荔枝汁结冰-解冻浓缩过程中品质的变化规律

以灭菌后的荔枝汁为原料,采用结冰-解冻浓缩工艺将其浓缩,研究了浓缩过程对荔枝汁的可溶性固形物含量、褐变度和可滴定酸度的影响,并运用气相色谱-质谱联用法对浓缩过程中的荔枝汁的挥发性风味物质进行测定,探讨其品质的变化规律。结果表明:荔枝汁中可溶性固形物的含量和褐变度随解冻所得的荔枝汁总体积的增加而逐渐降低;浓缩过程中,挥发性风味物质的相对含量的变化趋势因物质类型不同而不尽相同。综合考虑理化指标与风味物质的变化规律,可将解冻过程中荔枝汁总体积的40%(v/v)处选定为浓缩汁与剩余液的分界点,得到的浓缩汁中风味较高。

Influence of ice-thawing concentration treatment on the quality of litchi juice

Litchi juice after sterilized was concentrated by ice-thawing concentration.The effects of icethawing concentration on the total soluble solids,browning degree and titrable acidity were analyzed.And volatile aromatic compounds of litchi juice in the course of concentration were analyzed by headspace solid phase micro-extraction and gas chromatography-mass spectrometry(HS-SPME and GC-MS) method.The results indicated that the total soluble solids and browning degree in litchi juice were decreasing with thawing volume increasing.The kinds of volatile aromatic compounds of litchi juice in different stages concentrated by the ice-thawing concentrated way were different.The choice of the boundary point took the analysis about the physico-chemical index and volatile aromatic compounds into comprehensive consideration,and to get more volatile aromatic compounds in concentrated juice,the thawing litchi juice with 40% in volume was found as the boundary point separated the concentrated juice and the residual liquid.