The shape of a food can often changes as a result of microbial spoilage.
The addition of preservatives to packaged and prepared foods has been commonplace for many years now. Preservatives help keep foods from spoiling, giving them a longer life and saving consumers money. Not all preservatives are created equal, however. There are three main categories of preservatives, and each has a different way of keeping your food fresh.
Antimicrobials
Antimicrobials inhibit the growth of microbes on food, which prevents spoilage. Some foods, such as strawberries, cheese and apples, have natural antimicrobials built into them, though they too will eventually spoil. Antimicrobials include sulfites, nitrates, nitrites and propionates. They work on a cellular level to inhibit metabolic pathways, shutting down food sources for microbes to grow. They also alter cell wall permeability and block cellular transport, which lengthens the life of the food. Wine is a well-known sulfited food, as the antimicrobial properties of the sulfite extend the safe drinking period of the wine.
Antioxidants
Antioxidants are known for their ability to negate the effects of damaging free radicals in humans, and they play a similar role when used as a preservative in food. Food antioxidants reduce the effect of oxidation of food. Oxidation results from exposure to oxygen, which will eventually break the food down and make it spoil. Antioxidants slow the oxidation, extending the life of treated foods. Foods that spoil due to oxidation, such as oils and nuts, will take much longer to turn rancid. Food antioxidants include propyl gallate, butylated hydroxytoluene, tert-butylhydroquinone and butylated hydroxyanisole.
Metal Chelators
Fresh fruits and vegetables are usually picked before they are ripe to allow for more transport time because, once produce is ripe, it does not take long before it spoils. Harvesting before ripening gives it a longer shelf life. This extended life may still not be long enough, so metal chelators are sprayed on the produce to further stop the ripening process. The longer a fruit or veggie takes to ripen, the longer it will last.
Preservatives in Action
There is an easy experiment that can be done to see how preservatives work. Buy one loaf of bread from the supermarket shelf. It will have preservatives in it to keep it from growing mold. Buy another loaf freshly baked without preservatives from a bakery. Alternately, you could also bake a loaf yourself without preservatives. Put 10 drops of water on a slice from each loaf and place in separate plastic sandwich bags. Seal tightly and place in a dark area. Every few days, check each bag (don't open them though) and check for evidence of mold. The slice without preservatives will grow mold faster than the one with.
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