Sugar is produced in more than 120 countries and global production is now more than 174 Million tons a year. Approximately 70% of this is produced from sugar cane, largely grown in tropical …Full description
This document gives u an complete details of various departments in sugar factory, their roles and resposiblities, their functioning etc.
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Biuret Test for Proteins
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Different qualitative and quantitative test for different types of carbohydrates.
Benedict's Test for Non-reducing Sugars The Benedict's Test for Non-reducing Sugars determines the presence of non-reducing sugars - sugars which do not have an aldehyde functional group. Many students confuse the Benedict's Test for Non-Reducing Sugars with the Benedict's Test for Reducing Sugars, perhaps because some of the steps in the procedure are similar. Benedict's solution is the principle reagent in both tests. The test for non-reducing sugars is often conducted on a food sample which tested negative for reducing sugar. If reducing sugars have been shown to be present, a heavier precipitate is often observed when the test for non-reducing sugar is conducted. The Fehling's Test for Non-reducing sugar is an alternative to the Benedict's Test. However it is less popular as it less sensitive and requires tha the reagents - Fehling's solutions A and B be kept separate until the experiment is carried out.
What is a Non-Reducing Sugar? Sugars can be classified as either reducing or non-reducing based on their ability to reduce copper(II) ions to copper (I) ions during the Benedict's Test. Non-reducing sugars do not contain an aldehyde group - the reducing species. Reducing sugars are simple, disaccharide sugars. Sucrose is the most common disaccharide non-reducing sugar.
Procedure 1.A liquid food sample does not need prior preparation except dilution if viscous or concentrated. For a solid sample prepare a test solution by crushing the food and adding a moderate amount of distilled water. Decant the suspension to remove large particles. Use the decanted liquid as the test solution. 2.Add 2 cm3 of the sample solution to a test tube. 3.Add 1 cm3 of dilute hydrochloric acid and boil for one minute. 4.Allow the tube to cool and then neutralize the acid with sodium hydrogen carbonate. Exercise caution due to 'fizzing' or effervescence. Check with blue litmus paper or pH paper. Do not worry if the resulting solution is slightly alkaline; Benedict's solution is also alkaline since an alkaline medium in needed for oxidation of the copper (II) ions by the sugars Then carry out Benedict's Test as for reducing sugars: 5.Add an 2 cm3 of Benedict's solution to the test tube and swirl or vortex the mixture. 6.Leave the test tube in a boiling water bath for about 5 minutes, or until the colour of the mixture does not change. 7.Observe the colour changes during that time as well as the final colour. 8.To prepare a control, repeat steps 2-6 using 2 cm3 of distilled water instead of sample solution.
Observations and Interpretation OBSERVATION (FINAL COLOUR CHANGE)
INTERPRETATION
No colour change (mixture remains blue)
No non-reducing sugar present
Green
Trace amounts of non-reducing sugar present
Yellow
Low amounts of non-reducing sugar present
Orange
Moderate amounts of non-reducing sugar present
Brick Red
Large amounts of non-reducing sugar present
Whilst boiling the colours of the mixture transition in this order: blue--> green--> yellow--> orange--> brick red
The final colour may be any of the colours above, depending on the quantity of non-reducing sugar present. If you do no observe the brick-red colour, it does not mean that your experiment has not been successful. It is important to note that the Benedict's Test for Non-reducing Sugars is not specific to any one type of non-reducing sugar, and that the colour corresponds to the total reducing and non-reducing sugar present.
Principle of the Benedict's Test for Non-reducing Sugar Disaccharides are hydrolyzed to their constituent monosaccharides when boiled in dilute hydrochloric acid. The monosaccharides are reducing sugars are they contain the aldehyde group which is the reducing species. Neutralization of the mixture by sodium hydrogen carbonate is necessary as the reduction of the copper(II) ions will not take place in acidic conditions - of excess acid is present. Benedict's Solution contains copper(II) sulphate, sodium carbonate and sodium citrate. The blue copper(II) ions from copper(II) sulphate are reduced to red copper(I) ions by the aldehyde groups in the reducing sugars. This accounts for the colour changes observed. The red copper(I) oxide formed is insoluble in water and is precipitated out of solution. This accounts for the precipitate formed. As the concentration of reducing sugar increases, the nearer the final colour is to brick-red and the greater the precipitate formed. Sodium carbonate provides the alkaline conditions which are required for the redox reaction above. Sodium citrate complexes with the copper (II) ions so that they do not deteriorate to copper(I) ions during storage.
