The efficacy of nisin can drastically vary when produced in situ in model cheeses |
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Authors: | Samar Aly Juliane Floury Michel Piot Sylvie Lortal Sophie Jeanson |
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Affiliation: | INRA, UMR1253, Science and Technology of Milk and Eggs, F-35000 Rennes, France; Agrocampus Ouest, UMR1253, Science and Technology of Milk and Eggs, F-35000 Rennes, France. |
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Abstract: | Nisin, a bacteriocin produced by strains of Lactococcus lactis, has a broad inhibitory effect against Gram-positive bacteria. This study investigated the efficacy of nisin Z against Lactobacillus sakei when produced by a nisin-producing strain L. lactis in model cheeses manufactured with ultrafiltrated milk. These cheeses, containing 0, 4 or 10% of gelatin in their dry matter, were inoculated with both strains. Measurement of Lb. sakei loss of viability was an indirect indicator of nisin in situ efficacy. After 24 h, the loss of viability of Lb. sakei was from 0.73 ± 0.14 to 3.30 ± 0.60 log10 cfu g−1 in the cheeses with 0 and 10% of gelatin, respectively, indicating a better in situ efficacy of nisin when gelatin was incorporated. However, the concentration of nisin produced by Lactococcus was similar (3.5 μg g−1) in all model cheeses when measured using an enzyme-linked immune sorbent assay (ELISA). The growth of Lactococcus was slightly improved when gelatin was incorporated, leading to a higher lactate concentration, which is one of the factors explaining the increased nisin efficacy. These results reinforced previous observations that prediction of nisin efficacy in complex food systems remains difficult. |
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Keywords: | Nisin Efficacy Cheese Microstructure Lactococcus lactis ELISA |
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