Plum wine can be prepared from plum fruits either with skin or without skin of the fruit, but the wines have considerable differences in physicochemical characteristics. A comparison of the characteristics of plum wine is made in Table 15.3. Use of honey instead of sugar in plum wine fermentation has also been made (Joshi et al. 1990a).
Effect of Initial Sugars on Wine Quality
In the preparation of wine, initial sugar concentration (ISC) is one of the most important quality parameters because it is known to influence the quality and type of wine. In plum (cv. Black Beauty), an increase in ISC decreased the rate of fermentation, .
Effect of Osmotic Treatment of Fruit on Wine Quality
To produce quality wine, aside from acids, a proper balance of tannin and good fruity flavor are prerequisites. Application of osmotic techniques after blanching the fruit in water increased TSS and decreased acids, although a little loss of anthocyanin and mineral content also occurred.
The sensory quality of wine prepared from water-blanched and osmotically treated fruits were the best (Vyas et al. 1989).
Use of Preservative
The type of preservative used reportedly affects the quality of wine produced (Joshi and Sharma 1995). The use of sodium benzoate instead of potassium metabisulfite produces wine with better color and sensory qualities without affecting the physicochemical characteristics.
Potassium metabisulfite is commonly used in most of the wine fermentations, but it reduces the color of wine. Higher ethanol, propanol, and amyl alcohol contents have been reported in potassium metabisulfite–treated wine compared with sodium benzoate–treated wine.
Thus, the use of sodium benzoate does not interfere with normal alcoholic fermentation of plum into wine (Figure 15.2). With respect to sensory qualities, sodium benzoate– treated wine was found to be superior to potassium metabisulfite–treated wine (Joshi and Sharma 1995). The mineral composition of the wines was reportedly affected by the addition of different preservatives .
Microbiology of Fermentation
obtained. In general, wine yeast Scerevisiaevar. ellipsoideus is used to produce plum wine. In such a fermentation, the early stages of alcoholic fermentation are dominated by non-Saccharomyces species especially Kloeckera apiculata/Hanseniaspora uvarum and Candida pulcherrima.
These yeast strains were identified using killer sensitivity analysis. The activity of these non-Saccharomyces species however decreased after two days, at which point Saccharomyces species took over the fermentation process.
This pattern is almost similar to that of spontaneous fermentation of grapes (Fleet and Heard 1994). Acomparison of the physicochemical characteristics of fresh and fermented plum must using different sources of fermentation/spontaneous fermentation is given in Table .
Effect of Wine Yeast Strains
n inoculated studies or commercial production, the use of wine yeast S. cerevisiae var. ellipsoideus is an established practice. How the different wine yeaststrains affect the physicochemical characteristics of plum wine was also studied (Joshi et al. 2009).
The rate of fermentation of all the yeasts showed that the “Tablet” and “W” yeast strains gave the highest reduction in TSS, whereas UCD 505/522 gave the lowest rates. All the yeast strains recorded rates of fermentation higher than 1.6 and strains UCD 595, W, and Tablet had the same rate of fermentation.
The yeasts did not influence the acid with the wines and was desirable (Joshi et al. 2009). It was concluded that plum wines prepared by using strain UCD 595, W, and Tablet have better sensory qualities compared with that produced from UCD 522 and UCD 505 (Table 15.6).