| Wheat and flour were the core starch raw materials of soy sauce production, which had animportant impact on both color and flavor. At present, the industry’s need for raw starchroasting existed a considerable controvery. With a view of the roasted starch materialprocessing could improve the quality of soy sauce and enhance the flavor, there was still aview on the roasted starch material quality was less affected. In this paper, wheat and flourwere chosen as raw starch materials to investigate the effect of roasting on soy saucekoji-making, fermentation and flavor, in order to provide the theoretical guidance forhigh-quality soy sauce.The effects of roasting time on the quality of wheat and flour were studied. The increasetrends in gelatinization degree and color were observed with the prolonging of roasting time,on the contrary, moisture content gradually decreased. The moisture content had a significantnegative correlation to the degree of Wheat swelling while positive correlation to the degreeof flour swelling. Roasted for20minutes, the gelatinization degrees of wheat and flour wereup to40.33%and38.82%respectively, and the moisture were2.72%and1.67%separately.As higher temperature could accelerate the hydrolysis of the koji, the percent conversion oftotal suger and protein’s recovery rate in enzymatic hydrolysate increased first and thendecreased as the roasting time went by, and the indexes reached the maximum at20minutes.According to the comprehensive evaluation, roasting for20minutes was choosed.This study was about effect of the wheat and flour to preprocess roasting on enzymeactivities, physicochemical indexes and microbial community composition in koji-makingperiod. That is, the activities of protease, aminopeptidase and cellulose enzyme, spore andNSI of koji gained from roasted wheat increased by13.06%,12.58%,9.92%,37.04%and10.46%, respectively when compared with that from original wheat. As to the activities ofprotease, aminopeptidase, cellulose enzyme, spore and NSI of koji gained from roasted flour,indicators aforementioned respectively increased by32.88%,28.17%,18.07%,13.04%and10.79%. Dry matter loss kept pace with spore, as well as NSI and amino acid conversion rate.Both of bacteria and lactic acid bacteria communities fell by an order of magnitude. Androasting had the same impact on wheat and flour for kojis making. After fermentation, the total nitrogen content of soy sauces from roasted wheat and flourwere increased by6.54%,3.70%, and the content of amino acid nitrogen had an increase of8.33%,3.28%respectively. The total acid increased by5.14%,5.65%, and the color depthsubstances were increased by6.94%,11.85%accordingly. The roasting process couldaccelerate the releasing rate of the sugar and increase the red and yellow indexes during theearlier fermentation period, however, no significant enhance was found in reducing sugarcontent, red and yellow indexes after the end of the fermentation. The roasting pre-processingcould increase the contents of small molecular peptides during soy sauce fermentation.By GC-MS analysis, the four groups of soy sauce aroma were investigated. Roastedmaterial soy sauce had effect on the aroma substances content but the species is basically thesame. Acids were the most part in soy sauce, followed by aldehydes and ketones, alcohols andesters in wheat soy sauce. As for flour soy sauce, alcohols, esters and aldehydes and ketoneswere followed. The content of acids and esters was increased, espically for isoamyl acetate,octanoate and acetic acid, while the content of aldehydes and ketones was decreased, espicallyfor methyl butanal and benzaldehyde, but the content of phenylacetaldehyde (sweet),3-(methylthio)-propanal (cooked potato) was increased considerably, in the roasted wheat soysauce. While in the flour soy sauce, it was increased that the content of alcohol and esters,espically for ethanol and ethyl acetate, and the content of aldehydes and ketones was notchanged very much, while the content of acetic acid and acids was decreased. |
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