title: 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.
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.
authors: Department of Food Biotechnology, Instituto de la Grasa (C.S.I.C), Av\ Padre García Tejero no. 4. 41012, Seville, Spain. fnarroyo@cica.es
authors: F N
authors: FN
authors: Arroyo López
authors: M C Durán
authors: MC
authors: Quintana
authors: A Garrido
authors: AG
authors: Fernández
mesh_terms: D019343:Citric Acid / Q000494:pharmacology; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D016015:Logistic Models; D008954:Models, Biological; D031658:Olea / Q000382:microbiology*; D004718:Saccharomycetales / Q000187:drug effects / Q000254:growth & development*; D012965:Sodium Chloride / Q000494:pharmacology; D013011:Sorbic Acid / Q000494:pharmacology
chemical_list: D003470:Culture Media; D019343:Citric Acid; D012965:Sodium Chloride; D013011:Sorbic Acid