oxygen is the 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 tests, 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 means lower oxygen permeability of materials; high water vapor transmission rate means lower water vapor permeability of materials.

Oxygen Transmission Testing Use Labthink OX2/230 Oxygen Transmission Rate Test System and equal pressure method.

Before testing, place the specimen in a standard environment (23±2℃、50%RH) for 48h to make a air balance of specimen surface.

1. Select the smooth without wrinkle specimen and cut it into round shape
2. 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 a lower chamber by the specimen and then close and fix the test chambers
3. Pour high-purity oxygen into upper chamber, high-purity nitrogen into lower chamber
4. 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
5. We can get an oxygen concentration in lower chamber, and then the oxygen transmission rate through the specimen will be calculated.

Water Vapor Transmission Rate Test Use Labthink W3/030 Water Vapor Transmission Rate Tester and traditional cup method.

1. Pre condition specimen as oxygen testing and cut the specimen into round shape
2. 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
3. Set the test environment at 38 ℃ and 90%RH
4. 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:

Specimen Test Results

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

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。

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 choosing 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.

Costway US $348.00 Modern Fabric Loveseat Sofa for with Metal Legs and Armrest Pillows-Peacock Blue Costway US $1438.00 Modern Loveseat with Comfy Backrest Cushions-White Costway US $140.00 Loveseat Cushioned Patio Steel Frame Swing Glider -Beige Costway US $106.00 Oversized Camping Chair Folding Loveseat Camping Couch with Cup Holders & Thick Padding-Blue Costway US $144.00 Loveseat Cushioned Patio Steel Frame Swing Glider -Black Costway US $683.00 4 Pieces Outdoor Patio Rattan Furniture Set with Cushioned Loveseat and Storage Box-Brown Costway US $255.00 2-Person Double Rocking Loveseat with Mesh Fabric and Center Tempered Glass Table-Black Costway US $185.00 Outdoor Porch Steel Hanging 2-Seat Swing Loveseat with Canopy-Turquoise Costway US $218.00 Garden Bench Chair Outdoor Wooden Loveseat with Iron Armrest Costway US $212.00 Living Room Wooden Leg Armless Loveseat Sofa-Multicolor