Effect of Heat Treatment on the Antioxidant Activity, Color, and Free Phenolic Acid Profile of Malt

Abstract

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.

Dry and Wet Milling of Malt. A Preliminary Study Comparing Fermentable Sugar, Total Protein, Total Phenolics and the Ferulic Acid Content in Non-Hopped Worts

“…9 and Fig. 10), contrary to a number of other works that showed that it was present in barley and malt mainly in the bound (esterified) form 17,28,29 . The FA, as well as other phenolic acids, have repeatedly been shown to be present in different beers in the free form 2,32,36 , but some studies suggest that beer contains considerable amounts of esterified FA 35,48 .…”

“…Feruloylated arabinoxylans are present in all parts of the grain, mainly in the aleurone layer (75%) and the endosperm 38 . Only a minor part of FA (shown to be an effective antioxidant 7,19,20,44,50 ) is present in malts in free forms 17,28,29 . Malting and mashing result in a limited release of free FA from arabinoxylans 55,56 .…”

Antiradical and reducing potential of commercial beers

“…Hence, the higher antiradical and reducing potential determined in bock and porter beers in relation to the other beers can be attributed to higher amounts of naturally occurring antioxidants of barley malt, including polyphenols, thiols, carotenoids, and vitamins. However, the highest antiradical and reducing potential in dark beers may be due to the use of dark malt, which contains heat-induced compounds such as melanoidins and reductones, formed by the Maillard reaction during kilning or roasting (Inns et al 2007). Although there is still a debate whether dark beers have higher antioxidant capacity.…”

Phenolic acids from malt are efficient acetylcholinesterase and butyrylcholinesterase inhibitors

“…Also, the main phenolic acids from barley (ferulic, p-coumaric and vanillic acids) have been mentioned as potent antioxidants in beer (51,(57)(58)(59). The literature concerning the role of phenolic acids and their derivatives in the neuroprotection of the CNS is, however, still incomplete.…”