Department of Nutrition, Dietetics and Food Sciences, Utah State University, Logan 84322.
Department of Nutrition, Dietetics and Food Sciences, Utah State University, Logan 84322; Vivolac Cultures Corporation, Greenfield, IN 46140.
J Dairy Sci. 2022 Mar;105(3):2069-2081. doi: 10.3168/jds.2021-20958. Epub 2022 Jan 13.
Traditionally, starter cultures for Cheddar cheese are combinations of Lactococcus lactis and Lactococcus cremoris. Our goal was to compare growth and survival of individual strains during cheesemaking, and after salting and pressing. Cultures used were 2 strains of L. lactis (SSM 7605, SSM 7436) and 2 strains of L. cremoris (SSM 7136, SSM 7661). A standardized Cheddar cheese make procedure was used that included a 38°C cook temperature and salting levels of 2.0, 2.4, 2.8, 3.2, and 3.6% from which were selected cheeses with salt-in-moisture levels of 3.5, 4.5, and 5.5%. Vats of cheese were made using each strain on its own as biological duplicates on different days. Starter culture numbers were enumerated by plate counting during cheesemaking and after 6 d storage at 6°C. Flow cytometry with fluorescent staining by SYBR Green and propidium iodide was used to determine the number of live and dead cells in cheese at the different salt levels. Differences in cheese make times were strain dependent rather than species dependent. Even with correction for average culture chain length, cheeses made using L. lactis strains contained ∼4 times (∼0.6 log) more bacterial cells than those made using L. cremoris strains. Growth of the strains used in this study was not influenced by the amount of salt added to the curd. The higher pH of cheeses with higher salting levels was attributed to those cheeses having a lower moisture content. Based on flow cytometry, ∼5% of the total starter culture cells in the cheese were dead after 6 d of storage. Another 3 to 19% of the cells were designated as being live, but semipermeable, with L. cremoris strains having the higher number of semipermeable cells.
传统上，切达干酪的发酵剂是乳球菌（Lactococcus lactis）和乳球菌（Lactococcus cremoris）的组合。我们的目标是比较在干酪制作过程中以及盐腌和压榨后，单个菌株的生长和存活情况。使用的培养物是 2 株乳球菌（SSM 7605、SSM 7436）和 2 株乳球菌（SSM 7136、SSM 7661）。采用标准化的切达干酪制作程序，包括 38°C 的烹饪温度和 2.0、2.4、2.8、3.2 和 3.6%的盐腌水平，从中选择水分盐含量为 3.5、4.5 和 5.5%的奶酪。每天使用不同的生物重复，用每种菌株单独制作奶酪桶。在干酪制作过程中和 6°C 储存 6 天后，通过平板计数来计数发酵剂的数量。使用流式细胞术和 SYBR Green 和碘化丙啶荧光染色来确定不同盐度下奶酪中活细胞和死细胞的数量。奶酪制作时间的差异取决于菌株，而不是物种。即使对平均培养物链长进行了校正，使用乳球菌菌株制作的奶酪中的细菌细胞数量也比使用乳球菌菌株制作的奶酪多约 4 倍（约 0.6 对数）。研究中使用的菌株的生长不受添加到凝乳中的盐量的影响。盐含量较高的奶酪的较高 pH 值归因于这些奶酪的水分含量较低。基于流式细胞术，在储存 6 天后，奶酪中总发酵剂细胞的约 5%死亡。另外 3%至 19%的细胞被指定为活的，但半渗透性的，乳球菌菌株具有更高数量的半渗透性细胞。
