Role of carbohydrases on the release of reducing sugar, total phenolics and on antioxidant properties of oat bran Roaaya Alrahmany, Apollinaire Tsopmo ⇑ Food Science and Nutrition Program, Chemistry Department, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada K1S 5B6 article info Article history: Received 4 June 2011 Received in revised form 24 September 2011 Accepted 2 November 2011 Available online 10 November 2011 Keywords: Oat bran Carbohydrase Antioxidant Phenols abstract Aqueous solutions of medium oat bran flour were treated with four carbohydrases viscozyme, celluclast, alpha-amylase, and amyloglucosidase, and then extracted with equal volume of methanol. The resulting extracts were examined for their reducing sugar content, total phenolic content (TPC), oxygen radical scavenging absorbance capacity (ORAC), hydroxyl radical scavenging effect, superoxide scavenging activ- ity, and ferrous ion chelating potential. The amount of reducing sugar increased form 2.0% in the control sample to 21.4% in the sample treated with four fungal beta-glucanase units/g of bran. The increase in reducing sugar was also associated with subsequent increase of other extractable compounds. The total phenolic content as measured by Folin–Ciocalteu’s method ranged from 0.50 to 4.80 mg of gallic acid equivalents/g of bran, whereas the ORAC values were 14.4–25.4 lM of Trolox equivalents/g of bran. All the samples treated with carbohydrases had higher TPC content and higher ORAC values than the control sample (no enzyme treatment). In the hydroxyl radical scavenging assay, except for the alpha-amylase treated sample, all other samples demonstrated a greater inhibition power than the control. These results indicated that pre-treatment of oat bran with cell wall degrading enzymes (i.e. carbohydrases) is a way to increase the amount of extracted phenols as well as the antioxidant properties of oat bran samples. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Grains are important components of human nutrition as they provide approximately two-thirds of the caloric requirement (Madhujith & Shahidi, 2007). In addition to being the primary source of carbohydrates, cereals such as oat, wheat, corn, and bar- ley also provide vitamins, trace elements, dietary fibre, and bioac- tive phytochemicals (Flander et al., 2008). Previous research works indicate that a high consumption of grain products may reduce the risk of chronic diseases such as cardiovascular diseases and certain types of cancer (Banerjee & Rimm, 2003; Slavin, Jacobs, & Marqu- art, 1997). Cereals are reported to protect by altering serum choles- terol profiles, by exerting antioxidant and antithrombic actions, and through their favourable effects on vascular system as well as insulin sensitivity (Anderson & Hanna, 1999). Dietary antioxi- dants are believed to play a significant role in human health by prevention of radical damage to biomolecules such as DNA, RNA, proteins, and cellular organelles. Therefore, there is increasing interests in identifying and assessing commonly consumed foods that contain bioactives with the potential to inhibit radical damage. Oats have been grown in Canada since the arrival of the first set- tlers and were used primarily as feed for horses and other live- stock. However, oats are no longer considered a simple feed grain (Fraser & McCartney, 2004). In recent years oat has gained popularity due to the functional properties of its bioactive sub- stances, such as beta-glucan, arabinoxylan, oligosaccharides, tocols, and phenolic compounds. Today, oats are popular in North America because they provide a healthy meal that is very quick to prepare and require very little cooking skill (Pick et al., 1996). The phenolic compounds of oats are an interesting group be- cause of their ability to scavenge reactive oxygen species and the role they can play in protecting body molecules, such as lipids, DNA, or cholesterol from oxidation, and reduce the incidence of chronic diseases (e.g. cardiovascular, cancer). Phenolic compounds in oat and other grains mainly exist in bound forms and are typical components of complex structures such as lignins, hydrolysable tannins, and organic acids. Phenolic acids found in cell wall are linked to hemicelluloses such as 2-O-5 0 -O-(E)-feruluoyl-b-D-xylo- pyranosyl)-(1 ? 4)-D-xylopyranose. Ferulic acid one of the major phenolic compounds in cereals is attached to the cell wall arabin- oxylan via the acid group acetylating the primary hydroxyl at the C-5 position of a-L-arabinofuranosyl residues (Hatfield, Ralph, & Grabber, 1999; Ishii, 1997). Ferulates can also form dimers through oxidative cross-linking that may serve as an attachment to cell- wall polymers (Hatfield et al., 1999). 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2011.11.014 ⇑ Corresponding author. Tel.: +1 613 520 2600x3122. E-mail address: apollinaire_tsopmo@carleton.ca (A. Tsopmo). Food Chemistry 132 (2012) 413–418 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem