Influence of pH and sodium chloride on kinetics of thermal inactivation of the bacteriocin-like substance P34

Abstract

To investigate the kinetics of thermal inactivation of the bacteriocin-like substance P34 at different pH and sodium chloride concentration. Samples of bacteriocin were treated at different time-temperature combinations in the range of 0-300 min and 90-120°C and the kinetic parameters for bacteriocin inactivation were calculated. For all treatments, the thermal inactivation reaction fitted adequately to first-order model. D- and k-values were smaller and higher, respectively, for pH 4·5 than for 6·0 or 7·0, indicating that bacteriocin P34 was less thermostable at lower pH. At 120, 115 and 100°C, the addition of sodium chloride decreased thermal stability. For other temperatures, addition of NaCl increased stability of the peptide. The presence of greater amount of the salt (50 g l(-1) ) resulted in a higher thermal stability of bacteriocin P34, suggesting that the reduction in water activity of the solution interfered on the stability of the peptide. Based on an isothermal experiment in the temperature range of 90-120°C, and by thermal death time models, bacteriocin P34 is less heat stable at low pH and has increased thermal stability in the presence of NaCl. Addition of NaCl improved the stability of the peptide P34 at high temperatures. Studies on kinetics of thermal inactivation of bacteriocins are essential to allow their proper utilization in the food industry.