The Dreaded L Word
My husband and I divide the cooking duties. He is what I consider a superb Neanderthal chef: give the man a dead animal and an open fire, and he's unbeatable. I prefer more complex culinary endeavors, and think I do pretty well with stews, stir-fries, and casseroles. But if he catches me raiding the refrigerator for last Sunday's roast and yesterday's steamed vegetables as source material for one of these creations, trouble inevitably arises.
"Aargh! Leftovers! You're going to feed us leftovers?" he'll say, backing away with fingers X'd as if he were warding off the Evil Eye. As someone who'll cheerfully eat cold pizza for breakfast, I've never had much sympathy for any loathing of leftovers. Our debate over this matter of taste has proceeded unsettled and apparently unsettleable until recently, when he brought science to his defense.
According to a brief report in Science News, chemists and physiologists are collaborating in research on the "disappointing" warmed-over flavor beef can develop. Two processes seem to be important. The first to be identified involved iron, of which beef is an excellent source. However, as beef sits around, the iron stimulates within it the breakdown of lipids. These are fatty substances that combine with oxygen as they break down, and oxidized lipids taste rancid.
Researchers with the U.S. Department of Agriculture thought they'd solved that problem two years ago. They found that when a derivative of chitin is added to the meat, it binds to the iron and slows the lipid oxidation. Still, warmed-over beef tasted like warmed-over beef, even if it lacked rancid overtones. The meat lost what the article described as the "brothy" taste of beef.
Recently, incorporating previous work in Japan, food chemists at Rutgers University think they may have tracked down the culprit responsible for making old food taste old. In effect, they came at the problem backwards, because they were working toward identifying the crucial substance or substances that gives good, fresh meat its distinctive taste.
They found that certain enzymes in the meat stay active through refrigeration, cooking, and refrigerating again. By analyzing the chemistry of top-round steaks of various ages, they identified the substance the enzymes break down. It turned out to be a peptide that directly stimulates an array of taste receptors in the human mouth. The process might be seen as analogous to a pianist playing a chord---the peptide molecule simultaneously tickles receptors for sweet, salt, bitter, and sour, leading to a harmonious sense of flavor.
The scientists speculate that pieces of the enzyme-broken peptide molecule may connect only to certain of the receptors, so the brain registers sour or bitter sensations (flat notes in the beefy melody) instead of the combination required for a good, meaty taste. They also think the whole peptide may be the key to "umami," a possible fifth taste sensation which some scientists believe can be perceived by certain as yet unidentified receptors.
The Rutgers researchers hope to synthesize the peptide, with an eye toward providing it as a totally natural food additive capable not only of making leftovers taste fresh but even of making soybean curd taste like prime rib. They're also hunting for similar flavorsome-peptide/attacking-enzyme suites of chemicals in pork and poultry. Should they succeed, I'll finally have a surefire way of tricking my husband's touchy taste buds into accepting leftovers without protest---unless he catches me raiding the refrigerator.
Given that the march of science may be on my side, the least I can do is give him the last word. When he handed me the report on this research, he added, "I'm no chemist, but I bet I know where they can find plenty of the enzyme that makes leftovers taste bad. They really ought to look in broccoli."
