Evaluation of Amaranthus mantegazzianus as a novel source of antioxidante compounds

MARIA VIRGINIA CASTEL; OSCAR ANDRICH; FLAVIA NETTO; LILIANA SANTIAGO; CARLOS CARRARA

Oxford

Conferencia; 1st UK International Functional Food Conference- The science, claims and marketing of functional food; 2010

Functional Food Centre, Oxford Brookes University

The evaluation of antioxidant activity of different natural sources has gained increasing interest among the scientific community. Epidemiological studies have indicated that frequent consumption of natural antioxidants are associated with reduced occurrence of chronic degenerative diseases. The antioxidant activity (AA) of amaranth extracts from different varieties has been evaluated by several authors. However, the A. mantegazzianus variety has not been studied. The aim of this research was to evaluate the effect of protein concentration process and enzymatic hydrolysis on total phenolic content (PC) determination and AA of A. mantegazzianus. For this purpose, amaranth defatted flour (ADF) of this variety was prepared, from wich a protein concentrate (APC) was obtained by a pilot-scale extraction process: (pH 9.0) and isoelectric precipitation (pH 4.5). APC was hydrolyzed obtaining two samples: H1 and H2, with 8.08% and 16.80% degree of hydrolysis evaluated by pH-stat method. Methanol (ME) and water extracts (WE) of the samples were obtained. PC (mg gallic acid equivalents/g dry weight) was determined using Folin-Ciocalteureagent. AA (mg Trolox equivalents/g dw) was evaluated by DPPH radical scavenging assay. ME and WE of ADF presented higher PC than other varieties reported (0.98 ± 0.18 and 1.12 ± 0.05 mg GAE/g dw, respectively). APC presented PC values for ME and WE 2.6 and 3.4 times higher, respectively, than the ADF. Besides, PC of WE was higher than PC of ME, similarity to ADF extracts relationship. This could be explained by an unspecific reaction of Folin-Ciocalteu reagent with other components, resulting in an overestimation of PC in WE. H1 and H2 presented PC values 4.2 and 6.8 times higher than the ADF for ME, and 3.1 and 4.6 times for WE, suggesting that enzymatic hydrolysis had released phenolic compounds. ADF showed higher AA for ME than for WE (0.71 and 0.16 mg TE/g dw, respectively). ME and WE of APC presented higher AA values than ADF extracts (2.4 and 9 times higher, respectively). Also, ME and WE of H1 and H2 presented higher AA than ADF ones (between 3.2 and 13.1 times higher). It can be said that enzymatic hydrolysis significantly (P < 0.05) increased antioxidant capacity, which could be due to the release of phenolic compounds and/or peptides with AA. These results proved that both processes produce an improvement of the AA and PC of A. mantegazzianus.