MASS TRANSFER KINETICS OF BANANA SLICES DURING OSMO‐CONVECTIVE DRYING

Abstract

ABSTRACT The mass transfer kinetics of banana slices during osmotic dehydration in terms of water loss and solid gain in sugar syrup was studied. The effect of process parameters such as thickness of banana slices (4, 8 and 12 mm), sugar syrup concentration (40, 50 and 60% w/w) and sample‐to‐sugar syrup solution ratio (1:2, 1:4 and 1:6) on water loss and solute gain were also evaluated. Water losses and solid gains were increased with increase in sugar syrup concentration and banana slice sample‐to‐sugar syrup solution ratio and it has increased with the decrease in thickness of banana slices. Two‐factor analysis of variance for all experiments indicated that osmosis time of banana and sugar syrup solution concentration, sample‐to‐sugar ratio and thickness of banana slices were highly significant, whereas combination osmosis time and sugar syrup solution concentration, sample‐to‐sugar ratio and thickness of banana slices were nonsignificant. Osmotic time of 5–6 h was required to attain maximum water loss and solid gain by banana slices. The optimum best combination of banana osmosis for water loss and solid gain were found to be: 50% sugar syrup solution + 8 mm thickness of banana slices + 1:6 sample‐to‐sugar syrup solution ratio. Drying kinetics of osmosis banana slices were studied in a laboratory model tray dryer at 55, 60 and 65C air temperature. Seven thin‐layer drying models were fitted to the experimental moisture ratio data. Among the mathematical models investigated, the Wang and Singh model satisfactorily described the drying behavior of banana with high r2 values of 0.9989. The effective moisture diffusivity ranged from 5.3 × 10−8to 9.3 × 10−8 m2/s.PRACTICAL APPLICATIONSThe process of osmotic dehydration can be used for the preparation of shelf‐stable products for the purpose of use during off‐season. The quality of pre‐osmosed banana slices are much more superior to the product dehydrated with the convectional method of convective dehydration. The osmotically dehydrated banana slices can be used as banana‐figs, fruit candy, fruit toffee, infant food and it can become part of foodstuffs like cakes, pastries and many others.