Abstract: The objective of this paper was to optimize the fermentation conditions of lactose-free yogurt. The level of residual sugar was used as response variable. Moreover, lactose-free yogurt and ordinary were prepared under the same conditions and their sensory characteristics were compared. Also, differences in their instrumental quality characteristics were assessed using an electronic eye, an electronic nose and an electronic tongue. The results showed that the optimal fermentation conditions were as follows: lactase dose 3.9 U/L, inoculum size 2 U/1 000 kg, fermentation temperature 43 ℃ and time 5.5 h. The lactose content of the yogurt prepared under the optimized conditions was (0.29 ± 0.07) g/100 mL. The lactose-free yogurt showed a 1.5-fold increase in lactic acid bacterial count than the ordinary yogurt (P < 0.05), but there was no significant difference in acidity or viscosity between them (P > 0.05). Principal component analysis (PCA) demonstrated no significant difference (P > 0.05) in color, aroma or taste. Therefore, compared with the ordinary yogurt, the lactose-free yogurt had no significant difference in sensory quality.

Key words: lactose; lactose-free yogurt; sensory quality

摘要： 以乳糖残留量为指标，优化无乳糖酸乳的发酵条件，并在相同发酵条件下制备普通酸乳和无乳糖酸乳，比较其感官特性的差异。采用电子眼、电子舌和电子鼻等仪器，评价普通酸乳和无乳糖酸乳的质量差异。结果表明：无乳糖酸乳的最佳发酵条件为在加酶量3.9 U/L、接种量2 U/1 000 kg、43 ℃条件下发酵5.5 h，此时发酵酸乳中的乳糖含量为（0.29±0.07） g/100 mL；普通酸乳和无乳糖酸乳的酸度和黏度指标无显著差异（P＞0.05）；而无乳糖酸乳的乳酸菌数量约为普通酸乳的1.5 倍（P＜0.05）；经主成分

关键词: 乳糖；无乳糖酸乳；感官质量