Comparison of linear and GAB isotherms for estimating the shelf life of low moisture foods packaged in plastic films

Abstract

The shelf life of dried onion flakes and sliced green beans packaged in a plastic film and stored at 30 °C/75% RH and 40 °C/90% RH was calculated using the GAB and the linear approximation of the isotherm to ascertain whether or not the simplified linear model can be used with confidence to predict shelf life. This is of particular relevance to those in industry who may want to predict shelf life but lack the software to make the relevant calculations based on the more complex GAB isotherm. The results indicated that predicting the shelf life of low moisture foods packaged in plastic films using the simplified linear model can be done with confidence. The GAB model predicted longer shelf lives than were achieved in practice, with the over-estimation ranging from 5.8% for onion flakes at 30 °C/75% RH to 17.5% for onion flakes at 40 °C/90% RH. The corresponding range for green beans was 11.9% and 13.9% respectively. For industrial purposes, use of the GAB model for shelf life predictions does not appear to be warranted as predictions using the linear model were closer to the actual measured shelf lives. More comparative trials accompanying the experimental work would be required to confirm the validity over a wide range of practical applications. • • Shelf life of dried vegetables in plastic film can be predicted. • • Linear isotherm model gave good prediction of shelf life. • • GAB model predicted longer shelf lives than were achieved in practice. • • For industrial purposes, use of the linear rather than GAB model recommended.