Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

First Advisor

Thomas C.-Y. Hsieh

Abstract

Important flavor components in Louisiana brackish water clam (Rangia cuneata) were investigated in this dissertation research. Major achievements include: (1) positive identification of the major compound responsible for the objectionable musty/earthy off-flavor in the clam, (2) development of quantitative method to compare the levels of the off-flavor compound in clam samples before and after relaying, and (3) identification of desirable characteristic clam volatile flavor components. The identification of the musty/earthy off-flavor of rangia clam was accomplished by using dynamic headspace sampling (DHS) coupled with high resolution gas chromatography/mass spectrometry (HRGC/MS) in selective ion monitoring (SIM) mode and HRGC aroma perception. Geosmin (trans-1,10-dimethyl-trans-9-decalol) was positively identified as a major compound responsible for this off-flavor based on gas chromatographic retention indices, electron ionization mass spectra, and odor characteristics with the authentic geosmin standard as the reference. The quantification of geosmin was achieved by vacuum distillation followed by solvent extraction using an internal standard and multiple-level standard addition method in HRGC/SIM mass spectrometry. The concentrations of geosmin in dredged and 2-week relayed rangia clam samples in different seasons of the year were determined and compared. The volatile flavor components of rangia clam were extracted by dynamic headspace sampling (DHS) and simultaneous distillation and extraction (SDE). Twenty-two heterocyclic compounds were identified. The unique clam aromas were contributed by a combination of the heterocyclic sulfur- and nitrogen- containing compounds and ketones. Volatile flavor compounds in other chemical classes such as aldehydes, ketones, alcohols, and terpenes were also detected. Most of these volatile flavor components were identified in the rangia clam for the first time. These studies were the first series of comprehensive analytical flavor investigations on rangia clam. The information generated from this research may facilitate further research and development efforts leading to the ultimate commercialization of this abundant seafood source in the Gulf Coast. This information may also enhance current and future flavor research on other seafoods.

Pages

109

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