Physicochemical and sensory properties of Skate(Raja kenogei) fermented with Bacillus subtilis under Sous-vide method.

Abstract

To reduce time of Skate (Raja kenojei) fermentation, we used Sous-vide method to make the fermented Skate at low temperature. Sous-vide is a cooking method in plastic pouches “under vacuum”. The objective of this study is to optimize the fermentation condition of Skate and to evaluate the sensory and physicochemical properties of fermented Skate. Briefly, the fresh Skate was inoculated with B. subtilis solution, and was fermented at 30°C in a water-bath for 30 h. Then the fermented Skate was quickly chilled by using blast chiller. And then, the physicochemical (pH, VBN, Electronic Nose, and texture profile) and sensory (oder, flavor, texture, and overall acceptance) properties of the fermented Skates were evaluated. pH of samples for the duration of Sous-vide cooking start from 6.59, increased from the initial stage, pH 8.96 in 20 hours, pH 9.24 in 30 hours. pH 9.18 of traditionally fermented Skate (40 day) shows the similar results as above. Volatile basic nitrogen (VBN), which works as an important quality factor for fermented Skate, started from 93.5mg/% before fermentation, 271.5mg/% in Skate fermented by Sous-vide method, 401.7mg/% in traditionally fermented Skate. Electronic nose test of samples for the duration of Sous-vide cooking is increased by 106KCt in 10 h, 6,361KCt in 20 h and 42,557KCt in 30 h, 8,478KCt in traditionally fermented Skate, respectively. The volatile compounds of Sous-vide Skate were profiled the same as the traditionally fermented Skate, but the intensities of the identical volatile compounds were different, showing the good agreement of VBN. There was no statistically significant differences in sensory properties between the traditional and Sous-vide Skate.