Preventing protein haze in bottled white wine

Abstract

Slow denaturation of wine proteins is thought to lead to protein aggregation, flocculation into a hazy suspension and formation of precipitates. The majority of wine proteins responsible for haze are grape‐derived, have low isoelectric points and molecular weight. They are grape pathogenesis‐related (PR) proteins that are expressed throughout the ripening period post véraison, and are highly resistant to low pH and enzymatic or non‐enzymatic proteolysis. Protein levels in un‐fined white wine differ by variety and range up to 300 mg/L. Infection with some common grapevine pathogens or skin contact, such as occurs during transport of mechanically harvested fruit, results in enhanced concentrations of some PR proteins in juice and wine. Oenological control of protein instability is achieved through adsorption of wine proteins onto bentonite. The adsorption of proteins onto bentonite occurs within several minutes, suggesting that a continuous contacting process could be developed. The addition of proteolytic enzyme during short term heat exposure, to induce PR protein denaturation, showed promise as an alternative to bentonite fining. The addition of haze‐protective factors, yeast mannoproteins, to wines results in decreased particle size of haze, probably by competition with wine proteins for other non‐proteinaceous wine components required for the formation of large insoluble aggregations of protein. Other wine components likely to influence haze formation are ethanol concentration, pH, metal ions and phenolic compounds.

Identification and Partial Characterization of Extracellular Aspartic Protease Genes from Metschnikowia pulcherrima IWBT Y1123 and Candida apicola IWBT Y1384

“…The band at ϳ60 kDa may be grape invertase (27,30), and the intense band just beneath 25 kDa may be the common grape proteins thaumatin-like protein (22 kDa) and/or chitinase (25 kDa) (49,50). These proteins are known to be very stable due to their conformation, and thus degradation due to incubation con- ditions was not expected (51). Lane b shows the extracellular protein profile of M. pulcherrima IWBT Y1123 grown in the presence of grape juice proteins.…”

“…The proteases not only can increase the concentration of assimilable nitrogen sources for the growth of desirable (and spoilage) microbes but also can improve clarification and possibly reduce wine protein haze (21,25,41). Treatments such as bentonite fining and aging on total yeast lees to reduce the risk of haze formation can be expensive, among other disadvantages (51). Successful protease treatment prior to fining may reduce costs.…”

Bromelain from pineapple stem in alcoholic–acidic buffers for wine application

“…Finally, bentonite handling is also of concern on account of occupational health and safety issues. For these reasons, increasing attention is given today to the development of alternative practices for protein stabilization that would maintain quality, reduce costs and be more sustainable (Waters et al, 2005).…”

Effect of non-protein factors on heat stability of Chilean Sauvignon Blanc wines

“…Specific wine proteins, identified mainly as pathogenesis-related proteins, are heat unstable, resulting into haze formation (Waters et al, 1996;Waters et al, 1998). Protein instability in wines is a two-step phenomenon: protein unfolding, a temperature protein denaturation results into a hazy suspension with precipitate formation, which is a considerable drawback in bottled wines -mediated step, followed by colloidal aggregation due to intermolecular interactions among unfolded proteins (Waters et al, 2005;Dufrechou et al, 2010).…”