Characterisation of Low Alcohol Rose Wine Produced From Hibiscus Sabdariffa Calyces And Sorghum Bicolor Leaf Extracts

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Wine is a natural fermented product from the juices of grapes and other fruits, by the action of yeast cells. Wines produced directly with alcohol contents in the range of 1.2-5.5% are low alcohol wines. Rose wines are wines that have some colour typical of red wines but only enough to turn it pink. The project was undertaken to assess the nutritional composition of H.sabdariffa calyces (roselle) and Sorghum bicolorleaves establish the optimum conditions for blends of extracts for wine production, determine the physicochemical properties of the fermented extracts aged into wine and to evaluate the sensory quality of low alcohol rose wine produced from rosellecalyces and Sorghum bicolor leaves. The roselle calyces and S. bicolor leaves were solar dried, milled separately and standard analytical methods were used to evaluate the proximate and mineral composition. Extracts were prepared from the leaves and calyces by infusion and physico-chemical analyses such as pH, titratable acidity (TA) and total soluble solids (TSS). The response surface methodology was used to establish the optimum conditions for extract blend and time of fermentation for the wine production. The optimum conditions were used to prepare bulk extracts for fermentation using Saccharomyces cerevisiae. Two kinds of fermented extracts were prepared. One from only H.sabdariffa calyces and the other from a blend of H. sabdariffa calyces and S. bicolor leaves. Physicochemical analyses were carried out on the fermented extracts and were divided into four. Two of them each from the blend and H. sabdariffa calyx were taken through a clarification process using egg albumin and natural sedimentation process, such that two clarified and unclarified fermented extracts were subjected to an aging period of 20 weeks. The wines were analysed during the aging period after which sensory evaluation (Affective test) was carried out using 32 panelists. Both leaves and calyces contained appreciable amounts of energy, carbohydrate, calcium, potassium, magnesium and iron. However, the amounts of nutrients determined in H.sabdariffa calyces were higher than those in Sorghum bicolor leaves. Physico-chemical properties on the extracts revealed both calyces and leaves had total soluble solids (TSS) of 0 o Brix. Table sugar was added to raise the TSS level to a brix of 18.62 to aid in fermentation. A fermentation time of 7.75 days and extract blend of 100% H.sabdariffa (HS) calyces extract as well as 75% H.sabdariffa and 25% Sorghum bicolor leaves (HS-SB) extract were the optimum conditions established through the response surface methodology. The two types of fermented extracts produced (from HS and HS-SB), had a pH of 3.61 and 3.63, TA of 7.30 g/l and 7.18 g/l respectively, which were within the pH range of 3 - 4 and TA range of 7 - 9 g/l accepted by the International Organisation of Vine and Wine. Significant differences (p< 0.05) were observed in the effects of clarification and blending on the total phenols (TP), total red pigments (TRP) and total colour densities (TCD) of the clarified and unclarified wines. The levels of these parameters were higher in the unclarified samples than the clarified wine samples and decreased significantly (p<0.05) with aging time. TP decreased from 18.21 AU to 10.16 AU in the unclarified H. sabdariffa wine and also from 16.58 AU to 8.19 AU for clarified wine from H. sabdariffa calyces. On the other hand, the decrease in TP in the blended (HS-SB) clarified and unclarified wines were from 13.97 to 7.37 AU and 16.64 to 9.15AU respectively. Panelist rated clarified wine from H. sabdariffa calyces as the most preferred among the four test wines in terms of aroma, taste, alcohol, acidity, sweetness and overall acceptability.
This Dissertation Is Presented to the Department Of Food Science and Technology in Partial Fulfilment of the Requirement of M.Sc. (Hons) Degree in Food Science And Technology, April-2013