Palm wine and pasteurised palm sap volatiles were collected, concentrated on a Tenax GC and analysed by gas chromatography and gas chromatography-mass spectrometry. Eighty-two components were identified: 47 esters, 9 alcohols, 5 acids, 6 carbonyls, 2 acetals, 4 terpenes and 9 hydrocarbons. These had all been found previously in conventional wines. Odour evaluation of the separated palm wine components as they eluted suggested that no one compound is responsible for the characteristic palm wine odour. The acetates of higher alcohols and the ethyl esters of straight-chain aliphatic C,-Cl0 acids seemed to be important and may play a big role in imparting the fruity nuances of characteristic palm wine odour. Their association with alcohols seemed also to be necessary for the expression of typical palm wine odour. The qualitative difference between palm sap aroma and palm wine aroma appeared to be due mainly to the presence of these esters and alcohols in palm wine and their apparent absence from palm sap, as well as to the presence of some low-boiling esters and alcohols in palm sap and their apparent absence from palm wine.
Viscosity and soluble color changes in palm wine during fermentation were found to show an early increase followed by a gradual decline. Addition of absolute alcohol to palm wine precipitated gums that were absent in the palm sap, indicating production during fermentation. Precipitation of the gum was accompanied by loss in coloration and a signifcant reduction in viscosity. These properties were regained on reintroduction of the gum showing that the gums were responsible for the properties. Yeasts and bacteria isolated from palm wine were employed in pure culture fermentations of sterile palm sap to determine the origin of the gums. The results showed that the gums were produced mainly by leuconostocs, while two other bacteria not f i l l y identified and a homofermenting Lactobacillus spp, also produced some. Analysis showed the Lactobateriaceae gums to be a11 glucans, while the gums of the other bacteria were fructans. Palm wine was found to contain both types of gum (80% glucans, 20 % fructans), showing that many bacteria produce gums in palm wine concomitantly.
Solvent extracts of palm wine early in fermentation (12% sugar, pH 7), during active or mid fermentation (6% sugar, pH 3.6) and towards the end of fermentation (2 % sugar, pH 3.6) were obtained using dichloromethane and diethyl ether. The extracts were analyzed by gas chromatography and gas chromatography-muss spectrometry. Altogether, 73 compounds were identifed, 45 of which had not been previously reported in palm wine. The qualitative and quantitative differences between the chromatograms of extracts of palm wine early in fermentation and at mid fermentation suggest that the flavor volatiles of palm wine derive mainly from fermentation. The occurrence of acetic acid early ' 483 484 S.V.A UZOCHUKWU ETAL.in the fermentation suggests that it is the first volatile acid and in fact one of the first volatiles produced in palm wine fermentation, contrary to previous assumptions. The lactic fermentation, reported to initiate palm wine fermentation, is thought to be responsible for this. That fermentation must therefore be prevented in palm exudates destined to be used for any product where acetic acid is undesirable.
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