Sorption isotherms of fortified mango bars

Abstract

Sorption isotherms of plain mango bar (86.9% total sugars, 2.7% protein and 0.54% fat, db), mango-coconut bar (81.8% total sugars, 3.0% protein and 5.0% fat, db) and mango-soya protein concentrate bar (75.2% total sugars, 13.1% protein and 0.40% fat, db) were of a sigmoid shape having long second local isotherms. Their colour and texture were adversely affected during storage at RH ⩽ 54.1%, and mould growth was observed after 13–43 days storage at RH ⩾ 75.5%; the bars retained their quality best at RH 64.8%. The sorption data were fitted to five (BET, GAB, Henderson, Oswin and Smith) models of sorption isotherms. The BET and GAB models were found to predict well the moisture content only for the plain mango bar ( R 2 0.9067 and 0-9325, E % 5.59 and 10.76) whereas the Oswin model was applicable to all the three types of bars ( R 2 0.9201–0.9731, E % 22.65–31.44).