Effect of using bentonite during fermentation on protein stabilisation and sensory properties of white wine

The bentonite use to remove proteins from white wine is a widespread practice that prevents protein haze formation after bottling. However, an excess of bentonite can have negative effects on both the aromatic profile of young white wines and the quality of the foam of sparkling wines. Therefore, the optimisation of bentonite amount to be used and the moment of its application during winemaking to minimise wine quality losses are of great interest for winemakers. This paper analyses how applying an equal bentonite dose at different stages (must clarification; beginning, middle and end of fermentation) on two scales (industrial and pilot) affects the protein content and stability, physical–chemical characteristics, aromatic profile and foam quality of the obtained wines. No important differences in the oenological parameters were observed between industrial and pilot scales, whereas the scale of the experimental treatments affected protein stability, aroma composition and foam quality of the wines.     

Selection of low swelling materials for protein adsorption from white wines

Summary The protein adsorption capacity of different materials was evaluated to assess their potential efficacy as alternative adsorbents for the removal of proteins from wines, with the purpose of finding suitable low-swelling materials that could be used in a percolated bed. The adsorbents tested were thermally treated sodium bentonite, low-swelling adsorbing clays, ion exchange resins and other protein adsorbents (silica gel, hydroxyapatite and alumina). The materials were evaluated by analysing both the capacity to stabilize untreated white wines, according to a heat test, and by characterizing the adsorption isotherms of bovine serum albumin (BSA) in a model wine (water, ethanol and K-bitartrate). Breakthrough curves in a packed bed were determined experimentally for some materials, showing the influence of the adsorption isotherm shape. Some ion-exchange resins showed a favourable behaviour and have good potential as alternative adsorbents.     

Repercussion of the clarification treatment agents before the alcoholic fermentation on volatile composition of white wines

Albariño must was clarified with two fining agents, as bentonite and silica gel. Alcoholic fermentation was carried out at semi-industrial scale, and the concentration of free monoterpenes, norisoprenoids, C₆-alcohols, higher alcohols, fatty acids, ethyl esters, and acetates was then investigated. The use of bentonite allows loss of several volatile compounds compared to wine control. In a second step, the effect of clarification–stabilization treatments with silica gel on aromatic substances was compared in order to study this influence in white wines elaborated from different aromatic varieties (Albariño and Loureira). The results showed that the use of these fining agent plays a significant role in the wine volatile composition.     

Effects of fining with different bentonite labels and doses on colloidal stability and colour of a Valpolicella red wine

This study addressed four different labels of activated sodium bentonite during the fining of a young Valpolicella red wine. Preliminary tests determined the bentonite dose (0.15, 0.30 or 0.50 g L^?1) that would achieve colloidal stability, and this dose was further applied during laboratory‐scale trials. The bentonites were characterised by physico‐chemical parameters, and the effects of the label and dose on the wine colloidal stability, proteins, colour indices and phenolic compounds were measured. The results demonstrated that 0.50 g L^?1 for every bentonite label provided colloidal stabilisation without harshly affecting the colour. Unlike to what happens in white wines the least charged bentonite labels were effective at stabilising the red wine colloidal state by partially reducing its protein content. Simultaneously, the most negatively charged clay samples determined the largest depletions on the total polyphenols, anthocyanins, tannins and polymeric pigments. The differentiated action of clays with different surface charge density among white and red wines may be explained by the interaction mediated by positively charged anthocyanins towards either protein or tannin depletion. Although pioneering, these results may move towards the definition of a safe, allergen‐free, and effective adjuvant for colloidal stabilisation targeted to wine type.     

Comparing the impact of bentonite addition for both must clarification and wine fining on the chemical profile of wine from Chambave Muscat grapes

The impact of bentonite fining is generally studied on final wines, and few studies have evaluated it throughout the winemaking process. This work studied the fate of proteins and terpenols, the main targets of bentonite addition, during the processing of Chambave Muscat aromatic grapes. The experimental trials were performed in two vintages (2006 and 2007) and included the following processes: bentonite addition to must only (100 g hL^?1 in both vintages), fining of wine only (100 g hL^?1 in both vintages), double bentonite treatment on must and wine (200 and 150 g hL^?1 in 2006 and in 2007, respectively) and no treatment (control). The results demonstrated that the treatment allowing the best removal of protein was the addition of bentonite to must only. Moreover, a lower removal of free terpenols was observed in samples from double treatment compared with wines fined with bentonite only after alcoholic fermentation.     

Influence of the use of bentonite as a riddling agent on foam quality and protein fraction of sparkling wines (Cava)

This paper studies how the use of bentonite to facilitate the riddling process affects the foam properties and the protein fraction of sparkling wines (Cava). In all monovarietal sparkling wines (Macabeu, Xarel.lo, Parellada, Chardonnay and Pinot Noir), the addition of bentonite produced a statistically significant diminution of the Mosalux parameters (HM and HS). This depreciation of the foam quality may be attributed to the direct interaction of bentonite with wine proteins. Concretely the use of bentonite caused a diminution of more of 80% of total the soluble protein. Gel filtration by FPLC showed that bentonite particularly affected the 60 kDa and 20–30 kDa protein fraction. The high molecular fraction, on the other hand, was not affected.     

Effect of storage on the phenolic content,volatile composition and colour of white wines from the varieties Zalema and Colombard

Different quality attributes and chemical components of wines change during storage as a function of a series of factors. Thus, in young white wines, changes in phenolics, that lead to modifications of their colour as a result of oxidation processes, are well-known. These reactions can also alter their volatile profile giving rise to the appearance of new aromas, which in some cases are undesirable. In this study we have carried out a thorough evaluation of the changes in the colour, volatiles and phenolics of Zalema and Colombard wines during 1 year of storage under different conditions of temperature and position. The phenolics and colour were more affected than was the volatiles profile and wines kept in the cold could be clearly distinguished from the others, whilst the position of the bottles onlt slightly affected the wines during storage. Results showed that the blending of Zalema wines with Colombard wines may be an appropriate means of enhancing the acidity of the former without dramatically affecting its character.     

Characterization of natural haze protein in sauvignon white wine

The natural precipitate of a white Sauvignon wine was dissolved, lyophilized and analyzed by molecular exclusion FPLC and/or electrophoresis (SDS–PAGE, native and isoelectrofocusing) using three types of stains (Coomassie blue, silver stain and PAS stain). The protein spots were digested and analyzed by MALDI-TOF/TOF MS. Direct analysis of the precipitates by SDS–PAGE gave no bands with Coomassie blue stain and five bands with silver stain. It was not possible to identify these bands by MALDI-TOF/TOF MS. However, applying molecular exclusion FPLC prior to SDS–PAGE improved sensitivity and enabled three bands to be identified. These were the previously described thaumatin-like protein (VVTL1) and two proteins that to our knowledge have never been described as components of protein haze: β-(1-3)-glucanase and ripening-related protein grip22 precursor.     

Effect of clarification on the fatty acid composition of grape must and the fermentation kinetics of white wines

 The effect of different static and dynamic clarification treatments on grape must used in the manufacture of white wines was studied. Turbidity, yeast populations in the musts and must lees, fatty acid composition of the must and must lees after each treatment, and the fermentation kinetics using each cleaned must were measured. Fatty acids not previously found in grape must, such as tridecanoic acid and myristoleic acid, were detected. Dynamic clarification prolonged fermentation, and certain long-chain fatty acids helped activate fermentation. Received: 5 October 1998 / Revised version: 8 February 1999     

Colour correction in white wines by use of immobilized yeasts on κ-carragenate and alginate gels

Pale white wines of the sherry type were subjected to different colour correction treatments based on the use of gel beads consisting of variable proportions of yeasts immobilized on two different polysaccharides (κ-carragenate and alginate). All treatments were found to reduce colour in the control wine, the reduction increasing in a non-proportional way with the increase in yeasts concentration and the decrease in polysaccharide/yeasts ratio. On the same polysaccharide/yeast ratios, κ-carragenate gels proved more efficient than alginate gels. Except for some acids, the concentrations of phenolic compounds were reduced by all treatments (especially those involving κ-carragenate). Based on their colour-correcting ability, moderate retention of human healthy phenolic compounds and similarity to activated carbon in sensory terms, κ-carragenate gels containing a 2 g/L concentration of yeasts in a 2:2 polysaccharide/yeasts ratio represent an effective alternative to fining agents traditionally used in the production of white wines.     

Flavonol composition of Australian red and white wines determined by high‐performance liquid chromatography

Background and Aims: Flavonols are present in Vitis vinifera L. wine grapes as glycosides and are found in wines in both their glycosidic and aglycone forms. Flavonols and their glycosides are important components in wine because of their impact on colour, taste and health properties. An assessment of the flavonols and flavonol glycosides present in a wide selection of Australian red and white wines (n = 121 and 44, respectively) was undertaken. Methods and Results: Analyses were performed using HPLC, with compound identification being aided by HPLC‐MS. In the red wines, quercetin and myricetin dominated the flavonol profile, and quercetin‐3‐glucuronide was by far the most abundant glycoside present. White wines had considerably lower levels of flavonols and their glycosides, in most cases, being below the detection limit of the HPLC method. Conclusions: There appeared to be no correlation between the flavonol profile and wine variety or region in either white or red wines. Contrary to literature reports of rutin in wine, rutin was not found in any of the wines we analysed, and spiking experiments showed rutin rapidly degraded to the aglycone quercetin. Furthermore, changes in elution order for some quercetin glycoside standards were observed depending upon the acid used in the mobile phase. Significance of the Study: This is the first time the flavonol contents of an extensive cross section of Australian wines have been reported. The concentrations are consistent with those reported in wines from other countries. In light of the instability of rutin in wine, critical review should be given to reports discussing its presence.     

Emulsion Stability as Affected by Competitive Adsorption Between an Oil-Soluble Emulsifier and Milk Proteins at the Interface

The effect of an oil-soluble emulsifier upon adsorption properties of β-casein and β-lactoglobulin at the oil-water interface was studied. Addition of emulsifier improved the emulsification properties, but lowered emulsion stability. Higher concentrations decreased emulsification capacity, due to an increase in oil phase viscosity, and interfered with several protein assays, except the o-phthaldialdehyde (OPA) assay. Depletion measurements revealed that the emulsifier displaced β-casein more readily than β-lactoglobulin from the surface of droplets, which correlated with emulsification and stability measurements. Displacement of proteins was not complete due to emulsifier-induced formation of a multiple w-o-w emulsion, which accounted for the missing protein in the continuous phase.     

Fractionation of Sauvignon wine macromolecules by ultrafiltration and diafiltration: impact of protein composition on white wine haze stability

After ultrafiltration (UF) thermally unstable compounds of Sauvignon blanc wines were concentrated in the retentate fractions of 10–30 kDa increasing heat‐induced haze 8.9‐fold, while concentrating haze stabilising species into the retentate fractions of 100–300 kDa with a 5.3‐fold reduction of heat‐induced haze compared to unfiltered wine. Proteins having molecular weights of 18, 23, 33, 35, 40 and 60 kDa were identified as the main haze promoting agents for Sauvignon blanc, where the proteins of 56, 69 and 72 kDa were identified as thermally stable. Potassium sulphate (100 mg L^?1) and magnesium sulphate (25 mg L^?1) did not affect wine haziness at experimental diafiltration (DF) conditions using model wine solutions. Combination of UF and DF is a useful separation method of wine proteins, which is helpful to quantify haziness of individual species and to reveal the interactions between species involving protein haze.     

Changes in phenolic compounds and colour in pale Sherry wines subjected to fining treatments

 Changes in the concentrations of hydroxybenzoic acids, hydroxycinnamic acids and their esters, monomeric and dimeric derivatives of flavan-3-ol, and flavonols, as well as in the UV-visible absorbances of pale Sherry wines were studied. The wines were subjected to four different fining treatments: casein + bentonite, casein + bentonite + activated charcoal, casein + bentonite + polyvinylpyrrolidone (PVPP) and casein + bentonite + Riduxhigh. Based on the results, the treatments including activated charcoal and PVPP were the most effective at decreasing the overall concentration phenolic compounds, with no significant difference between them. Likewise, these treatments provided the best results in relation to wine colour in the visible spectral region, and particularly at 420 nm, at which wavelength browning compounds are usually measured. Received: 24 March 1997 / Revised version: 11 June 1997     

Changes in phenolic compounds and colour in pale Sherry wines subjected to fining treatments

 Changes in the concentrations of hydroxybenzoic acids, hydroxycinnamic acids and their esters, monomeric and dimeric derivatives of flavan-3-ol, and flavonols, as well as in the UV-visible absorbances of pale Sherry wines were studied. The wines were subjected to four different fining treatments: casein + bentonite, casein + bentonite + activated charcoal, casein + bentonite + polyvinylpyrrolidone (PVPP) and casein + bentonite + Riduxhigh. Based on the results, the treatments including activated charcoal and PVPP were the most effective at decreasing the overall concentration phenolic compounds, with no significant difference between them. Likewise, these treatments provided the best results in relation to wine colour in the visible spectral region, and particularly at 420 nm, at which wavelength browning compounds are usually measured. Received: 24 March 1997 / Revised version: 11 June 1997     

Comparative quantitative analysis of the effect of cultivar, wine growing region and vinification method on the protein profiles of some white wines

The influence of cultivar, growing region and method of vinification (industrial vs. laboratory) on the protein profiles of white wines of Portuguese and Austrian origin was comparatively analysed. The profiles were obtained by fractionation of the wine samples using anion exchange HPLC, resulting in fifteen fractions. A principal component analysis (PCA) was performed by considering the percentual peak area as the input factor and the results showed that there is a relationship between the occurrence of some of the protein fractions identified. Clustering techniques indicated that cultivars and the region of production were the factors that had a significant influence on the protein profile of a given wine, the former being particularly predominant.     

Browning development in white wines: dependence on compositional parameters and impact on antioxidant characteristics

Browning is a serious problem in relation to white wine quality and mostly affects the sensory attributes, whereas its impact on the dietary value of wines has never been investigated. Browning, however, is well known to be associated with polyphenol oxidation, and therefore it may be accompanied by changes in the antioxidant capacity. On the basis of this consideration, experimental white wines vinified and stored under identical conditions were subjected to accelerated browning, and efforts were made to distinguish compositional parameters that might be related to the extent of browning development. Further, the consequences of browning on the reducing power and antiradical activity were assessed. It was shown that none of the parameters examined (titratable acidity, pH, total SO₂, total polyphenols and total flavanols) play an important role in browning onset, but SO₂ appeared to exert a statistically significant influence (r²=0.6394, P<0.05) on the percentage change in the antiradical activity. Evidence also suggested that browning development might be prominently associated with decreases in both antiradical activity (r²=0.7891, P<0.01) and reducing power (r²=0.6925, P<0.05).     

Browning of white wines: correlation with antioxidant characteristics, total polyphenolic composition and flavanol content

Browning is a serious problem in relation to white wine quality, which mostly affects the sensory attributes. It is well known to be associated with polyphenol oxidation, and therefore it may be accompanied by changes in the antioxidant capacity. On the basis of this consideration, thirteen experimental white wines, vinified and stored under identical conditions, were subjected to accelerated browning, and efforts were made to distinguish compositional parameters that might be related to the extent of browning development. Further, the relation of browning with the reducing power and the antiradical activity were assessed. Regression analysis at 95% significance level indicated that the antiradical activity is likely to be exerted principally by the flavanol fraction (r² = 0.92) and to a lesser extent by total phenols (r² = 0.85), as opposed to reducing power, which is mainly affected by total phenols (r² = 0.78), suggesting that synergistic phenomena account for the overall antioxidant status of white wines. In addition, the total phenolic and flavanol concentration correlated significantly with the browning rate constants and provided strong evidence that browning development might be predominately associated with flavanol (r² = 0.84) and to a lesser extent with total phenolic (r² = 0.79) oxidation.