PVPP

This page is in progress
Please check back later for additional changes

PVPP removes the higher molecular weight polyphenols in particular, because it has a structure very similar to that of the proline acid.

PVPP effectively removes polyphenols (haze precursors) and haze from beer.

Polyvinylpolypyrrolidone (PVPP) shares structural similarity with polyproline and is often used as an adsorbent. According to research [98], 48% of total polyphenols were removed from beer treated with 100 g/hL PVPP. In other words, 78% of total flavanols, 90% of prodelphinidin B3, 96% of procyanidin B3, 79% of (+)-catechin, and 88% of (−)-epicatechin) bonded to PVPP. Lower levels of PVPP remove phenolic compounds with higher degrees of hydroxylation and oligomerization, and at higher levels, PVPP removes all polyphenols [99,100].

While the benefits of PPs removal by PVPP on increased shelf stability have been well established, questions arise about the potential for PVPP treatment to impact beer organoleptic quality and flavour stability9,19,51,81. Malt and hop derived PPs of the flavonoid family are considered the main natural antioxidants in wort and beer. PPs reportedly provide up to 60% of the endogenous reducing capacity77 to wort and beer58. Moreover, PP ability to scavenge free radicals11,56, interact with aldehydes34 and chelate pro-oxidant transition metals can provide protection against formation and degradation of important beer flavour components: the formation of stale carbonyls, protect degradation of UV-active compounds, guard isohumolunes from decomposition and shield sulphites from oxidation64,91,120. Although the aim of PVPP use is to eliminate the PPs involved in haze formation, the reality is that several PP classes are affected: simple phenolic acids, flavonol glycosides, procyanidins, prodelphinidins, proanthocyanidins and complexes of PPs and proteins104,105,106. Model experiments indicate that PVPP may preferentially adsorb the potentially prooxidant prodelphinidins, while maintaining the antioxidant pool of procyanidins, yet this phenomenon has not been sufficiently substantiated in beer. McMurrough et al.77 reported that the treatment of beer with PVPP at 100 g/hL effectively decreases beer reducing capacity by 9-38% as measured by DPPH● analysis. Despite this, the authors could not determine any marked differences in flavour stability of forced aged-lager beer following PVPP treatment. Moreover the addition of exogenous PPs to PVPP treated beer (prodelphinidin B3, procyanidin B3 and (+)-catechin), resulted in rapid flavanol oxidation as well as increased chill haze. However, the PP additions did not significantly affect development of staling indicators77,78. Mikyska et al.81 investigated the effect of a modified content of malt and hops in the brewhouse in conjunction with the effect of PVPP treatment of beer on beer haze and flavour stability. While the addition of malt and hop PPs in the course of wort boiling improved reducing activity and carbonyl content in fresh and stored beers, both types of PPs influenced ‘harsh taste’. PVPP treatment did not negatively affect stale flavour formation, but did have a positive effect on the flavour stability of heat-aged beers. Decreased staling of force-aged beers correlated well with PP content in the brewhouse; both hop and malt PPs slowed down flavour depreciation during a nine month storage period, with the primary effect seen during the first four months. Recently, Bushnell et al.19 reported that partial removal of PPs by PVPP did not significantly affect flavour stability of the beers studied by a sensory panel. However, in contrast to the 9 months of the Mikyska et al.81 study, beers in this study were only force-aged for 30 days (30°C) and exposed to one PVPP stabilization regime (0.18 g/L)19. According to O’Reilly92, effective PVPP dosing rates differ by beer type. If flavanoid dimers and oligomers are the target, lower doses (15-20 g/hL for single use) of PVPP may be applied, whereas extremely high doses on the order of 100 g/L are needed to remove excessive quantities of monomers79. This was corroborated by Mitchell et al.83 Attempts have been made to identify which PPs are specifically absorbed by PVPP45. Gerhäuser et al.44 used ultrafiltration to isolate adsorbed PVPP components. Initial results were not very encouraging as the PVPP residue consisted largely of degradation and rearrangement products of beer PPs, including five structural classes of compounds, 28 compounds in total that displayed little antioxidative potential in biological assays.

The removal of proanthocyanidins from beer by adsorption on to PVPP is reported to have little effect on flavor.

PVPP removes both haze active polyphenols (about 50%) and non-haze active polyphenols from beer45. Simple flavanoids, proanthocyanidins and tannoids are sorbed25–28. PVPP treatment is reported to decrease the reducing activity of beer21,27,28,35 and some authors did not find any significant effect of PVPP treatment on flavour stability28,35; while others came to opposite conclusions29.

The quantity of malt polyphenols was modified by the treatment of hot sweet wort with a high dose of PVPP (100 g/hL). After a 20 min contact, the sorbent was removed by filtration and the untreated sweet wort was filtered. Sweet wort handling proceeded under a CO2 atmosphere and approximately 50% of the malt total polyphenols, and 60% of the anthocyanogens, were removed by this procedure.

50g/hL PVPP was highly effective at extending haze shelf-life beyond 12 months. However, stabilizing effect also depended on the particular quality of the raw materials. Apparently, a large portion of the oxidizable polyphenols were removed with this treatment as well.

Significant sensory differences between 50g/hL PVPP stabilized and non-stabilized beers were not found (low oxygen brewing), although there is a trend toward improving overall quality. PVPP stabilization removed a substantial part of the beer polyphenols. The average decrease of total polyphenols, anthocyanogens and flavanols in the trial beers was 46%, 59% and 74%, respectively (Table II). The flavour quality of forced aged stabilized beers was better than that of the non-stabilized beers (Fig. 8). The development of less astringency in PVPP stabilized beers, after heat incidence forced ageing of beer, has been described by McMurrough27. Results of extended beer storage did not show any unambiguous effects of PVPP stabilisation on beer flavour deterioration (Fig. 9). This is in agreement with available evidence that indicates that the effect of PVPP treatments on flavour stability is either neutral or slightly positive25.

The oxidation of tannoids is a heterogeneous reaction; it occurs on the product adsorbed on the surface of the insoluble particles. Everything that opposes ad sorption of anthocyanogens should in consequence retard the process. This can be readily shown with the aid of a solution of PVP. If some 0.2% PVP (molecular weight 40,000) is added to the extracting water, it can be demonstrated that after two hours of agitation by air the solution still contains a considerable quantity of anthocyanogens, whereas the control without PVP is devoid of them. The tannoids which are fixed on the surface of the insoluble particles and then oxidized are so strongly retained that they can no longer take part in adsorption equilibria as the nonoxidized tannoids can. As a consequence, the insoluble particles again show considerable adsorbing power for fresh tannoids that are offered to them.

Partial removal of the flavanoid polyphenols from a beer was stated to decrease the rate of oxygen uptake, accompanied by a retardation in the development of "oxidized" flavor (48). Even so, careful control over the use of adsorbents, such as PVPP, to decrease polyphenol contents has been advocated (9). Removal of polyphenols from wort before boiling was reported to be disastrous for the flavor stability of the resulting beer (42).

Increasing dosages of PVPP progressively decreased the reducing capacity of the beers.

When used after fermentation (with high-oxygen brewing), PVPP either may help to increase the removal of the harsh/astingent oxidized phenolic flavors.

PVPP removes protein-polyphenol complexes from beer as well as the simple polyphenols.

Beers containing high levels of proanthocyanidins show poor colloidal stability, higher astringency, and an unpleasant harsh bitter­ ness. Therefore, the treatment with adsorbents is usually employed during filtration, such as PVPP (polyvinylpolypyrrolidone) and kiesel­guhr (also known as diatomaceous earth or diatomite). Beer filtration with kieselguhr led to a decrease of TPC in 5%, followed by 5% by PPVP and 14% after trap filter (combination of diatomite particles and PVPP fines) (Fumi et al., 2011). As expected, the reduction on tannins was evident after PVPP filter (37%) and trap filter (66%), due to the reten­tion of polymerized compounds (Fumi et al., 2011). PVPP has high molecular weight and similar structure to the amino acid proline, allowing a selective binding to polyphenols responsible for chill and permanent haze. The higher the degree of polymerisation the greater the tendency of the proanthocyanidins to bind to adsorbents. Studies con­ducted by our research group have shown that the adsorption of phenolic compounds to PVPP, at low concentrations, depends on the structure (number of OH groups, aromatic rings, and stereochemistry hindrance), increasing with the number of OH groups and reduced by derivatization of OH groups (methylation and glycosylation). A very good efficient adsorption of catechin, epicatechin, XN and some flavo­nols (e.g., quercetin and kaempferol) was demonstrated among several classes of phenolic compounds. In comparison, lower adsorption equi­librium constants were obtained for cinnamic and benzoic acids de­rivatives (Magalhães, Vieira, Gonçalves, Pacheco, Guido, & Barros, 2010).

Application of stabilising agents, such as polyvinylpolypyrrolidone, causes a significant reduction of phenolic compound content in beer, which results in reduced possible antioxidant potential of this beverage.

PVPP is commonly used in brewing to enhance the colloidal stability of beer by removal of haze-active polyphenols after fermentation (Siebert 1999, 2006). Complex formation between polyphenols, PVPP and protein are determined by the same forces: hydrogen bonding between the proton donor from the polyphenol and the carbonyl group from PVPP, π-bond overlap (delocalized electrons), hydrophobic and polar interactions between the aromatic ring of the polyphenol and the PVPP ring (Wannenmacher et al. 2018). Magalhaes et al. (2010) found adsorption equilibrium constants of phenolic compounds on PVPP to increase with the number of hydroxyl groups. This was especially evident with benzoic and cinnamic acid derivatives, whereas favonoids had higher adsorption constants. After fltration, the content of some individual phenolics increased depending on the structure of the compound (number of OH groups, aromatic rings, and stereochemistry hindrance). After all, the secondary fermentation (conditioning) had positive efect on the content of individual phenols in samples of fltered beer. As visible from Fig. 3a, b, the use of PVPP revealed to be very efcient for adsorption of polyphenols and flavonoids compounds.

PVPP is used to reduce phenolic substances – mainly tannins – in order to decrease astringency and instability in beer (Derdelinckx, 2008; Gromus and Bremen, 2001; Mikyska et al., 2002; Siebert and Lynn, 1998).

PVPP is used as stabilising agent because of its ability to bind with haze active polyphenols. PVPP has a structure similar to peptidically linked proline chain [11, 12, 15, 26]. Addition of PVPP has an explicit effect on the amounts of polyphenols in the finished beers [12]. As shown in table 3 and fi gure 3, application of PVPP at the end of wort boiling is related to a considerable decrease in total polyphenols, flavanoids, and haze-active proanthocyanidins in the fi nished beers. A pronounced decrease in haze-active proanthocyanidins, i.e. relatively 40 % compared to the reference beer, can already be noticed after a short contact time of 3 min during wort boiling. A contact time of 5 min results in a less efficient removal of the haze-active proanthocyanidins. The effect of PVPP treatment is also expressed by the strong decrease in reducing power of the resulting beers D and E (see Table 3, results obtained by TRAP and DPPH assays). This may result in a diminished flavor stability of these beers. Flavanoids in beer are expected to scavenge active oxygen species and prevent the oxidation of beer components during storage [21]. According to Mikyska et al. [16], both malt and hop polyphenols suppress formation of ageing carbonyls during the brewing process and upon beer storage. In particular polyphenols such as catechin and procyanidin B-3 (both flavanoids) act as powerful antioxidants, thereby protecting other components towards oxidation [16, 30, 31]. Finally, levels of sensitive proteins also seem to be affected in the finished beers by the treatment with PVPP at the end of wort boiling. The addition of PVPP in the upstream process has no negative effect on the beer taste of fresh beer. Despite of the lower reducing capacity of the beers treated with PVPP, in correlation to their reference, the ageing scores were similar as the reference beer.

• http://www.themodernbrewhouse.com/forum/viewtopic.php?f=4&t=1826
• see Handbook of Brewing 10.7
• http://www.themodernbrewhouse.com/wp-content/uploads/2017/02/Officiele_tekst_voor_Brewing_Science.pdf
• Adsorption by Polyvinylpolypyrrolidone of Catechins and Proanthocyanidins from Beer
• Experimental and theoretical binding affinity between polyvinylpolypyrrolidone and selected phenolic compounds from food matrices
• A Novel Stabilization of Beer with Polyclar® Brewbrite™
• Miky�ska, A., Ha�sková, D.,�Culík, J., Jurková, M., and�Cejka, P. (2010)Study of an influence of beer colloidal stabilization by sorbent Poly-clar 10 on polyphenolic antioxidants and sensorial stability of beer.Kvasny Prum.,56(3), 167–174.
• Bushnell, S. E., Guinard, J. X., & Bamforth, C. W. (2003). Effects of sulfur dioxide and polyvinylpolypyrrolidone on the flavor stability of beer as measured by sensory and chemical analysis. Journal of the American Society of Brewing Chemists, 61(3), 133–141.
• Van Gheluwe, G. E. A., Jamieson, A. M., and Valyi, Z. Studies on the oxygen content of beer and its implications in brewing. MBAA Tech. Q. 7:158, 1970.
• Optimising Beer Stabilisation by the Selective Removal of Tannoids and Sensitive Proteins

See also

• Phenolic compounds
• Haze