Bouksaim M, Lacroix C, Audet P, Simard R E
Dairy Research Centre STELA, Pavilion Paul Comtois, Université Laval, Ste-Foy, Québec, Canada.
Int J Food Microbiol. 2000 Sep 10;59(3):141-56. doi: 10.1016/s0168-1605(00)00295-6.
A starter culture system that produced both acid and nisin at acceptable rates in milk for manufacture of Gouda cheese was developed using nisin Z-producing L. lactis subsp. lactis biovar. diacetylactis UL 719 (UL 719) and a commercial Flora Danica (FD) starter culture. Different compositions of mixed cultures (0, 0.2, 0.4, 0.6 or 0.8% UL 719 with 1.4% FD) were tested for acidification and nisin Z production in milk after 12 h incubation at 30 degrees C. The 0.6/1.4% combination, selected as the optimal mixture of starter cultures, acidified milk to a suitable pH and produced nisin Z at a high concentration of 512 IU/ml. With this optimal combination, FD numbers of citrate-fermenting and non-fermenting bacteria did not change compared with the control (1.4% FD). However, with 0.8% of L. lactis strain UL 719 and 1.4% of the FD starter culture, the numbers of citrate-fermenting and non-fermenting bacteria in fermented milk decreased compared with those obtained when milk was inoculated with 0.2, 0.4 or 0.6% of UL 719 added to 1.4% FD or control cultures (1.4% FD). Mixed starter culture ratios 0.6/1.4%, 0.4/1.4% and 0.5/1.4% (UL 719/FD) were used to manufacture nisin Z containing Gouda cheese which was ripened up to 45 weeks. The composition of control cheeses made with 1.4% FD, and nisin Z-containing Gouda cheeses were similar with respect to percent moisture, fat, salt and protein. During the ripening period, the cell counts observed were approximately two logs higher in cheese made with the 0.6/1.4% mixed starter culture than in control cheese. In experimental cheese produced with 0.6/1.4% (UL 719/FD) mixed starter culture, nisin activity increased from 256 IU/g at the end of manufacture to a maximum of 512 IU/g after 6 weeks of ripening; the levels then decreased to 128 and 32 IU/g after 27 and 45 weeks of ripening, respectively. In contrast, nisin Z was not detected in experimental cheeses made with 0.4/1.4% or 0.5/1.4% (UL 719/FD) mixed starters. Using an affinity purified anti-nisin polyclonal antibody, anti-rabbit gold-conjugate and transmission electron microscopy, nisin Z was found to be localized in the cheese matrix, in fat globules, in the casein phase and concentrated at the fat-casein interface. After 27 weeks of ripening, nisin Z was detected preferentially in the fat globules of the experimental cheese.
利用产乳链菌肽Z的乳酸乳球菌乳酸亚种双乙酰乳酸亚种UL 719（UL 719）和商业弗洛拉·达尼卡（FD）发酵剂，开发了一种起始发酵剂系统，该系统在用于制造高达干酪的牛奶中能以可接受的速率同时产生酸和乳链菌肽。测试了不同组成的混合培养物（0、0.2、0.4、0.6或0.8%的UL 719与1.4%的FD）在30℃孵育12小时后在牛奶中的酸化和乳链菌肽Z的产生情况。0.6/1.4%的组合被选为最佳发酵剂混合物，它将牛奶酸化至合适的pH值，并以512 IU/ml的高浓度产生乳链菌肽Z。使用这种最佳组合，与对照（1.4%的FD）相比，柠檬酸盐发酵菌和非发酵菌的FD数量没有变化。然而，使用0.8%的乳酸乳球菌UL 719菌株和1.4%的FD发酵剂，与用添加到1.4%的FD或对照培养物（1.4%的FD）中的0.2、0.4或0.6%的UL 719接种牛奶时相比，发酵乳中柠檬酸盐发酵菌和非发酵菌的数量减少。混合发酵剂比例0.6/1.4%、0.4/1.4%和0.5/1.4%（UL 719/FD）用于制造含有乳链菌肽Z的高达干酪，并使其成熟长达45周。用1.4%的FD制成的对照干酪和含有乳链菌肽Z的高达干酪在水分、脂肪、盐和蛋白质百分比方面相似。在成熟期间，用0.6/1.4%混合发酵剂制成的干酪中观察到的细胞计数比对照干酪高出约两个对数。在用0.6/1.4%（UL 719/FD）混合发酵剂生产的实验干酪中，乳链菌肽活性从制造结束时的256 IU/g增加到成熟6周后的最高512 IU/g；然后在成熟27周和45周后分别降至128和32 IU/g。相比之下，在用0.4/1.4%或0.5/1.4%（UL 719/FD）混合发酵剂制成的实验干酪中未检测到乳链菌肽Z。使用亲和纯化的抗乳链菌肽多克隆抗体、抗兔金缀合物和透射电子显微镜，发现乳链菌肽Z位于干酪基质中、脂肪球中、酪蛋白相中，并集中在脂肪 - 酪蛋白界面处。成熟27周后，在实验干酪的脂肪球中优先检测到乳链菌肽Z。
