Using anthocyanin extracts from butterfly pea as ph indicator for intelligent gelatin film and methylcellulose film

Abstract

Among variety of intelligent food packaging, pH indicator packaging is becoming more popular, which can be made from synthetic and natural compounds. The search for natural pH indicator dyes that can be used in intelligent food packaging systems has recently focused on anthocyanins extracted from plants. Thus, this work aimed to develop and characterize an intelligent tag for pH indicator based on gelatin and methylcellulose-film with butterfly pea extract (BPE). The results showed that the colors of BPE solutions had a tendency to change from red to blue in a pH range of 4.0 to 8.0. The maximum absorption peak moved to a higher wavelength was observed at around 627 nm at pH 8.0 and shifted to 574 nm when the pH decreased to 5.0. After BPE was incorporated into the gelatin and methylcellulose-based films, the film’s properties were characterized. The color of the incorporated films changed from purple to blue and blue to green in buffers with pH ranging from 2.0 to 6.0 and 7.0 to 10.0, respectively. The incorporated gelatin-based film containing BPE showed a clearer response to pH variation and showed a high pigment releasing rate when immerse in buffer of pH 10. The incorporated methylcellulose-based film containing BPE had higher water solubility than that of gelatin-based film (p < 0.05), as well as improved mechanical properties and water vapor permeability (WVP). Therefore, it is possible to use the BPE (anthocyanins) as a visual pH indicator for food package.