Optimisation of pectin production from dragon fruit peels waste: drying, extraction and characterisation studies

Abstract

Reutilisation of agricultural wastes is a major challenge faced by the research community. The current study aimed to address this issue by recovering commercial pectin from dragon fruit peels by investigating the pretreatment and extraction process and their parameters. Optimum oven-drying temperature was identified at 45 °C with the highest pectin yield (6.27%) and the lowest ash content (8.34%). Investigation of the drying kinetics revealed Page’s model as the best-suited model to the experimental data in terms of the highest R2 (0.99685) and lowest RSME (0.0002). A three-factor, three-level Box–Behnken design was applied to optimise ultrasound-assisted pectin extraction for the parameters of time, temperature and solid-to-liquid ratio. Under the optimised condition of 32 min at 85 °C with a ratio of 1:30 g/ml, a maximum pectin yield (23.09%) was obtained as compared to the predicted value (22.84%). The extraction kinetics study showed the logarithmic model was the best-fitted model to represent pectin’s extraction in terms of the highest R2 (0.9384) and lowest RMSE (0.821). Degree of esterification of pectin pre- (36.36%) and post-optimisation (33.27%) characterised it as low methoxyl pectin. The ash content of pectin was reduced by 23.65% revealing that higher-purity pectin was extracted following optimisation. Comparison of the Fourier transform infrared spectra with commercial-grade pectin shows the extracted pectin from dragon fruit peels has high potential in food applications. The current study recommends waste dragon fruit peels as a sustainable alternative source for high-value pectin.