Sorption characteristics of ready-made mixtures containing oatflakes, apples, and cinnamon

^1* Department of Process Engineering, University of Food Technologies – Plovdiv, 26 Maritza Blvd. BG-4002 Plovdiv, Bulgaria
² Department of Mechanical and Instrument Engineering, Technical University - Sofia, Plovdiv Branch, 25 Tsanko Duistabanov Str., Plovdiv 4000, Bulgaria
³ Language Training Centre, University of Food Technologies – Plovdiv, 26 Maritza Blvd. BG-4002 Plovdiv, Bulgaria

^* Corresponding author: aldurakova@abv.bg

Abstract

The present paper studies the sorption characteristics of readymade mixtures containing oatflakes – 89.5%, apples – 10%, and cinnamon – 0.5 % at the temperatures of 10°C, 25°C and 40°C and for eight water activities in the 11% - 85% range. The results obtained demonstrate that at a constant water activity, the increase in temperature is coupled with a decrease in equilibrium moisture content. The sorption isotherms of the analyzed ready-made mixture belong to Type III according to the classification of Brunauer et аl. In order to describe the isotherms following the evaluation criteria, that is mean relative error, standard deviation, and distribution of residuals, the study recommends the threeparameter modified Oswin for adsorption and the Henderson model for desorption. Via linearization of the Brunauer-Emmett-Teller model, we calculate the values of monolayer moisture content (MMC) at aw < 0.5 for both processes. For adsorption, the ММC falls within the 2.51% - 3.57% d.b. range, whereas for desorption it is within the 3.41% - 3.71% d.b. range. Temperature affects the MMC since its increase leads to a decrease in the ММC for both processes. For adsorption, at a temperature between 10°C and 40°C the ММC decreases by 1.06%, and for desorption - by 0.3%.