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Relationship between time-to-detection (TTD) and the biological parameters of Pichia anomala IG02; modelling of TTD as a function of temperature, NaCl concentration, and pH and quantification of their effects

Arroyo Lopez, F.N., Duran Quintana, M.C., Garrido Fernandez, A.
Food microbiology 2006 v.23 no.4 pp. 315-324
food industry, yeasts, starter cultures, Pichia, olives, fermentation, culture media, temperature, pH, sodium chloride, salt concentration, inoculum density, microbial activity, microbial growth, absorbance, plate count, linear models, food microbiology, predictive microbiology
The time to detection (TTD) for Pichia anomala IG02 was defined, for inoculum sizes lower than 6 log10 cfu/ml, as the time elapsed from inoculation to the moment at which an OD of 0.12 was reached. In other cases, TTD can be estimated by interpolation within the time elapsed from the previous readings below OD=0.12 and the next above it. A linear relationship, which depended on the inoculum size, between ln TTD with ln λ and ln μm was found. These relationships can be used to estimate the biological parameters of cultures with low inoculum levels. In addition, TTD for P. anomala IG02 could be modelled as a function of environmental conditions. The model can also be applied to λ and μm through their relationships with TTD. The effects of temperature, NaCl content and pH were quantified by the generalized z-values. An increase of 5.97 in NaCl concentration, a decrease of 1.97 units of pH, or a decrease of 6.08 °C doubled the TTD or caused a 2.53-fold increase in λ and a 2.56-fold decrease in the μm.