Screening Yeast From Traditional Xuanwei Ham And Its Effect On Fermented Sausage Quality

Microorganisms play an important role in the maturation of traditional fermented meat products in China.Fermented and cured meat products can be used as a source of strains for screening excellent fermentation agents.In this study,yeasts on the surface of Xuanwei ham,a traditional fermented meat product in China,were isolated,purified,identified and preliminarily applied to sausages.A total of 113 strains of yeasts were screened from the surface of Xuanwei ham,and 48 strains of yeasts were isolated and purified by selective medium YPD(chloramphenicol).Using enzyme production,acid production,environmental tolerance and salt tolerance as the main screening indicators,a single strain with excellent fermentation performance was obtained.Molecular biological identification was carried out on the two selected yeasts.It was finally determined that the two selected yeasts were Debaryomyces Hansenii,named Y61 and Y67,respectively.Pure strain fermentation experiment was carried out for screening strains,and preliminary application in fermented sausage was carried out.The results showed that:(1)Sausage added with starter significantly affected the physical and chemical properties,product quality,appearance characteristics and sensory evaluation of sausage during 0-15 days of fermentation.Compared with the control group,inoculation of yeast starter Y61 and Y67 could significantly reduce the water content(14.02% and 8.37%),water activity(6.17%and 8.64%),TBARS(37.93% and 28.05%)and nitrite residues(14.20% and 3.55%)of sausages,and significantly increase the brightness value L* and redness value a*.(2)Compared with the control group,the two yeast inoculation groups effectively improved the degradation of protein and fat in fermented sausage,and accelerated the maturation process of sausage.The total free amino acids(11.97% and 17.82%)and essential amino acids(36.63% and 31.30%)of fermented sausage were significantly increased after inoculation with yeast Y61 and Y67.(3)The introduction of yeast starter promoted the formation of sausage flavor substances.A total of 64 volatile compounds were detected,including aldehydes,alcohols,ketones,esters,acids,alkanes,heterocyclic compounds and nitrogen compounds.26 volatile compounds were detected in the control group and 53 volatile compounds were detected in the inoculation group.Compared with the control group,the inoculation of yeast starter significantly increased the contents of acids(44.88% and 38.08%)and esters(87.14% and 83.31%)in sausage,which made sausage have characteristic fermentation flavor.Sensory evaluation results showed that the sausage flavor and overall acceptability were significantly improved by inoculating two kinds of yeast.