STUDY ON THE TEXTURAL AND VOLATILE CHARACTERISTICS OF OYSTER (Crassostrea gigas) DURING STORAGE

Yifen Wang and Jinglin Zhang, Auburn University, Auburn, AL

Oyster is a popular seashell food due to its special nutritive value and delicious taste which is normally consumed raw. However, oyster has a very short shelf life under normal storage conditions. Deterioration is not only associated with oyster flesh textural change but also accompanied by the change of volatile characteristics. The objective of this project was to study the change of textural and volatile characteristics of oyster during 4 ºC storage.

Live oysters were harvested in October 2013 from Douphin Island and were immediately transported to the laboratory in a cooler with ice and stored in 4 ºC storage. The oysters were shucked every 5 days to prepare texture profile analysis and cutting force test on both oyster body and adductor muscle. After textural analysis, the oysters were homogenized to identify and quantify the volatiles by a headspace solid-phase microextraction (HS-SPME) method coupled with GC-MS. The conditions impacting HS-SPME method, such as the extraction temperature, extraction time and NaCl concentration in the sample solution were optimized. The total volatile base nitrogen (TVB-N) which is the widely used freshness indicator in sea food was measured by Conway method.

More significant differences of textural properties were observed from oyster adductor muscle during storage than that from oyster body, suggesting that the adductor muscle was a suitable part for textural analysis to reveal the oyster deterioration. The optimized HS-SPME conditions were 80, 50 min and zero NaCl concentration. Differences in contents of some alcohols, aldehydes, ketones and organic acids between fresh and deteriorated oyster were observed, suggesting these volatiles arising from the oxidation of polyunsaturated fatty acid and amino acid degradation might cause the aroma change of oyster during the storage. The TVB-N values increased during the storage, however, the results shows that the changes of textural and volatile characteristics might be more precise indicators of deterioration for the oyster industry.