Protein-polyphenols, interaction

While most of the previously mentioned causes of haze can create product defects, they do not normally occur if a process is carried out properly. The most frequent cause of haze in clear beverages is protein-polyphenol interaction (Bamforth, 1999 Siebert, 1999). This occurs normally and even when a beverage is properly stabilized, protein-polyphenol haze usually develops eventually. The objective is to delay its onset so that any haze produced is imperceptible until after a product s intended shelf life. 

Siebert, K. J. (1999). Effects of protein-polyphenol interactions on beverage haze, stabilization, and analysis. J. Agric. Food Chem. 47, 353-362. 

It should be noted that this chapter has been limited to physical-chemical interactions between food macromolecules in model systems. The main reason is that in food systems, chemical protein-polysaccharide and protein-polyphenols interactions have not yet been sufficiently studied. A new trend in this area is covalent protein-polysaccharide hybrids (conjugates natural and synthetic) that are of great interest as functional additives and food ingredients... 

Protein-polyphenols interaction has been probed by various analytical methods that include high performance liquid chromatography (HPLC) [4,8], sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) [9], binding assay [2,10-11], nephelometry [12-15], and nuclear magnetic resonance (NMR) spectrometry [1,3,16,17], but with protein models that were often far from giving a realistic representation of salivary proteins bovine serum albumin (BSA) [18,19], gelatin [20,21], casein [1,22], polyvinylpolypyrrolidone (PVPP) [23,24], bradykinin [25,26], or diverse synthetic proteins [27,28]. 

The role of protein-polyphenol interactions with regard to the development of non-biological haze is discussed further in Chapter 22 together with the methods employed to inhibit these reactions and prolong the shelf-life of bottled beer. 

Siebert, K. J. and Lynn, P. Y. (1998). Comparison of polyphenol interactions with PVPP and haze-active protein. ]. Am. Soc. Brew. Chem. 56, 24431. 

McManus, J.P. et ak. Polyphenol interactions. Part 1. Introduction some observations on the reversible complexation of polyphenols with proteins and polysaccharides. J. Chem. Soc. Perkin Trans. II1429, 1985. 

Beart, J.E., Lilley, T.H., and Haslam, E. 1985. Polyphenol interactions. Part 2. Covalent binding of procyanidins to proteins during acid-catalysed decomposition observations on some pol ymeri c proanthocyanidins../. Chem. Soc. Perkin Trans. II 1439-1443. 

Flavonoids and other polyphenols can interact with lipids and proteins. The interactions with proteins could be both unspecific or specific, meanwhile the interactions with lipids seems to be rather unspecific, based essentially on physical adsorption. This physical adsorption would mostly depend on the hydrophobic/hydrophilic characteristics of the flavonoid molecule, the number of hydroxyl substituents, and the polymerization degree [Erlejman et al., 2004 Verstraeten et al., 2005, 2003, 2004]. 

Many of the wine macro-components (e.g. carbohydrates, proteins, polyphenols), come from the skins and the pulp of grapes and from the cell walls of the yeast. Although this varies, the molecular weight of the majority of macromolecules is over 10,000 D and their final concentration ranges from 0.3 to 1 g/L (Voilley et al. 1991). Most macromolecules will be eliminated by clarification and stabilization treatments of the wine. Because of their interactions with wine aroma... 

Haze formation is mostly attributed to proteins, polyphenols, and their interactions. It is also possible that there are also other factors that inbuence haze formation in beer, but their effect has not been yet clearly debned [ 15]. The amount of haze formed depends both on the concentration of proteins and polyphenols, and on their ratio. Polyphenols can combine with proteins to form colloidal suspensions that scatter light, which creates the cloudy appearance of beer. Beer polyphenols originate partly from barley and partly from hops. The beer polyphenols most closely associated with haze formation are the proanthocyanidins, which are dimers and trimers of catechin, epicatechin, and gaUocatechin. These have been shown to interact strongly with haze-active proteins [13,15-17] and their concentration in beer was directly related to the rate of haze formation [18]. Ahrenst-Larsen and Erdal [19] have demonstrated that anthocyanogen-free barley produces beer that is extremely resistant to haze formation, without any stabilizing treatment, provided that hops do not contribute polyphenols either. Not all proteins are equally involved in haze formation. It has been shown that haze-active proteins contain signibcant amounts of proline and that proteins that lack proline form little or no haze in the presence of polyphenols [13,15-17]. In beer, the source of the haze-active protein has been shown to be the barley hordein, an alcohol-soluble protein rich in proUne [16]. 

In most of the early work on cell wall analysis, the alcohol insoluble residue (AIR), or the alcohol-benzene extractive free residue, was used as the starting material. Such residues may be suitable for tissues relatively poor in intracellular proteins, polyphenols, and starch, such as grasses and certain fruits and vegetables. Even with these products, interactions between the cell wall polymers occur, due to the dehydration effects of alcohol, resulting in the formation of artifacts. However, for starch- and protein-rich products additional complications arise because of coprecipitation effects. In oats and potatoes, for example, the starch to... 

Baert, J.E., T.H. Lilley, and E. Haslam Polyphenol Interactions. Part 2. Covalent Binding of Procyanidins to Proteins During Acid-catalyzed Decomposition Observations on Some Polymeric Proanthocyanidins. J. Chem. Soc., Perkin Trans. 2, 1439 (1985). 

Siebert, K.J. Lynn, P.Y. Comparison of polyphenol interactions with polyvinylpolypyr-rolidone and haze-active protein. J. Amer. Soc. Brewing Chem. 1998, 56, 24-31. 

The crospovidones are easily compressed when anhydrous but readily regain their form upon exposure to moisture. This is an ideal situation for use in pharmaceutical tablet disintegration and they have found commercial appHcation in this technology. PVP strongly interacts with polyphenols, the crospovidones can readily remove them from beer, preventing subsequent interaction with beer proteins and the resulting formation of haze. The resin can be recovered and regenerated with dilute caustic. 

VELEZ A J, GARCIA L A, DE Rozo M p (1985) In vitro interaction of polyphenols of coffee pulp and some proteins. rc/i Latinoam Nutr. 35 297-305. 

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