Combined effect of nisin and moderate heat on destruction of Listeria monocytogenes in milk

Abstract

Summary -The kinetics of destruction of two strains of L monocytogenes in skim milk heated at60°C with and without addition of 25 or 50 lU/mi of nisin were studied. The survival curves displayed an initiallag phase followed by an accelerating killing phase. As both the length of the lag phase and the destruction rate depended on the temperature and the presence of nisin, a mathematical model was necessary to compare the survival curves and to determine the time to achieve a given reduction of the Listeria counts. Two models were compared, each allowing satisfactory goodness of fit. However, as they gave verY diverging D-values, the time to achieve a given reduction (3 and 6 10glO)of the numbers of Listeria in milk was calculated using one mode!. Addition of 25 or 50 lU/mi of nisin to milk heated between 54 and 65°C considerably reduced the heat resistance of one of the two strains of Listeria so that the time needed to achieve a 3 and 6 log10 reduction of populations of this bacterium was substantially diminished. For instance, 16 min at 54°C was sufficient to achieve a 103-fold reduction of the number of Listeria in milk containing 25 lU/mi nisin, compared to 77 min in absence of nisin. The cornbined effect of heat and nisin was somewhat enhanced if the bacteria were previously grown in milk at low temperatures. Factors that affect the heat resistance of Listeria are discussed as weil as the possible mode of action of nisin and heat on destruction of bacterial cells.

Nisin, temperature and pH effects on growth and viability of Pectinatus frisingensis, a Gram-negative, strictly anaerobic beer-spoilage bacterium

“…In starving P. frisingensis cells, combined effect of pH and temperature led to a strong K + release by the cells, the highest K + leaks were measured when pH was 6·2 and temperature was 50 °C, whatever the nisin level addition. This was in agreement with what was reported by Maisnier‐Patin et al . (1995), who showed that a combination of heat treatment and nisin could either enhance bactericidal action of nisin, or increase susceptibility of bacteria to the bacteriocin.…”

Evaluation of efficacy of turmeric as a preservative in paneer

“…No data are reported in the literature for effect of stage of addition of turmeric on extending the shelf life of paneer. However, similar observations were made by Hurst (1981) and Maisnier-Patin et al (1995) in case of nisin, wherein better action of nisin is reported in reducing the growth of bacteria when it was used in combination with heat treatment. According to Maisnier-Patin et al (1995) nisin enhances the effect of moderate heat and had a greater effect when used along with heat.…”

“…However, similar observations were made by Hurst (1981) and Maisnier-Patin et al (1995) in case of nisin, wherein better action of nisin is reported in reducing the growth of bacteria when it was used in combination with heat treatment. According to Maisnier-Patin et al (1995) nisin enhances the effect of moderate heat and had a greater effect when used along with heat. Taking into account that the mode of action of nisin involves pore formation in the cell membrane, the dramatic increase in thermal destruction of bacteria in the presence of nisin can be attributed to a synergistic effect of heat and nisin on the membrane damage, leading to rapid efflux of cytoplasmic constituents viz., ATP, amino acids, potassium, etc.…”

Predictive model for the reduction of heat resistance of Listeria monocytogenes in ground beef by the combined effect of sodium chloride and apple polyphenols

“…The most susceptible individuals are expectant mothers, the very young with developing immune systems, and elderly and/or levels, and presence of inhibitors (Doyle et al, 2001). The heat resistance of L. monocytogenes in foods increases with fat levels (MacDonald and Sutherland, 1993), pH (Juneja and Eblen, 1999), salt content (Juneja and Eblen, 1999), and absence of antimicrobials (Maisnier-Patin et al, 1995). The special properties of a specific food may help protect L. monocytogenes against heat lethality.…”