In this research, the possibilities of applying the extrusion process to produce functional food from quinoa enriched with goji berries were studied. The physical (expansion ratio, bulk density, hardness, and specific mechanical energy) and functional (water solubility index, water absorption index) characteristics were determined and optimized by the response surface methodology. Extrudates were produced using a laboratory single-screw extruder. The full factorial experimental design was used (N = 22) with three complementary center points to show the interactions of the amount of goji berry (1, 3, and 5%) and the feed moisture content (13, 16, and 19%) of the mixture on the physical and functional characteristics. Increasing moisture content from 13 to 19% resulted in extrudates with a lower expansion ratio, water absorption index, water solubility index, specific mechanical energy, and higher density and hardness. Increasing the amount of goji berries from 1 to 5% led to a decrease in expansion ratio, water absorption index, and hardness, and an increase in density, water solubility index, and specific mechanical energy. Optimal extrusion conditions for production of extrudates from quinoa enriched with goji berry were 16.3% feed moisture content and 1.32% goji berry’s amount.

The aim of the present work was to study the potential of ultrafiltration with three polyacrylonitrile membranes (1, 10, and 25 kDa) to concentrate polyphenolic antioxidants in apple juice and extract. The permeate flux, total polyphenols, polyphenolic profile, phenolic acid content, and total antioxidant capacity were determined using the FRAP and DPPH tests, the content of water-soluble proteins during ultrafiltration was established, and the concentration factors and rejections were determined. The permeate flux decreased by increasing the volume reduction ratio and decreasing the molecular weight cut-off of the membranes. The concentration factor and rejection of polyphenolics increased with the increase in the volume reduction ratio (VRR) for all membranes and both liquids. The concentration and rejection effectiveness of the 1 kDa membrane was higher than those observed for 10 and 25 kDa during the ultrafiltration of the apple extract, while these values were comparable for 1 and 10 kDa during the ultrafiltration of the apple juice. The concentration factors and rejections of total polyphenols were higher in the extract than in the juice. Chlorogenic acid was the main compound in the polyphenol profile of apple juice. The total content of phenolic acids, determined by using HPLC, increased by 15–20% as a result of the membrane concentration, but the separation process did not significantly change the ratio between the individual compounds.

Whey ultrafiltration was carried out with a UF25‐PAN polyacrylnitrilic membrane with 25 kDa molecular weight cutoff at volume reduction factors (VRF) = 2, VRF = 3, VRF = 4 and VRF = 5. The values of the principal components dry matter, protein, fat, lactose and mineral substances in the retentates and permeate obtained; the relative share of protein, fat, lactose and mineral substances in the dry matter; the concentration factor (CF) values for dry matter, protein, fat, lactose and mineral substances; and the retention factor values for protein, lactose and mineral substances were established. The results obtained for the process characteristics showed that when the degree of concentration increased, the dry matter, protein, fat, lactose and mineral substance CFs, and the protein, lactose and mineral substance retention factors also increased. It was established that the retentates obtained at degree of concentration VRF = 5 contained the individual components in amounts close to those in the milk from which the whey was initially obtained. This would enable their further inclusion and reuse in cheese production. PRACTICAL APPLICATIONS Kashkaval is the most widely produced hard cheese in our country. After Bulgaria's accession to the European Union, the requirements relating to dairy enterprises increased rapidly. This led to considerable investment aimed at enhancing competitiveness and economic efficiency through better utilization of milk components, and environmental efficiency regarding wastewater purity. Ultrafiltration is a modern process which has already been put to practical use in Bulgarian dairy enterprises, mostly for milk treatment purposes. The aim of our investigation was to study the ultrafiltration possibilities for utilization of whey obtained in kashkaval production and the potential reuse of its valuable components in the manufacture of cheese and other food products.

The equilibrium moisture contents (EMC) of deproteinized rapeseed meal (DRM) and model extrudate, prepared from DRM and corn grits (1:1), were determined at different temperatures (20°C, 30°C, and 40°C) and water activities (0.112 to 0.851) using the static gravimetric method. The model extrudate exhibited lower sorption capacity and significantly greater hysteresis loop than these of the DRM. Five models including the effect of the temperature were applied to analyze the experimental data. The modified models of Oswin and GAB were found suitable for describing the relationship between the equilibrium moisture content, the water activity, and the temperature. In the range of temperatures studied, the DRM and the extrudate were characterized by monolayer moisture at water activities of 0.10 and 0.16, respectively. For long‐term storage at 20°C, maintaining water activities from 0.10 to 0.60 and EMCs from 7.36% d.b to 17.09% d.b. for the DRM and water activities from 0.16 to 0.60 and EMCs from 6.43% d.b to 13.61% d.b. for the model extrudate were suggested. The study demonstrated the usability of the DRM for the production of a model extrudate suitable for long‐term storage. Practical applications The European Union developed a concept for recycling waste and by‐products from food and agricultural industries and their reuse in innovative food products. In this regard, characterization and investigation of the potential application of deproteinized rapeseed meal (DRM), appearing as a waste of protein isolation from industrial rapeseed meal, was initiated. The implementation of DRM in new extruded products with functional characteristics and long‐term storage would be economically, socially, and environmentally significant. Knowledge of the sorption behavior of food products is essential for their microbiological and biochemical stability during storage. Data generated in this study could be valuable for designing technological and/or storage parameters that allow optimization of heat and mass transfer processes while working with these materials.

Introduction. The effect of hydrocolloids (xanthan gum and guar gum) on dough properties and the quality of gluten-free bread from rice and corn flour enriched with whey protein concentrate was studied. Materials and methods. For the preparation of the whey protein concentrate it was used a laboratory system with a removable flat membrane module, equipped with a 25 kDa polyacrilonitrile ultrafiltration membrane. Dough consistency was measured by degree of immersion, using automatic penetrometer. Results and discussion. Based on the preliminary experiments (with 5, 10 and 15 %) it was found that the optimal quantity of whey protein concentrate was 10 %. That is why for the further experimental tests 10 % whey protein concentrate was added to control sample bread. Addition of higher quantities of xanthan gum resulted in weak dough consistency. Concerning the dough consistency it can be concluded that the addition of xanthan gum results in release of the dough, regardless of the quantity used. The best result was obtained when 1.5 % guar gum was added. Maximum increase in bread volume was obtained with 1.5 % guar gum. The specific volume of bread significantly improved with hydrocolloids addition. It was found that the control sample had a lower specific volume. The samples containing hydrocolloids had larger volume than the control. The addition of 1 % xanthan gum resulted in an increase in H/ D index by 50 %, compared to the control sample. When 1.5 % guar gum was added, the highest results were obtainedthe increase compared to the control sample was 100 %. Guar gum had greater influence on sensory properties of gluten-free bread from rice and corn flour than xanthan gum. Addition of 1.5 % guar gum led to the best results for almost all sensory properties (without the porosity and aftertaste). The results concerning porosity and aftertaste did not differ those obtained with the addition of 1 % guar gum. Addition of 1.5 % guar gum in formulation of gluten-free bread from rice and corn flour led to the highest volume, uniform crust and crumb color, with no rust and atypical shades. The flavor was pleasant and very well pronounced, evaluated by the panelists with 8 points, while the flavor of samples with xanthan gum had 3 points. The flavor was weaker when 1 % guar gum was used (5 points). The bread samples with guar gum were appreciated as more crisp, with a very pleasant taste and aftertaste. Conclusions. For the production of gluten-free bread of rice and corn flour enriched with whey protein concentrate, the addition of 1.5 % guar gum is most appropriate.