Preparation of pH sensitive film based on starch/carbon nano dots incorporating anthocyanin for monitoring spoilage of pork

Biodegradable colourimetric films incorporating anthocyanins which can respond to food spoilage is a novel and green development in packaging field. However, when it comes to commercial applications, these biodegradable matrices lack sufficient mechanical strength and water resistivity. Hence nanomaterials are being incorporated into the matrix to improve its properties. The aim of this work was to develop intelligent starch based biopolymer film by incorporating carbon dot (CD) and anthocyanin extracted from clitoria ternatea flower (CTE). The starch/CD/CTE film (SED) was prepared by solution casting technique and characterised as novel, high sensitive, pH indicator film having the potential to monitor the freshness of packed pork. SEM, FTIR and XRD analysis showed homogenous distribution of CD and CTE in starch matrix. SED films exhibited highest mechanical, barrier, thermal and antioxidant properties due to synergistic effect of CD and CTE. Besides, SED films exhibited colour variations in different pH due to the presence of anthocyanin in CTE. Hence SED film was used as a low cost visual indicator for monitoring freshness of packed pork sample. The film showed visual colour changes from purple to green as storage time increased. This study shows that food grade ingredients can be used to prepare active smart films which can in turn be used to monitor the freshness of food product like pork.