Department of Food Science, Parco Area delle Scienze 11/A, University of Parma, 43124 Parma, Italy.
Food Microbiol. 2013 Sep;35(2):116-20. doi: 10.1016/j.fm.2013.02.013. Epub 2013 Mar 7.
Cheese ripening involves a complex series of biochemical events that contribute to the development of each cheese characteristic taste, aroma and texture. Proteolysis, which has been the subject of active research in the last decade, is the most complex of these biochemical events. However, also aminoacyl derivates of non-proteolytic origin (γ-glutamyl-amino acids and lactoyl-amino acids) with interesting sensory properties have been identified in cheeses. In the present work, an enzymatic activity producing γ-glutamyl-phenylalanine in Parmigiano-Reggiano water soluble extracts was observed. It was hypothesized that γ-glutamyl-amino acids and lactoyl-amino acids could be originated by enzymes of bacterial origin. In order to confirm this hypothesis, Lactobacillus helveticus and Lactobacillus rhamnosus were chosen as representative of starter and non starter microbiota of Parmigiano Reggiano cheese. They were used as model bacteria, in the presence of suitable precursors, to verify their ability to produce γ-glutamyl-phenylalanine and lactoyl-phenylalanine. The eventual abilities of these strains were tested both during growth and after cell lyses. While γ-glutamyl-phenylalanine was produced only by lysed cells, lactoyl-phenylalanine was produced either by growing or lysed cells in different amount depending on the species, the cells condition and the time of incubation.
奶酪成熟涉及一系列复杂的生化事件，这些事件有助于每种奶酪独特的口感、香气和质地的形成。其中，蛋白水解作用是这些生化事件中最复杂的一种，也是过去十年中研究的热点。然而，人们也在奶酪中发现了具有有趣感官特性的非蛋白水解来源的氨基酸衍生（γ-谷氨酰基氨基酸和乳酰基氨基酸）。在本研究中，观察到 Parmigiano-Reggiano 水溶性提取物中产生γ-谷氨酰基苯丙氨酸的酶活性。据推测，γ-谷氨酰基氨基酸和乳酰基氨基酸可能来源于细菌来源的酶。为了验证这一假设，选择瑞士乳杆菌和鼠李糖乳杆菌作为 Parmigiano Reggiano 奶酪中代表性的起始菌和非起始菌微生物群。它们被用作模式细菌，在合适的前体存在下，验证它们产生γ-谷氨酰基苯丙氨酸和乳酰基苯丙氨酸的能力。这些菌株的潜在能力在生长过程中和细胞裂解后都进行了测试。虽然γ-谷氨酰基苯丙氨酸仅由裂解细胞产生，但乳酰基苯丙氨酸无论是在生长还是裂解细胞的情况下都能产生，具体取决于菌株、细胞状态和孵育时间，其产生量也有所不同。
