Modelling the lag time and growth rate of Aspergillus section Nigri IOC 4573 in mango nectar as a function of temperature and pH

Aims: To assess the behaviour of Aspergillus section Nigri IOC 4573 in mango nectar as affected by temperature and pH. Methods and Results: A central composite design (22 + 2*2 + 3) was used to estimate the influence of temperature (17 center dot 2-22 center dot 8 degrees C) and pH (3 center dot 28-4 center dot 7) on A. section Nigri growth (lambda, lag time; mu, growth rate). Secondary models (polynomial and Arrhenius-Davey) describing the effects of temperature and pH on lambda and mu were constructed. A decrease in temperature from 22 center dot 8 degrees C to 17 center dot 2 degrees C resulted in an a 16-fold increase in lambda. The increase in temperature from 20 degrees C to 22 center dot 8 degrees C at pH = 4 center dot 0 led to a fourfold increase in mu. The polynomial model was the best in fitting the data and the pH (linear), temperature (linear and quadratic terms) significantly influenced lambda. For mu, there was a significant influence by the pH (linear), temperature and pH (quadratic terms). Conclusions: The storage of mango nectar at < 15 degrees C and reduced pH could completely inhibit the growth of A. section Nigri. Significance and Impact of the Study: This is the first study to show how storage temperature and seasonal variability (pH) between harvests may affect mould growth in mango nectar.