SHELF LIVES: TIME, TEMPERATURE, MOISTURE, OXYGEN AND LIGHT
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Is your food insurance up to date?
Since the entire idea of a food storage program is that it should be available for you and yours in times of need, it is important to understand the conditions that can affect the edibles stored in your pantry.
A storage program is only as good as the quality of the food that goes into it. It cannot get any better than what originally went in, but it can certainly get worse. In the fullness of time, all stored foods will degrade in nutrients and palatability until they reach the inevitable end where even the dog won't eat them. It's because of this eventuality that every article, book, and teacher concerned with putting food by gives the same advice:
Date all food containers and rotate, Rotate,
ROTATE.
The first food in should be the first food out. This concept is often shortened to the acronym FIFO.
The reason for this emphasis on stock rotation is that when discussing the usefulness of foodstuffs there are really two shelf lives to be considered - the nutritional life and the palatability life. Nutritional content actually begins to fade at the moment of harvest with three major factors influencing nutrient retention: The food's initial nutrient content; the processing and preservation steps the food underwent; and the storage conditions in which it's kept. Given sufficient time, all but the most durable nutrients will dwindle away to nothing. Unfortunately, there is no good way outside of laboratory testing to know how much nutrition is left in a given food, but we can make our own determinations about other criteria which leads us to the palatability life mentioned also mentioned above.
A food's palatability life is the point at which undesirable changes occur to foods taste, texture, color and cooking qualities. This is the reason for the "use by" and "sell by" dates on many foods and for shelf lives in general. It will almost always be in excess of good nutritive life. If you don't have anything to replace old food with, it's not necessary to throw the food out just because it's reached the end of its best palatable storage life. Do, however, keep in mind that advancing age will only further decrease the useful nutrition, increase the foods' unattractiveness to being eaten and enlarge the chances that something may cause the food to spoil.
Within reason, the key to prolonging the shelf life of your edibles lies in lowering the temperature of the area they are stored in. The storage lives of most foods are cut in half by every increase of 18º F (10º Celsius). For example, if you've stored your food in a garage that has a temperature of 90º F, you should expect a shelf life less than half of what could be obtained at room temperature (70º F) this in turn is less than half the storage life that you could get if you kept them in your refrigerator at 40º F. Your storage area should be located where the temperature can be kept above freezing (32º F) and, if possible, below 72º F.
Ideally, your storage location should have a humidity level of 15% or less, but unless you live in the desert it's not terribly likely you'll be able to achieve this. Regardless, moisture is not good for your dry stored edibles so you want to minimize it as much as possible. This can be done by several methods. The first is to keep the area air-conditioned and/or dehumidified during the humid times of the year. The second is to use packaging impervious to moisture and then to deal with the moisture trapped inside. If you are able, there's no reason not to use both.
All containers should be kept off the floor and out of direct contact from exterior walls to reduce the chances of condensation brought on by temperature differences between the container and the surface it's resting against.
Another major threat to your food is oxygen. Chances are that if your foods are sealed in moisture-proof containers the containers are probably air-tight as well. This means that the oxygen can also be kept from doing its damage. If no more can get in, your only concern is the O2 that was trapped inside the container when it was sealed. Lowering the percentage of O2 to 2% or less of the atmosphere trapped inside the packaging (called head gas) can greatly contribute to extending its contents shelf life. The three main tactics for achieving this are vacuum sealing, flushing with inert gas or chemically absorbing the oxygen. Any one or a combination of the three can be used to good effect.
Once you have temperature, humidity and oxygen under control, it is then necessary to look at light. Light is a form of energy and when it shines on your stored foods long enough it transfers some of that energy to your food. This has the effect of degrading nutritional content and appearance. Fat soluble vitamins, such as A, D, E, and K are particularly sensitive to light degradation. It certainly is a pretty sight to look at rows and rows of jars full of delicious food, particularly if you were the one that put the food in those jars. However, if you want to keep them at their best, you'll admire them only when you turn the light on in the pantry to retrieve one. If you don't have a room that can be dedicated to this purpose then store the jars in the cardboard box they came in. This will protect them not only from light, but help to cushion them from shocks which might break a jar or cause it to lose its seal. For those of you in earthquake country, it's a particularly good idea. When "terra" is no longer "firma" your jars just might dance right off onto the floor.
Assuming they were properly processed in the first place, canned, dried and frozen (never thawed) foods do not become unsafe when stored longer than the recommended time, but their nutrient quality fades and their flavor, color and texture goes downhill. Following these rules of good storage will keep your food wholesome and nutritious for as long as possible:
#1 - First In, First Out (FIFO) means rotating your storage
#2 - Cooler is better
#3 - Drier is better
#4 - Less oxygen exposure means more shelf life.
#5 - Don't shed light on your food.
Think of rotating your food storage as paying your food insurance premiums -- slacking off on rotation cuts back on your coverage. Is your food insurance up to date?