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Unit 11.4

Testing for Reducing Sugars: (all except sucrose)

Equipment:

• Benedict solution

• Test tubes

• Pipette

• Bunsen Burner/Water Bath

• Food samples

• Test tube rack

Method:

1. Label six test tubes as A, B, C, D, E, F.

2. The food samples are then placed in each test tube

3. Add 2cm3 of Benedict solution of the reducing sugar to the samples.

4. Shake the mixture and then boil.

5. If the sample has a blue coloration this indicates that the sample has no reducing sugars, green shows a trace of reducing sugars, yellow means a low level of reducing sugars, orange means a moderate amount of reduced sugars and red indicates a high level of reducing sugars.

http://brilliantbiologystudent.weebly.com/benedicts-test-for-reducing-sugars.html

Testing for non-reducing sugar e.g. sucrose:

Equipment:

• Test tubes

• Sucrose solution

• Dilute Hydrochloric Acid

• Water Bath

• Sodium Hydrogen Carbonate Solution

• Litmus Paper (pH paper)

• Benedict's Solution

• Pipette

• Food samples

• Test tube rack

Method:

1. Label six test tubes as A, B, C, D, E, F. The food samples are then placed in each test tube.

2. Add 2cm3 of sucrose solution to the test tubes

3. Add cm3 of dilute Hydrochloric acid.

4. Boil the solution for 1 minute and allow to cool.

5. Neutralize with Sodium Hydrogen Carbonate Solution, this can be checked with pH paper. Be careful as effervescence (fizz) occurs.

6. Add Benedict’s solution and heat in a water bath until 80°.

7. The colours indicate for the results of the amount of non-reducing sugars in different foods. For example, blue means there is no non-reducing sugars present, green shows trace amounts of non-reducing sugars present, yellow indicates there are low amounts of reducing sugars present, orange means there is a moderate amount of reducing sugars present and red indicates large amounts of non-reducing sugars that are present.

http://brilliantbiologystudent.weebly.com/benedicts-test-for-non-reducing-sugars.html

Testing for Starch (Iodine/Potassium iodide test):

Equipment:

• Starch Solution

• Test tubes

• Pipette

• Iodine Potassium solution

• Test tube rack  

Method:

1. Label six test tubes as A, B, C, D, E, F. The food samples are then placed in each test tube.

2. Add 2cm3 of starch solution to the samples.

3. Then add a few drops Iodine Potassium solution.

4. The colour indicates whether there is starch is present in the food samples, no change in colour (iodine is brown so the colour would stay the same) means that starch is not present and a blue-black colour shows that starch is present.

   

Testing for Lipids (Emulsion test):  

Equipment:

• Samples

• Test tubes

• Test tube rack

• Ethanol

• Cold water

• Pipette

Method:

1. Label six test tubes as A, B, C, D, E, F. The food samples are then placed in each test tube.

2. Add 2cm3 of ethanol to the fat/food/oil

3. Shake the sample so that the lipid is dissolved

4. Add an equal amount of cold water

5. If a cloudy white suspension is near the top, this indicates the number of lipids present in the food sample.

Testing for a protein (Biuret test):

Equipment:

• Samples

• Test tubes

• Test tube rack

• Biuret reagent

• Pipette

Method:

1. Label six test tubes as A, B, C, D, E, F. The food samples are then placed in each test tube.

2. Add Biuret reagent to the samples

3. If the samples change colour, for example if the sample is purple this indicates that proteins are present, if the solution turns from blue to pink this shows that peptides are present.

Testing for Vitamin C:

Equipment:

• Samples

• Test tubes

• Test tube rack

• Pipette

• DCPIP (Dichlorophenolindophenol)

• Spotting tile

Method

1. Label six test tubes as A, B, C, D, E, F. The food samples are then placed in each test tube.

2. Add a few drops of DCPIP to the samples

3. If the blue colour of the DCPIP disappears then the food sample has vitamin C.

Testing for Minerals:

Equipment:

• Samples

• Test tubes

• Test tube rack

• Nichrome wire

• Nitric acid

• Bunsen Burner

Method:

1. Label six test tubes as A, B, C, D, E, F. The food samples are then placed in each test tube.

2. Clean the nichrome wire with nitric acid and then heating the wire until there is no colour in the flame.

3. Then dip the wire in the sample and burn the  sample over the Bunsen burner flame.

4. Repeat this method for each of samples.

5. If the flames are orange/yellow this indicates that sodium is present in the sample, lilac flame means potassium, white flame indicates magnesium and a red flame shows calcium.

Food Reducing Sugars Non-reducing sugars Starch Lipid Protein Vitamin C Minerals

A Green Blue Brown Clear Blue Blue Orange

B Blue Blue Brown Clear Blue Blue Red

C Blue Blue Purple/Black Clear Purple Blue Orange

D Blue Blue Brown Clear Blue Blue Yellow

E Blue Blue Brown White Purple Blue Orange

F Green Green/Yellow Brown White Blue Colourless Orange

 

http://www.diabetesinc.net/digestive-system-with-labels/

Distinction:

Respiration is needed for the body in order to survive, respiration is a reaction that allows oxygen to be bind with glucose which provides energy for the body. If this reactant produces water and carbon dioxide this is aerobic respiration (Glucose + oxygen carbon dioxide + water (energy)). By consuming foods glucose can be produced or stored in the liver, the glucose will be needed when energy is needed for example exercising requires a large amount of glucose. The cardiovascular system allows blood to circulate to the lungs and around the body however blood and vital fluids must have to travel through blood vessels to carry out their journey and function. There are 5 blood vessels: arteries, veins, capillaries, arterioles and venules, without these vessels it would be impossible for blood to travel around the body. The digestive system consists of organs converting food into energy to use or store away. The digestive system breaks down large molecules into smaller ones which can be absorbed into the body, the process starts from the mouth where me digestion starts, the food is then followed by a series of paths such as the esophagus which leads to the stomach which neutralizes foods, and the even further digestion occurs in the small and large intestine where the glucose, fat or proteins are absorbed and waste products are secreted from the rectum. The cardiovascular and the digestive system aid the respiratory system by the digestive system ingest glucose which is needed in respiration to provide the body with energy. The cardiovascular transports blood and fluids such as plasma, white blood cells, platelets, dissolved proteins and glucose, through interconnected vessels.

Firstly, digestion occurs in the mouth where food is mechanically digested which grinding and breaking down foods so that it is easier to digest. Furthermore, the mouth produces saliva which is rich with enzymes, there are three specified enzymes which breakdown large molecules into small soluble molecules. Amylase which digests starch in carbohydrates, lipase breaks down fats into fatty acids and glycerol and protease enzymes break down proteins into amino acids. The enzymes quicken the process of breaking- down foods as the nutrients have to be absorbed into the body. Whether to provide energy, build and repair cells or store for later use, digestion must occur for organisms to live. The small molecules of food are them swallowed and is pushed down the esophagus where the molecules are deposited in the stomach. The stomach partly digests the food molecules once again by churning the molecules smaller molecules, in addition the stomach also secretes acid which kills harmful microorganisms that have been ingested. The food is developed into a consistency that makes the intestines jobs easier to digest.  Proteins are broken into peptides

https://www.boundless.com/biology/textbooks/boundless-biology-textbook/animal-nutrition-and-the-digestive-system-34/digestive-system-processes-197/digestion-and-absorption-754-11987/

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