61B-17 |
Volatile components in deep-fat fried chaw tofu |
H. M. CHEUNG, Biology Department, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China and H. Y. Chung, Biology Dept., Food and Nutritional Sci. Programme, and Food Sci. Lab., The Chinese University of Hong Kong, Shatin, New Terrritories, Hong Kong SAR, China. Chaw tofu, also known as stinky tofu, is a traditional Chinese snack. It is well known for its typical stinky smell and interesting texture. To prepare chaw tofu, vegetables are soaked in brine solution for some time. Then fresh tofu is introduced and soaked in the same broth until the stinky smell develops. This stinky flavor and other thermally generated aromatic compounds vaporize during deep-fat frying to produce the typical odor of chaw tofu. Nevertheless, volatile components remain in the fried products, and their relative potencies have not been documented. The objectives of this study were to identify and quantify the volatile components of commercial chaw tofu after a deep-fat frying operation. Chaw tofu samples were purchased from food stalls in Hong Kong. Samples were then deep-fat fried and transferred to a closed glass system for equilibration before its headspace was withdrawn with a gas-tight syringe. The headspace was immediately injected into a gas chromatography/mass spectrometry (GC/MS) for analysis. Both qualification and quantification of compounds were carried out by utilization of the standard compounds and the standard curves. Aroma values of the identified compounds were calculated based on the published threshold values. Twenty-one compounds were found. Aldehydes (9) were the major chemical class in which the saturated (8) compounds dominated. Only one unsaturated aldehyde was found. Other classes included alcohols (5), acids (4), furans (2) and ketone (1). The aroma values of decanal, 1-butanol, pentanoic acid and hexanoic acid were among the highest. They generally possess unpleasant, medicinal, putrid, fecal and rancid odor. With the identities of the headspace components known and the aroma values found, important components can serve as markers in quality control when mass production of the product is carried out.
Session 61B, Food Chemistry: Flavor and aroma chemistry
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