Abstract

Freeze-drying is a process for drying foods without heat application. The physical, chemical and sensory properties of the food remain without significant changes. In this work, maltodextrin (MD), gum arabic (GA), and a blend of MD:GA (60:40) were used as encapsulating agents of Roselle (Hibiscus sabdariffa) calyces extracts. Lyophilized powders were obtained at different concentrations of encapsulating agent (0, 3, 5, and 10%, w/w). Powders were analyzed in yield and physicochemical (average size diameter (d₅₀), moisture content, water activity (a_w), bulk and compacted densities, and color), and antioxidants (anthocyanins content, total phenolic compounds, antioxidant capacity) characteristics. The yields of freeze-drying powders from different encapsulating agents ranged 82 to 95%. The average diameter (d₅₀) was higher for powders without gum (139.5±25.6 μm) than for powders with encapsulating agents (35 to 89 μm). The moisture content and a_w of the powders were in the ranges 5.3-11.2% and 0.20-0.29, respectively. The value of the red (a*) color parameter of all powders was 37.0±2.8, decreasing as increasing the gums concentration. Powders with 3% GA and MD showed the highest amount of anthocyanins: 560.93±10.13 and 543.46±15.68 mg/100 g of powder, respectively. The highest total phenolic compounds content was observed in the powder with the 3% MD:GA blend (4,705.70±140.54 mg/100 g of powder). Powder with 3% MD showed the highest antioxidant capacity (1,766.30±31.15 mg of Trolox equivalents/100 g powder).

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