Study On The Regulation Of Browning Of Concentrated Orange Juice During Storage

Orange juice is popular with consumers because of its unique taste,flavor as well as nutritional value which accounts for a large proportion of the global juice market,and the consumption is still on the rise.However,there are large differences between orange juice production and sales regions with large trade markets,and cross-regional trade is needed.Nonetheless,concentrated orange juice,as the main form of orange juice storage and processing product,is subject to browning during storage and transportation,which seriously affects the quality of orange juice and its commercial value.Therefore,the types of browning of concentrated orange juice during storage were first analyzed.Then the emphasis was put on discussing the main factors and the mechanism of browning by establishing a simulation system.Next,the browning kinetics during storage were studied.At last,the experiment was carried out to control the browning of concentrated orange juice by browning inhibitors(EGCG and L-cysteine),physical field(ultrasonic vacuum and high-pressure CO2),and their combined treatment.The main experiments and conclusion are as follows:(1)Browning of concentrated orange juice during storage is non-enzymatic browning.Through the establishment of the simulation system,it was found that the degradation of ascorbic acid and the maillard reaction were the main factors leading to the non-enzymatic browning of concentrated orange juice.And the caramelization reaction and the oxidation of phenols contributed little to the browning,which was almost negligible.After storage at 50°C for 40 days,the contribution of maillard reaction to browning was found to be slightly greater than ascorbic acid degradation,which was 28 times that of the caramelization reaction.Moreover,ascorbic acid degradation contributes more to browning in the early stage of storage,while browning in the late stage of storage is mainly caused by the maillard reaction.The contribution of sugars and amino acids to the browning in the maillard reaction was in the following order:fructose>sucrose>glucose;arginine>aspartic acid>alanine>serine.(2)During storage of concentrated orange juice,the browning index(BI),5-HMF,and a*value increased with the increase of temperature and time.And their changes were all following the joint kinetic model,with R~2 greater than 0.90,and the reaction activation energies were16.127 kcal/mol,19.694 kcal/mol,and 11.615 kcal/mol in order.The L*value and b*value of concentrated orange juice decreased with the increase in storage temperature and storage time.And their changes were all following the joint kinetic model,with R~2 greater than 0.95,and the reaction activation energies were 12.160 kcal/mol and 11.323 kcal/mol,respectively.(3)Both EGCG and L-cysteine could effectively inhibit the browning of concentrated orange juice during storage due to the maillard reaction.It significantly reduced the 5-HMF content and delayed the color loss of concentrated orange juice,and the combined addition of both had a more significant inhibitory effect.After optimization by response surface test,when the addition amount of EGCG and L-cysteine was 0.367%and 0.302%,it had the best effect of inhibiting or delaying browning.The results of electronic nose,electronic tongue,and rheological analysis showed no significant changes in flavor,taste,characteristic volatile compounds of concentrated orange juice,and the changes in rheological properties were very small and negligible.(4)Compared with traditional ultrasonic treatment,ultrasonic vacuum treatment can more effectively reduce the dissolved oxygen content of concentrated orange juice,and the loss of ascorbic acid during treatment is lower.The optimal conditions of ultrasonic vacuum treatment were optimized by the response surface method,when the ultrasonic power was 900 W and the treatment time was 15.6 min the concentrated orange juice had the lowest dissolved oxygen content and the least ascorbic acid loss.Ultrasonic vacuum treatment can effectively remove most of the dissolved oxygen from concentrated orange juice,and high-pressure CO2 treatment can reduce the oxygen in the headspace of storage containers,both of which can effectively reduce the aerobic degradation of ascorbic acid and delay the browning caused by ascorbic acid degradation.In addition,the results showed that ultrasonic vacuum combined with high-pressure CO2 treatment had a more significant effect on delaying the degradation of ascorbic acid,but it had little effect on browning caused by maillard reaction.Therefore,ultrasonic vacuum and high-pressure CO2 treatment combined with EGCG and L-cysteine have the best inhibition or delay effect on the browning of concentrated orange juice during storage,which can effectively reduce the quality deterioration and commercial value loss of concentrated orange juice.