Food-processing Application Key Lab of Sichuan Province, Chengdu Univ., Chengdu 610106, China.
J Food Sci. 2013 Feb;78(2):M297-302. doi: 10.1111/1750-3841.12038. Epub 2013 Jan 18.
Continued acid production by Lactobacillus delbrueckii subsp. bulgaricus during the chilled storage of yogurt is the major cause of postacidification, resulting in a short shelf life. Two H(+) -ATPase defective variants of L. delbrueckii subsp. bulgaricus were successfully isolated and their H(+) -ATPase activities were reduced by 51.3% and 34.3%, respectively. It was shown that growth and acid production of variants were remarkably inhibited. The variants were more sensitive to acidic condition and had a significant rate for inactivation of H(+) -ATPase by N, N-dicyclohexylcarbodiimide (DCCD), along with a low H(+) -extrusion, suggesting that H(+) -ATPase is direct response for H(+) -extrusion. In addition, the variants were also more sensitive to NaCl, while H(+) -ATPase activities of variants and parent strain were significantly enhanced by NaCl stress. Obviously, H(+) -ATPase might be involved in Na(+) transportation. Furthermore, variants were inoculated in fermented milk to ferment yogurt. There was no significant difference in flavor, whereas the postacidification of yogurt during chilled storage was remarkably inhibited. It is suggested that application of L. delbrueckii subsp. bulgaricus with reduced H(+) -ATPase activity in yogurt fermentation is one of effect, economic and simple avenues of inhibiting postacidification of yogurt during refrigerated storage, giving a longer shelf life.
During yogurt fermentation, continued acid production by Lactobacillus delbrueckii subsp. bulgaricus during the chilled storage of yogurt leads to milk fermentation with high postacidification, resulting in a short shelf life. In this work, 2 acid-sensitive variant strains of L. delbrueckii subsp. bulgaricus were isolated. The characteristics related to H(+) -ATPase were compared and it was observed that milk fermented by the variants had lower postacidification, giving a longer shelf life. Application of L. delbrueckii subsp. bulgaricus with reduced H(+) -ATPase activity in yogurt fermentation might be one of effect, economic and simple avenues of inhibiting yogurt postacidification during chilled storage, giving a longer shelf life.
在酸奶的冷藏储存过程中，乳杆菌保加利亚亚种继续产生酸是后酸化的主要原因，导致保质期短。成功分离出两种 H(+) -ATPase 缺陷型乳杆菌保加利亚亚种变异株，其 H(+) -ATPase 活性分别降低了 51.3%和 34.3%。结果表明，变异株的生长和产酸能力明显受到抑制。变异株对酸性条件更敏感，N, N-二环己基碳二亚胺（DCCD）对 H(+) -ATPase 的失活率显著，H(+) -外排率低，表明 H(+) -ATPase 是 H(+) -外排的直接反应。此外，变异株对 NaCl 也更敏感，而 NaCl 胁迫显著增强了变异株和亲本菌株的 H(+) -ATPase 活性。显然，H(+) -ATPase 可能参与 Na(+) 运输。此外，将变异株接种到发酵乳中发酵酸奶。在冷藏储存过程中，酸奶的后酸化得到了显著抑制，风味没有明显差异。这表明，在酸奶发酵过程中应用 H(+) -ATPase 活性降低的乳杆菌保加利亚亚种是抑制酸奶冷藏后酸化的有效、经济和简单途径之一，可延长保质期。
在酸奶发酵过程中，酸奶冷藏过程中乳杆菌保加利亚亚种继续产酸会导致牛奶发酵后酸化程度高，保质期短。在这项工作中，分离出了 2 株嗜酸变异株乳杆菌保加利亚亚种。比较了与 H(+) -ATPase 相关的特性，发现用变异株发酵的牛奶后酸化程度较低，保质期较长。在酸奶发酵中应用 H(+) -ATPase 活性降低的乳杆菌保加利亚亚种可能是抑制酸奶冷藏后酸化、延长保质期的有效、经济和简单途径之一。
