Modified starch with resistant starch content and antioxidant activity from unripe Carica papaya fruits

Abstract

Unripe Carica papaya fruits are often discarded during cultivation, contributing to environmental waste despite their rich fibre and nutritional value. This study aimed to modify starch from unripe papayas by using different physical methods, including steaming, drying, and microwaving. The starch samples were evaluated for their amylose content, resistant starch levels, phenolic content, and antioxidant activity based on DPPH radical scavenging activity. Among the methods tested, the combination of autoclaving and microwaving yielded the best results, with an amylose content of 2.76±0.02 mg/g, resistant starch at 2.82±0.08%, polyphenols at 45.97±0.19 mg GAE/g, and an IC₅₀ value for DPPH radical scavenging of 95.12 µg/mL, which showed slight antioxidant activity compared to the positive control (Trolox, IC₅₀= 10.07 µg/mL). Furthermore, the modified starch samples were assessed for physical properties, including water solubility index (31.16±0.63–44.04±0.80%), water absorption capacity (6.70±0.38–9.83±0.22 g/g), swelling power (20.27±0.42–27.60±0.29 g/g), and light transmittance (37.59±0.21–49.32±0.25% on day 1). The findings provide valuable data on modified starch from unripe Carica papaya fruits and offer a solution to reduce the annual disposal of unripe papayas, thereby mitigating their environmental impact.