Changes And Control On Sensory Quality Of Lactic Acid Bacteria Fermented Fruit And Vegetable Juices

Lactic acid bacteria fermented fruit and vegetable juice is one of the most popular probiotic drinks in recent years.In addition to its health value,its flavor change is also an important factor to attract consumers.The purpose of this paper is to study the characteristic of flavor quality.Lactobacillus plantarum,lactobacillus acidophilus and lactobacillus casei,which are commonly used in fermented fruit and vegetable juice,were selected in this paper.The ester aroma of apples and pears,fragrance of grapes and cucumber and olefin navel orange were as raw material.The effects of raw materials,strains and technological conditions on the flavor quality of different fruit and vegetable juices were explored by measuring the changes of various indexes before and after the fermentation of different strains,so as to provide a basis for the production of high-quality fermented fruit and vegetable juices and the directional change of flavor.The research results are as follows:(1)After the fermentation of 5 kinds of fruit and vegetable juice,the contents and kinds of volatile flavor substances increased,but the aldehydes decreased.The acidity and sweetness of the apple juice and pear juice were moderate after fermentation,and the typical aroma substances increased,highlighting the original fruity and floral aroma.In grape juice,a large number of aromatic alkanes were produced to increase aroma.The alcohol content of cucumber juice increased,which enhanced the wine flavor and pungent smell.The terpenes in orange juice reduced the fresh flavor and enhanced the fermentation flavor,and both cucumber juice and orange juice were too acidic after fermentation.After fermentation,the total amount of free amino acids decreased,and the increased flavor substances derived from aromatic amino acids and benzene reflected the correlation between free amino acids and volatile flavor substances in the fermentation process.(2)Compared with different strains,lactobacillus plantarum performs well and stably in the fermentation of fruit juice,adding alcohol and ester to enhance the aroma of fruits and flowers;The juice fermented by lactobacillus acidophilus has the strongest acidity,fermentation odor and pungent odor,and the difference with the original juice is the biggest.The number of viable bacteria and acidity are significantly higher when fermented in the juice with a lower initial pH value.Lactobacillus casei can achieve a low number of viable bacteria,the fermented juice volatile flavor substances change the least,pungent,vinegar,fermentation smell is the weakest,the aroma is soft and close to the original juice flavor,conducive to the olefin juice flavor.Both autochthonous and allochthonous lactobacillus plantarum have good metabolism in pear juice.The former has slightly better metabolism in pear juice,and tends to oxidize aldehydes into acids,while the latter tends to reduce aldehydes into alcohols.There is a synergistic effect between the two.(3)In the fermentation process of pear juice,lactobacillus plantarum mainly proliferates and metabolizes in the first 12 hours.After 12 hours,alcohol esters rapidly accumulate,giving strong floral and fruity flavor.After 24 hours,the continuous accumulation of alcohol substances enhances the wine flavor and reduces the floral and fruity flavor.The proliferation rate of bacteria with 2% inoculation was much faster than that with 4% inoculation,while the number of live bacteria in pear juice with 6% inoculation decreased after 6 hours of fermentation.The content of alcohol esters increased with the increase of inoculation,while the olefin substances decreased.The fermented pear juice with the inoculation amount of 4% had the highest pleasantness.The contents and types of flavor substances in pear juice after pasteurization and high pressure processing treatment were increased,and the aldehydes in pear juice after heat treatment were increased more,resulting in cooking taste.The high pressure pretreatment retained the flavor of the original fresh pear juice,and the olefins in the fermented pear juice were preserved better,which was more conducive to the preservation of the fresh flavor in the pear juice.