How do you test the presence of sugar in a food sample?
Answers
Answer:
Food Test 1: Sugar test-Benedict's solution
Benedict's solution is used to test for simple sugars, such as glucose. It is a clear blue solution of sodium and copper salts. In the presence of simple sugars, the blue solution changes color to green, yellow, and brick-red, depending on the amount of sugar.
Answer:
Food Chemistry Experiments
Food Chemistry Experiments Index
1. Sugar with Benedict's solution. 2. Protein with Biuret solution. 3. Fat with Sudan III stain. 4. Vitamin C with Vitamin C Reagent. 5. How much sugar is in my soda?
Using Simple Chemical Indicators
We can test for the presence of these important compounds in food by using chemical reagents that react in predictable ways in the presence of these nutrients.
Work in an area appropriate for handling chemicals that may stain furniture or the floor if spilled. Wear proper safety equipment including goggles, rubber gloves and a lab apron.
Outlined below are just the basic test procedures required to use these test solutions. You may wish to expand on them and design your own food testing project.
Supplies needed:
15 x 125mm test tubes. One per test sample.
Test tube clamps.
Test tube rack.
Mortar and Pestle.
Droppers.
Small beakers or glass jars.
Glass marking pen (Sharpie or China marker).
Hot water.
Nutrient solutions to be tested (made from foods you wish to test for sugar, protein, fat, and vitamin C content).
Food Test 1: Sugar test-Benedict's solution
Benedict's solution is used to test for simple sugars, such as glucose. It is a clear blue solution of sodium and copper salts. In the presence of simple sugars, the blue solution changes color to green, yellow, and brick-red, depending on the amount of sugar.
What to do.
Mix small amount of each food sample with distilled water to make a test liquid.
To a test tube, add 40 drops of liquid to be tested.
If testing more than one liquid, label each test tube with a marker.
Add 10 drops of Benedict's solution to each test tube. Carefully heat the test tubes by suspending in a hot water bath at about 40-50 degrees celsius for five minutes.
Note any color change. If sugar is present solution will turn green, yellow, or brick-red, depending on sugar concentration.
Food Test 2: Protein - Biuret solution
Biuret solution is used to identify the presence of protein. Biuret reagent is a blue solution that, when it reacts with protein, will change color to pink-purple.
What to do.
To a test tube, add 40 drops of liquid to be tested.
If testing more than one liquid, label each test tube with a marker.
Add 3 drops of Biuret reagent solution to each test tube. Shake gently to mix.
Note any color change. Proteins will turn solution pink or purple.
Food Test 3: Fat - Sudan III stain
Sudan III is used to identify the presence of lipids in liquids. It will stain fat cells red.
What to do.
To a test tube, add equal parts of test liquid and water to fill about half full.
If testing more than one liquid, label each test tube with a marker.
Add 3 drops of Sudan III stain to each test tube. Shake gently to mix.
A red-stained oil layer will separate out and float on the water surface if fat is present.
Food Test 4: Vitamin C
Vitamin C Reagent (dichlorophenolindophenol) indicator solution is blue. A colorless end point will be reached when a solution containing vitamin C (such as orange juice) is added to this indicator.
What to do.
First, prepare test solution by grinding vitamin C reagent tablet into a powder using a mortar and pestle or back of a spoon. Pour powder into dropper bottle and add 30ml (1 oz.) of distilled water.
If testing more than one liquid, label each test tube with a marker. Fill each with 50 drops of blue vitamin C indicator solution.
Now add juice one drop at a time to the indicator solution in the test tube.
Count drops until dark blue color turns clear. This is your end point.
Compare different juices. Those that require more drops to reach the clear end point are LOWER in vitamin C.
Explanation:
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