Sorption and mass exchange characteristics of extrudates enriched with cocoa bean shells

¹ Department of Process engineering, Technical Faculty, University of Food Technologies, 4002 Plovdiv, Bulgaria
² Department of Technology of cereals, fodder, bread and confectionary products, Technological Faculty, University of Food Technologies, 4002 Plovdiv, Bulgaria
³ Department of Analytical chemistry and Physical chemistry, Technological Faculty, University of Food Technologies, 4002 Plovdiv, Bulgaria

^* Corresponding author: nesho.t@abv.bg

Abstract

The aim of the experimental work was to determine the sorption isotherms of wheat extrudates enriched with cocoa bean shells at different temperatures (10 °C, 25 °C, 40 °C) and water activities (0.11 to 0.85) using the static gravimetric method. Five three parameter models (Chung-Pfost, Halsey, Oswin, Henderson, GAB) were applied to survey the experimental data. It was established that the isotherms demonstrate Types II, according to the Brunauer’s classification and the Oswin and Chung-Pfost models were suitable for describing the relationship between the equilibrium moisture content and the water activity. The monolayer moisture content was established using the Brunauer-Emmett-Teller equation and ranged within 5.08 % d.b. and 7.80 % d.b., respectively. The increase of temperature decreases the sorption characheristics of the examined extrudates. The specific surface area of sorption for wheat extrudates enriched with cocoa bean shells varies between 181.59 (m²/g) and 278.82 (m²/g). It was found that the increase of temperature of the matrix in the range of 10 °C to 40 °C decreases the values of monolayer moisture content and the specific surface area of sorption.