Effect of drying temperature on preservation of banana peel and its impact on degradation of targeted phytochemical by LC-Orbitrap-MS analysis

Banana peel contains many bioactive compounds that are health benefitting and face rapid deterioration due to its high moisture content. Addressing this challenge, we explored drying technique as a preservation method. Banana peels were dried at temperatures ranging from 40 to 70 °C using a hot air dryer, with resulting data fitted to nine mathematical models. The Midilli et al. model was found to be the best fit (R² = 0.9967, RMSE = 0.0130, x² = 0.0145) among all selected models, with values for an effective moisture diffusivity found between 4.22 × 10⁻¹⁰ and 9.126 × 10⁻¹⁰ m²/s and an activation energy 22.776 kJ/mol. Degradation kinetics of key constituents, including total phenolic contents, total flavonoid contents, and antioxidant activity, were elucidated using first-order kinetics. Notably, all parameters exhibited prolonged half-life at 40 °C, contrasting with increased degradation at 70 °C. Further, targeted LC-Orbitrap-MS analysis unveiled temperature-dependent changes in key phytochemicals viz., noradrenaline, dopamine, L-phenylalanine, and L-tyrosine. The average relative concentration of key phytochemicals degraded less than 50% at 40 °C and 50 °C; when drying temperature increased above 50 °C, there was an increase in the rate of degradation above 50%. Based on the interplay between drying parameters and phytochemical stability, an optimal drying temperature of 50 °C was delineated, ensuring extended preservation of banana peels for the development of functional nutraceuticals.