Wine Protein Haze: Mechanisms of Formation and Advances in Prevention

Abstract

Protein haze is an esthetic problem in white wines that can be prevented by removing grape proteins that have 13 survived the winemaking process. The haze-forming proteins are grape pathogenesis-related proteins that are highly stable during 14 winemaking, but some of them precipitate over time and with elevated temperatures. Protein removal is currently achieved by 15 bentonite addition, an inefficient process that can lead to higher costs and quality losses in winemaking. The development of 16 more efficient processes for protein removal and haze prevention requires understanding the mechanisms that are the main 17 drivers of protein instability and the impacts of various wine matrix components on haze formation. This review covers recent 18 developments in wine protein instability and removal and proposes a revised mechanism of protein haze formation. 24 by land area in the world. 1,2 Furthermore, much value is added 25 in the form of winemaking to over half the world's grapes, with 26 the production of 252 million hectoliters of wine in 2012. 2 The 27 contribution of the wine sector to the world economy in 2013 28 reached a value of U.S.$277.5 billion, 3 with a large proportion 29 of the wine exported. Thus, a substantial volume of wine is 30 subject to potentially damaging conditions during trans-31 portation and storage, such as inappropriate temperature or 32 humidity, that can cause deleterious modifications of the 33 organoleptic features of the wine. 4 f1 34Wine clarity, especially that of white wines (Figure 1), is 35 important to most consumers and is also one of the 36 characteristics that is most easily affected by inappropriate 37 shipping and storage conditions. For this reason, securing wine 38 stability prior to bottling is an essential step of the winemaking 39 process and presents a significant challenge for winemakers. A 40 stable white wine is one that is clear and free from precipitates 41 at the time of bottling, through transport and storage, to the 42 time of consumption. Hazy wine and the presence of 43 precipitates are most commonly caused by three factors: 44 microbial instability, tartrate instability, and protein heat 45 instability. 5 Microbial stability is achieved prior to bottling by 46 sulfur dioxide addition and filtration; 6 tartrate stability is 47 achieved by either cold stabilization, ion exchange resins, or 48 emr00 | ACSJCA | JCA10.0.1465/W Unicode | research.3f (R3.6.i7:4236 | 2.0 alpha 39) 2014/12/19 13:33:00 | PROD-JCAVA | rq_4578338 | 4/10/2015 14:19:11 | 11 | JCA-DEFAULT 55 lees through processing using rotary drum vacuum filtration, 56 specialized lees filtration equipment, or centrifugation 57 processes that are considered laborious and that can potentially 58 degrade wine quality. 8−10 Quality degradation and loss of wine 59 through bentonite usage has been estimated to cost the global 60 wine industry around U.S.$1 billion per year. 11 Other issues 61 and costs related to bentonite use include tank downtime for 62 bentonite treatment, ...

Enzymes for Wine Fermentation: Current and Perspective Applications

“…Proteins in must in wine are derived from the grapes, and from microbial cells (yeasts, lactic, acid bacteria) and their activities [59]. Another important source are protein-based wine additives (e.g., lysozyme, ovalbumin, gelatin, casein) which could pose allergenic-like reactions to consumers [60][61][62].…”

“…They are synthesized by the plants for defence against bacterial or fungal infections and in response to abiotic stress [63]. Due to their compact structures, they are resistant against acid wine conditions, heat, and proteolysis [59].…”

“…In combination with other wine ingredients, PR proteins can cause undesirable turbidity especially during cold storage of white wines with negative economic consequences [59]. Currently, protein removal is mainly achieved by bentonite addition [64], a process that can be associated with decreased wine quantity and quality.…”

Impact of drought stress on concentration and composition of wine proteins in Riesling

“…Stability means the absence of visible precipitates and opalescence. Since decades, protein instability especially of white wines is one of the most common challenges of the wine industry [1][2][3][4]. Hazy wine or the presence of precipitates may lead to product recalls followed by reputation loss of the responsible wineries.…”

A Theoretical Approach for Understanding the Haze Phenomenon in Bottled White Wines at Molecular Level

“…If this happens, it is expected that the complexes that could be formed between the globular or native protein and quercetin will be more stable and remains unaltered along the time. In this sense, a recent work postulates that the mechanism of haze formation seems to be independent of the protein (TLP or chitinase), and highlighted that only the TLP isoforms that denature will participate in haze formation (Van Sluyter et al, 2015). Based on the energetic results and from the previous experimental characterisation of TLP, which defined this structure as stable, we postulate that the mechanism of interaction observed between the TLP and quercetin could be responsible for modulating the formation of the haze in the long term, mediated by the presence of TLP.…”