超高压处理非浓缩还原橙汁的贮藏特性

Storage characteristics of high-pressure processing NFC orange juice

为探究超高压处理(high pressure processing,HPP)后非浓缩还原橙汁的贮藏特性,将超高压处理橙汁,在4℃下进行3个月的贮藏实验,对其贮藏期间的流变特性、色泽、总可溶性固形物(total soluble solids,TSS)含量、可滴定酸(titratable acid,TA)含量、维生素C含量和酶活性进行比较分析,并以热处理(thermal pasteurization,TP)为对照。结果表明,贮藏期内HPP橙汁和TP橙汁的流动性逐渐增强,流变特性在0~1.5个月内变化较大,2~3个月内变化变小并趋于稳定。在0~3个月内黏度系数前后分别降低8.03%~39.4%、17.8%~49.1%;流动系数分别升高8.47%~31.1%、8.94%~27.6%;表观黏度前后分别降低20.6%~64.8%、11.5%~59.3%;储存模量G′<损耗模量G″,且均呈现降低趋势,橙汁黏弹性降低。贮藏期间温度对HPP橙汁和TP橙汁的流变特性变化影响不显著。贮藏前期亮度值L^(*)、红绿值a^(*)升高,黄蓝值b^(*)降低,后期a^(*)、b^(*)值逐渐稳定,L^(*)值呈下降趋势,色泽逐渐变暗。前期橙汁中悬浮微粒沉淀,橙汁逐渐清澈,果胶甲酯酶(pectin methylesterase,PME)使橙汁颜色加深,而后期PME反应底物减少,造成体系色泽变化较小,溶质颗粒沉降,橙汁产生相分离,L^(*)值变低。HPP橙汁和TP橙汁中的TSS、TA、维生素C含量基本保持稳定;HPP橙汁TSS、TA含量略高于TP处理组,维生素C含量为TP处理组的3倍。处理后橙汁的多酚氧化酶、过氧化物酶几乎完全被钝灭,但HPP橙汁中PME酶活力约为TP组的4倍,PME水解果胶,导致橙汁M w的降低,使得橙汁黏度减小,在3个月的贮藏期内,2种橙汁在4℃下均保存良好,无酶活显著升高。总体上超高压处理的橙汁在3个月贮藏期内可保持良好的感官品质,在1.5个月内饮用更佳。

To explore the storage characteristics of ultra-high pressure treated NFC orange juice,600 MPa,orange juice treated by high-pressure processing(HPP)for 10 min was used for storage experiment at 4℃for 3 months.The rheological properties,color,total soluble solid(TSS)content,titratable acid(TA)content,vitamin C content,and enzyme activity were detected during storage.Results showed that during the storage period,the fluidity of HPP orange juice and thermal pasteurization(TP)orange juice gradually increased,the viscosity coefficient K decreased by 8.03%-39.4%and 17.8%-49.1%,and the flow coefficient N increased by 8.47%-31.1%and 8.94%-27.6%,respectively,in 0-3 months.The apparent viscosity decreased by 20.6%-64.8%and 11.5%-59.3%,respectively.The torage modulus G′was less than the loss modulus G″,both of them showed the decreasing trend,the viscoelasticity of orange juice decreased,and the influence of temperature on HPP orange juice remained unchanged.The rheological properties of orange juice varied greatly in 0-1.5 months but became stable in 2-3 months and its stability gradually decreased.At the early stage of storage,the brightness value L^(*)and red-green value a^(*)increased,while the yellow-blue value b^(*)decreased.At the later stage,the brightness value a^(*)and b^(*)gradually stabilized,while the L^(*)value showed a downward trend,and the color gradually darkened.In the early stage,suspended particles in orange juice precipitated,and orange juice gradually became clear,pectin methylesterase(PME)enzyme deepened the color of orange juice,while in the late stage,a substrate of the PME reaction decreased,resulting in a small color change of the system,solute particle settlement,phase separation of orange juice,and low L^(*)value.The contents of TSS,TA,and vitamin C in HPP orange juice and TP orange juice were basically stable.The contents of TSS and TA in HPP orange juice were slightly higher than those in the TP treatment group,and the vitamin C content was three times that in the TP treatment group.After treatment,polyphenoloxidase and peroxidase enzyme activities of orange juice were almost completely inactivated,so that there was almost no enzymatic browning during storage.The PME enzyme activity of HPP treatment was about 4 times that of the TP group,and the presence of PME hydrolyzed pectin products and Ca^(2+)complex formed then precipitated,causing the decrease of viscosity of orange juice.During the storage period of 3 months,both treatments could maintain the stability of enzyme activity.Overall,HPP orange juice maintained good sensory quality within 3 months and was better consumed within 1.5 months.