Sorption characteristics of flour mixtures enriched with grape seeds flour of Bulgarian and French raw materials

Abstract

The aim of the present scientific research is to study the moisture sorption characteristics of flour mixtures of Bulgarian and French origin. The mixtures are enriched with grape seeds flour in its being an enological residue. Equilibrium moisture content are determined at three different temperatures at 10 °C, 25 °C and 40°C through the standard static gravimetric method in the compulsory presence of water activity within the range from 0.1 to 0.9. The obtained adsorption and desorption isotherms have an S-shape profile i.e. they are from the IInd class typical of the majority of food products. The results confirm a regularity that the sorption capacity decreases with increasing of the temperature in the presence of constant water activity which is valid for both products as well as for both processes (adsorption and desorption). The mathematical modified models of Chung–Pfost, Oswin, Halsey and Henderson are evaluated for the description of the sorption data. The monolayer moisture content (MMC) of flour mixtures is calculated through the linearization of Brunauer-Emmett-Teller equation. For the Bulgarian mixture the values varied from 2.54% to 4.29% and for the French mixture – from 2.67% to 4.13%.

Keywords

• flour mixture
• isotherms
• moisture content
• sorption