Fats and Rancidity: A Food Storage Problem, by L. Joseph Mountain

Many of the dehydrated "food storage units" available these days specify that you need a certain amount of fats or oils to supplement their unit. You probably know these units, they generally sell as "1 person, 1 year" type of packages and they contain a variety of grains, legumes, fruits and other essentials. They are generally put together with the help of nutritionists that try to deliver a certain amount of calories and essential nutrients per day. You might wonder why they don't just include a container of oil to complete their units. Or even why we need them.

Fats (oils or lipids) are one of our bodies essential nutrients. This means they aren't optional, we get sick and die without them. While our bodies can manufacture some of the fat we need by using other nutrients, we can't make enough of them.

Fats are our body's method of storing energy, lubricating joints and we need them to absorb [the fat soluble] vitamins A, D, E and K which aren't normally soluble in water. And in times of starvation our body burns off stored fat by converting it into energy, mostly by turning it into glucose which is the favored food of our cells. Since this takes some work, and because our body favors the easiest to digest nutrition it finds, fat tends to get stored first and burned last when we have excess nutrition.

Fats are pretty chemically simple, being chains of carbon with hydrogen attached and tail with oxygen attached. Unfortunately the presence of these hydrogen and oxygen molecules aren't all that chemically stable and the hydrogen and oxygen tend to become attracted to and run off with the milk man so to speak. They can get together with each other and create water which will induce a milky or emulsified kind of appearing oil, and this would be a hydrolysis. We often see this with oils that have been "annealed" or subject to repeated heating and cooling.

The other thing is they can combine with oxygen and we have oxidation. We also call it "rancidity" and it's an unpleasant quality we smell and taste.  This unpleasant taste and odor is progressive, it gets worse and worse until the stuff is pretty much unpalatable. Oils and fats coat the inside of our mouths, making our taste buds more receptive to taste which is ordinarily great but if that taste is foul it's even harsher.

Chemically when oxygen gets in the door it starts breaking into fatty acids, specifically hydro-peroxide (measured as PV) and thiobarbituric values (TBA). Unfortunately there's no cheap do-it-yourself test kit for this chemistry at home besides your nose.

Peroxides are even more unstable and break down into ketones, alcohol and aldehydes. Think of a rotten banana Bananas are actually pretty oily and it's partially the oil oxygenating that gives that alcohol or ketone smell.

If you have ever smelled old oil paint from a long time ago, that kind of dank smell was it. This is because we used to use things like linseed and cottonseed oil in paints and it rancidified like all vegetable oils. Once you know what that flavor and odor is you won't forget it. Unfortunately it might be more familiar to you than you realize. Staleness is another flavor associated with rancidity but I've found a lot of people don't detect it. I honestly think we're used to it.  Foods take a lot longer to get from farm to table these days.

Some say that because we've gotten used to refined flours that don't contain as much oils as well as monounsaturated and polyunsaturated fats that some believe last longer on the shelf. In fact we've gotten used to leaving boxes of things like pancake mix in the cupboard for a year or more. And all the people you see buying 3 gallon jugs of cooking oil “to last all year” aren't doing themselves a favor. And in fact we don't really know how long that oil has been on a shelf or in a hot warehouse before it got to you. All in all it seems that buying oils in small quantities is the way to go.

There aren't the kind of immediate health risks with rancid oils as there are from bacteria or other mean little bugs that grow on spoiled food.  Until recently we didn't recognize any major mal effects besides loss of flavor. This is changing as we suspect rancid oils aren't able to do their job for us chemically as effectively as we need them to ask far as vitamin uptake. We're not sure that rancid oils don't contribute to long term health issues like obesity as these fats aren't as easily broken down into glucose. And there's the feeling these oils might turn into free radicals. All of these would have long term health effect implications.

It's worth spending a moment and making this point about brown rice, wheat berries or any whole grain flour. These all contain the germ and bran which contain a lot of fat and these create further challenges for long term storage. Low fat beans store longer than high fat ones, nuts go great in cans but nothing can stop the oils in them from rancidifying over time. This is why cheap nuts often taste bitter. They are older stock. White rice and white flours are optimal for storage. I know that's horrible news to those of us who love our whole grains and count on their enhanced nutrition. That's why we want to take every precaution when storing whole grains and high oil content foods.

We can slow rancidity down but we can't stop it. The ways to slow it down are the very same general rules we use for all foods in long term storage:

1. Keep it cool. It seems a lot of people store their oils up high next to the stove. Over-stove storage is for pots and pans, not for any food product.

2. Keep it out of sunlight. Some people seem to want to keep fancier oils out on the counter. We see this with infused oils that are pretty to look at but out in the light they are deteriorating rapidly.

3. Try to keep oxygen away from it. It would be good if oil came in mylar bags with spouts like cheap wine. The advantage here is the container shrinks along with the stored product leaving less room for oxygen. A large bottle will eventually contain mostly oxygen. Consider breaking your oils out into small containers so this effect is minimized. And note that not all plastics are air-impermeable meaning that air and gases will in fact leak through it. Food grade plastics can be trusted. Glass is best.

4. Don't let water adulterate it. The above steps help as does keeping stored foods at consistent temperatures because changing pressures won't tend to break seals. Keeping oils in sealed containers is our best defense against water.

My personal feeling is that the less refined (read saturated) fats seem to hold up best. Cold pressed extra virgin olive oil fits the bill but so does lard. Some of these cold pressed oils will hold up for months in proper storage and lard does great in cans (no light or oxygen penetration plus it's free of acids and flavors found in other oils). I don't really have science to back that up with other than the shortened carbon-hydrogen chains in these newer unsaturated fats leave it more unstable. I have heard that these unsaturated fatty acids will bind to protein to form lipid-protein globs that are insoluble and I find this as credible as it is undesirable.

[JWR Adds: Canned lard products like Crisco should be avoided, since they are often bordering on rancid even when bought "fresh" at your local store. The metaliziced cardboard containers used for Crisco are permeable to oxygen. As I detail in the Rawles Gets You Ready Preparedness Course, for long tern storage I recommend stocking up on case lots of virgin olive oil and coconut oil in full, sealed plastic bottles. These oils are available inexpensively at COSTCO and other Big Box stores. Although glass bottles are impermeable to oxygen, a plastic bottle allows oil to expand when stored frozen. (Glass bottles will shatter.) When stored frozen at 10 degrees F or lower, olive oil can have more than an eight year shelf life. Needless to say, date-mark the label of each bottle that you store, to facilitate first-in, first-out (FIFO) rotation. I hope that olive oil becomes available in gas impermeable mylar pouches, but for now, plastic bottles are the best available compromise. As I've mentioned before, raising livestock or hunting bears are the only sure ways to provide needed fats in long term isolation. But raising pigs isn't for everyone. Don't overlook chickens, since egg yolks are a good source of fat.]

Perhaps most interesting to me is how fats operate in freeze dried scenarios and upon rehydration. The fats are pretty much still there even with the removal of all that hydrogen and oxygen and I have to remind myself that in fats these are chemically bound to carbon. It's not water, it just contains the components thereof. With normal dehydration these oils are basically unaltered and are more prone to spoilage. With freeze-drying and subsequent packaging we don't permit free oxygen to get back in.

If your diet is severely lacking in fats and you can't find bacon, eat more whole grains. Eggs, milk, cheese all contain it. Corn is such a wonderful source of oil that if you grow enough you can press your own oil. It's almost hard to imagine most of us not getting enough fat in our normal habitual diet.

The cautions come in if you are utterly dependent upon your stored food and have no hope of obtaining food (with fat in it) from outside sources. Or perhaps if your diet is limited to refined starches. For me it's hard to imagine this scenario but other preppers presume this level of isolation even for long periods. The RDA (government's recommended daily allowance) of fat is about 60 grams so that's about two avocados worth. Avocados are wonderful sources of dietary fat but again, most of the other foods you eat have fat as well. For long term storage it looks like the best lipid pick is good old canned lard.

About The Author: L. Joseph Mountain recently published Hidden Harvest: Long Term Food Storage Techniques For Rich And Poor. His web site is www.LongTermStorageFood.com where "articles are sometimes archived, info is irregularly updated and questions are occasionally answered."