Ten grapevine rootstocks: effects on vegetative development, production and grape quality of cv. Mencia in the d.o. Bierzo (Spain)

Fining is a technique that is used to remove unwanted wine components that affect clarification, astringency, color, bitterness, and aroma. Fining involves the addition of adsorptive or reactive material in order to reduce or eliminate the presence of certain less desirable wine components and to ensure that a wine remains in a particular stable state for a given period of time Recently concerns have been raised about the addition of animal proteins, such as gelatin, to wine due to the disease known as bovine spongiform encephalopathy (Mad Cow disease). Although the origin of gelatins has been moved to porcine, winemakers are asking for substitute products with properties and application protocols similar to the traditional animal-derived ones, making the use of plant-derived proteins in fining a practically viable possibility. As a consequence, various fining agents derived from plants have been proposed, including proteins from cereals, legumes, and potato.

The use of high-power ultrasound (US) during the winemaking process has been extensively studied at laboratory scale in order to demonstrate its possible use to improve the extraction of compounds of interest. However, studies on semi-industrial and industrial scale are needed to confirm this positive effect, since the International Organization of Vine and Wine approved its industrial use in 2019 [1].

Despite their trace concentrations, volatile sulfur compounds (VSCs) are an important category of flavour-active compounds that significantly contribute to desirable or undesirable aromas of many foods and beverages. In wines, VSCs in the form of polyfunctional thiols, notably 3-sulfanylhexan-1-ol (3-SH), 3-sulfanylhexyl acetate (3-SHA), and 4-sulfanyl-4-methyl-pentan-2-one (4-MSP), possess extremely low olfactory thresholds (≈ ng/L) and pleasant “tropical aroma” notes. They have received much attention with respect to their sensory contributions, quantitative occurrences, biogenesis, and thiol management through viticulture and winemaking. However, the fate of these potent volatiles are still not fully understood.

Ovalbumin (ova), a natural clarifying protein, is particularly suitable for clarifying red wines. It helps improve the tannic and polyphenolic stability of the wine by removing the most astringent tannins and contributing to soften and refine the structure. Ova binds to suspended particles, proteins, polysaccharides, and, to a lesser extent, tannins through electrostatic and hydrophobic interactions, forming large complexes that can be removed from the wine through fining and/or filtration before bottling.

Hydroxytyrosol (HT) is a phenolic compound present in olives, virgin olive oil and wine. HT has attracted great scientific interest due to its biological activities which have been related with the ortho-dihydroxy conformation in the aromatic ring. In white and red wines, HT has been detected at concentrations ranging from 0.28 to 9.6 mg/L and its occurrence has been closely related with yeast metabolism of aromatic amino acids by Ehrlich pathway during alcoholic fermentation. One of the most promising properties of this compound is the neuroprotective activity against pathological mechanisms related with neurode-generative disorders including Alzheimer’s and Parkinson’s disease.