Study On Preparation Of Blueberry Compound Juice And Its Quality Changes During Storage

Blueberries,raspberries,blackberries,cranberries,black chokeberries and lonicera edulis are berry resources with extremely high nutritional value and economic value,which are rich in nutrients,containing a great number of bioactive substances such as polyphenols,flavonoids,anthocyanins,which are assumed to have a good health benefit for anti-oxidation and anti-aging.However,due to the relatively difficult storage,they are often processed into deep-processed products such as fruit juice and jam.At present,the juice products on the market are relatively simple,and most of the sterilization processes are high-temperature thermal sterilization methods,which have a severe impact on the nutrition and taste of the products.Therefore,there is a broad prospect for the research and development of natural compound fruit juice based on non-thermal sterilization.In this research,six kinds of small berry juices were used as raw materials,and their quality indexes and sensory indexes were compared firstly in order to screen out three kinds of berry juices suitable for blending.Then carried out research on ingredient ratio and clarification process optimization of blueberry compound juice.Meanwhile,the effect of high-pressure process and pasteurization on the sterilization effects and quality of blueberry compound fruit juice were explored.Finally,the quality change of fruit juice at different storage temperatures was monitored and its shelf life was predicted.This berry comparative study provided a reference for consumers' fresh food intake and selection of raw materials for the berry industry,and also provided theoretical and technical support for the deep processing research of blueberry compound juice.The main research results were as follows:1.The properties of different kinds of small berry juices were quite different.Compared with the other four berry juices,the black chokeberry juice and lonicera edulis juice had higher contents in amino acid,polyphenols and stronger antioxidant activity as well as more aroma components and types.However,because of their bitterness,the sensory scores were relatively lower and the blueberry juice was the highest.Therefore,blueberry,black chokeberry,and lonicera edulis were finally selected as raw materials for the compound juice by principal component and cluster analysis.2.Based on the Mixture-D-optimal design method and the fuzzy mathematical sensory score as the response value,the optimal process formula of the blueberry compound juice was: in terms of volume fraction,blueberry juice 55.66%,red grape juice 24.34%,black chokeberry juice 10% and lonicera edulis juice 10%.The pectinase was used to clarify the blueberry compound juice and the optimal process parameters were: 0.08 g/100 m L(the added amount),45°C(enzymolysis temperature)and 90 min(enzymolysis time).The light transmittance of the juice can reach 90.1±0.20%.Compared with the untreated juice,it greatly improved the clarity and stability of the blueberry compound juice.3.The HPP+CH sterilization had better bactericidal effects than HPP and CH.The HPP+CH group sterilization parameters were pre-added with 0.5% chitosan,and then treated at 400 MPa for 5 minutes at room temperature.The pasteurization conditions were 90°C for 1 minute(HTST).The total number of colonies of blueberry compound juice were less than 10 CFU/m L and no mold and yeast were detected after two sterilization treatments.4.There were no significant differences in the p H value,total flavonoid content and DPPH antioxidant capacity of the blueberry compound juice treated with HPP+CH and HTST compared with the untreated juice.The contents of total phenol,anthocyanin,titratable acid and browning degree in the HPP+CH group all increased,and the content of soluble solids decreased slightly.The content of soluble solids,total phenol,and anthocyanin in the HTST group decreased slightly,and the degree of browning increased.The color difference ?E of the HPP+CH group was 1.47±0.19,which was not visible to the naked eye.The color difference ?E of the HTST group was 2.06±0.48 which was visible.The volatile component composition of the HPP+CH group was similar to the untreated one and the overall flavor changed little.Generally,HPP+CH treatment was more suitable for sterilization of blueberry compound juice than HTST,which made less processing damage to juice.5.During storage,the blueberry compound juice treated with HPP+CH and HTST can meet the hygienic standard of fruit and vegetable juice beverages at three storage temperatures of 4?,27? and 37?.The p H value and soluble solids content of juice treated by these two sterilization methods were relatively stable.As the storage time prolonged,the anthocyanin content,DPPH antioxidant activity and sensory score of the HPP+CH group were better than HTST group.Meanwhile,the degree of browning and color difference were lower than the HTST group.The higher the storage temperature,the faster the quality of these two juices deteriorated.Shelf life prediction test showed that the shelf life of blueberry compound juice after HPP+CH treatment was 225 days under storage at 4°C,and HTST group was 116 days.