Changes Of Phenolics And Antioxidant Activity Of Navel Orange Whole Fruit Cloudy Juice

Citrus contains a large amount of nutrients and biologically active substances,which have important nutritional,health and medical research significance.At present,the consumption of citrus is mainly based on fresh food,processed canned food and juice.The processing of these products will result in the waste of a lot of citrus peel,which is rich in nutrients.In order to take full advantage of the nutrients and bioactive components of citrus,it can be prepared into whole fruit cloudy juice.In this paper,the preparation of navel orange whole fruit cloudy juice was carried out by using the navel orange as raw material,and the changes of polyphenols and antioxidant activities during the processing and storage of whole fruit cloudy juice were studied.The main results are as follows:(1)The particle size and polyphenol dissolution rate of the navel orange whole fruit pulp prepared by the wet superfine pulverizer and the broken wall cooking machine were studied.The results showed that the wet superfine pulverizer two times can effectively reduce the particle size of the whole fruit pulp of navel orange,improve the dissolution rate of total phenols and total flavonoids and antioxidant activity.The freeze-dried samples of navel orange whole fruit pulp obtained by wet superfine pulverization had the highest total phenols and total flavonoids,which were 709.29?g/g and 4584.16?g/g,respectively.14 major polyphenols in the whole fruit pulp of navel orange were detected.The highest content of phenolic acid was ferulic acid,and the highest content of flavonoids was hesperidin.(2)The effects of pasteurization,microwave sterilization and ultrasonic sterilization on the quality of navel orange juice were studied.The results showed that the pH and soluble solids of navel whole fruit cloudy juice were significantly decreased after pasteurization than before sterilization(P<0.05).After microwave sterilization,the pH did not change significantly(P>0.05),and the soluble solids decreased significantly(P<0.05).After ultrasonic sterilization,the pH decreased significantly(P<0.05),but the reduction is only 0.05,and the soluble solids did not change significantly(P>0.05).Combining the above conclusions,it is known that ultrasonic sterilization has little effect on the pH and soluble solid of navel whole fruit cloudy juice;Microwave sterilization and ultrasonic sterilization can effectively maintain the total phenols and total flavonoids in the cloudy juice of navel orange,and the retention rates are 92.05%and 95.22%,respectively.Before sterilization,the volatile matter content of the cloudy juice was 190.13?g/g,after pasteurization,the volatile matter content increased(210.08?g/g),the volatile matter decreased after microwave sterilization(183.88?g/g),and the volatile matter content after ultrasonic sterilization increased(195.70?g/g).Compared with before sterilization,there was no significant change in DPPH free radical scavenging rate,ABTS~+·clearance rate and iron ion reducing ability of cloudy juice after ultrasonic sterilization(P>0.05).Comprehensive analysis,ultrasonic sterilization is more conducive to maintaining the quality of the whole fruit cloudy juice of navel orange.(3)The navel whole fruit cloudy juice after ultrasonic sterilization was stored at 4?,25?and 37?for 21 d,respectively.During storage,the pH of the cloudy juice decreased with the storage time,and the higher the storage temperature,the larger the decrease value;The content of soluble solids and browning increased with the storage time,and the higher the temperature,the larger the increase value;After storage for 21days,the total phenolic content of the cloudy juice decreased,and the higher the temperature,the greater the decrease;the total flavonoid content was basically stable.Comprehensive consideration,storage at 4?is more conducive to retain the quality of navel whole fruit cloudy juice.