A simple time temperature indicator for real time microbial assessment in minimally processed fruits

Colorimetric time temperature indicator (TTI) which changes colour from colourless to brown due to phenol oxidation in the presence of Na2CO3 and ammonium per sulphate (APS; free radical initiator) is developed. Twelve TTI prototypes were prepared by using different concentrations of Na2CO3 (23-59 mM), APS (21-43 mM) with 2% (wt/vol) phenol. Significant (p < 0.05) effect of Na2CO3 and APS was observed on the activation energy (Ea(TTI)) of TTI. Activation energy (Ea(microbial)) of microbial spoilage in three minimally processed fruits (pineapple, pomegranate, jackfruit) was evaluated. Colour change of TTI having Ea(TTI) similar to the fruits Ea(microbial) demonstrated good correlation (R-2 >= 0.7) with microbial growth in all the three fruits. Microbial counts in fruit samples stored under temperature abuse conditions were estimated within an error of +/- 1 Log(10) CFU g(-1) by analysing colour change in TTI using DSLR camera. TTI was successfully employed for rapid determination of microbial quality.

Automated summary

A colorimetric time temperature indicator (TTI) that changes color from colorless to brown has been developed for rapid determination of microbial quality in fruits. The TTI shows a good correlation with microbial growth in fruits under temperature abuse conditions, making it a useful tool for estimating microbial counts in fruit samples.