Antioxidant Activity in Barley (Hordeum Vulgare L.) Grains Roasted in a Microwave Oven under Conditions Optimized Using Response Surface Methodology

Abstract

Microwave processing and cooking of foods is a recent development that is gaining momentum in household as well as large-scale food applications. Barley contains phenol compounds which possess antioxidant activity. In this study the microwave oven roasting condition was optimized to obtain grains with high antioxidant activity measured as the ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical. Antioxidant activity of grains roasted under optimum conditions was assessed based on DPPH radical scavenging activity, reducing power and inhibition of oxidation in linoleic acid system. The optimum condition for obtaining roasted barley with high antioxidant activity (90.5% DPPH inhibition) was found to be at 600 W microwave power, 8.5 min roasting time, and 61.5 g or 2 layers of grains. The roasting condition influenced antioxidant activity both individually and interactively. Statistical analysis showed that the model was significant (P < 0.0001). The acetone extract had significantly high inhibition of lipid peroxidation and DPPH radical scavenging activity compared to the aqueous extract and alpha-tocopherol. The reducing power of acetone extracts was not significantly different from alpha-tocopherol. The acetone extract had twice the amount of phenol content compared to the aqueous extract indicating its high extraction efficiency. GC-MS analysis revealed the presence of phenol acids, amino phenols, and quinones. The aqueous extract did not contain 3,4-dihydroxybenzaldehyde and 4-hydroxycinnamic acid which are phenol compounds reported to contribute to antioxidant activity in barley grain.

Effect of Drying Methods and Ultrasonication in Improving the Antioxidant Activity and Total Phenolic Content of Apple Pomace Powder

“…Table 3 shows that TPC, and AA increased significantly by 20.1%, and 47.9% on average when AP powder was MW dried after fermentation and ultrasonication as compare to oven drying during both the processes. Some other studies have also reported that the phenolic content was increased after microwave treatment of the plant materials (Boateng, Verghese, Walker, & Ogutu, 2008;Hayat et al, 2010;Omwamba & Hu, 2010). However, Sharma and Gujral (2011) found decrease in TPC of barley after microwave cooking.…”

Physicochemical, phytochemical and nutritional impact of fortified cereal-based extrudate snacks

“…Figure 1 shows and act as reductones [23] and play a major role in the reducing power of the extracts. Table 4 indicates that, when the temperature of extrusion cooking was kept constant (180°C) and feed moisture content was increased from 14% to 18%, the reducing power activity was increased significantly (p < 0.05),…”

Aqueous and enzyme-extracted phenolic compounds from brewers' spent grain (BSG): Assessment of their antioxidant potential

“…Similarly, in a study of alkaline‐extracted BSG phenolic extracts, the black phenolic extracts also had a higher average TPC compared with pale phenolic extracts (McCarthy et al, ). It has previously been shown that roasting barley grain increases the TPC, proportionate to roasting time, owing to the formation of Maillard browning reaction products (MRP) (Dabina‐Bicka, Karklina, & Kruma, ; Omwamba & Hu, ), also resulting in the simultaneous formation of compounds with antioxidant properties (Piggott et al, ). The TPC method is not specific to phenolic compounds as it measures any compound which is capable of reducing Folin–Ciocalteu reagent including MRP (Huang, Ou, & Prior, ).…”