Effect of particle size and temperature on the hygroscopic behaviour of cassava flour from dry group and storage time estimation

The cassava flour from dry group is marketed and consumed under three different particle sizes (coarse, medium and fine), mostly in the North and Northeast regions of Brazil. Thus, as a contribution to the packaging, storage and handling of this type of flour, moisture sorption isotherms were made at 25 degrees C, 35 degrees C and 45 degrees C, for three different particle sizes. Five mathematical models were fitted to the moisture sorption data and the isosteric heat of sorption (Q(st)) was calculated. The sorption isotherms indicated that the particle size did not interfere on the product's hygroscopicity and moistures below 9.55 g H2O/100 g ensures the product's microbiological stability when stored between 25 degrees C and 45 degrees C. The Oswin model displayed the best fit and the Q(st) values indicated that great amount of energy is involved in the product's drying process. The storage time of the product was estimated in 136 days.