Fermentation of black plum (Vitex doniana Sweet) juice for production of wine

Abstract

Introduction. V. doniana Sweet fruit juice is sweet and has been fermented for many years in Nigeria using a traditional technology to produce wine. In this country, black plum is collected from wild trees in the natural ecosystem or from trees cultivated in isolated farms. Our study compared the chemical and sensory properties of wine produced from traditional or controlled fermentation of black plum juice. Materials and methods. Four types of experiments, two with spontaneous fermentation and two with controlled fermentation, were carried out, each with five replicates. The proximate composition, alcohol content and pH of the solutions obtained after spontaneous or controlled fermentation were determined. Moulds and yeasts isolated in the fermented juice were identified. Results and discussion. Wine obtained from controlled fermentation had 10.5% alcohol content while the spontaneous fermentation produced a wine of 5.0% alcohol content. The chemical analysis of juice produced from harvested ripe Vitex doniana fruit showed that it contained a soluble protein content of 75.62 ${\rm mg} \cdot {\rm mL}^{-1}$, pH of 4.5, total sugars of 95.10 ${\rm mg} \cdot {\rm mL}^{-1}$, titratable acidity of 0.33 ${\rm mg}\cdot 100$ mL^-1, and ascorbic acid of 5.2 ${\rm mg} \cdot {\rm mL}^{-1}$. The yeasts isolated from the wine were Saccharomyces cerevisiae and S. coreanus, and filamentous moulds were Rhizopus stolonifer, Penicillium sp. and Aspergillus sp. Single cell protein was produced from the fruit juice by cultivation in it of Saccharomyces cerevisiae isolated from the fruit. The yeast had a protein content of 6.8 ${\rm mg} \cdot {\rm mL}^{-1}$ when grown at 20 °C for 36 h at pH 5.8. Conclusion. Wine produced from Vitex doniana Sweet juice has quite high alcohol content and is palatable with good flavor. The stability of the juice for yeast growth is an advantage for the production of single cell protein.