Effects of the Roasting Process Over the Content of Secondary Metabolites from Peanut Grains (Arachis hypogaea.L) with Different Colorations of Testa

Abstract

Peanut grains are source of proteins and lipids in food and generally consumed after the roasting process. This study focused on: (1) the evaluation of the content of the soluble and insoluble phenolic compounds and flavonoids, total anthocyanin and tocopherols and (2) the relationship of these compounds with the antioxidant activity (ABTS) in peanut grains with different colorations of testa (red, rose, striped and black), subject to the roasting process in an hot air oven and a microwave oven. Increases in the content of soluble phenolics along with reductions in insoluble phenolics, total anthocyanins and tocopherol were observed, without much interference in the antioxidant capacity (ABTS). The highest antioxidant capacity was found in the samples that initially had the highest soluble phenolic compounds. Although the roasting induced a release of insoluble phenolics, transforming them into soluble compounds, this change was not able to alter the antioxidant capacity of the peanuts. Practical Applications The roasting is the main method used in the pre-consumption of peanuts, providing several chemical and structural modifications due to the high temperatures used in this process. It is important to have the knowledge about changes promoted in the metabolic profile of peanut grains subjected to roasting process in microwave oven (more fast) and hot air oven (more slow), because these compounds have several important functions in the human body. With this study we observed three main answers: (1) roasting degrade the total phenolic compounds (soluble + insoluble) in most treatments; (2) the complexed phenolic compounds were more soluble after roasting the peanut grains; and (3) the roasting process in the microwave oven is faster and promote greater release of the metabolites insoluble to the soluble phase, when compared to roasted in oven.