Wine proteins bentonite fining

Duncan, B. (1992). Varietal differences in white grape protein Implications for bentonite fining. Aus. New Zealand Wine Ind.. 7,189-193. 

Hsu, J. C. and Heatherbell, D. A. (1987). Heat-unstable proteins in wine. I. Characterization and removal by bentonite fining and heat treatment. Am. J. Enol. Vitic. 38,11-16. 

Commercial wines are commonly tested for protein stability. Wine proteins, upon denaturation by heat or cold, may cause cloudiness and unsightly deposits after bottling. In addition, proteins may combine with iron and copper salts to form flocculate material in bottled wines. The reaction and absorption of proteins on bentonite is an effective means of removing protein from wines (109, 110, 111). Therefore, fining wines... 

Clarification and Stabilization Combinations. Wine clarification may be combined with a stabilization step to minimize handling of the wine. This type of clarification, timing, and sequence vary from winery to winery. Some options used are, after fermentation, rack the wine off yeast lees, bentonite fine for heat stability and chill for cold stability, then diatomaceous earth filter to remove remaining yeast, bentonite, and tartrate crystals after fermentation, centrifuge the wine to remove yeast solids, then chill and add bentonite, and filter to remove yeast and add bentonite, chill, then pad filter to remove bitartrates and protein. 

Fining is a winemaking technique used to enhance sensory or clarity properties of the wines. Common fining agents used with North Coast white wines are bentonite (a clay), casein (milk protein), gelatin (animal protein),... 

Fining can be done at several points in the winemaking cycle in the juice, usually for phenolic removal in press juice after fermentation, to clarify the wine or to reduce protein (bentonite) and prior to bottling, for sensory reasons, to reduce astringency of young wines. 

Care must be taken when fining a sparkling wine with bentonite in order to preserve its foaming properties. Excessive use of bentonite for the fining of sparkling wine cuv es can produce a finished product that has a large bubble size and a poor bubble stability as a result of a reduction in both protein and peptide contents. Cold stabilization procedures cause both a precipitation of potassium bitartrate crystals as well as proteins because of the downward shift in pH. This precipitation of proteins... 

The in-line dosing paradigm exploits the observation that protein adsorption by bentonite occurs rapidly - within several minutes (Blade and Boulton 1988 Muh-lack et al. 2006). Furthermore, if combined with centrifugation, the bentonite and wine can be separated and the bentonite lees are simultaneously compacted to reduce value losses. In-line dosing methods for bentonite fining are already used... 

Pocock, K.F., Waters, EJ. (2006). Protein haze in bottled white wines how well do stability tests and bentonite fining trials predict haze formation during storage and transport . Aust. J. Grape Wine Res., 12, 212-220... 

Bentonite has a negative charge that fixes the positive unstable colloids and pulls them down. It is more efficient than cold flocculation of the colloids. The problem is different in the case of protein-based fining agents. Some of the colloids are pnlled down by the flakes of tannin-protein complexes, while the rest are stabilized by residnal proteins that are also part of the wine s colloidal strnctnre. 

Wine is usually very acidic and below the isoelectric point of the suspended proteins. At a pH of 3.2, 100% of the proteins are positively charged and are capable of being removed with a Bentonite fining agent. 

Minerals, particularly Bentonite, ate used to remove proteins that tend to cause haze in white wines. The natural tannin of ted wines usually removes unstable proteins from them. Excess tannin and related phenols can be removed and haze from them prevented by addition of proteins or adsorbents such as polyvinylpyttohdone. Addition of protein such as gelatin along with tannic acid can even be used to remove other proteins from white wines. Egg whites or albumen ate often used to fine ted wines. Casein can be used for either process, because it becomes insoluble in acidic solutions like wines. 

If, after the laboratory tests, a wine is judged to be protein-unstable, a laboratory fining series is run, adding different levels of bentonite to the wine. The series is tested for protein instability with one of the tests previously mentioned, and the level of bentonite needed to prevent haze occurring under the test conditions is selected for use in the cellar. 

The most commonly used fining agents in the wine industry are bentonites (mainly containing montmorillonite) and proteins associated to tannins or a mineral agent. Gelatin has also been used in enology since the nineteenth century, but due to the crisis of the mad cow disease in 1999, plant proteins have widely been experimented and are now more and more used on an industrial scale. For this reason, this chapter will essentially focus on bentonite as well as plant proteins. 

Protein levels in white wine have been reported by several authors and have been shown to differ by variety. Lee (1986) reported a range of protein concentration from 18 to 81 mg/L in 14 wines from different Australian regions and made from different varieties. Some of these wines appeared to have been fined with bentonite prior to analysis. Pocock et al. (1998) reported concentrations in unfined Australian wines up to several hundred mg/L. Hsu and Heatherbell (1987b) found a range of 19 4 mg/L in four different unfined white wines from Oregon, while a very large variation (20—260 mg/L) was noted by Bayly and Berg (1967). 

Total Phenolics by Folin Ciocalteau. The Folin-Ciocalteau total phenol level decreased with all fining agents and significantly with carbon and bentonite at all levels and PVPP at the highest level (Table III). One interference in the Folin-Ciocalteau assay is protein (29). This is of specific importance in this study because the vsdnes are diluted to equivalent total phenol levels according to this assay for the subsequent LDL oxidation tests. New finished wines have very low levels of protein, however, the concentration of proteins that remain after fining has not been well documented. 

Several treatment agents of wine yeast cell walls, sodium caseinate, gelatin, bentonite were evaluated for their potential to bind with aroma compounds. The loss of sensory properties of wine, especially flavor modification, is partly caused by protein stabilization treatments with fining agents or ultrafiltration processing of wine (IS 14). Yeast cell walls are used in sluggish or stuck wine fermentation the effect on fermentation has been explained by the adsorption of toxic fatty acids present in the growth medium (15). Therefore yeast walls are also assumed to bind aroma compounds. 

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