Characterisation of protein-polyphenol interactions in beer during forced aging

Abstract

Proteins and proteinaceous material were extracted by acetone precipitation of beer that had undergone forced aging through 0 (control), 5 (medium) or 10 (high) heat/chill cycles (60°C 48h/0°C 24h). Size exclusion chromatography analysis of the crude beer extract showed that forced ageing led to a significant increase in binding of phenolic compounds to Protein Z and especially to lipid transfer protein 1 (LTP1). Protein‐polyphenol conjugates were also present in high molecular weight (> 100 kDa) and low molecular weight fractions (< 5 kDa), but these conjugates were already present in the fresh beer and were not affected by the forced aging. Treatment of the crude beer extract with sulphite (2 M) dissociated the protein‐polyphenol bindings in LTP1 and Protein Z that had been generated during medium forced aging. Identification and quantification of the free, the non‐covalently, and the covalently bound phenolic compounds were performed by UHPLC after extraction by methanol, acetic acid, and sulphite, respectively. The amounts of vanillic acid and caffeic acid decreased in the free polyphenol fraction, indicating binding to proteins during forced aging. Epicatechin and quercetin‐3‐O‐glucoside were found to be non‐covalently bound during forced aging. Finally, gallic acid, epicatechin, protocatechuic acid, and astragalin were found to be covalently bound already in the fresh beer. © 2020 The Institute of Brewing & Distilling

Haze in Beer: Its Formation and Alleviating Strategies, from a Protein–Polyphenol Complex Angle

“…The treatment condition and time were determined by the experimental purpose [ 4 , 9 ]. For example, Jongberg et al, used a forced aging method to investigate the haze formation in commercial beer [ 10 ]. The procedure is as follows: beer was exposed to aging treatment by heat/chill cycles of 60 °C for 48 h, followed by 0 °C for 24 h, according to the Analytica-EBC method 9.30 with slight modifications.…”

“…Forced aging of beer experiments have shown significant losses of gallic acid, salicylic acid, hydroxy-phenyl lactic acid, chlorogenic acid, epicatechin, vanillic acid, ferulic acid, pyrocatechuic acid, and luteolin during the forced aging. It was supposed that these phenolic compounds took part in the colloidal changes, proposedly upon polymerization into tannins [ 10 , 54 ]. It has been reported that proanthocyanidins, one of the flavanol compounds, were important for the haze stability of beer.…”

Impacts of hesperidin on whey protein functionality: Interacting mechanism, antioxidant capacity, and emulsion stabilizing effects

“…Various kinds of proteins (e.g., whey protein, casein, and gelatin) and polyphenols (e.g., tannic acid, curcumin, and phenolic acids) have been shown to form protein-polyphenol complexes with different functional properties (15)(16)(17)(18). For example, chlorogenic acid was reported to bind to casein and WP through non-covalent interactions, which altered the structure, solubility, and foaming capacity of the proteins (19).…”

Reducing the Flocculation of Milk Tea Using Different Stabilizers to Regulate Tea Proteins

“…However, milk tea is a complex and dispersed system composed of many ingredients [ 3 ]. During its preparation, due to the interaction of tea polyphenols with proteins, compounds can easily flocculate and precipitate [ 4 ]. Even solid milk tea flocculates and forms polyphenol–protein complexes after long-term storage [ 5 , 6 ].…”

“…The proteins and proteinaceous material were extracted through the acetone precipitation of beer that had undergone forced aging. Treatment of the crude beer extract with sulphite (2M) dissociated the protein–polyphenol bonds of lipid transfer protein 1 (LTP1) and Protein Z, which were generated during moderate forced aging [ 4 ].…”