Modelling of the desorption characteristics of a mixture of linseed and fruit granules

A growing tendency in the production and in the application of ready mixtures, fully composed of dry components is observed in the last years. Their use does not require mixing, homogenizing and preservation of their components separately, which makes easier their application in the so-called craft bakeries, as well as in home conditions in the preparation of bread, pastry and confectionery. The desorption capacity of a ready mixture of golden linseed - 46%; brown linseed - 25%; plum granules - 9% and date palm granules - 8% - biological farming ingredients is examined in the present research. The research is conducted in three temperatures 10°C, 25°C and 40°C and eight water activities in the range of 0.11 to 0.85. The achievement of equilibrium moisture content is followed, a mathematical analysis of the results is done and the monolayer moisture content (MMC) of the examined product is calculated through Brunauer-Emmett-Teller (BET) model linearization. The received results indicate dependences which are proved in the years, namely that the temperature increase in constant water activity, leads to the reduction of the equilibrium moisture content. The sorption isotherms are of the characteristic type III for nutrients according to the Brunauer et al classification. According to the common suitability criteria - average relative error, standard deviation and residues distribution, two three parametrical modified models are recommended for the desorption isotherms description, as the Chung-Pfost model is the first suitable model and the Henderson model is the second one. The MMC calculated values of the ready mixture for the three temperatures with experimental points for water activity aw < 0.5 are the following: 10°C - 4.37% d.m., 25°C - 3.54% d.m. and 40°C - 3.15% d.m.