UHT乳贮藏期间理化特性和感官品质的变化

为探讨超高温瞬时杀菌(ultra-high temperature instantaneous sterilization,UHT)乳的营养价值随贮藏时间的变化,对不同贮藏期UHT乳的理化特性和感官品质进行监测。在6个月的贮藏期内,UHT乳中脂肪、蛋白质、乳糖以及固形物的总量并无明显变化,维生素C和泛酸的含量均损失了约25%,游离氨基酸和钙离子分别增加了5.35%和6.73%。不同贮藏期UHT乳的黏度变化不显著(P>0.05),但粒径大小强烈依赖于贮藏时间,乳脂肪球和酪蛋白胶束的尺寸在贮藏初期分别增加了约38 nm和14 nm,然后分别稳定在约173 nm和612 nm。贮藏1个月的UHT乳样品在风味和口感方面整体表现较好,贮藏6个月后,UHT乳的感官品质大幅下降,出现了许多不良风味。

Changes in Physicochemical Properties and Sensory Quality of UHT Milk during Storage

In order to investigate the effect of storage time on the nutritional quality of ultra-high temperature instantaneous sterilization(UHT)milk,the physicochemical properties and sensory quality of UHT milk in different storage periods were monitored. The total amount of lipid,protein,lactose,and solids in UHT milk did not change significantly during the 6-month storage;both vitamin C(VC)and pantothenic acid lost about 25 %,and the content of free amino acids and calcium ion increased by 5.35 % and 6.73 %,respectively. The viscosity of UHT milk did not change significantly(P >0.05) with the storage period,but its particle size strongly depended on the storage time. The size of the milk fat globules and casein micelles increased by about 38 nm and 14 nm at the beginning of storage,and then stabilized at about 612 nm and 173 nm,respectively. The UHT milk samples stored for one month performed better overall in terms of flavor and mouthfeel,while UHT milk stored for six months had many unpleasant flavors and its sensory quality was greatly reduced.