In the back of the cave, Og groans in misery. Ogga is smug -she told him to leave that two-day-old meat alone. But it looked fine to Og, and as usual, he thought with his stomach instead of his head. Og swears to the gods of food that if only they will let him get through this, he will never touch meat again.
Food, by virtue of once being alive, has a tendency to do what all dead things do: decompose. Food decomposes when its molecules break down into simpler molecules and elements. To do this, it needs the assistance of several helpful organisms and chemicals within its own body.
INVASION OF THE MICROSCOPIC KILLER SPONGES!
Bacteria are little more than live microscopic sponges. The cellular wall of a bacterium (that's what they call one bacteria) is porous -just like a sponge. To eat, it simply soaks up whatever it happens to be lying in. (What a life!)
In its natural state, food is wet, warm, and out in the open. Take away any one of these conditions, and you take away a bacterium's ability to thrive. Therefore, in order to preserve our food we wrap it (to take away its air) and/or chill it (to slow down its rate of reproduction). Alternately, we can dry it (a bacterium can't eat what it can't soak up).
BACTERIA ARE OUR BUDDIES
All bacteria aren't deadly, of course -in fact, most are harmless. We have bacteria all through us, both inside and out. We couldn't live without them. The deadly bacteria are the ones that produce toxins as they eat and reproduce. Some familiar examples are salmonella, e. coli, anthrax, and the bacteria that cause botulism.
DANGER! DANGER! ENGAGE DEFENSE MECHANISM!
If bacteria are threatened (say, by excessive heat), they have a special defense mechanism. They produce spores, which are sort of like seeds that protect the bacteria until they're in a condition where they can thrive again. And like seeds, they're tough. They resist heat, And they can wait around for ages.
That's why it isn't a good idea to reheat meat too many times. Every time the meat is reheated, more spores have a chance to form. Then, if the meat is put back into the fridge, the spores have a chance to germinate (make baby bacteria) before it gets too cold. If you keep heating and cooling, you're just creating more and more heat-resistance spores that will develop into bacteria whenever conditions are ripe.
FUNGI: NATURE'S RECYCLING PROGRAM
When a fungus invades your food, it's just doing its job, which is to recycle dead matter into nutrients. Unfortunately, if you ever smelled fertilizer, you know how awful those nutrients smell. And just because they're good for plants, it doesn't necessarily mean they're good for people.
When you digest your food, you keep your digestive enzymes in your stomach. But fungi releases its enzymes into its surroundings (like that loaf of bread you've had hanging around for a week), and allows them to go to work breaking down the food into a form it can absorb. (Image credit: Flickr user Orange Coast College Biology Department)
"HOW'S THE MUSHROOM SANDWICH TODAY?"
Molds and mildew are both forms of fungus. The fuzzy stuff on that old bread are actually tiny mushrooms. A fungus reproduces by forming mushrooms that release tiny spores into the air. And like bacterial spores, the fungus's job is to find a good place to live (and eat!). Where is such a place? Well, a fungus does not need light to survive, so any warm, dark, wet place suits it just fine (which is why its nice to have a window in your bathroom).
ATTACK OF THE ENZYMES
Enzymes are another culprit in food spoilage. They aren't alive; they're chemicals produced by everything that lives. Enzymes are present in all foods, and they don't just sit there, they have a very important job: to assist in the break-down process by speeding up chemical reactions.
RIPE FOR THE PLUCKING
One example is the ripening of fruit. Once the fruit is ripe, the process doesn't stop. After all, one of the goals of a fruit (if you can attribute goals to fruit) is to scatter its seeds. And one way to do this is to create a food succulent enough to entice a creature to eat it and discard the seeds. Those fruits that aren't eaten become overripe and eventually fall apart in a gooey mess. Which is another way to disperse seeds. (Image credit: Andrew Dunn)
"WHAT'S THAT SMELL?"
Meats containing lots of fat have a nasty tendency to go rancid. Rancidity (yes, that's a scientific term) is a chemical reaction that breaks down fatty acid molecules into smaller molecule-weight fatty acids. As it does so, some of the molecules evaporate, releasing unpleasant odors. This actually happens with all meat, but the process is faster with fatty meats.
"WHAT'S THAT BLACK STUFF?"
Some spoiled foods are easy to identify. Mold growing on bread looks fuzzy; if you miss it and take a bite anyway, the musty flavor should tip you off. Old milk smells sour and tastes worse -if it gets old enough, it actually curdles. If meat gets old enough, it'll turn brown without the benefit of cooking.
(Image credit: Flickr user Quinn Dombrowski)"BUT IT LOOKS FINE TO ME!"
But sometimes you can't tell when food is spoiled, like when bacteria leave an invisible slime on meat. You can check for slime by running a knife blade across the meat. If the blade has a cloudy, slippery stuff on it, your meat has been slimed.
It's even harder to tell if an egg is bad. One way you can test it is to put it in a bowl of water. If it sinks, it's fine. If it floats, better get rid of it (preferably without breaking its shell).
OLD MUSTARD NEVER DIES
Not all foods go bad so readily. The yellow mustard that's been in your fridge for three years, for instance, is a preservative in itself -that's why it won't go bad (though it will lose its flavor). (Image credit: Flickr user busbeytheelder)
Then there are antimicrobials (they keep bacteria and fungi from invading your food) and antioxidants (they prevent rancidity, browning, and black spots). Other preservatives absorb water, preserve texture, and prevent trace metals from turning your food strange colors. Some old-fashioned preservatives are salt (to preserve meat and fish), sugar (to preserve fruit), and alcoholic beverages (which is why Aunt Bess's fruitcake can keep for years).
IT CAME FROM THE BACK OF THE FRIDGE
But, as you probably know, not all food can be preserved. And if you've ever neglected to clean out your fridge for a while, you've undoubtedly discovered that stuff that lurks in the back has been doing a slow morph into something alien, evil-smelling, and possibly so dangerous it should come with its own Surgeon General's warning.
___________________The article above was reprinted with permission from Uncle John's Bathroom Reader Plunges Into the Universe.
Since 1988, the Bathroom Reader Institute had published a series of popular books containing irresistible bits of trivia and obscure yet fascinating facts.
If you like Neatorama, you'll love the Bathroom Reader Institute's books - go ahead and check 'em out!