Why does beef jerky exist? Why does any dried or dehydrated product exist? There are a couple reasons, but the main one is to increase the amount of time that product is still able to be consumed safely. It seems like a lot of people equate products like jerky or dried fruit with being indefinitely shelf stable and able to withstand all different types of storage conditions. While it is much more stable than it's fresh counterpart, how jerky is stored definitely plays a role in how long it will last. The more that can be done to protect jerky from elements that will continue to break it down, the longer it will last.
"Water Activity" or aW is water in food which is not bound to food molecules and can support the growth of bacteria, yeasts and molds (fungi). The term water activity (aw) refers to this unbound water. The water activity of a food is not the same thing as its moisture content. Although moist foods tend to have greater water activity than dry foods, this is not always true; in fact a variety of foods may have exactly the same moisture content and yet have quite different water activities. Moist jerky generally has a higher level of sugar, as sugar does a good job of "occupying" water molecules, so jerky with more sugar, can seem more moist as the sugar is keeping the water from reacting with the atmosphere. Very dry jerky generally has much less sugar in it's recipe, both of these jerky products could have exactly the same water activity.
Packaging plays a big role in how long food will last on the shelf. Plastic packaging, even the best, has what is called a "Barrier Rating" The "Barrier Rating" describes how well the package keeps the product, and it's aroma, in the package. It also describes how well it keeps oxygen and moisture out. There are two basic criteria on which bags are rated: Oxygen Transfer Rating (OTR) and Moisture Vapor Transfer Rate (WVTR or MVTR). The OTR is defined by how much oxygen passes through a certain size area of film in a 24 hour period. The lower the rating number, the more impervious the barrier. Take a look at the chart below to compare some common materials. Foil is at the top of the list with a rating of 0 and Low Density Polyethylene LLDPE is sometimes referred to as a "screen door" to oxygen. There are big differences in plastic bags.
The top enemies of shelf life are: Heat, Light to include UV, Temperature Fluctuation and Rough Handling. If these can be minimized to the greatest degree, it is possible to improve shelf life by months, if not years. Let's look a little more closely at some of the things that can shorten the life of America's favorite meat snack.
Some may remember a lesson from earth science in high school – to speed any reaction, simply add heat. The same is true when it comes to breaking down meat. Storing jerky in too warm of environment is the same thing as cooking the meat, but it just takes much, much longer. Too much heat in a storage environment will bring a normal shelf life to a much quicker end. Ideal storage temperatures for jerky range from 35F – 70F. Generally speaking, the cooler the better, jerky stored in the refrigerator in a sealed container will last almost indefinitely.
Ever notice how most things left to sit in the sun tend to deteriorate faster than items protected from the sun?? Skin will also react adversely to high levels of UV light. Light is heat's first cousin and can be just as damaging if not more damaging. If jerky is stored in direct sunlight, the light helps the oxidization process move along quickly. This will result in the jerky becoming tougher and darker in color. Sunlight can also break down the packaging that jerky is stored in, UV rays are particularly hard on plastics. Sunlight is best avoided all together if you're looking for a long term storage solution.
Any storage environment that has wide swings in temperature will break down food products more quickly. If you've ever seen dew on the grass you've seen the phenomena, warm air will support more moisture, when air cools moisture turns into precipitation. Jerky is packaged with a small amount of atmosphere in the bag, if the temperature swings down quickly enough, this moisture will become water particles. This doesn't necessarily hurt anything or make the storage container unsanitary, but every time phase change happens in the bag, it's making changes inside the jerky as well, generally that will be the jerky breaking down more quickly.
Rough handling takes a toll on food products in a number of ways. First, it's a good way to rupture a package. It literally only takes a pin hole to ruin an otherwise perfect barrier seal. Jerky should be handled in such a way that it is not pressed down tightly, squeezed, packed or twisted. The edges of jerky, especially slab style jerky are hard and sharp enough to pierce even a strong package. Once there is a hole in the bag, the jerky's days are short. Keep factory packaged jerky stored in a loosely packed container, better yet, one that shields the inner packs from light and atmosphere and you'll be enjoying your jerky for at least a couple years to come.
When you take a look at all of these enemies of shelf life, it seems that our ancestors who used to dig root cellars knew a little bit about what they were doing. The old root cellar addresses all of the enemies of shelf life with stark simplicity – it maintains a constant cool temperature, it shields food from sunlight and UV rays. The only thing that it didn't account for was the barrier that the item may have been stored in….and that's where it gets it's name. "Root" cellar is used because as long as these roots were in the ground, they'd keep just fine for months if not years. If it was a more delicate foodstuff, say fruits, vegetables and meat, people would can them. Which involved cooking fruits and vegetables then sealing them in a glass jar under pressure to kill all the bacteria while providing an air tight, impervious seal. There are records of canned food being good after decades of storage.
No food lasts forever but properly sealed foods with low moisture (water activity) will last a lot longer than the rest. If you are interested in having jerky, or any other food keep for a longer period of time, pay attention to how and where it's stored and you'll be eating will for a long time to come.
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