Sorption isotherms, glass transition and storage stability of drum-dried mango peels obtained with and without process additives

Abstract

The study aimed to evaluate the stability of mango peel flakes obtained by drum-drying through sorption isotherms, glass transition temperature, and controlled storage. Two products were produced using drum-drying (146 °C/15 s): without (DMP) and with process additives (DMPA) (5% corn starch d.b.; 1% glyceryl monostearate d.b.). The isotherms, obtained by gravimetric method (25 °C), had the best fit with the GAB model (R2=0.99), revealing a monolayer of 0.0954 g water/g d.b. (aw=0.5089) for DMP, and 0.0826 g water/g d.b. (aw=0.4818) for DMPA. The glass transition temperatures (Tg) were fitted through Roos and Gordon-Taylor, demonstrating the plasticizing effect of water. Combined GAB-Gordon Taylor analysis pointed out critical storage conditions (25 °C): aw=0.061 and moisture content of 0.7 g/100 g for DMPA; aw=0.055 and moisture content of 0.6 g/100 g for DMP. The storage of DMPA (aw=0.219; moisture content of 1.27 g/100 g) at 25 °C (240 days) and 35 °C (120 days) showed high retention of vitamin C, color, and phenolic compounds.