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Red beetroot as a rich source of bioactive and health enhancing compounds has a high potential for use in a wide range of foods and its powder with containing these compounds, can be used as a natural antioxidant and colorant in the food industry. In the present study, red beetroot pulp powder was produced by foam-mat drying technique. Drying kinetics, physicochemical and microstructural properties of the resulting powder were investigated. To prepare foam, 2% ovalbumin (w/v) was added to the red beetroot pulp and stirred for a specific time and speed. Prepared foam was spread on aluminum plates at thicknesses of 5, 6 and 7 mm and then dried in a hot air cabinet dryer at 50 ºC and constant air velocity of 1 m/s. Results showed that increasing foam thickness from 5 to 7 mm had no significant effect on moisture content and moisture ratio but significantly (p <0.05) reduced the drying rate by about 29.63%. The effective moisture diffusion coefficient was significantly affected by the foam thickness and ranged between 5.550 × 10−9 and 7.388 × 10−9 m2/s. Also, with increasing foam thickness, due to increasing drying time and more denaturation of proteins, an increase in Carr index and Hausner ratio was observed, resulting in a decreasing trend in the flowability of the powders. Bulk and tapped densities of powders were significantly decreased due to the change in moisture content, caused by the increase in foam thickness. Thickness had no significant effect on water solubility index and water absorption index. The microstructure analysis of the produced powders by field emission scanning electron microscope showed that with increasing foam thickness, cracking and surface roughness of powder particles increased. The results of this study and further studies can lead to optimization of red beetroot powder production as a natural food coloring and better preservation of its nutritional and functional properties. [ABSTRACT FROM AUTHOR]

In this study, the effect of chia seed gum (0.1-0.3%) and albumin (5-15%) onphysicochemical properties of barberry powder (stability and density of foam, pH, density of powder, total anthocyanin content, Hygroscopic, water solubility index and Water absorption index) produced by foam-mat drying was evaluated. Results showed the increase of albumin and chia seed gum increased the stability of the foam and the solubility of the powder, while the foam density and hygroscopic of powder decreased. Increasing the concentration of albumin reduced the density and total anthocyanin content of the samples. Increasing the chia seed gum (0.1-0.2%) increased the density of powder, while increasing the chia seed gum (0.2-0.3%) reduced the density of powder and incorporated chia seed gum had no significant effect (P<0.05) on total anthocyanin content. Based on the results, pH of powders produced in the range of 3.35-3.31. The incorporation of albumin to 10%, had no significant effect (P<0.05) on pH, while incorporation of albumin (10 to 15%) significantly increased pH. Also, increasing chia seed gum (0.1-0.3 %) significantly increased the pH of the powders. [ABSTRACT FROM AUTHOR]