Effect Of Post-treatment Process Of Raw Vinegar Fermentation On The Formation And Quality Of Vinegar Precipitation

China has a long history of vinegar,rich varieties,polymorphic craftsmanship,and rich flavors.Sichuan bran vinegar is a typical solid raw meal fermented vinegar.Due to incomplete decomposition of raw materials,improper processing technology,heavy metals and biological pollution during the vinegar brewing process,vinegar products are prone to precipitation and unstable quality.Therefore,in this paper,the amount and composition of vinegar precipitation and its components,microbial,physicochemical,and sensory indexes of vinegar liquid were measured in different treatment processes after fermentation of raw vinegar in Sichuan bran vinegar.The key link in the formation of precipitation,and at the same time explore the impact of each treatment process on the sensory flavor of vinegar,in order to provide data support and theoretical basis for the improvement of post-fermentation processing technology of bran vinegar,the reduction of precipitation and the improvement of flavor quality.The main results are as follows:1.The effect of raw vinegar post-treatment process on precipitation amount and conventional precipitation ingredientsThe amount of vinegar precipitation and conventional ingredients after different treatment procedures were measured.The results showed that the double-effect falling film,cooking,aging,sterilization and storage stages will promote the formation of precipitates.The amount of precipitation after membrane filtration and plate filtration is controlled,and the effect of membrane filtration is better than that of plate and frame filtration.The main components in the sediment are water,protein,sugar and starch.After double-effect falling film and cooking,the total sugar and pectin content in the precipitate have successively increased,and the contents of other ingredients have decreased;after entering the aging stage,all the ingredients in the precipitate have increased;plate and frame filtration and membrane filtration will The total sugar,starch and metal ion content in the precipitate are reduced.After pasteurization and storage,the total sugar,starch and pectin content in the precipitate are significantly increased.2.The effect of raw vinegar post-treatment process on the quality of vinegarThe microbes in the vinegar and the conventional physical and chemical indicators were measured after different treatment procedures.The results showed that the number of microbes in the raw vinegar was 10~6CFU/mL.No microbes were detected after cooking and pasteurization;there were two times in the plate filtration stage Pollution caused a slight increase in the number of microorganisms.With the progress of the process,the amount of sedimentation changed inversely with the number of microorganisms.It was preliminarily concluded that the precipitation formed during the treatment of raw vinegar fermentation was dominated by abiotic factors.The content of total acid and amino acid nitrogen in raw vinegar are at a low level,and the improvement of both is particularly obvious after the double-effect falling film;the total acid content after plate filtration is increased;the total acid and amino acid nitrogen are pasteurized.It has a certain destructive effect;after 60 days of storage,the content of amino acid nitrogen in the vinegar has decreased,and the total acid content has remained stable.Using solid-phase microextraction and gas chromatography-mass spectrometry to detect the volatile components in the sample vinegar,it was found that acetic acid and furfural were the most important volatile components in the vinegar after the fermentation process.After the raw vinegar became cooked vinegar,The types and contents of volatile acids and aldehydes increased significantly(mainly acetic acid and furfural),and the types and contents of volatile esters,phenols and alcohols decreased significantly;after aging vinegar,the content of acetic acid decreased significantly and the content of furfural Increased;after pasteurization,volatile acids decreased significantly,phenols and alcohols increased;after storage,acids increased,phenols and alcohols decreased.In terms of amino acid content,16 kinds of free amino acids were detected in the bran vinegar processed in different processes,glutamic acid and alanine are the most important amino acids in bran vinegar,The five amino acids glutamic acid,alanine,leucine,proline and valine account for 75%of the total amino acids;after the double-effect falling film,the content of different amino acids has increased;after being cooked at high temperature,except for cysteine,the remaining amino acids are destroyed to a certain extent or Decomposition;after plate filtration,the content of amino acids has increased and maintained at a high level.The overall analysis and evaluation of the vinegar after each process through the taste fingerprint analyzer and the sensory score showed that after cooking,the sensory score of color,aroma,taste and shape of the vinegar was significantly increased,which was significantly different from the raw vinegar taste;There is a significant difference between cooked vinegar after sterilization and storage for 60 days,the taste difference of vinegar in other processes is not significant,and the overall sensory evaluation of the sample after aging and membrane filtration is good.3.The effects of different sterilization conditions on vinegar precipitation and flavor qualityThe pasteurization and three high-temperature(ultra-high temperature)instantaneous sterilization vinegar samples were analyzed.The results showed that no microorganisms were detected in both sterilization methods.The precipitation amount was the least under 110?,30 s sterilization conditions.The contents of sugar,starch,tannin and pectin decrease with the increase of temperature,and the content of metal ions increase with the increase of temperature;with the increase of temperature,the total acid and amino acid nitrogen content increase slightly,in the condition of 138?,30 s,the content is lower than other temperatures;after 110?,30 s treatment and storage,the overall flavor change of the vinegar is the smallest,and the sensory evaluation is the highest.