Study On The Brewing Process,Antioxidant Activity And Aging Of The Non-astringent Persimmon Vinegar

With the living standards rising rapidly,people's demand for food quality and nutrition is higher and higher.As it's rich in vitamins,minerals,phenolics and dietary fibers,persimmon is ardently favored by consumers.Persimmon resources are abundant in China,but persimmon is mainly used as fresh eating at present,and the deep processing utilization rate is low,while the persimmon is highly perishable fruit and not resistant to storage.As a result,the problems which overproduction and lagging sales have become increasingly serious,and greatly economic losses.Non-astringent persimmon is used as raw material to produce persimmon vinegar,which can not only enrich the function beverage market,but also greatly improved the economic value of the non-astringent persimmon.Therefore,the non-astringent persimmon vinegar has broad application prospect.Luotian non-astringent persimmon is a high-quality raw material for brewing fruit vinegar,due to it has high sugar content,good nutritional qualities and little kernels that are easy to process.In this study,the non-astringent persimmon vinegar with unique flavor and rich nutrition was produced by using non-astringent persimmon as raw material and high-sugar broken rice wine instead of the traditional method of adding sugar.This paper conducts the systematic study of the fermentation of sweet broken rice wine,the non-astringent persimmon pulp process,the fermentation of alcohol and acetic acid and the clarification of vinegar,and the optimum process parameters of persimmon vinegar brewing were determined.In addition,the synergistic effect of ultrasound-assisted enzymolysis treatment on the extraction of juice was investigated.Besides,the antioxidant capacity of the non-astringent persimmon vinegar was explored.Furthermore,the change rules of the physical and chemical indicators,organic acids and volatility substances that in the aging of non-astringent persimmon vinegar were explored,and the mechanism of combined aging on improving the quality of the non-astringent persimmon vinegar was revealed.This work provides theoretical basis and practical reference for the production of persimmon vinegar.The main research contents and results are as follows:1. Broken rice wine was produced with broken rice as raw materials through traditional fermentation technology.The research showed that the best parameters for fermented sugar production of crushed rice liqueur are:the ratio of material to water 1:1,the fermentation time 3d,the amount of koji 0.8%,the fermentation temperature30?,and the highest sugar yield was 46.04%.Under the above conditions,the high-sugar broken rice wine:TSS was 22.17%,reducing sugar concentration was 249.70g/L,alcohol content was 1.57%vol,content of total acid was 6.51 g/L,and content of amino acid nitrogen was 2.33 g/100m L.2. Non-astringent persimmon juice was prepared by combining ultrasound and enzymatic pretreatment.Response surface optimization was used to optimize the process parameters of the juice,and the synergistic effect of this combined pretreatment on the extraction of juice was investigated.The results showed that the optimum conditions were pectinase concentration 0.03%,incubation temperature 51?and ultrasound time 22 min that contributed to the high yield and great clarity of persimmon juice was 81.64%and 90.83%,respectively.In addition,the quality characteristics illustrated that the combined pretreatment could significantly increase the yield and total phenolic content,and enhance the antioxidant activity in contrast to the single treatment.Additionally,the results of SEM indicated that ultrasound and enzymatic pretreatment had a synergistic effect which accelerated the cell structure collapse of persimmon tissues,improved the enzymatic hydrolysis efficiency and the dissolution rate of phenolic substances,and thus improved the quality of non-astringent persimmon juice.3. The persimmon vinegar alcohol and acetic acid fermentation process was optimized by orthogonal and response surface method,respectively.In the process of alcohol fermentation,the optimum parameters are as follows:the ratio of non-astringent persimmon fruit pulp,sweet broken rice wine and water 1:1:1?w:w:w?,fermentation time 4 d,fermentation temperature 28?,inoculation amount of yeast 0.1%and initial p H value 5,the highest alcohol content is 8.7%vol.In the process of acetic acid fermentation,the optimum parameters are as follows:initial alcoholic degree 7%vol,fermentation temperature 30?,inoculation amount of acetic acid bacteria 6%,initial p H value 5,the highest total acid content is 5.31 g/100m L.4. The clarification effects of gelatin,pectinase,chitosan and bentonite on persimmon vinegar were explored,and the antioxidant activity of non-astringent persimmon vinegar was studied.The results showed that the optimal composite ratio of gelatin and chitosan 1:0.8,which the addition of gelatin and chitosan was 0.05%and0.04%,respectively.Under the above conditions,the light transmittance could reach93.64%,and the final vinegar has good stability.In addition,the research showed that when the concentration was 50%,the hydroxyl radical scavenging rate of the non-astringent persimmon vinegar reached 90.17%,far higher than two commercial persimmon vinegar,and DPPH radical scavenging rate,ABST+·radical scavenging rate and Fe³⁺reducing capacity were between the two commercial persimmon vinegars,which showed good in vitro antioxidant activity.5. The effects of different ultrasound and microwave conditions on the physical and chemical indexes,total esters,color and sensory quality of the non-astringent persimmon vinegar were investigated.In addition,HPLC and SPME coupled with GC-MS techniques were used to analyze the organic acids and volatile substance in the non-astringent persimmon vinegar.The results showed that compared with untreated vinegar,the total ester content of the persimmon vinegar treated by ultrasonic combined with microwave increased by 10.70%,the score of sensory evaluation increased by30.61%,and the chroma value increased significantly.The research found that compared with untreated vinegar,the content of acetic acid of treated non-astringent persimmon vinegar reduced by 6.05%,and the content of non-volatile organic acid content was higher than untreated vinegar.Besides,it was found that,after treated by ultrasonic combined with microwave,the volatile substance of persimmon vinegar changed to varying degrees,the content of esters was significantly increased,the content of acids was significantly decreased,and the content of alcohols and aldehydes were no significantly change.Studies confirmed that after treated by ultrasonic combined with microwave,the ester aroma was enhanced,the pungent smell has weakened,and the flavor was more harmonious,which was in line with the natural aging trend.Therefore,the aging fuction of ultrasound combined with microwave treatment was identified,and it could be an alternative way to improve the quality of persimmon vinegar.