Chapter 1 – Shelf Lives: Time, Temperature, Moisture, Oxygen and Light

Time, Moisture, Oxygen and Light

Is your food insurance up to date?

We create food storage programs with the idea that the food which has been put by will be available later should there come a time of need. The quality of the food at that time necessarily depends on its quality when it was stocked and the conditions in which it was stored. It cannot be any better than what it was when it went in, but it can certainly be worse when it comes out. In the fullness of time, all stored foods will degrade in nutrients and palatability until they reach the inevitable end where they cannot be eaten at all. 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 FIFO. The reason for this emphasis on stock rotation is because nearly all foods have a limited shelf life or, more correctly, it should be said that nearly all foods have shelf lives. There are really two we are concerned with here – the length of time a food retains substantial important nutrients and the length of time a food remains palatable.

Nutritional content actually begins to fade at the moment of harvest. Three major factors influence how much nutrition a food will have left by the time you eat it:

  • The food’s initial nutrient content;
  • the preservation process 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 above.

A food’s palatability life is the point at which undesirable changes occur to taste, texture, color or 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 which means that by the time the flavor or color begins to fade or the texture goes mushy the more perishable nutrients like sensitive vitamins will have long since plummeted.

Within reason, the key to prolonging the shelf life of your chow lies in lowering the temperature of the area in which it’s stored. The storage lives of most foods are cut in half by every increase of 18º F (10º C). For example, if you’ve stored your food in a garage that has a temperature of 90º F (32º C) you should expect a shelf life of about half what could be obtained at a lower temperature, perhaps in your pantry at 70º F (21º C), which in turn is half the storage life that you could get if you kept it in your basement or refrigerator at 50º F (10º C). Your storage area should be located where the temperature can be kept above freezing and, if possible, below 72º F (22º C). Avoid major temperature fluctuations in this area if you can.

Ideally, your storage area should have a humidity level of 15% or less, but unless you live in the desert it’s not likely you’ll be able to achieve this. Regardless, moisture is not good for your dry stored edibles so you want to minimize it where possible. This can be done by a couple of 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 deal with any moisture trapped inside. If you are able, use both.

All containers should be kept off the floor and out of direct contact with exterior walls to reduce the chances of condensation brought on by temperature differences between the container and the surface on which it is resting.

Another major threat to your food is oxygen (O2). Chances are that if your foods are sealed in moisture-proof containers they are probably air-tight as well. If air cannot get in, your only concern is the oxygen 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.Depending on the nature of a particular foodstuff any one or a combination of the three can be used to good effect.

Once you have temperature, humidity and oxygen under control, we next 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 the food which can damage its nutritional content and appearance. Fat soluble vitamins, such as A, D, E, and K are particularly sensitive to light degradation. It’s a pretty sight to look at rows of jars of food, but 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 also help to cushion them from shocks which might cause breakage. For those of you in earthquake country, this is a particularly good idea. Should “terra” suddenly stop being “firma” your jars might just dance right off onto the floor.

Providing they were properly processed, canned, dried, frozen, or freeze dried foods do not become unsafe to eat when stored longer than their recommended times, but their nutrient quality fades and their flavor, color and texture go 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?