Environment friendly qualitatively responsive ethyl cellulose films as smart food packaging

Abstract

The present study assessed the applicability of pH indicators in the polymeric films that can be used as smart packaging in the food industries. The pH responsive films using Ethyl cellulose (EC) and azo indicators [i.e., Methyl Orange (MO) and Methyl Red (MR)] have been developed, which have shown remarkable sensitivity towards the pH variation. After activation in different pH range, the colour variation was measured for each film with the CIE Lab methodology. A significant L * [the parameter L * represents the lightness of colours from 0 (dark) to 100 (light), in CIELAB units] variation of EC-MO was seen ranging from 59 (at 0% acid) to 32 (at 60% acid) while for EC-MR, the variation in L * parameter was seen ranging from 89 (at 0% acid) to 32 (at 50% acid). These qualitatively responsive films were further tested for their water absorption capacity and mechanical properties. The water absorption capacity of the EC film incorporated with indicators were observed to be low as compared to the EC-standard film. The incorporation of MO resulted in a regular increase in water absorption capacity range from 34.08–47.11 while the MR incorporated films showed an irregular increase from 41.13–42.13, during a 24 hrs interval. The film with MO also showed a good mechanical property when tested by a micro UTM. The peak load was observed at around 2.7 N. Necking was more observant in the EC film incorporated with MO as compared to other samples, thus showing good plasticity.