ARS | Publication request: Potential of Spray Dried Peanut Skin Extract as a Food Ingredient with Antioxidant Properties

Submitted to: Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 2011
Publication Date: June 10, 2011
Citation: Constanza, K.E., Dean, L.L., Davis, J.P., Sanders, T.H. 2011. Potential of Spray Dried Peanut Skin Extract as a Food Ingredient with Antioxidant Properties. Institute of Food Technologists. 1.

Interpretive Summary: The chemical composition of peanut skins includes many compounds that have antioxidant activity. The peanut industry produces hundreds of tons of this material each year, mostly at blanching plants. This material has very low economic value as the use in animal feed is limited. This study examined the feasibility of removing the compounds that are phenolic in nature and capturing them by spray drying to make powders that would be high in antioxidant activity. These powders would then be of higher value for possible nutraceutical uses. The remaining material after extraction would be low in bitter tasting phenolics and thus more palatable to animals, increasing its value as an animal feed ingredient that has levels of fat, protein and crude fiber close to that of the original skin material.

Technical Abstract: Peanut skins are known to be rich in phenolic compounds; however, they currently possess little economic value to the food industry. Blanched peanut skins were milled into a fine powder, extracted with 70% ethanol, and separated into soluble extract (SE) and insoluble fraction (IF) by filtration. The ethanol was then removed from the SE and the percent moisture and solid content for the SE and IF were determined. The SE was found to contain 5.04±0.18% solids, while the IF contained 41.64±0.71% solids. The composition of the IF was analyzed and compared to the composition of the blanched milled skins. Analysis showed little change between proximate levels from blanched milled skins and IF on a dried weight basis indicating IF would have value for animal feed. Result of the analysis no difference in percent fat, protein, fiber, and ash on a dry weight basis between the blanched milled skins and the IF. The SE was spray dried with a maltodextrin carrier agent in a 1:4 solids to maltodextrin ratio and again without the addition of a carrier agent. The SE, spray dried extract (SDE), and spray dried encapsulated extract (SDEE) were further analyzed for total phenolic content using the Folin-Ciocalteu method. The SE, SDEE, and SDE were determined to contain 2400±130, 11600±440, and 77400±3300 mg GAE/100g, respectively. The antioxidant capacities were also determined using hydrophilic oxygen radical antioxidant capacity (H-ORAC) and found to be 6500±880 for the SE, 58000±3100 for the SDEE, and 252000±78000 µmoles Trolox/100g for the SDE. Results of the H-ORAC and total phenol assays show a concentration effect in both phenolic compounds and antioxidant capacity post spray drying. The solubility of the SDE and SDEE was increased by approximately 2-fold from the milled peanut skins. Spray drying of peanut skin extract produces a phenolic concentrated powder that has potential use in the food industry as a functional ingredient with high antioxidant capacity.