Abstract
In food packaging, smart indicator films based on natural resources have greatly attracted researchers to minimize the environmental issues as well as to satisfy consumer preferences for food safety. In this research, pH-sensitive films were prepared using purple-fleshed sweet potato starch (SPS) and sweet potato peel (SPP). Two categories of the film (i) SPS and (ii) SPS/SPP, were fabricated via solvent casting technique, incorporating different concentrations of commercial purple sweet potato anthocyanin (CA) at 0%, 1%, 1.5%, and 2% (w/v) and the physicochemical, mechanical, thermal, and morphological properties of the films were investigated. The thickness, water solubility, and swelling degree of the films increased with the increment of CA, whereas there were no significant changes in the water content (WC) of the films. Water vapor permeability (WVP) was decreased for SPS films while statistically similar for SPS/SPP films. The addition of CA reduced the tensile strength (TS) and tensile modulus (TM) yet increased the elongation at break (EaB) of the films as compared to films without CA. The FTIR results confirmed the immobilization of anthocyanin into the film. In SEM images, roughness in the surfaces of the CA-associated films was observed. A reduction of thermal stability was found for the films with anthocyanin except for the SPS/SPP CA 2% film. Furthermore, the CA-associated films showed a remarkable color response when subjected to pH buffers (pH 1 to 12) and successfully monitored chicken freshness. The fastest color migration was observed in acidic conditions when the films were immersed into aqueous, acidic, low fat, and fatty food simulants. The findings of this work demonstrated that the developed pH indicator films have the potential to be implemented as smart packaging to monitor food freshness and quality for safe consumption.
Highlights
commercial anthocyanin (CA) 2%, sweet potato starch (SPS)/sweet potato peel (SPP) CA 0%, and SPS/SPP CA 2% were considered for Fourier Transform Infrared Spectroscopy (FTIR) operation, and
This study revealed anthocyanin incorporation in the SPS and SPS/SPP films has improved the elasticity with considerable tensile strength and rigidity
After the addition of CA into the SPS and SPS/SPP films, the thickness, water solubility and swelling of the films increased whereas the moisture content was not significantly affected to both types of films
Summary
As a substitute for plastic, the use of biopolymers for food packaging can play a vital role in minimizing this problem. Biopolymers are considered an important raw material for packaging films because of their plentiful availability, cheap rate, and biodegradability [1,2]. Biopolymers can be natural or synthetic, of which the natural one is more eco-friendly compared to the synthetic one [3]. Decent film-forming ability, biocompatibility, and biodegradability features make this hydrocolloid biopolymer the most promising packaging material [6]. To prepare starch-based biopolymers various sources of starch such as corn, rice, wheat, potato, and cassava along with other starchy foods such as yams, peas, and lentils are used as raw materials [7]
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