New approach to extend shelf life of Mozzarella cheese using antimicrobial microbes

Mozzarella cheese is a very popular Italian pasta filata product; its shelf life is approximately 5 to 7 days [1]. It is spoiled above all by Pseudomonas spp., mostly coming from water used during manufacture; Pseudomonas - due to its intense proteolytic activity - can grow in Mozzarella cheese modifying texture and reducing its shelf life. Another factor that reduces its shelf life is the presence of coliforms; effectively, Escherichia coli can grow in Mozzarella cheese reducing its safe life and, consequently, also its shelf life. Obviously, proteolytic and lipolytic reactions are of high importance in its preservation [2]; in details, the influence of the ratio of rods to cocci is one of the subjects of much interest because of its effect on proteolytic activity [3]. In order to extend shelf life of Mozzarella cheese, different options were recently evaluated: innovative active packaging systems [4,5], addition of chitosan [1], milk bactofugation [6]. However, in spite of the research carried out, at present no valid method to efficaciously inhibit the fast microbial spoilage of Mozzarella cheese can be employed. In our opinion, utilization of antimicrobial microbes can be an innovative strategy to gain this result. Recently, a strain of Lactobacillus was efficaciously tested to control Pseudomonas growth in Cottage cheese [7]. So, our aim was to select adjunct cultures of Lactobacillus spp. possessing antagonistic activity against both Pseudomonas and Escherichia coli. Through a preliminary screening in Petri plate of several lactic acid bacteria belonging to the collection of our laboratory, we identified the strain L356 of Lactobacillus paracasei ssp. paracasei exhibiting antagonistic activity against both Escherichia coli [8] and Pseudomonas spp. [data not published]. Accordingly, the strain L356 of Lactobacillus paracasei ssp. paracasei was used in co-fermentation (1:1) with a commercial strain of Lactococcus, specifically selected to control the fermentation of Mozzarella cheese: strain Lyobac-D, MO 097, Mofin Alce Group. The milk was inoculated with 5% of a preculture in milk of the Lactococcus strain and 5% of a preculture in milk of the Lactobacillus strain. We compared the co-fermentation performance towards the standard fermentation, obtained using only the Lactococcus strain. The analyses were performed after the Mozzarella cheese production (0 days) and after 7 days of storage at 5°C and at 10°C. We investigated Mozzarella cheese for the following physico-chemical and microbiological parameters: Aw; pH; % of lactic acid; % of dry matter; colour, expressed as L*, a*, and b*; total coliforms, Pseudomonas, coccal-shaped lactic acid bacteria, and Lactobacilli. Some of these analyses were also carried out on the governing liquid.Our preliminary results and the relevant related literature are discussed considering, above all, the advantages for dairy industry and the consequences for starter and adjunct culture selection.[1] C. Altieri et al. Use of chitosan to prolong Mozzarella cheese shelf life. J. Dairy Sci. 88, 2683-2688, 2005.[2] N. Y. Farkye et al. Proteolysis in Mozzarella cheese during refrigerated storage. J. Dairy Sci. 74, 1433-1438, 1991.[3] J. J. Yun et al. Mozzarella cheese: impact of rod:coccus ratio on composition, proteolysis and functional properties. J. Dairy Sci. 78, 751-760, 1995.[4] A. L. Brody. Say cheese and package it, please! Food Technol. 55, 76-77, 2001.[5] A. Conte et al. Innovative active packaging systems to prolong the shelf life of Mozzarella cheese. J. Dairy Sci. 90, 2126-2131, 2006.[6] M. Faccia et al. Influence of the milk bactofugation and natural whey culture on the microbiological and physico-chemical characteristics of Mozzarella cheese. J. Food Process Technol. 4, 7pp, 2013.[7] K. A. Neugebauer and S. E. Gilliland. Antagonistic action of Lactobacillus delbrueckii ssp. lactis RM2-5 toward spoilage organisms in Cottage cheese. J. Dairy Sci. 88, 1335-1341, 2005.[8] A. Caridi. Identification and first characterization of lactic acid bacteria isolated from the artisanal ovine cheese Pecorino del Poro. Int. J. Dairy Technol. 56, 105-110, 2003.