Tuesday, December 12, 2006

Food Safety: What's Safe

Since we are just coming through a big food safety scare, on the heels of the big spinach scare, I thought I'd post a little about food safety in general. Today's topic will be foods that are generally safe; tomorrow, I'll talk about foods that are generally not safe; and later, I'll get to the gray area--foods that have been thought safe, but are causing problems now.

Foods are germ-free when there is some process or chemical that kills the germs; they stay germ-free while the process continues, while the chemicals remain, or while they are sealed up from the outside germs.

The main processes that kill food are heat (of course) and dehydration. Food that is kept hot--at or above 140 degrees--is safe. Once the heat process is over, the food should be eaten immediately, or sealed and chilled to less than 40 degrees.

Foods with low water content are also safe. This includes the obviously dehydrated foods--jerky, rasins, other dried fruits--but also foods with low levels of water, or foods where the water is bound up with other chemicals and isn't available for bacterial growth. Low-moisture foods include cooking oils, crispy snacks like chips and crackers, and honey (ever notice that honey doesn't really spoil? It's because there's not enough water in it to feed germs). Low water-activity foods include chocolate and cheese. Salted meats also have a lowered level of water activity, at least compared to fresh meats, that keep them edible much longer than raw meat.

Salt isn't the only chemical agent that keeps the nasties at bay--acids also do a good job of that. There are lots of foods that are fortified with acids--mostly lactic acid--by naturally-occurring bacteria that take over and make the neighborhood hostile for the bad guys. Cheese, hard sausages (salami, pepperoni, and summer sausage), and various pickles (sauerkraut, anyone?) are all acidified foods, and they are all safe and long-lasting when done right. (My last batch of kraut sat, sealed, on the counter for about three weeks, and in the fridge for three more, and it's still terrific.) Alcohol is another natural chemical preservative. Once again, we invite in good microbes (yeast, in this case), and its waste (alcohol) pollutes the food supply for the bad bugs.

The safest foods are processed and still sealed from the factory. They have been heat-processed (or received other de-bugging treatments), sealed super tight, and kept at the right temperature. Factory foods aren't necessarily the best tasting, or the best for you, but they are quite safe.

Tomorrow, we'll talk about the foods that are generally unsafe, and what to do about them.

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