Lactobacilli isolated from lump sheep's cheeses and their antimicrobial properties

Abstract

Smetanková J., Hladíková Z., Zimanová M., Greif G., Greifová M. (2014): Lactobacilli isolated from lump sheep's cheeses and their antimicrobial properties. Czech J. Food Sci., 32: 152-157.A total of 34 strains of lactobacilli were isolated from the lump sheep's cheeses produced from raw sheep milk. The strains were identified by MALDI-TOF MS, and 20 of them demonstrating the best fermentation and sensoric properties in milk were chosen and tested for their antimicrobial activity. All selected strains were active against the indicator bacteria and moulds. The highest inhibitory effect was observed with the strains lactobacillus paracasei 314, l. paracasei 316, l. plantarum K816, l. plantarum L718, and l. plantarum 2L2. The subsequent research was focused on the metabolites causing this inhibition. The production of lactic and acetic acids was studied under different cultivation conditions (0, 2, 4, and 6.5% NaCl addition; cultivation at 15, 30, 37, and 45°C; and pH value of the broth before sterilisation 5 and 9). l. plantarum L718 produced the highest concentration of lactic and acetic acids under most of the cultivation conditions. Antimicrobial substances such as phenyllactic acid (62.54-101.62 mg/dm 3 ), H 2 O 2 (0.78-2.30 μg/cm 3 ), and diacetyl (produced by l. plantarum K816 and L718) were studied as well. Keywords: lactobacillus plantarum; lactobacillus paracasei; antimicrobial potentialIt is known that the natural microflora, present in the traditional biotechnological processes during manufacturing, participates in the production of the characteristic aroma, taste, and texture of different cheeses. At first, only artisanal starters were used for the dairy although fermentations. Although they are still used in certain cases, their microbiological instability promoted the evolution of more precisely defined mixtures of lactic acid bacteria (LAB). As cheesemaking became more industrialised, pasteurised milk and standardised bacterial and fungal inocula were introduced with the aim of obtaining a more stable acidifying activity and consistent quality of the products (Carminati et al. 2010). In spite of this trend, the production of raw milk cheeses is still significant, as consumers seek organic foods or traditional sensory characteristics. However, the diversity of microbial populations that have developed in the original cheesemaking environments is largely undefined and is a valuable source of new strains for commercial uses (Laurenčík et al. 2008). For example, non-starter LABs with the potential to inhibit the undesirable microflora are used in the biopreservation of foods (Rodríguez et al. 2000).As far as the technology is concerned, several characteristic properties of the bacterial strains of LAB (acid production in different media and at different temperatures, proteinase and peptidase activities, autolysis, production of volatile compounds, resistance to bacteriophages, production of inhibitory compounds) are important for their use as starters or adjuncts and have been evaluated in the sc...

Application of multiple factor analysis for the descriptive sensory evaluation and instrumental measurements of bryndza cheese as affected by vacuum packaging

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Research advances in the degradation of aflatoxin by lactic acid bacteria

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