Changes in Wine

Depending on pH, and unless corrected by post-MLF acidulation, wine color may develop violet-to-blue hues. 

---

TABLE 4.1 Changes in wine color parameters for a Cabernet Sauvignon wine subject to MOX for 7 months at 5 mL/L/month data from Atanasova et at. (2002)... 

The most rapid changes in wine color composition appear to occur during the first year, when the wine is normally in bulk storage (Somers, 1971). This phase is considered to be distinct from reactions occurring latter when the wine is in bottle and well protected from further contact with air (Ribereau-Gayon et ah, 1983). 

Traditionally, large oak barrels are used to facilitate the diffusion of oxygen. This is assumed to play a major role in the many chemical reactions occurring during aging. Oxidation reactions promote desired changes in wine phenolics (e.g., anthocyanins, flavonoids, and tartaric esters of hydrocinnamic acids) as well as oak phenolics extracted from the... 

Simpson, R. F. (1978). Aroma and compositional changes in wine with oxidation, storage end aging. Vitis 17, 274-287. 

Besides carrying out MLF, under certain conditions LAB can also cause undesirable changes in wine flavour which render the wine undrinkable. Many species of LAB do not conduct MLF and their growth in wine can cause some serious wine spoilage. The nature and extent of this spoilage depend on several factors such as the type of bacteria, composition of the wine and vinification practices specific types of spoilage are associated with a restricted number of lactobacilli. 

The biological aging process involves various changes in wine composition. Such changes are essentially the result of the metabolism of flor yeasts and, to a lesser extent, of other phenomena common to all types of aging processes including crystal precipitation, chemical reactions between wine components and extraction of substances from cask wood. 

Aside from deacidification, MLF may also influence the sensory qualities of a wine by the production of many flavor and aroma compounds (Davis et al., 1985, 1988 Henick-Kling, 1993 Kunkee, 1967 Rankine, 1977). However, there is still debate regarding the contribution of MLF to the sensory properties of a wine. Early work by Kunkee et al. (1964) and Rankine (1972) indicated that MLF may not have a measurable effect on the sensory properties of a wine. On the other hand, many other studies have shown that MLF causes significant changes in wine aroma and flavor (Boido et al., 2002 Delaquis-Pascal et al., 2000 De Revel et al., 1999 Gambaro et al., 2001 Henick-Kling, 1995 Laurent et al., 1994 Maicas et al., 1999 McDaniel et al., 1987 Nielsen and Richelieu, 1999). 

Figure 4, Anthocyanin and color changes in wine-like model...

The catabohsm of sugars, malic acid and citric acid are normal occurrences during fermentation. Lactic disease only exists if O. oeni mnlfiplies prematnrely. Many other transformations also occnr and some depend on the nature of the strain. Malolacfic fermentation has been confirmed to canse chromatic changes in wines and a decrease in their color, while stabilizing it. 

---