Process Optimization and Flavor Composition Analysis of Seriola lalandi Roe by Yeast Fermentation

To explore the effects of yeast fermentation on deodorization and flavor enhancement of Seriola lalandi roe, the nutritional value of Seriola lalandi roe were studied in this paper at first, and then high sugar type instant dry yeast was selected as the fermenting agent, the optimal fermentation process conditions were optimized by single-factor experimental analysis according to the sensory score, pH and total acid content. Fresh fish roe and unfermented fish roe were used as controls to analyze the difference in sensory quality, free amino acids and volatile flavor composition of the fermented fish roe. The results showed that, the Seriola lalandi roe was rich in polyunsaturated fatty acids, zinc and selenium elements, and had high nutritional value. The best deodorization effect by 1.5% yeast inoculum, 5% sucrose addition, 1.5 h fermentation time and 28 ℃ fermentation temperature. The contents of sweet amino acids and umami amino acids in fermented roe increased significantly（P<0.05）, and the sum of TAV values was greater than that of bitter amino acids, indicating that the bitter taste of the fish roe was masked after yeast fermentation. A total of 81 volatile compounds were detected in the three fish roe samples, and the types and contents of volatile compounds in fish roe increased after yeast fermentation. The main volatile compounds in fresh and unfermented fish roe were aldehydes such as heptanal, nonanal and (E,E)-2,4-heptadiena. 1-octen-3-ol and (E,E)-2,4-heptadiena with fishy smell were higher relative contents. Yeast fermented fish roe were rich in esters such as ethyl octanoate and ethyl decanoate, while the relative content of fishy substances was significantly lower (P<0.05). According to the relative odor activity values (ROAV), the flavor active components of yeast fermented fish roe were (E,Z)-2,6-nonadienal, (E,E)-2,4-decadienal, phenylethanol, 1-octen-3-ol and 3-methylthiopropanol, and the ROAV of 1-octen-3-ol producing fishy odor decreased significantly. After fermentation, phenylethanol and 3-methylthiopropanol were added as the key flavor compounds, which provided the rose flower, sweet and meat aroma. In summary, yeast fermentation played a role in eliminating fishy smell and produced pleasant aromatic flavor.