Crab-shell derivative retards rancidity.

Crab-shell derivative retards rancidity 

Researchers have spent decades seeking uses for chitin, Earth's seond most abundant natural polymer (long-chain molecule). The shellfish industry discards huge amounts of this strong, biodegradable and nonallergenic material, the main constituent of crustacean shells. Last year, Canadian scientists reported plans to fashion chitin-based coatings to extend the shelf life of fruits (SN: 6/25/88, p.410). Now, chemists at the USDA's Southern Regional Research Center in New Orleans have developed another shelf-life-extending chitin derivative. This one binds with the iron in meats to slow chemical reactions that cause rancidity and flavor loss.

In meats, iron activates oxygen in the air to produce highly reactive free radicals that attack fatty substances called lipids. The oxidative breakdown of polyunsaturated fatty acids causes much of the flavor breakdown associated with rancidity, explains chemist John R. Vercellotti. The chitin-based compound he's working with--N-carboxymethylchitosan, or NCMC--essentially ties up meat's iron atoms. This greatly retards the atoms] ability to generate lipid-damaging free radicals, report Vercellotti and Allen J. St. Angelo, who together developed NCMC's newly patented antioxident application.

Dilute solutions of NCMC can be injected into meats, from steaks to top round roasts -- probably at the slaughterhouse, Vercellotti says. Alternatively, cooks cam mix the antioxidant into raw ground beef or sprinkle it into stews and gravies. A 500-parts-per-million concentration of NCMC prevented oxidative rancidity in cooked ground beef throughout a week of refrigeration -- generally the maximum useful life of leftovers. In fact, Vercellotti says, scant oxidation occurred in treated, cooked meat over the course of a month. NCMC might also protect fish, poultry and even dairy products.

Vercellotti says an industrial consortium has sprung up to make NCMC for a range of such applications.