Screening Of Dominant Acetic Acid Bacteria In RAW Material Vinegar And Acid-production Characteristics

Vinegar has a long brewing history.It has a fragrant taste,rich nutrition,and has bactericidal and blood pressure-lowering effects.The raw material vinegar that appeared in Changzhi City,Shanxi Province.The main difference from traditional vinegar is that the raw materials do not need to be cooked,and they are directly added to the fermentation agent to ferment,more types of microorganisms,more mellow and taste.Because it can save a lot of labor and cooking equipment,more and more vinegar factories are now paying attention.Because starchy raw materials have not been subjected to high temperature and gelatinization is difficult,most factories have problems such as low vinegar production rate.At present,the research on the screening of dominant vinegar strains is relatively blank at home and abroad,and there are relatively few reports on its acid production performance.In this paper,the dominant acetic acid bacteria were screened from raw meal vinegar and their fermentation characteristics were studied,which provided a theoretical basis for quality control of vinegar and factory practice.This article includes three aspects of research: First,the acetic acid bacteria were isolated and purified from raw material vinegar.The superior acetic acid bacteria were screened by observing their tolerance to temperature,peroxidation,and acid production,and their classification status was determined after morphological observation and biological identification;Secondly,acetic acid?ethanol content,and carbon source species were changed,the effects of these variables on the organic acid production characteristics of the strains were observed;Finally,initial acetic acid amount,initial ethanol amount,and inoculation amount were optimized,and the differences of the organic acid between before optimized and after optimization were analyzed.The experimental results are as follows:5 strains of acetic acid bacteria were isolated and purified from raw material vinegar,and identify them as Acetobacter pasteurianus through morphology and biological identification.By observing the temperature tolerance(28,37,42,47,52 ?),peroxidation(cultured to 15 d),and acid production characteristics,A.pasteurianus L4 were screened which has a high temperature resistance of 52 ?,less peroxidation,and higher types and contents of organic acids.By plotting the growth curve and the acid production curve of A.pasteurianus L4,it was concluded the biomass of strain L4 reached a maximum of 2.0 × 108 CFU/mL at 16 h;detected five organic acids,fermented to 118 h,and the contents of lactic acid and acetic acid increased from 0.60,0.70 mg/mL to 2.1,1.8 mg/mL.They are the main acids in vinegar.And the other three acids are maintained at 0.004~0.012?0.08~0.11?0.04~0.31 mg/mL,which mainly play a role in reconciling the taste.Five organic acids together form the flavor body of vinegar.Different types of carbon sources and different contents of acetic acid and ethanol were added to the culture medium,the results showed that when the added carbon source was glucose,five organic acids could be detected(oxalic acid,lactic acid,acetic acid,citric acid,and succinic acid),and the highest content is 0.02?4.19?4.81?0.19?0.33 mg/mL;when acetic acid content is 5%,four organic acids could be detected(oxalic acid,lactic acid,acetic acid,and citric acid),and the content is 0.01?3.12?2.21,0.11 mg/mL;when the content of ethanol is 5%,the four organic acids of oxalic acid,lactic acid,acetic acid,and citric acid are 0.02?4.77?2.71,and 0.13 mg/mL.The fermentation conditions of A.pasteurianus was optimize by initial acetic acid amount,initial ethanol amount,and inoculation amount.The single factor experiment showed that the 5th day of fermentation had the highest total acid content.The optimal initial acetic acid amount,initial ethanol amount,and inoculation amount were 2%,4%,and 4%.The response surface method analysis showed that the optimal conditions were that the initial amount of acetic acid and ethanol were 2% and 4.5%,and the inoculation amount of acetic acid bacteria was 4%.At this time,the total acid could reach 48.65 mg/mL.The fermentation conditions before optimization were 0% initial acetic acid amount,4% initial ethanol amount,and 2% inoculation amount.The organic acid content was detected in the two fermentation broths before and after the optimization.The organic acid with a significantly increased content after the optimization was acetic acid,which was an increase of 29.65 mg/mL compared with before optimization.It is the main taste substance in vinegar.The lactic acid production increased slightly,from 1.75 mg/mL to 2.80 mg/mL.There was no significant change in oxalic acid,citric acid,and succinic acid production,which respectively were 0.08?0.17?and 0.47 mg/mL.