Collins Yvonne F, McSweeney Paul L H, Wilkinson Martin G
Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Co Cork, Ireland.
J Dairy Res. 2003 Feb;70(1):105-13. doi: 10.1017/s0022029902005915.
Cell viability, autolysis and lipolysis were studied in Cheddar cheese made using Lactococcus lactis subsp. cremoris AM2 or Lactococcus lactis subsp. cremoris HP. Cheddar cheese was made in triplicate over a 3 month period and ripened for 238 days at 8 degrees C. Cell viability in cheese was lower for AM2 (a non-bitter strain) than for strain HP (a bitter strain). Autolysis, monitored by the level of the intracellular marker enzyme, lactate dehydrogenase (EC 1.1.1.27) in cheese 'juice' extracted by hydraulic pressure, was much greater in the cheese made using AM2 than that made with HP. Lipolysis was determined by the increase during ripening of individual free fatty acids (FFA) from butyric (C4:0) to linolenic acid (C18:3) measured using a high performance liquid chromatographic technique. Levels of individual FFA from butyric (C4:0) to linolenic (C18:3) acids increased significantly (P<0.05) during ripening in cheeses made with either starter culture. Palmitic (C16:0) and oleic (C18:1) acids were the most abundant FFA throughout ripening in all cheeses. Levels of caprylic (C8:0), myristic (C14:0), palmitic (C16:0) and stearic (C18:0) acids were significantly higher (P<0.05) in cheeses manufactured with Lc. lactis subsp. cremoris AM2 than in cheeses manufactured with Lc. lactis subsp. cremoris HP. Differences in levels of lipolysis between strains was not due to differences in the specific lipolytic or esterolytic activities in cell free extracts of the strains as measured by activity on triolein (lipase) and p-nitrophenylbutyrate (esterase) substrates. Therefore, evidence is provided for a relationship between the extent of starter cell autolysis and the level of lipolysis during Cheddar cheese ripening.
研究了使用乳酸乳球菌乳脂亚种AM2或乳酸乳球菌乳脂亚种HP制作的切达干酪中的细胞活力、自溶和脂解情况。在3个月的时间内分三次制作切达干酪，并在8摄氏度下成熟238天。AM2（一种不产苦味的菌株）制作的干酪中的细胞活力低于HP菌株（一种产苦味的菌株）。通过液压提取的干酪“汁液”中细胞内标记酶乳酸脱氢酶（EC 1.1.1.27）的水平监测自溶情况，使用AM2制作的干酪中的自溶程度比使用HP制作的干酪大得多。使用高效液相色谱技术测定脂解情况，通过在成熟过程中从丁酸（C4:0）到亚麻酸（C18:3）的各个游离脂肪酸（FFA）的增加来确定。在使用任何一种发酵剂制作的干酪成熟过程中，从丁酸（C4:0）到亚麻酸（C18:3）的各个FFA水平均显著增加（P<0.05）。在所有干酪的整个成熟过程中，棕榈酸（C16:0）和油酸（C18:1）是含量最丰富的FFA。使用乳酸乳球菌乳脂亚种AM2制作的干酪中辛酸（C8:0）、肉豆蔻酸（C14:0）、棕榈酸（C16:0）和硬脂酸（C18:0）的水平显著高于（P<0.05）使用乳酸乳球菌乳脂亚种HP制作的干酪。菌株之间脂解水平的差异并非由于菌株无细胞提取物中通过对三油酸甘油酯（脂肪酶）和对硝基苯丁酸酯（酯酶）底物的活性测定的特定脂解或酯解活性的差异。因此，为切达干酪成熟过程中发酵剂细胞自溶程度与脂解水平之间的关系提供了证据。
