Probiotic, technological, and health-related characteristics of lactobacilli isolated from breast milk.

AIMS: Isolation and characterization of lactobacilli from human milk and determination of their probiotic, technological, and in vitro health-promoting properties with a view to their potential use in food fermentation. METHODS AND RESULTS: Seven lactobacilli isolates were obtained from human milk and identified as Lacticaseibacillus paracasei (isolates BM1-BM6) and Lactobacillus gasseri (BM7). The isolates were examined in vitro for their technological, probiotic, and health-promoting potential. Overall, all isolates showed important technological properties based on the ability to grow in milk whey, a high to moderate acidification capacity and the absence of undesirable enzymatic activities. Lacticaseibacillus gasseri (BM7) differed from the L. paracasei isolates by the absence of several glycosidases and the inability to ferment lactose. Isolates L. paracasei BM3 and BM5 produced exopolysaccharides (EPS) from lactose. All isolates showed probiotic potential as they were tolerant to simulated gastrointestinal conditions, had high cell surface hydrophobicity, had not acquired resistance to relevant antibiotics and had no virulence characteristics. All L. paracasei showed high antimicrobial activity against various pathogenic bacteria and fungi, while L. gasseri showed a narrower spectrum of antimicrobial activity. All isolates showed health-promoting potential in vitro, as evidenced by high cholesterol-lowering activity, high ACE inhibitory activity and marked antioxidant activity. CONCLUSIONS: All strains showed excellent probiotic and technological properties for use in lactic ferments.

Prevention of Fungal Contamination in Semi-Hard Cheeses by Whey-Gelatin Film Incorporated with Levilactobacillus brevis SJC120.

Cheese whey fermented by lactic acid bacteria (LAB) was used to develop an edible film with antifungal properties. Five LAB strains isolated from artisanal cheeses were screened for antifungal activity and incorporated into a whey-gelatin film. Of the strains tested, Levilactobacillus brevis SJC120 showed the strongest activity against five filamentous fungi isolated from cheese and cheese-making environment, at both 10 °C and 20 °C. The cell-free supernatant from L. brevis inhibited fungal growth by more than 80%. Incorporation of bacterial cells into the film did not alter the moisture content, water vapor permeability, or mechanical and optical properties. The whey-gelatin film was also able to maintain the viability of L. brevis cells at 107 log CFU/g after 30 days at 10 °C. In cheeses wrapped with L. brevis film, the size of fungal colonies decreased by 55% to 76%. Furthermore, no significant differences (p > 0.05) were observed in cheese proteolysis or in the moisture, fat, and protein content of the cheese wrapped with films. The results showed that whey-gelatin film with L. brevis SJC120 can reduce the contamination of cheese with filamentous fungi and could be used as an alternative to conventional cheese preservation and packaging.

Application of enterocin-whey films to reduce Listeria monocytogenes contamination on ripened cheese.

An enterocin whey solution, obtained by growing Enterococcus faecalis L2B21K3 and L3A21K6 in sweet whey - enterocin whey solution (EWS), was incorporated into gelatin/glycerol films that were tested for the control of Listeria monocytogenes. The films containing enterocins produced by either strain (EWS L2 and EWS K6 films) were shown to serve as a suitable matrix for bacteriocin release, preserve the anti-listerial activity for up to 90 days. When applied in cheese, EWS L2 and EWS K6 films were able to reduce L. monocytogenes contamination to undetected levels after 20 or 30 days, respectively, and prevented the migration of this pathogen from the films to cheese. The incorporation of EWS into films did not affect (p < 0.05) moisture content, solubility, permeability (water vapor and limonene), and elongation at break compared to control films (without EWS). However, thickness, swelling index and tensile strength were higher (p < 0.05) in EWS films. These results suggest that active EWS gelatin/glycerol films could be an effective, and safe application to control L. monocytogenes in cheese. In addition, the use of cheese whey as a culture medium for the production of the bacteriocins complemented with the incorporation in films formulation as a packaging material represents an alternative approach to reuse this by-product of cheese production.

Application of Bacteriocins and Protective Cultures in Dairy Food Preservation.

In the last years, consumers are becoming increasingly aware of the human health risk posed by the use of chemical preservatives in foods. In contrast, the increasing demand by the dairy industry to extend shelf-life and prevent spoilage of dairy products has appeal for new preservatives and new methods of conservation. Bacteriocins are antimicrobial peptides, which can be considered as safe since they can be easily degraded by proteolytic enzymes of the mammalian gastrointestinal tract. Also, most bacteriocin producers belong to lactic acid bacteria (LAB), a group that occurs naturally in foods and have a long history of safe use in dairy industry. Since they pose no health risk concerns, bacteriocins, either purified or excreted by bacteriocin producing strains, are a great alternative to the use of chemical preservatives in dairy products. Bacteriocins can be applied to dairy foods on a purified/crude form or as a bacteriocin-producing LAB as a part of fermentation process or as adjuvant culture. A number of applications of bacteriocins and bacteriocin-producing LAB have been reported to successful control pathogens in milk, yogurt, and cheeses. One of the more recent trends consists in the incorporation of bacteriocins, directly as purified or semi-purified form or in incorporation of bacteriocin-producing LAB into bioactive films and coatings, applied directly onto the food surfaces and packaging. This review is focused on recent developments and applications of bacteriocins and bacteriocin-producing LAB for reducing the microbiological spoilage and improve safety of dairy products.