Abstract

Food packaging plays a significant role in food product marketing. Attempts have been made to develop the
spoilage indicator for milk based on the diffusion of lactic acid, which is temperature dependent. Four lactic-
acid based indicators were obtained at different substrate concentrations. An irreversible color change of the pH
sensitive indicator (from light green to red) clearly and progressively occurred due to gradual pH reduction; here,
the vapor diffusion of lactic acid occurs which indicates the pH reduction. This indicator used as both external
and internal indicators for the detection of milk spoilage. This indicator incorporated in the packed milk film
with the help of the unidirectional permeable membrane. The unidirectional permeable membrane allows only
one direction that is from milk to the indicator and avoids backward flow which prevents the migration into the
milk. Time-temperature indicator (TTI) to be considered as good candidates to monitor quality losses of food the
activation (Ea) values of TTIs and activation (Ea) values of quality food losses have to match.