Abstract:

Primary models (Gompertz) and secondary models (square root and Arrhenius) were built to describe the growth
of yeast and lactic acid bacteria in vacuum-packed fresh-cut purple sweet potatoes at different temperatures. The accuracy of
models was verified by accuracy factor (Af) and bias factor (Bf). The advantages of two secondary models were compared.
According to sensory evaluation, the spoilage limit for purple sweet potatoes was determined. Then the predictive model for
the shelf life of sweet potatoes was built and verified. The results showed that the growth of yeast and lactic acid bacteria
could be well described by the Gompertz models, with correlation coefficients R2 near 0.9; the mathematical parameters
(Af and Bf near 1.0) were both in acceptable range. For both microbial species, the square root models were better than the
Arrhenius models in terms of mathematical parameters. Yeast was a better indicator of the shelf life of purple sweet potatoes
than lactic acid bacteria. The spoilage limit of yeast was 6.64 (lg(CFU/g)). A predictive model for the growth of yeast at 4 ℃
was established and validated. The measured shelf life of purple sweet potatoes at 4 ℃ was 7.0 d, while that obtained from
the mode was 7.737 d. The good agreement indicated that this model is reliable.

Key words: fresh-cut purple sweet potato, yeast, lactic acid bacteria, predictive model, shelf life