Abstract: In order to evaluate the functional characteristics of Tibetan kefir, the conditions for the fermentation of skim milk with Tibetan kefir were preliminarily optimized by one-factor-at-a-time method based on titratable acidity and sensory evaluation, and the antioxidant capacity and cholesterol-lowering ability of the fermented milk were studied in vitro. It was found that the optimal fermentation conditions were as follows: inoculum size 6%, fermentation time 7.5 h, and temperature 37 ℃. The fermented milk produced under the optimized conditions had a medium acidity, delicate taste, uniform texture and unique flavor, and its lactic acid bacterial population was 1.48 × 108 CFU/mL. The hardness of the fermented milk was 178.43 g, higher than that of traditional fermented milk, the adhesion was -103.52 g·s and the non-fat solid content, protein content and titratable acidity all conformed to the national standard for fermented milk. The quality of the fermented milk was good overall. Compared with traditional fermented milk, its antioxidant activity was not particularly prominent, but the cholesterol-lowering ability was particularly considerable, with removal rate of as high as 37.98% (fermented skim milk) and 40.68% (fermented whole milk).

Key words: Tibetan kefir, fermented milk, process conditions, antioxidant activity, cholesterol-lowering ability

摘要： 为研究藏灵菇功能特性，以滴定酸度和感官评价为指标，通过单因素试验对藏灵菇脱脂发酵乳工艺条件进行初步优化，并通过体外实验对藏灵菇脱脂发酵乳抗氧化能力和降胆固醇能力进行测定。结果表明：确定藏灵菇接种量6%、发酵温度37 ℃、发酵时间7.5 h为藏灵菇脱脂发酵乳的最优工艺条件，此条件下制得的脱脂发酵乳酸度适宜、口感细腻、质地均匀，具有独特风味，乳酸菌数为1.48×108 CFU/mL，硬度为178.43 g，高于传统发酵乳，黏附性为－103.52 g·s，且非脂乳固体含量、蛋白质含量和滴定酸度均符合发酵乳标准GB 19302—2010《食品安全国家标准 发酵乳》，品质较好；藏灵菇发酵乳抗氧化能力虽与传统发酵乳差异不显著，但具有较好的降胆固醇能力，藏灵菇脱脂发酵乳胆固醇去除率高达37.98%，藏灵菇全脂发酵乳胆固醇去除率高达40.68%。

关键词: 藏灵菇, 发酵乳, 工艺条件, 抗氧化活性, 降胆固醇能力