In the present paper, we examined the antioxidant activity of a defatted grape seeds flour of different grape varieties locally grown in Bulgaria. The seeds are retrieved after alcoholic fermentation and the antioxidant activity of the flour was assessed by using four different methods, namely DPPH, ABTS, FRAP and CUPRAC. The results are presented in mM TE/g extract. The values are 586,08 (±41,55); 945,41 (±90,97); 553,39 (±45,57) and 667,73 (±64,30), respectively. The results are also showed in mM TE/g flour. The values are 58,67 (±4,16); 94,64 (±9,11); 55,40 (±4,56) and 66,85 (±6,44), respectively. During three-month storage of the flour in plastic bags (temperature 25 ºC and relative humidity 75%), no living cells of pathogenic organisms (Escherichia coli, Staphylococcus aureus and Salmonella spp.) or apparent molding were detected. The flour particle size has not changed either.

Sorption characteristics are an integral part of scientific research on new products since they provide data on the means of processing, transportation, and storage of food products. The present study focuses on the adsorption characteristics of a ready-made mixture of golden linseed – 46%; brown linseed – 25%; granulated plums – 9% and granulated dates – 8% which are organic farming ingredients. The experiment was conducted at temperatures of 10°C, 25°C and 40°C and water activities in the 11.2% -86.8% range. The results demonstrate that at constant water activities the increase in temperature is coupled by a decrease in equilibrium moisture content. The sorption isotherms obtained belong to Type III, typical of food products, according to the classification of Brunauer et al. For the description of adsorption isotherms, we recommend Oswin’s modified three-parameter model. Via the linearization of Brunauer-Emmett-Teller’s model, we calculated the values of the monolayer moisture content (MMC) of the mixture for the three temperatures: 10ºС – 4.85% d.m.; 25ºС – 3.92% d.m. and 40ºС – 3.34% d.m. with control points for water activity of aw < 0.5.

The consumption of healthy food will always be topical since the intake of unhealthy food has an important impact on a person’s energy resources, their state of mind and weight. This served as an impetus for the present study, namely the preparation of a new ready-made mixture for biscuits enriched with bioactive Lucuma fruit powder. We analysed the antioxidant capacity of the product via four different methods DPPH, ABTS, FRAP and CUPRAC, expressed as mM TE/g powder (2.31±0.53; 9.89±0.29; 8.08±0.51; 24.15±1.13, respectively). The essential objective of this study is to obtain experimental data on adsorption and desorption. We evaluated the sorption isotherms for both processes using the static gravimetric method for the temperatures of 10°C, 25°C and 40°C and relative humidity within the 0.11 -0.90 range. Our results showed that the sorption capacity decreases with the increase in temperature under the conditions of constant water activity. The obtained isotherms were described with four different mathematical models – modified Chung–Pfost, modified Oswin, modified Halsey and modified Henderson. According to our calculations, the modified Halsey model could be recommended for a satisfactory description of the sorption isotherms of the new biscuit mixture. The monolayer moisture content of each temperature was calculated using the Brunauer-Emmett-Teller (BET) equation for adsorption and desorption.

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%.

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