Fernández, “Combined effect of nisin, carvacrol and thymol on the viability of Bacillus cereus heat-treated vegetative cells

The influence of mild heat pretreatment on the bactericidal action of nisin, carvacrol and thymol on stationary and exponential phase cells of two Bacillus cereus strains was studied. Carvacrol or thymol concentrations of 0.3mmol/L had no bactericidal effect on unheated, and a minor effect on heated B. cereus cells either in stationary or exponential growth phases. Nisin (0.15 mg/mL) alone decreased the viable counts in all cases (unheated and heated cells in stationary and exponential phase) although the two strains tested showed different sensitivity to this natural antimicrobial between them. When carvacrol or thymol were combined with nisin, it resulted in a greater loss of viability of heated cells than when nisin was applied alone. There was a synergistic effect of nisin and both essential oils with a mild heat pretreatment on the viability of B. cereus cells. This study pointed out the potential use of nisin alone and in combination with carvacrol or thymol applied after a mild heat pretreatment for preservation of minimally processed foods. Key Words: Bacillus cereus, preservation, nisin, carvacrol, thymol, hurdles, heating. Se ha estudiado la influencia de un precalentamiento moderado sobre el efecto bactericida de la nisina, el carvacrol y el timol en dos cepas de B. cereus, en fases de crecimiento exponencial y estacionario. Una concentración de 0.3mmol/L de carvacrol o de timol no tuvo ningún efecto sobre células no precalentada