Sorption isotherm and shelf life of malted quinoa flour

Abstract

This work aimed to study the sorption isotherm of flour from three varieties of quinoa at 25 °C. For this, a sample of 2 g was placed in a water activity analyzer, considering data from 0.05 to 0.90 of water activity. Data of moisture content as function of water activity was plotted and fitted using different isotherm models: GAB, BET, Henderson, Halsey and Oswin. The fitting goodness was evaluated by the determination coefficient and the mean relative error. As results, GAB and Oswin models presented the best fitting of the experimental data. However, only GAB model was considered for further analysis since it has parameters with physical meaning. Using the model of Heiss and Eichner, the shelf life of the flours were determined, obtaining that mating process increase the shelf life from 13.7 to 28.5 months for white quinoa; from 13.3 to 33.9 months for black quinoa: and from 30.1 to 51.8 months for red quinoa, when stored at 25°C in low density polyethylene packs.