Food is wonderful. It sustains us, it delights our senses, and at holidays it can bring together family members who would normally be at each others’ throats, most likely with switchblades.
Food is also incredibly scary. If improperly prepared, it can sicken, or even kill. And I’m not just referring to fugu. With all of the potential risks in eating, it’s natural to be leery of food that is prepared in a non-traditional manner.
For an example of such a non-traditional food, I bring you ceviche. Ceviche is prepared by cooking raw fish in a citrus-juice marinade. The acid bath (citrus juice contains both citric acid and ascorbic acid – vitamin C) denatures the proteins in the fish, cooking it and killing some of the harmful organisms that could be in the food. This is a good place, though, for an
IMPORTANT DISCLAIMER: ACID COOKING IS NOT AS EFFECTIVE AS HEAT COOKING AT KILLING HARMFUL ORGANISMS IN FOOD.
Let me clarify. All living things use enzymes to carry out the basic functions of life. For viruses, harmful bacteria, and parasites, the basic functions of their life include making your life miserable. The enzymes that let them do this are, fortunately, fairly fragile. Enzymes, and all proteins, react poorly when moved out of their comfort zone. They can exist in small ranges of temperature and acidity. Bump the environment out of that range, and the protein is denatured and rendered useless. This denaturation is responsible for the browning of meat when it is cooked.
If changes to both acidity and temperature can denature proteins, why is acid cooking less effective at rendering the food safe? The short answer is this: the acid can’t cook what it can’t reach. When cooking meat, it’s important to make sure that the interior is cooked through. This applies whether you are cooking with heat or with acid. If the proteins haven’t been denatured, the microorganisms present haven’t been killed. In the preparation of ceviche, the fish is not cooked through. This occurs for a number of reasons. First, the lime juice, while acidic, is not strongly acidic enough to kill all of the microorganisms present. In addition, if the fish is marinated for a short time, the juice will not be fully absorbed into the fish, and it will not be denatured all the way through.
The problem posed by this is mitigated somewhat if the fish is fresh and healthy. While a fish is alive, its immune system will fight off many kinds of harmful organisms. Once caught and killed, however, it is open to invasion. The fresher the fish, the better the chances of it being safe to eat. In addition, longer marinating times and more concentrated juices will more thoroughly cook the fish – although this will change the flavor.
Although there have been outbreaks of food poisoning from ceviche and other acid-cooked foods, there have also been outbreaks from improperly handled fruits and vegetables. In short, food cooked with acid is no more dangerous than a steak ordered rare.
Applied Phlogiston 