Sorption isotherms, glass transition and storage stability of drum-dried mango peels obtained with and without process additives
Paula Ramos Antoniolli, Cristhiane Caroline Ferrari, Daniele Fidelis Borges, Sílvia Pimentel Marconi Germer
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.