Influence of Grape Polysaccharide Extracts on the Phenolic Compounds and Color Characteristics of Different Red Wines.

Polysaccharides have an important role in the technological and sensory characteristics of wines. The aim of this work was to study the effects of the addition of four polysaccharide extracts obtained from grape products and byproducts to red wines during storage for 2 months on their phenolic composition and color. The four extracts rich in polysaccharides were obtained from grape must, white grape pomace, red grape marc, and red wine, and they were compared with a commercial inactivated yeast. These products were studied in three wines selected for their highest astringency and acidity characteristics. The highest differences were found in the red wines with high initial phenolic concentrations, which reduced their values. The addition of polysaccharide extracts from grape pomace or marc, must, or yeast can mainly be interesting in wines with high phenolic content since they may be useful to modulate the astringency of red wines. This is the first work that studies the effect of polysaccharide extracts obtained from grape byproducts in red wines, showing great possibilities of these products.

The Effects of Grape Polysaccharides Extracted from Grape By-Products on the Chemical Composition and Sensory Characteristics of White Wines.

There is an increasing interest in the valorization of wine waste by-products. Grape pomace/marc can be an important source of polyphenols but also of polysaccharides (PSs). Therefore, the aim of this work was to extract PSs from grape pomace and musts and incorporate them into wines to improve their quality and valorize these residues. Two white wines were elaborated and treated with four different PS extracts obtained from white grape pomace, white must, a wine purified extract rich in RG-II, and commercial inactivated yeasts. In general, the use of grape PSs extracted from grape pomace or must improve some characteristics of wine, increasing the polysaccharide and volatile concentrations. These PS extracts can be useful to modulate some taste attributes such as an excess of acidity and bitterness and can also prevent the loss of volatile compounds associated with fruity and floral notes over time. This is the first study that shows the effects of grape polysaccharides on the chemical composition and sensory characteristics of white wines. Considering the obtained results, the grape pomace and surplus of musts can be considered valuable sources to obtain polysaccharide-rich products, opening a new opportunity to take advantage of by-products from the wine industry.

Evaluating the influence of simultaneous inoculation of SiO2-alginate encapsulated bacteria and yeasts on volatiles, amino acids, biogenic amines and sensory profile of red wine with lysozyme addition.

The influence of the timing of inoculation (sequential and simultaneous alcoholic fermentation (AF)/malolactic fermentation (MLF)) on the chemical and sensory properties of red wines was studied. The impact of the encapsulation of Oenococcus oeni into SiO2-alginate hydrogel (Si-ALG) and the addition of lysozyme in wines inoculated with encapsulated bacteria were also analysed. There was a significant influence of the timing of inoculation on the volatile composition of the wines just as on the amino acid and biogenic amine content. The wines produced by simultaneous AF/MLF showed the highest contents of some volatile compounds, such as ethyl esters and terpenes, as well as amino acids and tyramine. Bacterial encapsulation affected the volatile and amino acid profile of the wines, while the biogenic amine composition was not modified. The chemical composition of the wines was not altered by the presence of lysozyme. A trained panel did not perceive substantial differences between treatments.

Optimization of a solid-phase extraction method using copolymer sorbents for isolation of phenolic compounds in red wines and quantification by HPLC.

Different solid-phase extraction (SPE) cartridges for the isolation of most of the phenolic compounds present in wines in low concentration were assayed and compared with the C18 SPE sorbent, which is the most common sorbent used for the isolation of these compounds. The use of C18 cartridges has several disadvantages; therefore, a SPE method using copolymer cartridges was developed, optimized, and validated. The method proposed seems to be a good alternative to replace C18 cartridges for the isolation of wine phenolic compounds. The advantages of the proposed SPE method with the HLB cartridge are that interferences can be eliminated with water without losing the compounds of great interest; the method has very good repeatability, reproducibility, and high percentages of recovery; it has a higher sensitivity and loading capacity than silica-based C18 cartridges due to the larger surface area of this type of sorbent, and the method is not adversely affected by drying, being more reproducible than C18 cartridge.