APPLICATION OF PELEG'S EQUATION IN DESORPTION STUDIES OF FOOD SYSTEMS: A CASE STUDY WITH SAGO METROXYLON SAGU ROTTB STARCH

Abstract

Moisture desorption is pertinent to the modelling of dehydration of food systems. The variation of moisture content with time during desorption of sago starch from six towns in Papua New Guinea was analysed using Peleg's equation. Three temperatures (30° 407deg; and 45° C) and four aw ranging from 0.103 - 0.923 were studied. The equation gave a highly significant fit to the experimental data ( r2 - 0.998 - 1.000), the two constants (Ki and K2) were obtained and both constants varied significantly (p< 0.05) with the source of the starch, temperature and aw. Kz was used to calculate the (true) equilibrium moisture content and this was unaffected by the length of the curve used in the computation. The true equilibrium moisture content approximated the moisture content that would have been obtained when weight changes were fairly constant (pseudo-equilibrium moisture content) The true equilibrium moisture content was shown to be more reliable and consequently recommended for sorption studies.