| Pingguo pear is mainly produced in Yanbian Prefecture,Jilin Province.It is nutritious,delicious,and contains a variety of trace elements.It has the functions of anti-inflammatory,cough relieving,dampness drying and spleen strengthening.Aronia melanocarpa is rich in polyphenols,flavonoids and anthocyanins.It has antioxidant,anti-inflammatory,anti-cancer,hypoglycemic and lipid-lowering,liver protection and other physiological functions,and has special curative effect on cardiovascular and cerebrovascular diseases.In this study,Pingguo pear and Aronia melanocarpa were used as raw materials to develop a compound juice.After heat treatment and ultra-high pressure sterilization,the quality and aroma components of the juice stored at different temperatures were compared and analyzed,and the effects of simulated gastrointestinal digestion in vitro on total phenolics and antioxidant activity were further explored.The main results are as follows:(1)The basic formula of pingguo pear and Aronia melanocarpa compound juice was optimized.The best color protection technology: citric acid concentration 0.6 g/L,D-sodium isoascorbate concentration 0.6 g /L,vitamin C concentration 0.6 g/L;the best basic formula: apple pear juice 82.93%,Sorbus mandshurica juice 15.00%,citric acid 0.07%,sugar 2.00%.(2)The effects of heat treatment(95?,10 min)and ultra-high pressure treatment(450 MPa,20 min)on physicochemical indexes,nutritional indexes and antioxidant capacity of fruit juice were studied under 4? and 25? storage conditions.The results showed that the ultra-high pressure and heat treatment could effectively kill the microorganisms in the juice,which made the juice to achieve the commercial aseptic state.There was no significant change in p H and soluble solid content during storage.After ultra-high pressure treatment,the contents of flavonoids,anthocyanins and total phenols decreased by 23.09%,29.11%,23.61% and 41.57%,39.54%,35.93%respectively at 4? and 25?.After heat treatment,the contents of flavonoids,anthocyanins and total phenols decreased by 33.18%,34.03%,27.91% and 45.82%,46.41%,41.18% respectively at 4? and 25?.The rates of DPPH,ABTS and Hydroxyl free radical scavenging capacity decreased from 93.40%,92.60% and 93.50% to 78.00%,74.93%,78.67% and 65.63%,61.40%and 71.27% respectively at 4? and 25? after ultra-high pressure treatment;the rates of DPPH,ABTS and Hydroxyl free radical scavenging capacity decreased from 89.43%,83.43% and 85.43%respectively at 4? and 25? after heat treatment 40% to 69.47%,63.40%,64.80% and 55.97%,51.97%,58.63% respectively.In conclusion,ultra-high pressure treatment combined with low temperature storage can better retain the nutritional components and antioxidant capacity of fruit juice.(3)Objective to explore the types and relative contents of volatile compounds in pingguo pear and Aronia melanocarpa compound juice during storage.The results showed that there were 21 kinds of aroma components in the first week after UHP treatment.At the 35 th day of storage,there were 16 kinds of aroma components at 4? and only 13 kinds at 25?.After ultra-high pressure sterilization,the relative content of aldehydes was relatively high,with 2-hexenal and n-hexanal accounting for the largest proportion respectively,and n-hexanal was relatively stable at 4?,but not detected after 14 days at 25?.The results showed that the relative content of esters was more stable at 4? than at 25? after ultra-high pressure sterilization.The results showed that ultrahigh pressure treatment combined with low temperature storage could better retain the aroma components of fruit juice,and the aroma components were more stable during storage.(4)The content of total phenols and antioxidant capacity of fruit juice changed during simulated gastrointestinal digestion in vitro.The results showed that pepsin and gastric acid environment promoted the release of total phenols to a certain extent,and the maximum value was1350.29 mg/L,which was 1.23 times of the initial value of 1100.23 mg/L The results showed that the free radical scavenging rate of DPPH increased from 31.92% to 34.07% in simulated gastric digestion acid environment,and decreased from 21.34% to 16.12% in simulated intestinal digestion stage;the free radical scavenging rate of ABTS decreased from 25.89% to 21.72% in simulated gastric digestion acid environment,and increased from 17.43% to 19.80% in simulated intestinal digestion stage,and then decreased to 18.12% in simulated gastric digestion acid environment The scavenging rate of hydroxyl radical decreased from 23.18% to 19.08%,and from16.53% to 14.97%. |
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