Characterisation of Low Alcohol Rose Wine Produced From Hibiscus Sabdariffa Calyces And Sorghum Bicolor Leaf Extracts
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Date
2013-04-18
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Abstract
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.
Description
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