Red dragon fruit peel extract as fish shelf-life detector bioactive agent for a chitosan-based smart packaging

Abstract

Red dragon fruit contains betalain pigment that is responsible for its deep red-purple deep colour. Betalain is known as a bioactive agent in smart packaging to sense pH change and ammonia. In this research, dragon fruit peel extract, as a betalain source, was formulated with a chitosan/polyvinyl alcohol (chitosan/PVA) mixture for developing a smart biodegradable packaging film for tilapia fish. The film was prepared by blending chitosan solution in acetic acid and PVA solution at 80 ^o C followed by the addition of the red dragon fruit peel extract at various quantities. The mixture was then cast into a thin layer and dried at ambient room temperature for 5 d. The developed films were then tested to monitor the freshness of tilapia fish fillet after 16 h at room temperature and chiller temperature. The film incorporating red dragon fruit peel extract, attached to the packaging container’s headspace containing the fish samples, shows the increase of colour intensity with time. In a separate measurement, the pH of fish fillet tends to increase, as measured every 4 h for 16 h. The increase of fillet fish pH may correlate with the emerging of ammonia from decayed fish. The independent tests of the developed films toward ammonia also show a notable response. This result implies that dragon fruit peel extract response to the pH change as well as the emerging ammonia from the fish sample. The developed chitosan/PVA enriched with red dragon fruit peel extract also shows some accepted mechanical properties such as 6.4 MPa of tensile strength and 36.37% of elongation.