Alpha-amylase treatment increases extractable phenolics and antioxidant capacity of oat (Avena nuda L.) flour

In this work, α-amylase was used to treat oat flour with the intent to release phenolic compounds with known antioxidant properties. After methanol extraction, the amounts of nine beneficial phenolic compounds were measured using HPLC. The antioxidant activities of the extracts were assessed using 2,2′-azinobis (3- ethylbenzothiazoline-6-sulfonic acid) (ABTS),2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and protein oxidative damage protection assays. Compared with heating-only treated oat flour, that treated with α-amylase showed significant increase of extractable total phenolic content (0.46–1.35 μmol gallic acid equivalents per gram oat), total antioxidant capacity, and an increased ability on the protection of protein from oxidative damage. Heating-only increased caffeic acid and vanillin content by 17 (0.03 vs 0.54 μg/g oat) and 1.8 (0.62 vs 1.11 μg/g oat) folds, but slightly increased the content of other phenols. Excluding heating effect, α-amylase treatment increased gallic acid content by 2.6 folds (0.38 vs 1.38 μg/g oat), caffeic acid content by 2.4 (0.54 vs 1.82 μg/g oat) folds, and other phenols by 1.0–1.8 folds. In conclusion, α-amylase treatment can yield oat products containing more extractable phenolic compounds with increased antioxidant capacity.     

Bioactivity and chemical components of Thai rice in five stages of grain development

Tracking changes in the bioactive compounds of white (ML-W), red (ML-R) and black (RB) rice during the 5 stages of grain development were studied. Total anthocyanin (TAC) was found only in RB (stages 3–5) and proanthocyanidin (TPAC) contents were only found in ML-R (stages 2–5). Considerable amounts of total phenolic contents (TPC) were found in stages 2–4 of ML-R, while total flavonoid contents (TFC) were most detected in stages 4–5 of RB. The DPPH activity of ML-W and ML-R decreased from stages 1–5. The highest FRAP activity was found in ML-R (stages 2–3) indicating that it is highly related to the bioactive compound content. Cyanidin-3-glucoside and peonidin-3-glucoside were found in RB at stages 3–5. The cyanidin of RB in stages 4–5 was related to the amount of TAC. The proanthocyanidin compound catechin was first found and reported in stages 2–3 of ML-R. Principal component analysis indicated that antioxidant activity and the bioactive components were highly related. The data from this study suggests that ML-R at stage 2 and RB at stage 4 are the most suitable stages for harvesting to achieve the highest level of bioactive compounds, which have many health benefits.     

Physicochemical and functional characterization of wheat milling co-products: Fine grinding to achieve high fiber antioxidant-rich fractions

Milling of wheat produces co-products rich in dietary fiber, micronutrients and phytochemicals which can be used to integrate healthy functional foods. In the study different co-products including bran, shorts, and red dog were identified by physicochemical and functional analyses. The results showed that the fat, protein and starch contents decreased in order of red dog > shorts > bran (P < 0.05). The ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, water and oil holding capacities (WHC, OHC) were in order bran > shorts > red dog, respectively (P < 0.05). Antioxidant capacity was in order red dog > shorts > bran (P < 0.05). The bran was selected as the co-product with the highest fiber that was finely grounded to four different fractions (>355, 250–355, 180–250, <180 μm) and they were characterized more detail. The fat, protein and starch contents decreased with increasing bran particle size (P < 0.05). The ash, crude fiber, NDF, ADF, hemicellulose and WHC and OHC increased with the increasing bran particle size (P < 0.05). DPPH radical scavenging activity increased with increasing particle size (P < 0.05). The bran fractions 250–355 and >355 μm can be used as high fiber ingredients rich in antioxidants to generate functional foods.