Mango and pomegranate peels as ingredients to promote antioxidant activity in cereal bars
Cereal bars (CB) stand out as healthy and functional foods. The incorporation of fruit processing by-products, such as dehydrated mango peels (DMP) and pomegranate peel powder (PPP), into a balanced cereal formulation, can promote antioxidant activity. To a CB formulation (F0), the effect of the addition of dehydrated soybean sprouts (F1) and 5 to 20% DMP and PPP (F2-F5) was evaluated. The total soluble polyphenol content was determined according to the Folin-Ciocalteu colorimetric method, the main antioxidant compounds were identified by high-performance liquid chromatography analysis (HPLC-MS) and the antioxidant activity (TEAC) by ABTS, FRAPP, and DPPH. Statistical analysis was performed in triplicate and the data were subjected to analysis of variance and Tukey's test at 5% probability. The content of total phenolic compounds ranged from 3.18 to 6.42 mg EAG/g, for treatment F0 and F5 respectively. Formulation F5 (6.42 mg EAG/g) doubled the value of phenolic compounds, compared to the control formulation (F0) (3.1 mg EAG/g). The antioxidant capacity increased with the addition of the sprouts and by-products. All treatments (F1-F5), presented significantly higher values of antioxidant activity compared to the F0 (control) treatment. However, after the addition of 10% of by-products, there were no statistically significant differences in the antioxidant activity measured with the ABTS (F1:20.5 - F5:48.4 µMol TE/g) and DPPH (F1:4.2 - F5:21.7 µMol TE/g) methods. For FRAP (F1:6.9 - F5:72.1 µMol TE/g) there were statistically significant differences from treatment F3 onwards. The antioxidant activity determined in the different CB formulations is attributed to ellagic acid, caffeic acid, aspartic acid, and other compounds identified by HPLC-MS, with proven antioxidant action, mainly ellagic acid present in pomegranate peel. The addition of agroindustrial by-products in the CB formulation increased the content and activity of antioxidant compounds, indicating that the addition of by-products as an ingredient in CB formulations favors the increase of compounds with antioxidant activity.
Key words: Antioxidant, Cereal bar, Fruit peels, Functional Foods.