| Fruit vinegar is a nutritious acidic beverage or seasoning produced through the process of alcohol fermentation and acetic acid fermentation,which has the nutritional and health functions of fruits and vinegar.Alcohol fermentation is an important step in producing high-quality fruit vinegar,and yeast,as the key strain in this step,is of great significance for the quality of fruit vinegar brewing.At present,the alcohol fermentation stage in fruit vinegar brewing mainly uses a single commercial brewing yeast for brewing,resulting in severe homogenization of fruit vinegar products and a single flavor.This article uses navel orange juice as raw material and uses a mixture of different brewing yeast and aroma producing yeast to produce navel orange fruit wine.Then,acetic acid bacteria are inoculated to prepare navel orange fruit vinegar.By measuring and evaluating the physical and chemical indicators,nutritional components,and volatile flavor substances of different brewing yeast and aroma producing yeast in producing fruit vinegar,suitable brewing yeast and aroma producing yeast for producing high-quality navel orange fruit vinegar are selected and applied to a fermentation tank for small-scale testing,Using total acid as the evaluation index,optimize the dissolved oxygen conditions during the acetic acid fermentation stage,and then compare with shake flask fermentation to explore the feasibility of two yeast strains in deep liquid fermentation.Finally,develop a navel orange fruit vinegar beverage through formula optimization.The main research findings are as follows:(1)Based on preliminary research in the laboratory,the fermentation performance of five strains of Saccharomyces cerevisiae with strong alcohol production capacity preserved in the laboratory was determined,and commercial yeast was used as a control.Two strains of Saccharomyces cerevisiae were selected and used for the actual production of navel orange fruit vinegar.By tracking the changes in physical and chemical indicators,total phenols,total flavonoids,and organic acids during the fermentation process,it was found that S cerevisiae NCUF 309.1 has the lowest residual sugar content(8.41 g/L),the highest utilization rate of sugar,and the strongest ethanol production ability(7.79%)in the actual production of navel orange fruit vinegar.Its brewed fruit vinegar has the highest total acid content(54.8 g/L)and the highest total flavonoid content(0.23 g/L);Meanwhile,using high-performance liquid chromatography(HPLC)to determine the content of six organic acids in each group of fruit vinegar samples,it was found that S cerevisiae NCUF309.1 brewed fruit vinegar has the highest acetic acid content,accounting for 82.4% of the total organic acids,and has the highest non-volatile acid content,making the vinegar have a smooth and mellow acidity.Therefore,S cerevisiae NCUF 309.1 for subsequent experiments.(2)Using three different aroma producing yeast strains,Torulaspora delbrueckii NCUF305.2,Pichia kudriavzevii NCUF302.2,and Wickerhamyces anomalus NCUF307.1,respectively,to produce aroma,they were compared with S.cerevisiae NCUF 309.1 mixed fermentation of navel orange fruit vinegar was conducted to investigate the relationship between different aroma producing yeast and S.cerevisiae.Effect of S.cerevisiae 309.1 mixed fermentation on the quality of navel orange vinegar.The results showed that compared with pure breed fermentation,the mixed fermentation of various aroma producing yeast and brewing yeast had stronger fermentation ability,with aroma producing yeast T delbrueckii and S.cerevisiae.The cerevisiae mixed fermentation group(ST)has the strongest fermentation ability and can consume reducing sugars faster to produce ethanol.W.anomalus and S.cerevisiae mixed fermentation group(SW)and ST group had the highest ethanol content(6.1%)in the wine samples.The total acid content of ST vinegar sample is 42.8 g/L,second only to SW(44.6 g/L).In addition,the mixed fermentation method will not change the trend of continuous increase in total phenol and total flavonoid content during the fermentation process.The ST fruit vinegar sample has the highest total phenol content(0.76 g/L),with a total flavonoid content of 0.30 g/L,second only to the SW vinegar sample(0.33 g/L).Moreover,the malic acid content in mixed bacterial fermented vinegar samples measured by HPLC was lower than that in pure seed fermentation,with ST vinegar samples having the lowest content(0.55 g/L),which can effectively weaken the green and astringent taste of fruit vinegar.Finally,the changes in volatile flavor compounds during the brewing process of navel orange fruit vinegar were measured and analyzed.It was found that the types and content of volatile flavor compounds showed a trend of first increasing and then decreasing throughout the entire fermentation process of fruit vinegar;Compared with pure strain fermentation with a single brewing yeast,the types of higher alcohols,acids,aldehydes,ketones,terpenes,and phenols in fruit vinegar of each mixed strain fermentation group increased.The ST and SP fruit vinegar samples have the highest types and content of volatile flavor compounds,both containing 41 volatile flavor compounds,an increase of 9 compared to the pure strain fermentation group of brewing yeast,and the aroma producing yeast The mixed fermentation of T.delbrueckii and P.kudriavzevii with S.cerevisiae 309.1increased ester content by 0.4 times,aldehyde and ketone content by 0.6 and 1.1 times,and terpene content by 3.3 and 4.4 times,respectively.Aromatherapy yeast W anomalus can effectively increase the content of flavor compounds,especially esters,aldehydes,ketones,and terpenes,in navel orange wine.(3)Add S.cerevisiae NCUF 309.1 and aroma producing yeast T.delbrueckii NCUF305.2 were applied to a fermentation tank for scale-up research,and the effect of different dissolved oxygen levels(DO)on the total acid during the acetic acid fermentation stage of fruit vinegar brewing was explored.It was found that under 15%DO conditions,the navel orange fruit vinegar had the fastest acid production rate,the highest total acid content(56.7 g/L),and the acetic acid conversion rate reached 95.0%.The organic acid content of navel orange fruit vinegar brewed under 15% DO conditions was determined by HPLC,and it was found that the mixed fermentation of S.cerevisiae NCUF 309.1 and aroma producing yeast T.delbrueckii NCUF305.2 is more conducive to the generation and accumulation of organic acids in fruit vinegar under deep liquid fermentation.Finally,the formula optimization of fruit vinegar was carried out,and it was determined that when the addition amounts of navel orange juice,raw fruit vinegar,xylitol,and baking soda were 35%,30%,8%,and 1.2%,respectively,the developed navel orange fruit vinegar beverage had a navel orange fruit and vinegar aroma,a soft taste,a sweet and sour taste,and a carbonated beverage with a refreshing aftertaste.After quality evaluation,the physicochemical and hygiene indicators of the developed navel orange fruit vinegar beverage meet the requirements of the fruit vinegar beverage standard. |
