Oh Nam Su, Lee Hyun Ah, Myung Jae Hee, Joung Jae Yeon, Lee Ji Young, Shin Yong Kook, Baick Seung Chun
R&D Center, Seoul Dairy Cooperative, Ansan 425-839, Republic of Korea.
J Microbiol Biotechnol. 2014 Jun 28;24(6):795-802. doi: 10.4014/jmb.1402.02007.
The aim of this study was to determine the effects of temperature and supplementation with skim milk powder (SMP) on the microbial and proteolytic properties during the storage of cottage cheese. Cottage cheese was manufactured using skim milk with 2% SMP and without SMP as the control, and then stored at 5°C or 12°C during 28 days. The chemical composition of the cottage cheese and the survival of the cheese microbiota containing starter lactic acid bacteria (SLAB) and non-starter culture lactic acid bacteria (NSLAB) were evaluated. In addition, changes in the concentration of lactose and lactic acid were analyzed, and proteolysis was evaluated through the measurement of acid soluble nitrogen (ASN) and nonprotein nitrogen (NPN), as well as electrophoresis profile analysis. The counts of SLAB and NSLAB increased through the addition of SMP and with a higher storage temperature (12°C), which coincided with the results of the lactose decrease and lactic acid production. Collaborating with these microbial changes, of the end of storage for 28 days, the level of ASN in samples at 12°C was higher than those at 5°C. The NPN content was also progressively increased in all samples stored at 12°C. Taken together, the rate of SLAB and NSLAB proliferation during storage at 12°C was higher than at 5°C, and consequently it led to increased proteolysis in the cottage cheese during storage. However, it was relatively less affected by SMP fortification. These findings indicated that the storage temperature is the important factor for the quality of commercial cottage cheese.
本研究的目的是确定温度和添加脱脂奶粉（SMP）对农家干酪储存期间微生物和蛋白水解特性的影响。以添加2% SMP的脱脂乳和不添加SMP的脱脂乳为对照制作农家干酪，然后在5°C或12°C下储存28天。评估了农家干酪的化学成分以及含有发酵剂乳酸菌（SLAB）和非发酵剂乳酸菌（NSLAB）的干酪微生物群的存活情况。此外，分析了乳糖和乳酸浓度的变化，并通过测定酸溶性氮（ASN）和非蛋白氮（NPN）以及电泳图谱分析来评估蛋白水解情况。通过添加SMP以及在较高储存温度（12°C）下，SLAB和NSLAB的数量增加，这与乳糖减少和乳酸产生的结果一致。与这些微生物变化相关的是，在储存28天结束时，12°C下样品中的ASN水平高于5°C下的样品。在12°C下储存的所有样品中，NPN含量也逐渐增加。总体而言，在12°C下储存期间SLAB和NSLAB的增殖速率高于5°C，因此导致农家干酪在储存期间蛋白水解增加。然而，它受SMP强化的影响相对较小。这些发现表明储存温度是影响市售农家干酪质量的重要因素。
