Study On The Technology And Mechanism Of Chitosan/Sodium Alginate Composite Clarification Of Bayberry Juice

Bayberry juice can improve the resource utilization and economic value of bayberry fruit.However,bayberry juice is prone to haze during the processing,storage and transportation,which affects the quality of the product.The use of clarifier is a common method to improve the clarity of fruit juice,which has the advantages of mild conditions,simple operation and low cost.However,the effect of using a single kind of clarifier is poor,and the composite use of clarifiers can achieve better clarification effect.Therefore,the development of a better and more efficient composite clarification technology has essential theoretical and practical significance for the processing of bayberry juice.Chitosan/sodium alginate composite clarifiers have the advantages of strong adsorption capacity,high efficiency,low p H sensitivity,and high safety,but there is no application in fruit juice clarification.In this paper,the clarification effect of chitosan/sodium alginate on bayberry juice was studied.In addition,physicochemical quality and aroma of bayberry juice before or after clarification were compared and evaluated.Finally,the mechanism of chitosan/sodium alginate composite clarification of bayberry juice was studied.The main results are as follows:(1)The optimum clarification process of chitosan/sodium alginate was obtained by single factor and orthogonal test: using chitosan 0.05 g/L first and then sodium alginate 0.05 g/L as composite clarifiers,standing for 2 h at 25℃.The transmittance was 91.52%;the turbidity was 8.98 NTU;the sedimentation time was about 8 min.Compared with the clarification effect of using chitosan(44.29%,283.33 NTU)or sodium alginate(38.46%,347.33 NTU)alone,it was found that composite clarified bayberry juice had higher transmittance,lower turbidity,higher clarification efficiency,better stability,the smaller average particle size and the fewer insoluble particles.The comprehensive effect of clarifying juice by chitosan/sodium alginate was better than using chitosan and sodium alginate alone.(2)The effects of chitosan/sodium alginate composite clarifier on the physicochemical properties and aroma of bayberry juice were studied.The results showed that the protein and pectin of the bayberry juice treated with chitosan/sodium alginate decreased by 98% and 86%,respectively,indicating that the main components causing turbidity were effectively removed.The loss rate of anthocyanins in bayberry juice after clarification by chitosan/sodium alginate was low,only 9.16%,which was beneficial to the retention of anthocyanins compared with using chitosan or sodium alginate alone.After the clarification of chitosan/sodium alginate,the L* and a* value of bayberry juice increased significantly while the hue angle h° was decreased,which indicated that the color of composite clarified bayberry juice was improved.The results of HS-SPME-GC-MS showed that the types of volatile compounds clarified by chitosan/sodium alginate increased from 53 to 61,which indicated that chitosan/sodium alginate composite clarifiers were beneficial to the volatilization of aroma substances.The results of PCA showed that the aroma could be improved by enhancing sweet,green,flower and fruit aroma after chitosan/sodium alginate clarification.(3)Based on the analysis of clarifiers,flocculant,turbidity type and simulation system,the clarification mechanism of composite clarifiers to bayberry juice was studied.The results showed that under the p H of bayberry juice,there was an electrostatic interaction between chitosan and sodium alginate,which could form a complex with higher molecular weight,and the interaction between chitosan and sodium alginate was the most sufficient at 1:1.Compared with chitosan and sodium alginate,the mixture of chitosan and sodium alginate can form a reticular structure with smaller pore size.In the clarification process,gel-like substances would be formed,and in the bayberry juice system,impurity particles would be encapsulated and adsorbed to form larger flocs.In addition,according to the turbidity type of bayberry juice,the most haze was protein-polyphenol type,and protein was the main reason to participate in precipitation.The clarification test of the simulation system showed that chitosan/sodium alginate was more suitable to be used in beverage systems containing polyphenols and pectin.In the binary and ternary mixed system,the turbidity of chitosan/sodium alginate was lower than that of chitosan or sodium alginate alone,which further verified the superiority of chitosan/sodium alginate composite clarifiers.