The Influence of Nisin on the Thermal Resistance of Bacillus cereus

Abstract

Decimal reduction times (D-values) at cooking and autoclaving temperatures (80 to 120°C) of spores of Bacillus cereus ATCC 1479-8 in rice and milk (13% wt/vol) supplemented with nisin (25 μg/ml) were evaluated. The mean D-values at 97.8°C in cooked white rice, phosphate buffer (pH 7.0), and rice water (pH 6.7) were 3.62, 1.99, and 1.34 min, respectively. From 80 to 100°C, the mean reduction in D-values due to the addition of nisin to milk was 40%. The D-value at 110°C was ~0.86 min for milk (control) and milk with nisin. The z-values ranged from 7.32°C (phosphate buffer) to 10.37°C (milk control).

Use of nisin and other bacteriocins for preservation of dairy products

“…Synergism has been reported between bacteriocins and traditional and novel treatments: mixtures of LAB bacteriocins (O'Sullivan, Ryan, Ross, & Hill, 2003) or LAB bacteriocins combined with other antibacterial compounds (Koza´kova´, Holubova´, Plockova´, Chumchalova´, & Curda, 2005) may enhance their antibacterial effect. An increase in microbial inactivation has been also reported by adding bacteriocins prior to a mild thermal (Penna & Moraes, 2002) or non-thermal (Sobrino-Lo´pez, Raybaudi-Massilia, & Martı´n-Belloso, 2006) treatment.…”

“…From a hurdle approach, nisin is known to influence the thermal resistance of microorganisms. The D value of B. cereus in milk was reduced in the presence of nisin by up to 40% at temperatures in the range 80-100 1C (Penna & Moraes, 2002), while the apparent D values of B. stearothermophilus at 130 1C were reduced by 21% due to the presence of 4000 IU nisin mL À1 (Wandling, Sheldon, & Foegeding, 1999). Consequently, the use of nisin in combination with those heat treatments extended the shelf life of milk, even with poor refrigeration conditions, making possible the substitution of the current thermal treatment for milder treatments and, consequently, better sensory quality.…”

Effects of temperature, pH, and controlled water activity on inactivation of spores of Bacillus cereus in paprika powder by near-IR radiation

“…5). No substantial effect was attained by reducing the pH from 4.5 to 4.0, though there was a tendency for decreased heating medium pH to reduce the apparent heat resistance of B. cereus spores at lower product temperatures (Gaillard et al, 1998;Penna and Moraes, 2002), i.e. at 90°C the reduction in spore concentration at pH 4.0 was approximately 1 log 10 CFU/g greater than at pH 4.5, whereas at 100°C same results were obtained at both tested pH values.…”

Infrared Decontamination of Oregano: Effects on Bacillus cereus Spores, Water Activity, Color, and Volatile Compounds

“…Due to the occurrence of B. cereus in herbs and spices (EFSA , ; Daelman and others ), and the fact that spores are more resistant to thermal treatment than vegetative cells (Setlow ), spores of B. cereus were used as a suitable indicator to monitor the efficiency of the IR decontamination process in oregano. The strain B. cereus ATCC 14579 was selected as an indicator strain due to its mesophilic characteristics, and the fact that it has previously been used when evaluating thermal resistance of B. cereus spores (Penna and Moraes ). The Bacillus strain was used to prepare spores according to Andersson and others (), but with modifications of the growth medium used.…”