Date of Award

1998

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

First Advisor

Samuel P. Meyers

Abstract

Undersized processed crawfish are proposed to be a resource for effective recovery of crawfish flavors. Tail puree from undersized crawfish was hydrolyzed using protease APL-440 through response surface methodology to enrich flavor production. Optimal hydrolytic conditions were determined to be pH $8{\sim}9,\ 65\sp\circ$C, 0.3% (V/W) enzyme/substrate ratio with the reaction maintained at 33.3% puree concentration over 60 min period. Effects of storage time and extraction method on the crawfish flavor profile were evaluated. Shorter storage time gave superior flavor stocks with less oxidized flavors. The shelf-life of frozen crawfish puree was at least six months. Atmospheric simultaneous distillation-solvent extraction (A-SDE) is a more suitable technique than vacuum SDE for flavor analysis. Volatile crawfish aromas were characterized and compared by instrumental, olfactometric and statistical techniques. Gas chromatography/mass spectrometry allowed for identification of 120 aromas including 24 aldehydes, 25 ketones, 19 alcohols, 15 nitrogen-containing volatiles, 7 sulfur-containing volatiles, 24 aromatics, and 6 miscellaneous compounds. Among these, 38 major compounds were categorized into three flavor groups designated as metabolic, thermal, and oxidative flavor groups for comparison. Flavor profiles from four crawfish purees (i.e., crawfish tail puree (TP), crawfish whole-animal puree (WP), tail puree hydrolysate (TPH), and fructose-added tail puree (FTP)) were compared using TP as a control. WP showed a significant increase in oxidative volatile aromas and a significant decrease in metabolic flavor group, which was attributed to the inclusion of the crawfish head. TPH evidenced a significant increase of 46% in the total amount of flavors compared with that of TP. This was attributed to the increased water-soluble precursors released by enzymatic hydrolysis. Thus, TPH was considered to be the best potential material for crawfish flavor preparation. The significant increase of nutty flavors in FTP indicated the strengthened Maillard reaction with addition of fructose. Principal component analysis (PCA) confirmed flavor quantitative differences between WP, TP, TPH, and FTP. However, aroma extract dilution analysis (AEDA) indicated that the aforementioned four purees had similar flavor profiles for the majority of flavors, except for several aromas. Pyrazines, aldehydes, terpenic compounds and aromatic aromas were considered to be important in contributing to a typical crawfish flavor.

ISBN

9780591766578

Pages

184

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