Quantification of reducing sugar in wine - Lab Report Example

Quantification of reducing sugar in wine A= the amount in ml of sodium thiosulfate to titrate H2O blank = 28ml B = the amount in ml of sodium thiosulfate to titrate wine sample = 21.2 mlPercentage reducing sugar in 9g/ml) = 2.8 (1 – 21.2/28) = 0.68 x 100 = 68% 2. In the Gold Coast test for reducing sugars, the main principle is reduction of excess copper by reducing sugars. The excess copper is then reduced with excess iodide ion to produce an equivalent amount of iodine. Sodium thiosulfate is used to titrate the iodine.

The blue color is produced by starch due to the reaction between starch and iodine. A deionized water blank is run and the results of the sample titration and blank are compared.3. Examples of reducing sugars in fruits include; i) Fructoseii) Glucose4. The two predominant sugars found in grapes are;i) Glucoseii) FructoseThis is because sucrose molecules are hydrolyzed to glucose and fructose by enzyme invertase during ripening. The grapes is usually composed of 15 – 20% reducing sugars by the time of harvest. 5. The winemaker might want to know the amount of sugar remaining in wine as it nears the fermentation process because during fermentation, the yeast converts sugars to alcohol and carbon dioxide.

The amount of alcohol is produced is related to the sugar initially present in the juice. Thus by controlling the amount of sugar, the winemaker can control the amount of alcohol in the wine. The remaining sugar present in the wine after fermentation might destroy yeast after a certain alcohol content is reached. 6. Sucrose is a disaccharide sugar composed of one molecule of glucose and one molecule of fructose joined together forming a glycosidic bond between the reducing ends of the reducing sugars.

Sucrose is therefore not a reducing sugar because it doesn’t have a free aldehyde or keto group which are anomeric hydroxyl groups. 7. The Gold Coast test can be used to measure the amount of sucrose that can be added to wine for extra sweetness. However, the sucrose needs to be converted to fructose and glucose which are reducing sugars though hydrolysis by enzyme sucrose first. This is referred to as the Gold-Coast invert. 8. Lactose is a disaccharide sugar composed of one molecule of glucose and one molecule of galactose joined together forming a glycosidic linkage.

Lactose is not a reducing sugar because it does not have free aldehyde or keto group and cannot act as a reducing agent.9. The Gold Coat test can be used to measure the lactose content in milk. Enzyme lactase must be added first to convert lactose into galactose and glucose which are reducing sugars for the test to be effective. Lactose is a non-reducing sugar and the Gold Coast test is used to measure the content of reducing sugars.10. A Gold Coast test can be used to measure the completeness of conversion of starch to syrup because it will help determine the important properties of the syrup such as sucrose and dextrose content.

This is essential in quality control of the syrup product.