14B-7

Y. CHEN, Food Science Department, Rutgers University, 65 Dudley Road, New Brunswick, 08901 and C. T. Ho, Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, 08901.

JUSTIFICATION: Urea occurs naturally in meats and many food products, where its presence affects food quality. However, little is known about its impact on thermal flavor generation in food production.

OBJECTIVES: To investigate the effects of urea and pH on thermal flavor generation using the model system of cysteine with ribose, and as a minor objective, to determine the urea contents in beef, pork and chicken.

METHODS: Determination of urea content was conducted enzymatically. The model system of ribose and cysteine was used for the investigation of urea effect on flavor generation. Reaction mixtures with or without urea were heated at 180°C for 2 hours and then extracted with methylene chloride. The extracts were concentrated and subjected to GC and GC/MS analysis. The identified compounds were verified with authentic compounds in database and previous publications.

RESULTS: The results revealed relative large amounts of urea in these meats and demonstrated that pH affects aroma generation. Volatiles identified from the reaction system of ribose and cysteine showed that the sulfur-containing compounds such as thiophenes, thiazoles and thiophenethiols were the most abundant compounds. The addition of urea into the reaction mixture caused the disappearance or reduction in contents of some sulfur-containing compounds but resulted in the generation of several important nitrogen-containing volatiles like pyrazine, methylpyrazine, (2, 5 and 2, 6)-dimethylpyrazine and other alkyl pyrazines, which are known to elicit roasty, nutty flavor notes. A plausible explanation for this phenomenon is that ammonia can be released from urea upon heating and the formed ammonia competes with hydrogen sulfide to react with Maillard reaction precursors to produce the nitrogen-containing compounds like alkylpyrazines.

SIGNIFICANCE: Results have implications in flavor industry for artificial synthesis of meaty flavors. By modifying the content of urea in the reaction system, it is possible to modify the overall flavor profile.