Studies on the Immobilized Fermentation Process and the Formation of Aroma Substances in Yellow Rice Wine

Saccharomyces cerevisiae was embedded in calcium alginate to produce immobilized yeast. The difference between physical and chemical indexes and aroma substances in yellow rice wine fermentation process between free yeast and immobilized yeast was investigated. The results showed that after primary fermentation 5 d (28℃), after fermentation 15 d (15℃), there was no significant difference in alcohol content, total sugar and total acid change curve between immobilized yeast and free fermentation process, indicating that fermentation performance of immobilized yeast was stable and the contamination of heteromyces was controlled. The characteristic aroma compounds of 9 kinds of rice wine, such as ethyl acetate, were analyzed by gas chromatography (GC), it was found that the total alcohol content of n-propanol, isobutanol, isoamyl alcohol and beta benzoyl alcohol in yellow wine with free fermentation was 680.91 mg/L, and the total higher alcohols content of the first to fifth batch of immobilized fermentation in yellow rice wine was 633.63, 649.79, 658.17, 637.63 mg/L and 614.68 mg/L. It was suggested that immobilized fermentation was beneficial to control the content of higher alcohols in yellow wine. And the total amount of esters in the fermentation products of immobilized yeast was higher than free yeast, with the increase of the number of immobilized yeast fermentation, the total amount of esters increased: The fifth (115.90 mg/L) > the fourth(90.81 mg/L) > the first to three batch of immobilized fermentation (80.10-81.81 mg/L) > free yeast fermentation(55.66 mg/L). It showed that immobilized fermentation made the aroma of ester of yellow wine stronger. According to the calculation of the aroma threshold, the aroma of the yellow wine obtained by the immobilized fermentation was no worse than the yellow wine produced by the free yeast. Therefore, the production of yellow wine by immobilized yeast has the prospect of commercial application. © 2020, Editorial Office of Journal of CIFST. All right reserved.