Study Of Lactic Acid Bacteria On The Main Material Changes In Fermented Yak Meat Sausage

Yak meat is a nutritional animal foodstuff.The problems of long processing time,lipid oxidation,instable flavor components,and poisonous or harmful substances seriously influenced the consumption and economic value of traditional fermented meat.Research indicates that lactic acid bacteria can obviously reduce the processing time and improve fermented product quality.Currently,the applications and effects of lactic acid bacteria and its combinations on the changes of main substances in the fermented yak meat sausage have not been reported.In this study,yak lean meat was used for sausage preparations,and Lactobacillus sake(L.s),Lactobacillus plantarum(L.p),Pediococcus pentosaceus(P.p)and their combined treatments were inoculated artificially.Physico-chemical properties and sensory characteristics were evaluated,using headspace solid-phase microextraction and gas chromatography mass spectrometry(HS-SPME/GC-MS),electrophoresis(SDS-PAGE),reversed phase high performance liquid chromatography(RP-HPLC)technologys or methods,to explore the changes of major substances in the fermented yak meat sausages.The research contents and results were summarized as follows: 1.The physico-chemical indexes(pH value,protein degradation and the generation of peptides,lipid oxidation,volatile flavor components)and sensory evaluation were studied in the fermented yak meat sausage.The results showed that there were no significant differences among the treatments in sensory basis.The pH value showed a decline trend.However,they did not show any significant changes before 40 h during the fermentation.It declined faster than the blank control after 40 h.The pH value of L.s+P.p decreased faster than their single bacteria fermentation.Effects of different lactic acid bacteria on lipid oxidation in the fermented yak meat sausage were significantly different(P<0.5).TBA value of L.s was the lowest(0.202 mg/100g).At extraction temperature 40?,60?,or 80?,the relative content of volatile flavour components was 55.72%,55.72%,or 92.19%,and detected 4,20,or 31 kinds of flavor components,respectively.The optimal temperature for detection of flavor components of yak meat sausage was between 60?~80?.The relative contents of alcohols,ketones,aldehyde s in L.s+L.p samples were higher,which proved it a good starter.The fermented yak meat sausages produced a lot of peptides with strong polarity,and were soluble in water.The effect of P.p on the generation of polarity peptide in fermented yak meat sausage was larger than L.s or L.p.In the degradation of whole muscle proteins,L.s combined with P.p showed a strong degradative activity for large molecular protein;L.p or P.p showed much effective in the degradation of sarcoplasmic protein,and their degradation effects were stronger than L.s.The results showed that the degradation effects of lactic acid bacteria on myofibrillar protein of yak meat sausage were weak.2.Changes of major substances in the yak meat sausage fermented lactic acid bacteria were studied in the constant temperature fermentation and natural air dry fermentation,including sensory evaluation,pH value,protein degradation and the generation of peptides,biogenic amines,lipid oxidation,volatile flavor components.The results showed that sensory differences among the treatments were not significant in the constant temperature fermentation.At 12~32 d,the sensory quality of yak meat sausage fermented L.s + P.p,L.p + P.p were relatively optimal.The pH values of all samples were falling fastly in the constant temperature fermentation,and reached a stable value in the natural fermentation.Lactic acid bacteria and fermentation time had a great influence on TBA value of yak meat sausage.During the fermentation,TBA values of L.s + L.p were relatively smaller.Different effects of the strains in the kinds and contents of flavor components were showed in the yak meat sausages.Synergistic effects of coccus with bacillus were better than that of two kinds of bacillus,among combination effect of L.s and L.p was better.Effects of different lactic acid bacteria on the peptide content in the yak meat sausage were significant(P<0.01).The peptide content of L.p was the largest(1.83×105 mAU·s).Fermented yak meat sausages were detected ?-phenethylamine,putrescine,spermine,tyramine and tryptamine,cadaverine and spermine,histamine.However single biogenic amine and their total did not exceed the reported limits.In this study,putrescine was detected between 0~17.28 mg/kg(detection rate 96.67%)and cadaverine was detected between 0~286.86 mg/kg.As the extension of fermentation time,protein distribution changed vastly,and large molecules protein(between 150 ~ 250 kDa)showed a considerable degradation.3.Physico-chemical indexes(including total number of colonies,protein degradation,lipid oxidation,volatile flavor components)and sensory evaluation were researched in the yak meat sausage fermented by Lactobacillus sake(L.s)and Pediococcus pentosaceus(P.p).The results showed that sensory differences of all samples were smaller in the constant temperature fermentation.At 12~32 d,color,structure,flavor and appearance quality of trehalose and glucose samples were better,which were easy to be cut and not loose.As the extension of fermentation time,TBA values of yak meat sausage on the whole increased gradually(P<0.5).At 2 d,TBA value of glucose sausage was the minimum(0.056 mg/kg).At 12~32 d,TBA values of glucose and trehalose sausages were relatively low.During the fermentation,the total number of colonies increased firstly and then reduced(P<0.5).At the end of fermentation,total number of colonies of trehalose sausage was the highest(7.14 lg(CFU/g)).In this study,69 kinds of volatile flavor components(35 kinds at 2 d,48 kinds at 32 d)was detected in the yak meat sausage,including 22 kinds of aldehydes,11 kinds of alcohols,11 kinds of ketones,8 kinds of hydrocarbons mainly.At 22~32 d,aldehyde kinds of trehalose was the maximum.During fermentation,protein degradation was enhanced by trehalose and glucose greatly.The results of this study suggested that when Lactobacillus sake(L.s)and Pediococcus pentosaceus(P.p)(1:1)strains used as starter cultures and trehalose served as carbon source,fermented yak sausage with optimal quality and best flavor could be obtained.This is the first time to use Lactobacillus sake(L.s),Lactobacillus plantarum(L.p),Pediococcus pentosaceus(P.p)and their combinations to investigate the changes of the major substances in the fermented yak meat sausage.The results provide a scientifically theoretical basis and reference for choosing lactic acid bacteria and carbon source in preparation of yak meat sausage,developing novel lactobacillus products,and ensuring the quality and safety of yak meat sausage.It also has great significance for promoting scientific production and industrial management,and for enriching the market of yak meat products.