Modelling of the growth-no growth interface of Issatchenkia occidentalis, an olive spoiling yeast, as a function of the culture media, NaCl, citric and sorbic acid concentrations: study of its inactivation in the no growth region

Int J Food Microbiol. 2007 Jun 30;117(2):150-9. doi: 10.1016/j.ijfoodmicro.2007.03.005. Epub 2007 Mar 21.

Abstract

A global logistic model incorporating a dummy variable for the growth medium (laboratory media or table olives brine) was used for the estimation of the growth-no growth interface of Issatchenkia occidentalis as a function of NaCl, citric and sorbic acid concentrations. The model permitted the deduction of the region where the combination of citric and sorbic acids in laboratory media (above 0.3% and 0.03% wt/vol, respectively) and brine (above 0.1% and 0.03% wt/vol), at 5% NaCl, inhibited the growth of the yeast. Subsequently, the model was validated in laboratory media within the no growth region by a response surface D-optimal design. Inactivation concentrations of sorbic acid produced a progressive loss of viability in I. occidentalis that followed a first order kinetic or downward concave inactivation curves, depending on environmental variables. These curves were properly described by a (primary) model deduced from the Weibull distribution, whose parameters, first decimal reduction time (D(beta)) and shape (beta), were expressed as a function of sorbic acid concentrations (secondary model). At 5% NaCl and within the experimental region checked, an increase of 0.010% and 0.008% sorbic acid reduced D(beta) in 10 h and decrease beta by 10%. Finally, the model was also validated in real "seasoned" table olives packing reporting a complete inactivation of the yeasts' population.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Citric Acid / pharmacology
  • Colony Count, Microbial
  • Culture Media / chemistry*
  • Dose-Response Relationship, Drug
  • Food Contamination / analysis*
  • Food Microbiology
  • Hydrogen-Ion Concentration
  • Kinetics
  • Logistic Models
  • Models, Biological*
  • Olea / microbiology*
  • Saccharomycetales / drug effects
  • Saccharomycetales / growth & development*
  • Sodium Chloride / pharmacology
  • Sorbic Acid / pharmacology

Substances

  • Culture Media
  • Citric Acid
  • Sodium Chloride
  • Sorbic Acid