Screening,Identification,Performance Detection And Optimization Of Flavoring Conditions Of Zinc-rich Flavoring Yeast

Ester-producing yeast,also known as fragrant yeast or membrane-producing yeast,can produce a variety of aroma components after being metabolized,such as ethyl acetate,ethyl caproate and various alcohols,and its application research in the food industry has attracted increasing attention.Zinc is the second most essential trace element for animals and humans.It plays a key role in many biological processes.Zinc deficiency can lead to growth retardation,hyposexual function,cell-mediated immune dysfunction and cognitive impairment.Zinc-rich yeast(ZnY)produced by yeast fermentation is rich in protein,peptides and amino acids,and compared with inorganic zinc,it also has higher bioavailability and fewer side effects.However,few studies have been conducted on yeast that has both the ability to produce aroma and the ability to enrich zinc.Therefore,this research aims to screen out dual-function yeast that can produce aroma and rich in zinc,with a view to expanding the application of yeast in food,wine making,and health care.A zinc-rich selective medium was used to screen out zinc-tolerant aroma yeasts with strain growth density as the primary screening index and sensory evaluation as the re-screening index.Determine the zinc adsorption capacity of the strain and the influence of different concentrations of zinc on its growth state,and obtain a stable zinc-rich aroma yeast;By measuring the growth characteristics and performance of the strain,and comparing with the strain before enrichment,determine the research value of the strain in food,wine making and health care;Take the total amount of ester produced by the strain as an indicator,and optimize the aroma-producing conditions of the strain through the Plackett-Burman design combined with the orthogonal design experiment.The main results are as follows:1.Using strain growth density and sensory evaluation as screening indicators,a stable zinc-rich aroma yeast(Zinc-rich Aroma-producing yeast,ZnAY-5)was selected by measuring the zinc adsorption capacity of the target strain under different zinc concentrations and the influence on its growth status.The optimum amount of zinc in the culture medium was 300mg/L,and the zinc adsorption capacity of zinc-rich fragrant yeast ZnAY-5 was 338 mg/kg.2.Preliminary identification of ZnAY-5 morphological characteristics using WL nutrient medium,and molecular biology method to sequence its 5.8S-ITSr DNA,and compared it with the constructed phylogenetic tree to determine that the bacterium was abnormal Wickham Yeast.3.Through the determination of the growth characteristics of ZnAY-5,it was found that the optimum growth temperature,pH and glucose concentration of ZnAY-5 did not change significantly regardless of whether the strain cells were enriched in zinc,which were 32?,5?6 and 8%respectively;In addition,the maximum tolerance of ZnAY-5 to temperature,pH,ethanol concentration,Na Cl concentration,glucose concentration and SO₂ concentration has not changed,which were 40?,2,14%,8%,36%and 1200 mg/Lrespectively.However,the tolerance of zinc-rich yeast to ethanol was improved compared with that of non-zinc-rich yeast,from 10%to 14%.4.The determination of the fermentability of ZnAY-5 has shown that the best fermentation time for non-zinc-rich yeast and zinc-rich yeast was 1-4 days,and the efficiency was higher than other fragrant yeast;the ester-producing power and enzyme activity of zinc-rich yeast were respectively 1.59g/(L×(5log10CFU)/m L),139.39 mg/(g×100h),both of which were significantly higher than the ester-producing ability and enzyme activity of other fragrant yeast;the determination of its antioxidant capacity has shown that zinc-rich fermentation broth,bacteria and intracellular substances all had certain antioxidant power.When the zinc addition was 300 mg/L,the ZnAY-5 fermentation broth and the yeast itself had the highest antioxidant power.5.From the test results of the volatile components of the fermentation broth product of ZnAY-5,it can be seen that in the volatile components of the fermentation broth product under optimized conditions,the types of alcohols and esters were improved compared with the non-zinc-rich group and the zinc-rich group.The content of ethyl acetate was as high as92.772%of the detected volatile components.The optimization plan for ester production was:the best culture temperature was 32?,the best culture time was 144 h,and the best acetic acid addition amount was 0.2%.Under these conditions,the total amount of ester production was 1.633±0.0018 g/L.In summary,the tolerance and antioxidant capacity of zinc-rich ZnAY-5 strains to ethanol have been improved to a certain extent.Under the optimized conditions for ester production,the types and total amount of esters produced by zinc-rich ZnAY-5 have been improved.Therefore,zinc-rich aroma-producing yeast ZnAY-5 can not only be used as a nutritional improver,but also as an effective means to improve complex aroma.The above research results will provide data support and theoretical basis for its application in the food and wine industries.