Green malt was kilned at 95 degrees C following two regimens: a standard regimen (SKR) and a rapid regimen (RKR). Both resulting malts were treated further in a tray dryer heated to 120 degrees C, as was green malt previously dried to 65 degrees C (TDR). Each regimen was monitored by determining the color, antioxidant activity (by both ABTS(.+) and FRAP methods), and polyphenolic profile. SKR and RKR malts exhibited decreased L* and increased b* values above approximately 80 degrees C. TDR malts changed significantly less, and color did not develop until 110 degrees C, implying that different chemical reactions lead to color in those malts. Antioxidant activity increased progressively with each regimen, although with TDR malts this became significant only at 110-120 degrees C. The RKR malt ABTS(.+) values were higher than those of the SKR malt. The main phenolics, that is, ferulic, p-coumaric, and vanillic acids, were monitored throughout heating. Ferulic acid levels increased upon heating to 80 degrees C for SKR and to 70 degrees C for RKR, with subsequent decreases. However, the levels for TDR malts did not increase significantly. The increase in free phenolics early in kilning could be due to enzymatic release of bound phenolics and/or easier extractability due to changes in the matrix. The differences between the kilning regimens used suggest that further modification of the regimens could lead to greater release of bound phenolics with consequent beneficial effects on flavor stability in beer and, more generally, on human health.

Barley phenolic antioxidants change in response to the kilning regimen used to prepare malt. Green malt was kilned using four different regimens. There were no major differences among the finished malts in parameters routinely used by the malting industry, including, moisture, color, and diastatic activity. Ferulic acid esterase activity and free ferulic acid were higher in malts subjected to the coolest kilning regimen, but malt ethyl acetate extracts (containing ferulic acid) contributed only ∼5% of the total malt antioxidant activity. Finished malt from the hottest kilning regimen possessed the highest antioxidant activity, attributed to higher levels of Maillard reaction products. Modifying kilning conditions leads to changes in release of bound ferulic acid and antioxidant activity with potential beneficial effects on flavor stability in malt and beer.

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