Study On The Quality Change In The Processing Of Pitaya Juice And Its Functional Activity

In this experiment,the effect of enzymolysis conditions on betacyanin content and juice yield were studied by using red pitaya as raw materials,and the optimum clarification process of pitaya enzyme solution is obtained.Principal component analysis was used to study the quality change of pitaya concentrated juice during processing and compare the effects of three concentration methods on the quality of pitaya concentrated juice.The effect of various factors on betacyanin in pitaya and concentrated juice was studied,and its influence mechanism was preliminarily explored and the biological functional activity of pitaya juice was evaluated.The main results are as follows:?1?The effects of enzyme concentration,enzymolysis time,enzymolysis temperature and substrate pH all affect the content of betacyanin in the juice after enzymatic hydrolysis.The retention rate of betacyanin in red pitaya juice could reach 80.8%,the juice yield could reach to 64.4%and the juice transmittance was 89.5%respectively when the enzyme concentration was 285 U/g,the substrate pH was 3.7,and the enzymolysis temperature at46?for 2 h.The pitaya juice obtained under the condition of enzymatic hydrolysis had higher betacyanin retention rate,and also had higher juice yield and clarity.?2?After different processing unit,the total color difference??E?,fructose content,glucose content,vitamin C content and betacyanin content of pitaya juice were lower than those of fresh squeezed pitaya juice,during the processing of pitaya concentrated juice.The polyphenol content and DPPH·clearance rates increased significantly after enzymatic hydrolysis,but after inactivating the enzyme and concentrating,the polyphenol content and DPPH·clearance rate showed a downward trend.The results of principal component analysis showed that the quality of fruit juice decreased during the process of processing.In the three concentrating methods,the synthetic score of the concentrated juice obtained by heating was the lowest,which was-0.798,and the comprehensive score of the juice sample obtained by the freeze concentration was 0.135 and the quality was the best.?3?The stability of betacyanin was poor under the condition of heating,the retention rate of betacyanin was only 12.85%after 240 min heat preservation at 85?.The stability of betacyanin in pitaya juice reaches the highest at pH 4-5.Na⁺?K⁺and Mg²⁺had little effect on the stability of betacyanin in pitaya juice,and the addition of Fe³⁺and Cu²⁺will lead to the instability of betacyanin in pitaya juice.Ascorbic acid,D-isoascorbic acid,EDTA-2Na had a good protective effect on betacyanin in pitaya juice.?4?Seven kinds of betacyanin were identified in pitaya juice,various factors had different effect on the stability of each betacyanin.Isobetanidin-5-0-?-glucoside showed higher thermal stability than Betanidin-5-0-?-glucoside,Isophyllocactin showed higher thermostability than phyllocactin;overacid or over alkaline reduced the stability of.betacyanin in pitaya juice.After the addition of Fe³⁺and Cu²⁺,the 17-decarboxy-isobetanin component could not be detected,and the stability of other betacyanin showed a significant decrease.Ascorbic acid can increase the stability of various betacyanin in pitaya juice,especially 17-decarboxy-betanin,17-decarboxy-isobetanin and Isophyllocactin.EDTA-2Na had no significant effect on the stability of Betanidin-5-0-?-glucoside?p>0.05?,but it increased the stability of Isobetanidin-5-0-?-glucoside,17-decarboxy-isobetanin,and17-decarboxy-isophyllocactin.?5?In the process of simulated digestion,the maximum release of polyphenols reached the highest concentration of 550.62 mg/L at 2 h in peptic digestion,but the content of polyphenols decreased gradually during intestinal digestion,and the polyphenol content was only 359.17 mg/L after intestinal digestion of 4 h.The betacyanin can be well preserved in peptic digestion,but the loss rate of betacyanin in intestinal digestion process is large,reached to 65.34%in 4 h,and the loss rate of different betacyanin is also different.The antioxidant activity of pitaya juice reached the highest level at 0.5 h in peptic digestion,and the clearance rate of ABTS·⁺was 81.86%.However,the antioxidant activity of pitaya juice decreased continuously during intestinal digestion.The effect of pitaya juice on the proliferation of lactic acid bacteria showed that the pitaya juice had a good effect on the proliferation of Lactobacillus acidophilus and Leuconostoc mesenteroides.