Enhancement of bioactive compounds content and antioxidant activity of aqueous extract of mate (Ilex paraguariensis A. St. Hil.) through freeze concentration technology

Abstract

The purpose of this study was to evaluate the effects of freeze concentration of aqueous extract of mate leaves on the content of bioactive components and antioxidant activity of the concentrated fluid and the ice obtained. Five stages of freeze concentration were studied. In relation to the total dry matter content, the concentration factor increased eightfold by the end of the process. The concentrated fluid showed increasing values of phenolic compounds in all the freeze concentration stages. Although process efficiency reduced significantly in comparison with the first stage due to the retention of phenolic compounds in ice, it remained about 75% in all the stages. The isolated phenolic compounds detected by HPLC, such as chlorogenic acid, 3,5-dicaffeoylquinic acid, caffeic acid, p-coumaric acid, 3,4-dihidroxibenzoic acid and gallic acid, improved substantially in all freeze concentration stages. The methylxanthines caffeine and theobromine contents also increased significantly with the application of the freeze concentration procedure. The antioxidant activity of the concentrated fluid of each freeze concentration stage, measured by FRAP and DPPH assay, was significantly higher in comparison to that of the feed extract. Moreover, the values of both antioxidant assays were significantly correlated with the content of phenolic compounds and methylxanthines of the aqueous extract of mate. Freeze concentration is an effective technique to raise the content of bioactive components and enhance the antioxidant activity of aqueous extract of mate leaves.