Microencapsulation of walnut, peanut and pecan oils by spray drying

- Walnut, pecan and peanut oil powders were obtained by spray drying.
- Oils of nuts were encapsulated in a blend of gum Arabic-maltodextrin-gelatin.
- Peroxides, water activity and density barely changed in stored oil powders.
- Antioxidant activity of nut oil powders was reduced during storage.
- Micrographs show larger spherical size as the oils concentration increased.

The aim of this study was to evaluate some physicochemical (peroxide index, water activity), antioxidant (DPPH method), and morphological (electron microscopy) characteristics of microencapsulated oils of walnuts (Juglans regia L.), peanuts (Arachis hypogaea), and pecans (Carya illinoinensis (Wangenh.) K. Koch obtained by spray-drying. Emulsions with two concentrations of nut oils (1 and 3%) were prepared with gum Arabic (3.1%), maltodextrin (4.7%), and gelatin (2.2%). The inlet and outlet temperatures in the drying system were 180 and 84 °C, respectively; the feeding flow rate of emulsions was 17 mL/min. Powders were stored for 28 days at room temperature. During storage, the peroxide index (PI) increased from 0.99 to 2.84-2.97 meq/kg in all types of nuts microencapsulates regardless of the amount of oil used. Water activity was lower in microencapsulates from emulsion with 1% oil. The antioxidant capacity (AC) of microencapsulates was below that found in fresh oils. However, it was observed that the AC was slightly higher in microencapsulates from emulsion with 3% oil (51.4-60.3 mg of Trolox/g) compared to those from 1% oil (46.5-49.30 mg of Trolox/g). During storage, the antioxidant capacity increased from 21.3 to 33.3% in microencapsulates from emulsion with 3% oil. Microencapsulates from emulsion with 3% oil showed a lager particle size. Therefore, one way of maintaining nut oils in good nutritious conditions is by encapsulating them in a concentration of 3%. Powders of nut oils can be used as is by including them into some daily prepared foods at home or be included in complex processed foods for improving their nutritious characteristics.

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