Fermentation Characteristics And Flavor Components Analysis Of Siraitia Grosvenorii Vinegar

Siraitia grosvenorii,a nutritious fruit also known as "Guang Guo Mu Bie",is a perennial vine of Cucurbitaceae mainly distributed in Guangdong and Guangxi,most plantation in Guilin,Guangxi.According to statistics,the annual output of Siraitia grosvenorii is as high as 100,000 tons in Guangxi,but Siraitia grosvenorii products are single at presents market.Fruit vinegar,a new type of healthy drink,are gradually favored in consumers due to its effect on beauty,fat reduction and weight lost.To promote the development and optimize the structure of Siraitia grosvenorii industry,while increase the variety in fruit vinegar processing industry,In this study,Siraitia grosvenorii was used as raw material to study the key parameters affecting the fermentation of Siraitia grosvenorii vinegar,and the changes of characteristic nutrients during the fermentation were analyzed.The main results are as follows:1.Screening of fermentation materials and microorganisms of Siraitia grosvenorii vinegar.The quality characteristics of fresh Siraitia grosvenorii fruit,high-temperature dried fruit and low-temperature dehydrated fruit were compared,It was found that the low temperature dehydration extract of Siraitia Grosvenorii could effectively preserve the sweet smell of Siraitia Grosvenorii,which had good taste and bright color.With the sensory and total acid evaluation as the index,the fermentation effects of Kluyveromyces marxianus,Saccharomyces cerevisiae,Gluconacetobacter xylinum,Acetobacter aceti,Gluconacetobacter hansenii,Lactobacillus casei,Lactobacillus plantarum and their mixed strains were analyzed and compared,it was found that the combination of Kluyveromyces marxianus and Gluconacetobacter hansenii had the best fermentation effect on the production of Siraitia grosvenorii vinegar.The total acid could reach24.17 g/kg in 15 days.2.Study on the key fermentation parameters of Siraitia grosvenorii vinegar.The acetic acid fermentation process was studied by using the sucrose concentration,the bacteria loading quantity,the fermentation temperature and the material-liquid ratio as influencing factors.Response Surface Methodology(RSM)was used to optimize the total acid content of fruit vinegar.The optimum fermentation conditions were as follows:1% of Kluyveromyces marxianus,1.80% of sucrose,7.20% of Gluconacetobacter hansenii,34.2 ℃,9.24% of material-liquid ratio.The total acid content of Siraitia grosvenorii vinegar was 22.45 g/kg.3.Analysis on the change rule of characteristic nutrients in the fermentation process of Siraitia grosvenorii vinegar.Through the analysis of the composition content in the process of fruit vinegar fermentation,it was found that Siraitia grosvenorii mogroside Ⅴ decreased from1555 μg/m L to 70.73 μg/m L in the alcohol fermentation stage,while slowly decreased in the acetic acid fermentation stage,from 70.73 μg/m L to 27.36 μg/m L.The results showed that Yeast and Acetobacter could promote the transformation of mogroside Ⅴ,but more obvious in Yeast.The content of total saponin decreased from 4.21 mg/m L to 2.14-2.99 mg/m L in 4 daysbefore fermentation,and remained s after 6 days of fermentation.The concentration of reducing sugar was 9.08 mg/m L before fermentation,but it decreased to 2.32 mg/m L after 2 days of alcohol fermentation,and don’t change a lot during acetic acid fermentation.4.The changes of flavor compounds of Siraitia grosvenorii in fermentation was explored by GC-IMS technology.There were 16 compounds before fermentation,including 1 ester,1organic acid,5 ketones,5 alcohols and 4 aldehydes.But 27 compounds were identified after fermentation,including 6 esters,2 organic acids,7 ketones,5 alcohols,3 aldehydes and 4 others.By comparative analysis of two-dimensional difference spectra,comparative analysis of peak intensity of volatile compounds and cluster analysis,the result showed that the volatile compounds increase significantly such as esters,organic acids,ketones,alcohols,etc giving a rise to the changes of aroma.5.Through single factor and orthogonal test,the best formula of Siraitia grosvenorii vinegar beverage was obtained as Siraitia grosvenorii vinegar 30%,Siraitia grosvenorii extract30%,Siraitia grosvenorii fresh fruit powder 0.02 g/100 m L.The results of test were accordance with NY/T2987-2016 green food fruit vinegar beverage standard in the sensory,physical,chemical and microbial indexes of the mixed fruit vinegar beverage.