**Acknowledgements**

*Pectins - Extraction, Purification, Characterization and Applications*

Other interesting oenological property of MP is their capacity to stimulate the growth of lactic acid bacteria and consequently the malolactic fermentation [117, 118]. In fact, MP can stimulate the malolactic bacteria through two mechanisms. Firstly, the adsorption of the medium chain fatty acids synthesized by Saccharomyces. These compounds have been shown to inhibit lactic acid bacteria growth and hence their removal by MP promotes the detoxification of the medium [119]. Secondly, the enzymatic hydrolysis of yeast MP and/or other macromolecules and polysaccharides by lactic acid bacteria can enhance the nutritional content of the medium, and thus potentially stimulate the lactic acid bacteria growth [117]. In the same way, yeast MP are able to adsorb the ochratoxin A (OTA), which is a dangerous mycotoxin [120]. This adsorption seems to be more effective in white wines than in red wines, due to the competition between polyphenols and OTA for the same binding sites on the surface of the yeast cells [106, 121]. There are several factors that can significantly affect the ability of OTA adsorption by MP as yeast strain [122, 123], mannosylphosphate content in the MP of wine yeasts, dissimilar fermenta-

tion, and cell sedimentation dynamics, cell dimension, and flocculence [120]. MP also affect the foam quality of sparkling wines [64, 65, 124–126]. Specifically, these molecules play a major role in foam stabilization [65, 127], particularly the MP with low content of protein (5%) [127]. The hydrophobic nature of MP causes them to preferentially adsorb to the gas/liquid interface of foam bubbles [128, 129], resulting in more stable foam [125]. In fact, the use of MP or cell wall extracts as additives has been proposed to improve the foam properties of sparkling wines elaborated by the traditional method. Therefore, the addition of yeast cell wall MP with a relative molecular weight between 10 and 30 kDa improved the foaming of sparkling wines [124]. However, the addition of commercial dry yeast products rich in MP to the tirage liquor did not modify the foam properties of sparkling wines [101]. In a previous work it was shown that MP and PRAG were poor foam formers but good foam stabilizers. Moreover, a higher positive correlation was found between foam stability time and PRAG (*r* = 0.723) than MP (*r* = 0.465) [65]. Finally, MP also contribute to the flocculation of yeast strains [130], and thus improve their elimination from the bottle during disgorging. MP could also serve as markers to follow the autolysis process because they are the major polysaccharides released by yeast [1, 3, 54]. Moreover, MP also seem to participate in film forming yeast or flor velum in Sherry type wines [131]. These wines are produced by "biological aging" that follows alcoholic fermentation. According to the study conducted by Alexandre et al. [132], a 49 kDa hydrophobic cell wall MP present in a velum yeast has been correlated with velum formation during the aging system used

Polysaccharides are one of the main groups of macromolecules in wines. They play an important role in both the technological and organoleptic properties of the wines. The oenological interest of polysaccharides has induced the development of several commercial products. In fact, there are nowadays in the market different commercial products based on purified MP or yeast derived cell walls, which are used in many wineries in order to improve the tartaric or proteic stability of the wines, or the sensory properties of some wines. However, these products have not always shown a clear effect in the wines. Recent studies indicate that other oligosaccharides and polysaccharide families from grapes could have a great potential to modify and improve the sensory and physicochemical properties of the wines. Unfortunately, these polysaccharide families are very difficult to obtain and they

in sherry wine (Spain) or Vin Jaune (France).

**134**

**4. Conclusions**

The authors would like to thank the *Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA)* for the funding provided for this study through the project RTA2017-00005-C02-02.
