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A response surface approach was used to investigate the effects of temperature, concentration, and time on the antioxidant properties (total flavonoid (TF), total phenol (TP), peroxide scavenging activity (PS), iron chelating activity (IC), DPPH radical-scavenging ability (DPPH), ABTS assay (ABTS)) of aqueous extract of tea-ginger (2:1) powder. Color indices, pH, and redox potential of the tea-ginger powder were also measured and used as independent variables for the prediction of antioxidant properties of the extract using ordinary least square (OLSR), principal component (PCR), and partial least square (PLSR) regression. The R2 values for TP, TF, ABTS, and PS response surface models were 0.8873, 0.9639, 0.6485, and 0.5721, respectively. The OLSR, PCR, and PLSR were able to provide predictive models for DPPH, TP, and TF of the tea-ginger extract (P < 0.05). The PLSR gave the most parsimonious model with an R2 of 0.851, 0.736, and 0.905 for DPPH, TP, and TF, respectively.

Tea and ginger are plants with high antioxidant potential. Combinations of antioxidants from different sources could also produce synergistic antioxidant effects. This study investigated the influence of solvent on antioxidant content of tea, ginger, and tea + ginger blends. Under the investigated extraction conditions, water was the most effective extraction solvent to maximise peroxide scavenging and iron chelating activity of tea, ginger, and their blends. Aqueous ethanol was the most effective solvent to maximise ABTS radical scavenging activity and ethanol was the best solvent to maximise DPPH radical scavenging activity. A good multivariate regression model that explains the relationship between the total flavonoid content of the extracts and their antioxidant activities was obtained (R 2 and Q 2 of 0.93 and 0.83, respectively). Extracts of tea-ginger blends exhibited synergistic effects in their ABTS and DPPH radical scavenging activity.

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Sorghum (Sorghum bicolor (L) Moench), is used as human food such as bread, malt drinks and beers; as livestock feed, renewable energy source such as bioethanol. The experimental monitoring of enzyme activity during malting permits the detection of germination-specific genes. The products of αamylase (simple sugars), β-amylase (maltose), protease (free amino nitrogen) and polyphenol oxidase (quinone), combined during kilning and mashing, with the development of characteristics flavor and coloured malt. In this study, we investigate malting properties of white and yellow varieties of sorghum while the variation in the activity of the three enzymes namely polyphenol oxidases, amylases and proteases, were monitored as the malting progresses. The result obtained were 95% and 86% germinative energy, 1.49 g and 1.09 g water absorption, 0.751 mg/ml and 0.639 mg/ml crude protein for yellow and white sorghum respectively. The activity of the three enzymes was higher in dormant yellow sorghum than dormant white sorghum. For both varieties, polyphenol oxidase activities were lowest during steeping than in dormant grain, while the highest activities were obtained during germination. Amylases activity did not changed significantly from dormant to germination. The proteases activities were highest during steeping than in dormant while gradually decreased to zero level during germination.