Comparative analysis of sorption characteristics of Bulgarian grape seeds and flours and flakes produced by them

Abstract

The present paper contains a comparative characteristics of results obtained from statics of the sorption characteristics of grape seeds and biologically active products obtained from them - full-fatted flour, defatted flour and full-fatted flakes. The statics of the sorption processes is conducted for three temperatures - 10°C, 25°C and 40°C and eight water activities in the range from 0.112 to 0.868. For all of the examined products the temperature rise leads to a decrease of their sorption capacity. For the description of the equilibrium curves of the examined products the three parametric modified models of Oswin, Halsey, Henderson, Chung-Pfost are used. By the method of the smallest squares, using a programme for nonlinear regression “Statistics”, the coefficients of the used models are calculated, as on the basis of universally used criteria of suitability, a relevant model is recommended for each of the four Bulgarian products. The calculation of the values of the monolayer moisture content (MMC) in water activities below 0.5 is done through linearization of the Brunauer-Emmett-Teller (BET) model. The obtained results for MMC vary within the range from 2.34% to 4.96% dry substance (d.b.) for the processes of adsorption and desorption.