Before answering the question, "What can barrier packaging really do for pet food?," one might ask, "What is barrier packaging?" Barrier packaging is both a type of packaging material and a method of packaging. It seals off the contents of the package to the atmosphere and protects it from oxygen, moisture, grease, light, odors, insects, etc. Barrier packaging is a part of the modified/controlled atmosphere packaging (MAP/CAP) family and is represented by the glossy packages which you find preserving gourmet coffees, fresh meats, fresh produce, roasted nuts and salty snack foods in the grocery store.
Oxygen transmission rates
The key to barrier packaging is packaging materials used: Multiple layer construction of films such as polyester, polyethylene and aluminum foil. Some of these are polymer based, or "plastic" and this nickname is often associated with it. These constructions are categorized by their oxygen transmission rate (OTR) and moisture vapor transmission rate (MVTR). These parameters are measured by the volume of oxygen and mass of moisture, respectively, which can pass through a 100 square inch piece in a 24 hour period (cc/100 in2/24 hr.). The packaging methods used for barrier packaging can vary from vertical form, fill and seal equipment (VFFS) using roll stock, to specially designed bag closers/sealers which are placed in line with standard 15-40 lb. bag hanging equipment. A barrier package made of bonded film layers and completely heat seal closed can have a total OTR of less than 0.01 cc/100 in 2/24 hr. In comparison, a paper-based pet food package with a polypropylene liner will have an OTR of 100-200 cc/100 in2/24 hr. just for the packaging material (20,000 times more oxygen transmission). This does not include oxygen transmission due to a stitched or pinched top closure. Although these types of paper bags have served well over the years in containing pet foods, they are not considered a barrier package.
Several benefits
Our company, fres-co System USA, Inc., a leader in barrier packaging and MAP/CAP, began focusing on the pet-food industry in 1992. This focus was fueled by three major factors.
- First, there were several known, bag/product appearance benefits: Barrier packaging means "freshness" to consumers, it is highly resistant to grease, and it prevents odor escape which can lead to infestation.
- Second was the fact that successful conversions from paper-based packaging to barrier packaging had been made by Fres-co in the agricultural chemical and hygroscopic resins markets, one of which helped propel a major agricultural chemical producer from fourth to first in its market in a period of two years.
- Finally, there was the logic that if barrier packaging was effective for preserving taste and extending shelf life for other oxygen and moisture sensitive products (e.g., coffee), then it should also be effective in the same areas for pet foods.
Figure 1. In palatability studies, dog food preserved by barrier packaging alone (i.e. no antioxidants added) was consumed at much higher levels versus the same dog food preserved by paper and a polypropylene (OPP) liner.
Plastic problems?
Our first step was to address a pervasive assumption in the pet food industry that "plastic" packaging could not be used for pet food. This assumption stemmed from the idea that dogs' and cats' highly developed senses
of taste and smell would distinguish undesirable elements migrating from the "plastic" into the pet food. Another fear was that desirable properties of the pet food would be lost due to scalping by the
"plastic."
Research conducted with leading pet food producers showed that some materials used for barrier packaging do cause problems. But, it also resulted in fres-co's development of barrier materials which were
ideal for packaging pet food. These were trademarked by fres-co under the name fres-petTM.
The ultimate question
Still, the ultimate question remained: Can barrier packaging actually have a tangible, valuable benefit for the pet-food inside of it? In other words, what can it really do for the pet food itself? We again worked with pet food producers to answer this question. Research results indicated that barrier packaging can have substantial, positive effects on pet food, including improved palatability, reduced rancidity and protection of nutrients. As most of these studies were done with the utmost of confidentiality and propriety, specific information and data could not be shared with other pet food producers. Therefore, we commissioned our own study of the preservation effects of fres-petTM barrier packaging compared to the preservation effects of both conventional paper packages and a popular synthetic antioxidant. Two diets were produced which simulated a leading premium pet food. Both diets were identical in all respects, except that one had the maximum allowable amount of synthetic antioxidant added and the other had no antioxidant added. These two diets were then packed in barrier packaging and paper packaging and stored at room temperature (75°F, 50% relative humidity). Palatability, chemical and nutrient studies were done at three, six and nine month intervals.
Palatability studies
In palatability studies, dog food preserved by barrier packaging alone (i.e., no antioxidants added) was consumed at much higher levels (3.8 to 1) versus dog food preserved by paper and a polypropylene (OPP) liner (see Figure 1
above). This finding is especially relevant to producers of natural pet foods. Barrier packaging can be used to enhance the performance of natural antioxidants which are generally less effective, harder to disperse and more
expensive than synthetic antioxidants.
In another palatability study, dog food in barrier packaging and preserved with the maximum allowable amount of synthetic antioxidant, was preferred 1.6 to 1 versus the same pet-food
stored in multi-wall paper packaging without a liner. Another palatability study showed that premium dog food preserved by barrier packaging material alone, had intakes similar to the same diet preserved with the maximum
allowable amount of synthetic antioxidant and packaged in paper packaging with OPP liner. These two studies showed that for preserving palatability, barrier packaging had an effectiveness equal to, if not better than, the most
popular synthetic pet-food antioxidant.
Peroxide values
Peroxide value tests were conducted to determine if rancidity can be controlled as effectively with barrier packaging as it can be with synthetic antioxidants. Barrier packaging was able to control rancidity in product without synthetic antioxidant. On the other hand, product in paper with OPP liner had peroxide values over 200 meq/kg after six months (see Figure 2 Below)..
Figure 2. Barrier packaging was able to control rancidity in product without synthetic antioxidant. On the other hand, product in paper with OPP liner ha peroxide values over 200 meg/kg after six months.
Nutrient protection
Vitamin A levels also were measured and indications are that barrier packaging is able to retard loss of vitamin A. This leads to the possibility that barrier packaging may protect other nutrients as well. This may tie in with studies which show a relation between the freshness of animal feed and digestibility, which in turn may promote animal growth or have other benefits yet to be explored (Kjeldsen, 1983). Unlike antioxidants, barrier packaging's effectiveness is consistent over time. This is essential for many applications, especially export, where storage temperatures are well above the "ideal" room temperatures used in our studies and undesirable reactions in the pet food can occur faster. All of these conclusions have answered the question. Barrier packaging not only provides appealing packages for marketing, it also preserves taste and extends shelf life.
Reference
Kjeldsen, N.J., V. Danielsen, A. Just, H.E. Nielsen and B.O. Eggum, 1983. Inclusion of fish meal manufactured from fish with different degrees of freshness in diets for early weaned pigs. Natl. Inst. Anim. Sci., Copenhagen, Newsletter No. 449
Reproduced from Petfood Industry July/August 1997 - A Watt Publication