Thermal reaction of anisaldehyde in the presence of L-cysteine, a model reaction of Chinese stew meat flavor generation

Chinese stew meat is very popular in China due to its special flavor generated during cooking process. However, how these flavors are produced has not been studied yet. Star anise is one of the indispensable ingredients in the formation of Chinese stewed meat flavor. One of the most important volatile components in star anise is anisaldehyde. Anisaldehyde may react with sulfur-containing constituents of meat such as cysteine to form components of sensory significant during the cooking of stewed meat. Cysteine is major precursor for meat flavor generation.;We present here results of a study that tested the thermal reaction of anisaldehyde in the presence of cysteine under certain conditions. Anisaldehyde was mixed with cysteine, then the mixture was heated to both 60 °C, 80 °C, 120 °C and 150 °C for two hours by oil bath. To determine both volatile and non-volatile compounds, products were separated into two parts. In order to detect non-volatile compounds, one part of the products was extracted by ethyl acetate. One major non-volatile product was purified from the sample by HPLC. Mass spectrometry was used to determine the structure of that major non-volatile compound, which is identified as 4-methoxybenzothialdehyde. For volatile compound detection, the other part of the product was extracted by dichloromethane and the volatile compounds were then determined by using GC/MS. Several major sulfur containing aroma compounds were identified besides various products generated during cysteine thermal degradation. Detection for both volatile and non-volatile compounds indicates that anisaldehyde can react with cysteine and may influence the meat flavor generation during the Chinese stew meat cooking process.