Determination of Phenolic Content in Different Barley Varieties and Corresponding Malts by Liquid Chromatography-diode Array Detection-Electrospray Ionization Tandem Mass Spectrometry.

A simple and reliable method for the simultaneous determination of nine phenolic compounds in barley and malted barley was established, using liquid chromatography-diode array detection-electrospray ionization tandem mass spectrometry (HPLC-DAD-ESI-MS/MS). The phenolic compounds can be easily detected with both systems, despite significant differences in sensitivity. Concentrations approximately 180-fold lower could be achieved by mass spectrometry analysis compared to diode array detection, especially for the flavan-3-ols (+)-catechin and (-)-epicatechin, which have poor absorptivity in the UV region. Malt samples were characterized by higher phenolic content comparing to corresponding barley varieties, revealing a significant increase of the levels of (+)-catechin and (-)-epicatechin during the malting process. Moreover, the industrial malting is responsible for modification on the phenolic profile from barley to malt, namely on the synthesis or release of sinapinic acid and epicatechin. Accordingly, the selection of the malting parameters, as well as the barley variety plays an important role when considering the quality and antioxidant stability of beer.

Correlation of malt quality parameters and beer flavor stability: multivariate analysis.

Malt is known to have an impact on beer flavor stability mainly due to the presence of antioxidants. In this study, five barley varieties were malted at industrial and micro scale, and quality parameters of the resulting malts were measured (diastatic power, friability, beta-glucan content, antiradical power, reducing power, lipoxygenase activity, and nonenal potential) and correlated with the sensory data obtained for the corresponding fresh and forced aged beers. A statistical strategy using multiple linear regressions was applied to explore relationships between the malt chemical parameters and beer sensory data, showing antiradical power as the major contribution of malt to beer flavor stability. Additionally, the measured antiradical power, which is well correlated with the polyphenolic content, was found to be very similar for malt and barley, emphasizing the key role of barley endogenous polyphenols.