Study On The Optimal Clarification Process And Copigmentation Of Bayberry Juice

Chinese bayberry(Myrica Rubra Sieb.et Zucc)is a subtropical fruit with a long history of cultivation and abundant resources in China.Chinese bayberry has sweet-sour taste with organic acids,vitamins and minerals.In addition,it is rich in phenolic substances.Bayberry juice is difficult to clarify by simple centrifugal filtration and the like,and the instability of color during storage leading its short shelf life.Therefore,it is of great significance to solve the problem of clarification and discoloration of bayberry juice.The present study aimed to optimize the enzymatic hydrolysis process parameters,research the copigmentation of tannic acid,ferulic acid,sinapic acid,chlorogenic acid and syringic acid with bayberry anthocyanins in the simulation system and the real system and investigate the preliminary mechanism of copigmentation by hermodynamic parameters and HPLC analysis.The main results of this paper were as follow:1.The protease and the pectinase was combined with membrane filtration to clarify the bayberry juice.According to the effect of enzymatic hydrolysis on the clarification,the optimal enzymolysis process was explored.Based on these experiment and orthogonal experiment design result,we found out the best enzymolysis condition of clarifing juice.The best condition is adding proteolytic enzyme 0.1 g/L,keeping the reaction temperature on 65?,and pectinase 1g/L,the reaction temperature 50?.Then we can get the bayberry juice whose light transmittance reaches 89.63%.Finally,the fruit juice was further clarified by membrane filtration to obtain juice with a light transmittance of 95.27%.2.The five copigments of tannic acid,ferulic acid,sinapic acid,chlorogenic acid and syringic acid had significant effects on the color enhancement of bayberry anthocyanins(p<0.05).When the molar ratio of anthocyanin to copigments were 1:1,the sinapic acid copigmentation group was the only one group making significant difference in the maximum absorbance value from that in the control group(p<0.05).When the molar ratio was more than 1:20,five copigmentation groups were significantly different from that in the control group(p<0.05).The results also showed that the maximum absorption wavelength of the anthocyanins aqueous solution exihibited bathochromic shift,the L*value decreased,and the a*value increased with the increasing of molar ratio.After copigmentation,the thermal stability of the pigment of bayberry anthocyanin was significantly improved.Compared with the control group,the rates of changes of A512,L*,a*,b*values in the copigmentation groups were slowed down,and the rates of color changes were reduced.The copigmentation effects of tannic acid and sinapic acid with anthocyanins could be observed by the naked eyes.No new anthocyanin derivatives produced after copigmentation,assuming that the copigmentation reaction was non-covalently bound.The Gibbs free energy(?G)of the five processes were all less than zero,indicating that the copigmentations were spontaneous;while ?H and ?S were all negative,showing the generally spontaneous exothermic character of the processes.The equilibrium constant(K)of tannic acid group was greatest and indicated that tannic acid was more favorable in the combination with anthocyanins,and sinapic acid second.3.In bayberry juice,five copgments(tannic acid,ferulic acid,sinapic acid,chlorogenic acid,syringic acid)could enhance the color stability of bayberry juice,reduce its anthocyanin degradation rate,extend the half-life of the degradation reaction,and reduce degradation rates of a*?C*and TCD.In the early stage of storage at 4?,the trends of color changes were not obvious,and the obvious change trend appeared in the middle and later stages.Instead,the storage at 25? and 37? could accelerate the whole reaction and showed the copigmentation effects in a short time;The tannic acid and sinapic acid were the more powerful copigments compared with other three copigments.The predicted half-life degradation periods of anthocyanin in bayberry juice adding tannic acid and sinapic acid according to the first-order reaction model by storing 90 days at 4 ? were extending nearly twice the time compared to the control sample.However,tannic acid has a greater influence on the light transmittance of bayberry juice,and it causes turbidity easily.Therefore,sinapinic acid is the most suitable as a copigemnt for bayberry juice.