Simple & better - Accelerated cheese ripening using a mesophilic starter based on a single strain with superior autolytic properties

Abstract

In the manufacture of rennet-coagulated cheese, autolysis is a rate-limiting step for ripening. Previously, a highly autolytic and thermotolerant Lactococcus lactis strain, RD07, was generated, which in preliminary laboratory cheese trials demonstrated great potential as a cheese ripening accelerant. RD07 is proteinase positive (Prt⁺) and capable of metabolizing citrate (Cit⁺). In this study, we obtained two derivatives of RD07: EC8 lacking the citrate plasmid, and EC2 lacking the proteinase plasmid. EC2 and EC8 retained the autolytic properties of RD07, and autolyzed 20 times faster than Flora Danica (FD) and SD96, where the latter is the parent of RD07. The three strains EC2, EC8 and RD07 were used in a ratio of 90:8:2, to create a simple starter termed ERC. ERC was less sensitive to cooking when cultured in milk and autolyzed well after entering the stationary phase upon facing sugar starvation. The ERC starter was benchmarked against FD and SD96 in laboratory cheese trials. The free amino acid content in cheese prepared using the ERC culture was 31 % and 34 % higher than in cheese prepared using FD and SD96, respectively. Overall, the ERC culture resulted in a more rapid release of free amino acids. A large-scale (5000 L) Gouda cheese trial at a Danish dairy demonstrated that the single strain ERC starter was comparable in performance to FD + an adjunct Lactobacillus helveticus culture. Furthermore, a large-scale Danbo cheese trial demonstrated that ERC could reduce the ripening period by 50 % for long-term ripened (25 weeks) cheese, resulting in better cheese.

Keywords: Autolysis; Cheese starter; Intracellular peptidase; Lactic acid bacteria; Thermotolerance.