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 (aw), 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 aw 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).
Highlights
IntroductionThe encapsulation of food compounds is used to reduce their degradation due to environmental factors (such as oxygen, light, temperature and pro-oxidants) to improve their stability during processing or to control their release in the food system (Santos and Meireles, 2010)
The encapsulation of food compounds is used to reduce their degradation due to environmental factors to improve their stability during processing or to control their release in the food system (Santos and Meireles, 2010)
The Roselle extracts (RE) used for adding gum arabic (GA), MD and MD:GA (60:40) had 88.86 ±2.82, 95.19 ±6.84 and 84.31 ± 20.93 mg of C-3-G/100 mL, respectively, of Total monomeric anthocyanins (TMA), 591.20 ± 20.20, 709.65 ± 85.12, and 788.28 ± 100.19 mg gallic acid equivalents (GAE)/100 mL, respectively, of Total phenolic compounds (TPC) and 251.61 ± 11.58, 239.37 ± 12.02 and 235.62 ± 8.85 mg trolox equivalents (TE)/100 mL, respectively, of Antioxidant capacity (AC)
Summary
The encapsulation of food compounds is used to reduce their degradation due to environmental factors (such as oxygen, light, temperature and pro-oxidants) to improve their stability during processing or to control their release in the food system (Santos and Meireles, 2010). Encapsulating agents include natural polymers or lipids. Maltodextrins and gum arabic are the most commonly used encapsulating agents in spray drying for obtaining microencapsulates. Maltodextrins provide low viscosities at high concentrations and good solubility; its emulsifying capacity is low. Gum arabic is a very efficient encapsulating agent; it is a polymer which has 2% protein in its structure providing excellent emulsifying properties; at high concentrations its viscosity increases (Gharsallaoui et al, 2007). It has been seen that mixtures of these two carrier agents may provide better results in spray drying (Zhang et al, 2007; Lopez et al, 2009; Idham et al, 2012; Fazaeli et al, 2012)
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