Burton's BlogAll foods spoil, though some degrade faster than others. This is a fact of life. Still, there are people who would disagree with this incontrovertible statement. We’re not sure, but these may be the same people that believe the world is flat. You’ve bought great food. You’ve done the easy part, but paying attention to handling and pet food storage at home is one of the most important ways to help maintain the long-term health of your pet.

We’d have to take a poll. It would probably even behoove the manufacturer to be more forthright in explaining how quickly food can deteriorate through oxidation because it would encourage people to buy smaller bags of food more often. Instead, food manufacturers push their larger bags of food by advertising new packaging and “natural preservation procedures” that claim to be better at preserving the food you buy. Most of the sales on pet food also occur on the 40 lb. bags. These sales are designed to look good in the accounting books but generally do not encourage better pet health. As a rule, you shouldn’t buy more food than your pet can consume in one month. For most breeds of dog, 40 lbs. is well beyond their consumptive capacity.

food bins - food handling and spoilage

Two examples of food container storage.

Air, moisture, temperature and chemical composition all play independent roles in food spoilage. Over time, there are thousands of chemical reactions that affect food, to both its nutritional detriment and benefit, and through this article we hope to offer a few simple explanations about food chemistry and the processes that most directly apply to pet owners.


Life on earth cannot exist without moisture. It is therefore no coincidence that moisture breeds bacteria, molds and yeasts – all of which happen to be notorious agents of organic decay. The greater the moisture content, the greater the presence of organisms that accelerate spoilage. An open can of wet food spoils much faster than kibble. The proteins degrade rapidly; putrefaction can be detected in a matter of hours. Dogs, as we’re probably aware, will eat just about anything. Slightly rotten food? No problem. Bring on seconds! Cats, however, are much pickier about the freshness of their meals. This contrast in mealtime behavior is almost surely a result of their differing paths to domestication. Dogs first co-existed alongside man as scavengers surviving off the scraps of human detritus (but that doesn’t mean it’s good for them!) whereas cats have always been exquisite hunters employed by humans for activities such as rodent control.

People that buy large volumes of food because it is cheaper make a big mistake if the food is improperly handled after purchase. Dry kibble, left open, immediately begins to deteriorate. Proteins and fats oxidize to form free radicals which when consumed slowly, but persistently, wear down the body. Free radicals are highly reactive atoms or molecules containing unpaired electrons which catalyze chemical chain reactions that can damage cells. In abundance and over time, these free radicals can attack every cell in our and our pets’ bodies. Antioxidants have become a health buzz-word and for good reason – they terminate these detrimental chain reactions and inhibit further cellular oxidation. Raw fruits and vegetables (yes, even for your dog! But make sure you know which ones dogs can and cannot eat) are especially beneficial in providing antioxidants. Since cats are obligate carnivores, the availability of raw fruit and vegetables isn’t really a relevant discussion; instead concern yourself with the quality and freshness of the meat they consume.



This type of preservation protects against a myriad of possibilities, but what chemical preservation has in common with all other types of preservation is that it prevents oxidation. Ethoxyquin (a quinoline-based antioxidant used to combat the rancidification of fats) is a chemical preservative that has fallen out of favor because of suggestive ties to certain health problems; however, it is still one of the most effective. Acid preservation of meat is common, but also a fading practice as evidenced by the disappearance of pickled pig’s feet and eggs at bars and saloons. (For this we have no explanation, but it is forever a part of our curious culinary history.) More natural antioxidants such as Vitamin E, rosemary extract, and Vitamin C are currently more popular for pet foods. The bottom line is that the use of increasingly more natural antioxidants has reduced the shelf life of pet foods. While this may be better for the health of our pets, it also places an onus on the consumer to take an active role in preventing food spoilage.

Even cats would confess to being pickier eaters than their canine counterparts.


Another method of preservation involves the combination of salt and other chemicals such as bisulfites and/or sugar along with dehydration to preserve fruits and meat. You can find examples of this technique in any grocery, corner, or convenience store. This is the process by which all kinds of meat jerkies and dried fruits are created.


This method slows the process of oxidation but does not eliminate it. The colder the freeze, the more effective the preservation. This means that that really choice filet you’ve got stashed in your freezer from the Carter administration isn’t still edible. We’re sorry to break the bad news to you, but your Kenmore is not equipped for advanced cryogenics. When buying frozen raw diets at your pet store, make sure the pet food storage temperature is 0ºF or below.

Barrier Bags

Paper bags provide very little protection, yet manufacturers have used them for decades because they’re a cheap alternative to our modern barrier bags used to package better foods. But as more truth emerges about the relationship between packaging and food decay, manufacturers have been forced to create better bags. Even human cereal is protected by a wax paper barrier to keep the product fresh. Pet food companies have introduced new barrier bags made of petroleum products; these are very good at keeping air and moisture out while the product is stored on retail shelves. The paper bags used for cheaper foods are particularly oxygen-porous which greatly diminishes the longevity of the food. It is only in the last fifteen years that these oxygen and vapor tight barrier bags have begun appearing on shelves. These bags are expensive but are very good at their job; however, their effectiveness does not extend beyond the moment you open the bag. It should be noted that some of the best advancements in packaging techniques such as barrier bags, nitrogen packing, and vacuum sealing are taking place with small animal and bird foods. Don’t pass up those crinkled vacuum packed bags just because they look a bit odd. Vacuum packaging retains freshness. The consumer needs to look beyond the aesthetics of the bag; this is exactly the goal of companies that skimp on product quality but spend on excellent marketing and graphic design because the latter is much less expensive.


Canning involves the combined talents of a couple of preservation methods: heat and airtight containers. Extreme heat kills harmful organisms and an exclusion of air prevents re-inoculation. This technique has been around since the invention of the glass jar with a screw on lid in 1858 by John Landis Mason. Those that do their own canning know that acidic fruits and vegetables are easier to preserve than more alkaline foods. Improperly canned products of lesser acidity can result in botulism because the acidity negates the effect of the bacteria that produce the botulism toxin. This is why tomatoes are the perfect canning vegetable whereas the green bean, an acidic lightweight, is a poor candidate. Commercial canners add salt to many canned vegetables to compound the preservation, but they still have to be diligent about their methods. Botulism is bad news, and even though dogs are relatively impervious to the toxin, they can still contract dangerous maladies from spoiled and rotten foods.


Yogurt is milk acidified by bacterial action. Bacterial groups of Lactobacillus and Bifidobacteria produce so much acid during the fermentation process that other molds and bacteria find it nearly impossible to invade the culture. Fermentation is also a natural nutritional aid. Take for example the nomadic Mongolian warriors of Genghis and Kublai Kahn. This army conquered most of the known world while drinking the fermented milk of the animals they rode into battle. Now that is efficiency. There are numerous types of beneficial vitamins and enzymes produced in the fermentation process. In moderation, beer and wine are also good for us.


Kibble has a shelf life of various durations for a few reasons: we allow food to be exposed to varying amounts of air, fluctuating temperatures, high temperatures, and moisture. Maintaining low moisture and antioxidant levels blocks the effect of incompletely oxidized fats and proteins (these are those pesky free radicals again). In cars, the incomplete combustion of gas results in certain nitrogen products and carbon monoxide emissions. This is why we have platinum catalytic converters – to provide an environment for chemical reactions whereby toxic combustion by-products are converted to less-toxic substances. The prevention of kibble oxidation involves a similar exercise in chemistry. And you probably never thought you’d read a conversation comparing kibble to car parts. You’re welcome.

When a bag of pet food is purchased, as we’ve said, don’t buy more than your pet can consume in a month. If you do make it a practice to buy foods in bulk, think about freezing all but a 30-day supply. Remember, the quality of the food begins to deteriorate rapidly the minute that bag is opened. Manufacturers like Eagle, Wysong, Merrick, Solid Gold, Wellness, Eukanuba, etc. all use vapor proof bags that preserve the food much better before it is opened.

Don’t take the food from the bag. It may seem like a sound pet food storage solution to pour the food from the bag into a plastic storage container of some kind; however, if there is a recall, it is important to know the lot number of your particular bag so the offending ingredient can be tracked and you can have the piece of mind knowing that your particular bag of food has not been implicated. If the food has been contaminated, holding onto the bag means you also know to whom and how to respond. This goes for both human and pet foods. Additionally, foods removed from their bags typically have increased rates of oxidation when in a plastic container that is opened every day.

We suggest you keep pet food, once opened, in its original bag and then place that bag and its contents in a plastic container. Ideally you would take a week of food out at a time so that you do not continually expose the stored food to air and moisture each day. The less often food is exposed to moisture and oxygen, the less it deteriorates. Also do not store food in areas with rapid temperature fluctuations such as your porch, basement or garage. These environments increase condensation. Bags left on the floor, especially bags that are not vapor sealed, inhale moisture and deliver it directly to the kibble. Moisture results in the formation of molds that we don’t always see; molds can be especially damaging because they can produce a toxin called aflatoxin that will attack your pet’s liver (and even your own, if you’re not careful). The deterioration of food, especially in low-density fats like chicken and fish oils that are so healthy when produced from quality sources, causes those nasty free radicals, rancidity and protein deterioration that put great stress on primary organs such as the heart, liver and kidneys.


Think about what it would smell like if you let a stick of butter or a chicken breast go rancid on your countertop. Now think about how your pets can smell at least 100 times better than we can. Is it any wonder why pets sometimes turn their noses up at their food? The processes that destroy the makeup in that piece of chicken are the same at work on the freshness of your pet’s kibble. So if your pet suddenly refuses a food he’s eaten for months or even years, it may not be time to completely switch foods… instead, maybe it’s time to improve your methods of pet food storage.

free radicals - food spoilage


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