Development of intelligent packaging for real-time monitoring of the freshness of Canadian fish (tilapia and salmon) and pork during storage

In the present work, the freshness of fish fillets and pork was monitored in real time with intelligent packaging that utilised pH-sensitive food dye strips as indicators of freshness. Strips were attached to the inner sections of transparent plastic lids where the meat samples were stored. pH-sensitive dyes interacted with compounds such as ammonia, dimethylamine, and trimethylamine, collectively referred to as total volatile basic nitrogen, which are released by a deteriorating meat sample into the headspace of the packaging. Deterioration of the Canadian-based pork samples was observed at room temperature (25°C), and all pH strips indicated colour change. For the fish sample, phenol red and bromocresol purple dye indicators were tested. The phenol red dye strip worked best as a colorimetric indicator for monitoring freshness. The phenol red dye strip changed from yellow to a more noticeable red colour when compared to bromocresol purple. For the pork sample, four dyes were compared: bromocresol green, phenol red, methyl red, and bromothymol blue. Bromocresol green was the most reactive of all the dye strips. To further validate the reactivity of the dye strips to deterioration, total viable counts and Pseudomonas spp. counts were determined. The results showed a positive correlation between microbial load and colour change in dye strips within a 60-h period. The total viable count ranged from log 7.59 - 9.8 CFU/g, while the Pseudomonas spp. count ranged from log 6.93 - 10.15 CFU/g. Overall, this method would be an inexpensive approach to food packaging that will benefit the meat industries for monitoring the shelf life of meat samples, thereby increasing consumer confidence.