Effects of Processing Steps on the Phenolic Content and Antioxidant Activity of Beer

Abstract

A new analytical method (liquid chromatography-antioxidant, LC-AOx) was used that is intended to separate beer polyphenols and to determine the potential antioxidant activity of these constituents after they were allowed to react online with a buffered solution of the radical cation 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(•+)). Using the LC-AOx method, it was possible to demonstrate that the extent of the antioxidant activity was very much dependent on the phenolic compound considered. The method was also applied to the analysis of beer extracts and allowed the evaluation of their antioxidant activity at different steps of beer processing: brewing, boiling, and fermentation. This study showed that the total antioxidant activity remained unchanged throughout beer processing, as opposed to the polyphenolic content, which showed a 3-fold increase. Hopping and fermentation steps were the main causes of this increase. However, the increase measured after fermentation was attributed to a better extraction of polyphenols due to the presence of ethanol, rather than to a real increase in their content. Moreover, this method allowed the detection of three unknown antioxidant compounds, which accounted for 64 ± 4% of the total antioxidant activity of beer and were individually more efficient than caffeic acid and epicatechin.

Biological Activities and Effects of Food Processing on Flavonoids as Phenolic Antioxidants

“…In some cases, the antioxidant capacity of flavonoids in a food matrix is enhanced (Freeman et al, 2010) ; while in other cases, the antioxidant capacity is reduced (Hidalgo et al, 2010). Thus, in other studies, antioxidant activity remains constant (Leitao et al, 2011) or can be decreased (Davidov-Pardo et al, 2011). Table 5.…”

Comparative Study of the Effects of Drying Methods on Antioxidant Activity of Dried Strawberry (Fragaria Var. Camarosa)

“…Depending on this environment, synergies between antioxidant compounds and the food matrix can occur (Wang, Meckling, Marcone, Kakuda, & Tsao, 2011). In some cases, the antioxidant capacity of flavonoids in a food matrix is enhanced (Freeman, Eggett, & Parker, 2010); while in others, this antioxidant activity is reduced (Davidov-Pardo, Arozarena, & Marín-Arroyo, 2011;Hidalgo, Sánchez-Moreno, & de Pascual-Teresa, 2010), or it remains constant (Leitao et al, 2011). …”

Effect of Maillard reaction on reducing power of malts and beers

“…Gallic acid and flavan-3-ols possess much higher AOA than ferulic acid or p-coumaric acid, the least active compounds. In addition to the set of the known phenolics, Leitao et al (2011) found three unknown antioxidant compounds possessing 64% of the total AOC in ethyl acetate extracts of beer. Unfortunately, no detailed characteristics of these unknown compounds, including UV-Vis spectra, were introduced.…”

“…On the other hand, Leitao et al (2011) documented statistically non-significant changes in AOC throughout beer processing (i.e., brewing, boiling, and fermentation), using an ABTS…”