Senggani fruit (Melastoma malabathricum Linn.) extract as a natural indicator in pH-responsive PVA-taro starch plastic packaging

Abstract

Polyvinyl alcohol (PVA)-starch-based bioplastics are widely used in many applications. pH-responsive plastic packaging was produced through the incorporation of senggani ( Melastoma malabathricum Linn.) fruit extract into PVA-taro starch-based plastic packaging. The objective of this research was to examine the characteristics of senggani fruit extract under different pH conditions and explore its application as a pH indicator in intelligent packaging. The senggani fruit was extracted through the maceration method using a solvent comprising 96% ethanol and 3% citric acid, with a ratio of 85:15 (v/v). The senggani fruit extract solution underwent color changes, appearing pink at pH levels below 6, pale purple at pH 7–11, and brownish-yellow at pH 12–14. Notably, the color of the senggani fruit extract solution remained stable at pH < 5. Before the addition of the senggani fruit extract, the PVA-taro starch solution produced a brownish-yellow plastic packaging. However, following the addition of senggani fruit extract, the plastic packaging turned pink. The addition of senggani fruit extract affected the mechanical properties of plastic packaging, resulting in a reduction in swelling from 103.679 ± 2.456% to 57.827 ± 3.563%, a decrease in tensile strength value from 3.827 ± 0.603 Mpa to 1.991 ± 0.460 Mpa, and a decline in the percent elongation value from 156.250 ± 12.392% to 116 ± 6.722%. Plastic packaging incorporating senggani fruit extract exhibits color changes across the pH range of 1–14, accompanied by varying color parameter values (L, a, b, E, and WI). Therefore, it has the potential to be used as intelligent packaging for monitoring food freshness and quality.