不同乳酸菌对凝固型荔枝酸奶的发酵特性和质构的影响

以纯牛奶和荔枝汁为主要原料,以干酪乳杆菌、保加利亚乳杆菌和嗜热链球菌为发酵菌种,探讨三种乳酸菌的不同组合发酵对凝固型荔枝酸奶的发酵特性和质构的影响。结果表明:干酪乳杆菌产胞外多糖能力较强,单独发酵时胞外多糖含量达到22.50g/L,而嗜热链球菌和保加利亚乳杆菌单独发酵时胞外多糖的含量分别为5.73 g/L和0.29 g/L;各种不同乳酸菌组合发酵后酸奶的表观粘度和持水力与胞外多糖的含量呈正相关(R2=0.98);干酪乳杆菌产酸能力弱,单独发酵后p H高于其它添加有嗜热链球菌和保加利亚乳杆菌的组合,导致酸奶的硬度偏低,但干酪乳杆菌联合嗜热链球菌或保加利亚乳杆菌发酵时,发酵酸奶的硬度和乳酸菌活菌数均明显优于单独发酵组。因此,当干酪乳杆菌与嗜热链球菌及保加利亚乳杆菌联合发酵时,能充分发挥三个菌种的各自优势,菌落总数、胞外多糖含量和质构均能达到较好的品质水平。

Effects of Different Lactic Acid Bacteria on Fermentation Characteristics and Texture of Set-style Yogurt Fortified with Lychee Juice

Pure milk and lychee juice were used as the main raw materials, with Lactobacillus casei, Lactobacillus bulgaricus and Streptococcus thermophilus as fermentation strains. The effects of different combinations of three lactic acid bacteria on the fermentation characteristics and texture of set-style yogurt fortified with lychee juice were investigated. The results showed that L. casei showed relatively high ability to produce exopolysaccharide, with the exopolysaccharide content reaching 22.50 g/L when used alone (compared to 5.73 g/L and 0.29 g/L for the fermentation using S. thermophilus or L. bulgaricus alone). After fermentation with different combinations of the three bacteria, the apparent viscosity and water-holding capacity of the yoghurts were positively correlated (R2 = 0.98) with exopolysaccharide content. The L. casei showed a weak acid-producing ability, and the pH after fermentation with the strain alone was higher causing lower hardness, compared with those for the fermentation with its combinations of S. thermophilus or L. bulgaricus. However, the hardness and number of viable lactic acid bacteria were significantly (p < 0.05) higher for the yoghurt fermented by L. casei combined with S. thermophilus or L. bulgaricus, compared with those fermented with Lactobacillus casei alone. Therefore, when the fermentation is performed using the combination of L. casei with S. thermophilus and L. bulgaricus, the advantages of the three strains can be fully utilized, and the total number of colonies, exopolysaccharide content and texture can reach a higher quality level.