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

Abstract

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 (2(2)+2*2+3) was used to estimate the influence of temperature (17·2-22·8°C) and pH (3·28-4·7) on A. section Nigri growth (λ, lag time; μ, growth rate). Secondary models (polynomial and Arrhenius-Davey) describing the effects of temperature and pH on λ and μ were constructed. A decrease in temperature from 22·8°C to 17·2°C resulted in an a 16-fold increase in λ. The increase in temperature from 20°C to 22·8°C at pH=4·0 led to a fourfold increase in μ. The polynomial model was the best in fitting the data and the pH (linear), temperature (linear and quadratic terms) significantly influenced λ. For μ, there was a significant influence by the pH (linear), temperature and pH (quadratic terms).

Conclusions: The storage of mango nectar at <15°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.