title: Improved model based on the Weibull distribution to describe the combined effect of pH and temperature on the heat resistance of Bacillus cereus in carrot juice.
abstract: The effect of pH and temperature on the thermal inactivation of different strains of Bacillus cereus was modeled. Inactivation tests were carried out in carrot broth, following a full factorial design at four levels for temperature (from 90 to 105 degrees C, depending on the strain) and pH (6.2, 5.8, 5.2, and 4.7). Individual inactivation curves were analyzed by applying the Weibull model function (with percent discrepancy close to 20% for most cases), and the effects of pH and temperature on the scale parameter (designated D(beta)) and the shape parameter (beta) were also studied. Temperature and pH did not have a significant effect on the shape parameter (beta). The effect of temperature on the scale parameter was modeled by the zeta concept. The scale parameter decreased with pH, although the behavior of the strains was not homogeneous. Two global models with a small number of parameters were developed, providing a satisfactory description of the thermal inactivation of B. cereus, with percent discrepancy ranging from 18 to 25%.
authors.affiliation: Instituto de Agroquímica y Tecnología de Alimentos (C.S.I.C.), Apartado de Correos 73, 46100 Burjassot, Valencia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Collado
authors.forename: A
authors.initials: A
authors.lastname: Fernández
authors.forename: L M
authors.initials: LM
authors.lastname: Cunha
authors.forename: M J
authors.initials: MJ
authors.lastname: Ocio
authors.forename: A
authors.initials: A
authors.lastname: Martínez
mesh_terms: D001409:Bacillus cereus / Q000254:growth & development / Q000502:physiology*; D001628:Beverages / Q000382:microbiology*; D018552:Daucus carota / Q000382:microbiology*; D005516:Food Microbiology; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008954:Models, Biological; D016008:Statistical Distributions