Donato Colangelo

Effect of Bentonite Characteristics on Wine Proteins, Polyphenols, and Metals under Conditions of Different pH

Studies have yet to evaluate how bentonite properties may affect the protein profile, polyphenol content, metal concentration, and heat stability of a white wine at different pH values. Therefore, this work assessed the proteins, polyphenols, metals, and haze forming tendency when heating white wine samples before and after a fining treatment with four activated sodium bentonites in a typical wine pH range (3.00 to 3.60). Soluble wine proteins were separated by sodium dodecyl sulfate - polyacrylamide gel electrophoresis, and gel images were compared using the Quantity One software package (Bio-Rad Laboratories, Inc., Hercules, CA). The wine haze forming tendency, metals, and polyphenols were measured using heat tests and International Organisation of Vine and Wine (OIV) methods. Low molecular mass proteins were efficiently removed by all of the bentonites, regardless of the pH. High and medium molecular mass proteins were less likely to be removed and the efficiency, which depended on the pH, was variable. Reductions of vacuolar invertase (GIN1) and VVTL1 fractions of the thaumatin-like proteins were induced by bentonites with pH values less than 10. These bentonites were affected to a lesser extent by the negative effect of acidic pH. The reduction in haze forming tendency of the unfined Erbaluce wine was particularly noticeable in bentonite fined samples heated at 50 to 60°C, 60 to 80°C, and 70 to 80°C at pH 3.17, pH 3.30, and pH 3.60, respectively. The poor removal of glycoproteins (YGP1 and Hmp1) at higher pH values contributed to an increased thermal stability. The exchange of cationic species, notably sodium and potassium, between the bentonites and the wine was related more to the wine pH than to the clay type. Finally, the extent of polyphenol removal correlated with the amount of protein removed. When protein removal did not occur, the reduction of polyphenols was driven by the specific surface area and the surface charge density of the bentonite.

Innovations in the Use of Bentonite in Oenology: Interactions with Grape and Wine Proteins, Colloids, Polyphenols and Aroma Compounds

Bentonite is used in oenology to improve the limpidity and the stability of wine and to predict the formation of deposits in the bottle. The exchangeable cations in its lamellar structures strongly influence some properties, such as the specific surface, the exchange capacity and the adsorption behavior. The unintended use of bentonite for juice settling and/or for wine fining produces jeopardized effects on colloidal and protein stability, the aroma compounds and sensory profiles. The interactions with haze-forming proteins, other colloids, as well as aroma compounds and phenols would have been to discover as the modulation of wine colloids by an adjuvant severely affects the wine resilience and the sensory profile. This chapter reviews several studies that focus on the impact of commercial bentonite samples used for both juice clarification and wine fining on the colloids, proteins, phenols and aroma compounds of white and red wines. Some parameters of practical value, such as the wine heat stability, the concentrations of total and haze-forming proteins and the content of the most relevant aromas, have been assessed to track the effects of bentonite and to achieve findings that are applicable to the field of oenology.

The use of chitosan as alternative to bentonite for wine fining: Effects on heat-stability, proteins, organic acids, colour, and volatile compounds in an aromatic white wine

This investigation focuses on the use of chitosan treatment simulating a bentonite fining in order to detect any modification of the wine haze potential by simultaneously evaluating the secondary effects on untargeted fixed and volatile compounds. A significant removal of chitinases was observed after fining an aromatic white wine with 1u202fg/L of a fungoid chitosan. Even if the more stable thaumatin like protein fractions were not significantly affected, the heat stability of the fined chitosan wine samples were highly improved in the 55-62u202f°C range. Among the secondary effects of a fining treatment, a reduction of tartaric acid, malic acid, potassium and iron was showed. All the free terpenols with the exception of α-terpineol were reduced in significant amounts, whilst the glycosylated forms and the fermentative aroma compounds were not affected by a 1u202fg/L chitosan addition.

Modeling by Response Surface Methodology of the Clarifying Process of Muscat blanc Must for the Production of a Sweet Sparkling Wine

This study optimized clarifying Muscat blanc must with either Ca- or Na- bentonite and related mixes in a dose range of 10÷100 g/hL through a central composite design. Response surface methodology (RSM) estimated the combined effect of the bentonite type and dose on free (i.e., aglycons) and glycosylated aroma compounds. Heat stability, turbidity, and color were further analyzed. Results indicate that Na-prevalent bentonite mixes significantly reduced the must haziness, while mixes with 50% Ca-bentonite or higher led to negligible decreases. The surface plots from RSM predicted that aglycons of aroma compounds were removed by Na-bentonite at lower doses and by Ca-bentonite regardless of the dose. Further, the model estimated the removal of glycosylated aroma compounds, especially by Ca-prevalent bentonite at 50 g/hL. Despite the study’s experimental limitations, these outcomes will help the enological sector improve aromatic sparkling wine production.