5种不同浓缩方式对荔枝汁品质的影响

Effect of Five Different Concentration Methods on the Quality of Litchi Juice

为了获得优质荔枝浓缩汁,比较分析5种不同浓缩方式(真空浓缩、结冰-解冻浓缩、冷冻浓缩、二级冷冻浓缩、一级冷冻联合真空浓缩)对浓缩汁品质的影响。结果显示,不同浓缩处理组品质差异显著,其中,真空浓缩较其他浓缩方式总酚含量提高8.32%~21.17%、抗氧化能力提高2.38%~35.37%、粒径值降低9.69%~48.69%、总色差ΔE^(*)值最小,稳定性最高;一级冷冻浓缩联合真空浓缩处理组菌落总数、霉菌和酵母、乳酸菌菌落数均显著低于其他组,二者具有协同杀菌的效果;二级冷冻浓缩处理组挥发性物质种类(32种)、含量(409.4 mg/L)以及荔枝典型性香气物质香叶醇含量(152.51 mg/L)均为最多,风味流失最少;说明真空浓缩、一级冷冻联合真空浓缩、二级冷冻浓缩分别在保护荔枝汁理化品质、杀菌效果、挥发性物质上各有优势,鉴于理化品质为评价果汁品质较重要的指标,并结合真空浓缩处理组效率最高、时间成本最低,可将真空浓缩作为当前相对较适宜的浓缩荔枝汁方式,未来可在真空浓缩和冷冻浓缩的耦合联用方面进行深入研究,以期获得更佳的浓缩处理模式。

In order to obtain high-quality concentrated litchi juice,the effects of 5 different concentration methods(vacuum concentration,freezing-thawing concentration,freezing concentration,secondary freeze concentration,primary freezing combined with vacuum concentration on the quality of concentrated juice were compared and analyzed.The results showed that the quality of the concentrated juice samples obtained by different concentration treatments differed significantly.Compared with the other concentration methods,vacuum concentration made the total phenol content being increased by 8.32%~21.17%,antioxidant capacity being increased by 2.38%~35.37%,particle size being decreased by 9.69%~48.69%,total color differenceΔE^(*)value becoming the smallest,and stability becoming the highest.Compared with the other groups,the combination of primary freezing and vacuum concentration exhibited a synergistic bactericidal effect,causing the decreases in the total number of colonies and the number of molds,yeasts and lactic acid bacteria.The secondary freeze concentration led to the highest number of species type(32 kinds)and highest content(409.4 mg/L)of volatile substances as well as the higest content of geraniol(152.51 mg/L),with the least flavor loss.The results indicated that vacuum concentration,primary freezing combined with vacuum concentration and secondary freezing concentration had their respective advantages in protecting physicochemical quality,bactericidal effect and volatile profile of lychee juice.In view of the fact that the physico-chemical quality is an important index for evaluating the quality of fruit juice,while considering the highest efficiency and the lowest time cost of vacuum concentration,it is suggested that at present vacuum concentration can be used as a relatively suitable method to concentrate litchi juice.Further research on the coupling of vacuum concentration and freezing concentration can be carried out in the future in order to obtain a better concentration treatment mode.