| Blackberry is a kind of berry with various health care functions.In recent years,with the strengthening of people’s health care awareness,blackberry and blackberry products have gradually attracted more attention,and the related research has also deepened.This paper aims to develop a low-alcohol blackberry wine,including strain screening,high-density culture,determination of fermentation process,clarification process,high power pulsed microwave sterilization process and product quality detection.The main results are as follows:1.In order to screen fermentation strains,the sugar,alcohol and SO2 tolerance of Saccharomyces cerevisiae(S.cerevisiae)FM-S-115,FY4 and Lmb-1 were tested,and the stress resistance of the three was preliminarily cleared.Then,they were inoculated into blackberry juice for fermentation,physical and chemical indexes and sensory scores were measured.A strain of low-alcohol blackberry wine was screened out by comparison with RHTYHM(JM),a commercial S.cerevisiae from Hansen Company of Denmark.Results showed that strain FM-S-115 had good resistance and fermenting property,and the blackberry wine fermented by whom had high quality.Compared with JM,fermentation time of strain FM-S-115 was shortened by two days.2.In order to increase cell density of S.cerevisiae FM-S-115,single factor experiments were carried out on seven conditions to determine three most significant factors,including carbon source and content,nitrogen source and content,temperature,pH and inoculum size.Next,orthogonal experiments were designed and combined with microencapsulation method to culture FM-S-115.Results showed that single factor temperature,pH and carbon source content had the greatest influence on cell density,and the optimum culture condition was sucrose with 16%,30℃ and pH4.5.Under this circumstances,the total number of colonies was 1.79×108 CFU/mL,which is 1.75 times of 1.02×108 CFU/mL under normal culture condition.FM-S-115 in microencapsulation cultured four generations under the optimal conditions for static,the total number of colonies was 8.10×108 CFU/g,which was 7.94 times that of normal culture and 4.53 times that of culture under the optimal condition.Cell density was greatly improved.3.Strain FM-S-115 was inoculated into blackberry juice for fermentation.In order to determine the fermentation time and process,six parameters including residual sugar content,total phenol content,anthocyanin content,tannin content,color difference and alcohol content were tested as indicators in the whole process.Results showed that the process took 8 days.During that period,residual sugar content gradually decreased to a stable level,total phenol,anthocyanin and tannin content showed a trend of increasing first and then decreasing,color difference and alcohol content both increased first and stabilized later.4.To optimize the fermentation conditions of low-alcohol blackberry wine,three factors of sugar content,inoculum amount and fermentation temperature were used to design single factor and orthogonal experiment.Physical and chemical properties and sensory quality were taken as comprehensive evaluation indexes to achieve purpose.Results showed that 10.0%sugar,7.0%inoculum at 18℃were the best fermentation condition.Under these conditions,the fermented blackberry wine had harmonious taste,bright color and appropriate alcohol content.5.To clarify blackberry wine,the usage amount of PVPP and HACC compound clarifiers,clarification time and temperature were taken as factors to design single factor and orthogonal experiment,and the changes of physical and chemical indexes and thermal stability before and after clarification were detected to determine the wine quality.Results showed that blackberry wine had the best clarifying effect and highest sensory quality as PVPP and HACC with mass concentration of 0.33 g/L and 0.55 g/L mixed at 20 for 48 h.There was no significant change in residual sugar,alcohol and total acid content before and after clarification,but the contents of protein,total phenol,anthocyanin,tannin and soluble solids decreased significantly.And,the thermal stability was obviously increased after clarified.6.High-power pulsed microwave sterilizer was used to sterilize clarified blackberry wine.The response surface optimization experiments were designed based on three factors of fruit wine initial temperature,pulse frequency and time.Through analysis of 17 groups’results by software,the optimal sterilization process was as follows:initial temperature 45℃ pulse frequency 250 Hz in 9 minutes.Under these conditions,the bacterial colony count of blackberry wine was less than 10 CFU/mL,which met the hygienic standard.To verify the sterilization effect,blackberry wine indexes before and after pulse microwave sterilization were tested compared with pasteurization.The results showed that thermosensitive substances and some active substances in blackberry wine with high-power pulsed microwave sterilized were well preserved without significant decrease,which indicated that this sterilization method was of great significance to maintain thermosensitive components in blackberry wine. |
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