Application of Concentrated Freeze-Dried Starter in Fermented Duck Sausage

A concentrated freeze-dried starter was used in fermented duck sausage and the effects of liquid starter and natural fermentation applied in the sausage fermentation process were compared. The results showed that the pH value of sausage inoculated with the freeze-dried starter decreased to 5.3 at 48 h, suggesting that the fermentation process can produce much more acids, allowing to rapidly reach the pH range within which the safety of the fermented sausage can be easily controlled. Meanwhile, the water content showed a decreasing trend and was reduced to 30% at the end of fermentation. Texture properties of duck sausages with different treatments were analyzed. The hardness, springiness and chewiness of duck sausages inoculated with freeze-dried starter or liquid starter were individually much higher than those of the natural fermentation(control check, CK). During the fermentation process, acid value(AV) showed an increasing tendency. Peroxide value(POV) increased first and then decreased, and the treatment groups differed in POV but the difference was not significant. This suggests that the effect of endogenous lipase is much greater than that of lipase from microbial starters. Various types of fatty acids from all the treatments showed the decreasing order: saturated monounsaturated polyunsaturated, and the total free fatty acid(FFA) content of duck sausages inoculated with freeze-dried starter was significantly higher than that of control group. These results indicate that inoculated starters can increase the release of FFAs, promoting more flavor precursors to a certain extent.