Influence of pre-treatments on the desorption isotherm characteristics of plantain

Abstract

The desorption isother.msof fresh and pre-treated plantain, at 50 and 60°C, for relative humidity (RH) range 10-80 per cent were constructed. The sorption data were fitted to three known models and the monolayer moisture contents determined. Three pre-treatments used were: blanching at 90°C for 5 min, and two moist-infusing treatments with 40° Bsucrose and a combined solution of 15° B sucrose in 0.06 kg/kg NaC I, at 4 °C for 16 h. The last two pre-treatments reduced the monolayer moisture contents of plantain. The equilibrium moisture contents (e.m.c) of the pretreated plantain were lower, at RH < 45 per cent but higher, at RH > 45 per cent, than those of the fresh plantain. At 50°C and RH < 45 per cent, the e.m.c range for pre-treated plaintain was 2-5 per cent (d.s), compared to 4-8 per cent (d.s) for fresh plantain. At RH > 45 per cent, howerver, the e.m.c ranges were 10-48 and 10-28 per cent (d.s), respectively. Thus, at the same drying temperature, a much lower humidity condition will be required for the proper drying of pretreated than for fresh plantain