FOOD TEST PRACTICALS

Food tests are tests used to determine which nutrients are present in a

food substance

When doing the food test, the following are important things to consider:

food to be tested, required materials, procedure, observation, and

conclusion. For the report to be simple and easy to understand, a table

with four columns is used, and consists of the following headings: Food

tested, Procedure, Observation and Inference

Food to be tested:

Food tested can be reducing sugar, non-reducing sugar, starch, lipids or

protein. Most of food substances are mixed with water to make a solution

or a mixture before testing.

They can also be boiled or heated before testing to make them mix

thoroughly with reagents used. The solution or mixture which is made

from food substance is kept in a container and is referred to as a stock. A

small portion of solution or mixture which is taken from the stock solution

for experiment is termed as food sample.

Procedure: This involves the steps to be followed when carrying out the

test for a particular food substance. Steps differ when testing for one food

type from another. Failure to follow these steps often results into a wrong

conclusion. Therefore, in each step, the procedures to be followed should

be stated clearly. The amount of food sample which has been taken from

the stock solution in a certain procedure should be stated together with its

unit of measurement. The apparatus used should also be stated clearly.

Observation: It refers to series of changes that occur when carrying Out

an experiment. Different changes are experienced as a person attempts one

Stage after another. These changes can be colour, smell, sound or heat

changes. The changes differ from one experiment to another. During

observation, it is important to make sure the colour of the reagent is

known so as to be clear with the new changes,

Cu + e →Cu

Inference:

It refers to the conclusion that is made following the observation. The

conclusion tells whether the type of food tested is present or absent,

Food substances tested at this level are;

❖ Carbohydrates (reducing sugar, non-reducing sugar and starch)

❖ Proteins and

❖ Lipids.

Carbohydrates

Carbohydrates are among of the fundamental classes of macromolecules found in

living organisms. They are primary products of photosynthesis, and energy

providing substrates for various organisms including mammals. Carbohydrates

contain three elements, namely carbon, hydrogen, and oxygen, in which

hydrogen and oxygen are in the ratio of 2:1

There are three types of carbohydrates that we can test for.

(a)

Reducing sugar.

All monosaccharides and some disaccharides including maltose and

lactose are reducing sugars, meaning that they carry out a type of chemical

reaction known as reduction.

Chemical reagent used to test reducing sugar is called Benedict’s solution.

The function of Benedict’s solution.

To indicate the presence of reducing sugars by changing colour in

solution containing reducing sugar from blue, green, yellow and finally

orange colour which is observed when the mixture is heated. Heating

(boiling) is important since speed up the reduction of copper II (blue) to

copper I (orange)

Benedict’s solution contains copper sulphate. Reducing sugars reduce

soluble blue copper sulphate; containing copper (II) ions (Cu

2+)

insoluble red-brown copper oxide containing copper (I).

2+ - +

[Blue solution Brick red ppt]

Natural sources of reducing sugar are;

❖ Ripe bananas,

❖ Ripe oranges,

❖ Ripe pawpaw,

❖ Ripe mango and

❖ Onion bulb.

❖ Carrots

❖ Ginger

Functions of reducing sugars;

❖ They provide energy to the body

❖ They building blocks of molecules like cellulose.

Properties of reducing sugar

❖ They have sweet taste

❖ More soluble in water due to the presence of large number of

OH groups make reducing sugar much more water soluble than

most other molecules of similar molecular weight. They reduce

mild oxidizing agents, such as Benedict’s reagents.

❖ They are crystalline

(b)

non-Reducing sugar (disaccharide and polysaccharide)

Disaccharides and polysaccharides are also called complex sugars. Other

disaccharides such as sucrose do not have the ability to reduce copper (II)

Ions to copper (I) ions. These are called non-reducing sugars. Therefore,

non-reducing sugars cannot be tested directly by Benedict's solution.

instead it is first convened to reducing sugar

Chemicals or reagents used to test non-reducing sugar are;

(i)

Dilute hydrochloric acid: -

Function of dilute hydrochloric acid, is to break the bonds of

complex sugars to simple sugar (reducing sugar).

(ii)

Sodium hydroxide solution: Its function is to neutralize dilute

hydrochloric acid solution added in the mixture solution.

(iii)

Benedict’s solution which is blue in colour:-The function of

Benedict’s solution is to indicate the colour changes in solution

containing non-reducing sugars from blue, green, yellow, orange,

and finally brick red color solution observed when the mixture is

heated. Heating facilitates the breakdown (Hydrolysis) of complex

sugar and reduction of copper II (blue) to copper I (orange)

Natural sources of non-reducing sugar are;

❖ Sugarcane,

❖ Honey Bee,

❖ Sprouted Cereals (Germinating Cereals Like Maize, Millet and

Wheat).

Functions of non-reducing sugar

❖ They are source of energy

❖ They are building blocks of molecules e.g. cellulose

Digestion of non-reducing sugar also ends in ileum and can be shown by

word equation; Sucrose+ Water Glucose + fructose

(c)

Starch– This is a carbohydrate made by the condensation of many

glucose molecules. Starch occurs naturally in plant cells as small particles

called granules. It is found in abundance in plants.

Biochemical test for starch

The presence of starch in biological materials can be tested by using

Iodine solution. If is added to a sample that contains starch, the color

changes to a dark blue (or blue-black). In the absence of starch, the

orange-brown colour of the aqueous solution remains.

The function of Iodine solution

To indicate the presence of starch where blue-black colour will be

observed

Natural sources of starch are;

❖ Cassava Root,

❖ Maize Grain,

❖ Irish Potato,

❖ Millet Grain,

❖ Sorghum Grain.

❖ Rice grains

Digestion of starch starts in the mouth and ends in the small intestine

(ileum). In the mouth, the enzyme responsible for digestion of starch is

known as salivary amylase produced by salivary gland in form of saliva.

The word equation for hydrolysis of starch;

Starch + Water maltose

The composition of saliva

❖ Salivary amylase, an enzyme that convert starch into maltose.

❖ Water for moistening the food and provide medium for

enzymatic activities.

❖ Sodium and calcium salts to ensure alkaline PH suitable for

salivary amylase functioning.

❖ Mucus to lubricate the food and make it easier to swallow the

food.

The second portion for the digestion of starch is in the duodenum. In the

duodenum the hydrolysis of starch is converted to maltose by the enzyme

pancreatic amylase produced by the pancreas.

The last portion for the digestion of starch is the ileum. In the ileum the

hydrolysis of maltose is converted to glucose by an enzyme called maltase

produced by the intestinal wall. The word equation for the hydrolysis of

maltose is;

Maltose + Water glucose

Excess glucose is stored in the liver muscles in the form of glycogen.

Glucose is converted to glycogen by insulin.

Glucose glycogen.

Functions of starch are;

❖ To provide energy to the body.

❖ It is important component of cell membrane.

Properties of starch

❖ Not sweet

❖ Insoluble in water

Proteins

Proteins are the compounds made up of the elements Carbon, Hydrogen,

Oxygen and Nitrogen or Sulphur depending on the type of amino acid.

Chemicals used to test proteins are;

(i)

Sodium hydroxide solution and

(ii)

1% of copper (II) sulphate (1% CUSO

) solution.

Sodium hydroxide solution is added first, followed by drop by drop of 1%

of copper (II)sulphate (1% CUSO

) solution. If protein is present in the

sample solution (food components), the purple or violet colour will be

observed in the mixture solution.

Natural sources of proteins are;

❖ Beef (Meat)

❖ Fish

❖ Chicken

❖ Milk

❖ Egg Albumen

❖ Bean Seeds

❖ Pea Seeds

❖ Groundnuts

❖ Mushrooms.

❖ Castor seeds

Properties of proteins

❖ They have large molecules so they form colloids instead of true

solution.

❖ They are affected by pH

❖ Proteins are denatured by strong heat.

Functions of proteins are;

❖ To promote growth and repair of body tissues.

❖ It is the major component of the cell membrane.

❖ They play role in transportation of materials across cell

membrane.

❖ They form part of the cell structure like glycoproteins.

❖ They form antibodies that fight against pathogens in the body.

❖ They form enzymes.

Deficiency of protein in Children

It leads to disease called kwashiorkor.

Symptoms of kwashiorkor;

❖ Poor growth (stunted growth)

❖ Swollen abdomen due to the liver distortion

❖ Yellowish and weak hairs

❖ Dry skin that cracks easily

❖ A child develops diarrhoea

❖ Reduced resistance to infections

❖ Moon –faced appearance due to swelling of lower chicks

NOTE

Protein is not stored in the body. The reason is that, the end product of

protein which is amino acid is broken down through the process called

Deamination in the liver to form ammonia (from amino group) which is

extremely toxic(poisonous) to the body tissues. Hence ammonia is made

less poisonous (less toxic) as it is converted to urea in the liver through the

processes called Detoxification. Urea is processed to the kidney and

removed from the human body in form of urine through the process

known as urination.

The remaining part of amino acid (with carboxyl group) is converted to

glucose and stored in the liver in form of glycogen.

Lipids

Lipids are the compounds made of the elements Carbon, Hydrogen and

Oxygen. A lipid is composed of glycerol molecule and fatty acids joined

through condensation. Unlike carbohydrates, lipids have much less oxygen

compared to carbon and hydrogen.

Lipids can be tested in various ways;

1. Sudan III test.

2drops of Sudan III solution are added to 2ml of the sample

solution in a test tube. If lipid is present in the sample solution

(food component) droplets that turns red (red ring) will be

observed on the top of the mixture solution.

2. Grease spot test

(i)

Rub a drop of the sample on to a piece of paper.

(ii)

Allow time for any water to evaporate.

(iii)

Warm gently in order to speed up the process or reaction.

If A permanent translucent spot on the paper indicates the

presence of lipid on a food sample.

Natural sources of lipids are;

❖ Milk

❖ Avocado

❖ Sunflower Seeds

❖ Fish

❖ Groundnuts seeds

❖ Olives

❖ Coconuts.

❖ Castor seeds

Properties of lipids

❖ Lipids are insoluble in water.

❖ They dissolve in organic solvents

❖ When

fat

rubbed

against

paper,

the

paper

becomes

translucent.

❖ In a mixture of water and Oil, Oil takes up Sudan III dye to

form a red layer or ring on the top, leaving the water clear.

❖ Oils react with organic acid and stain black.

Functions of lipids are;

❖ Lipids are a source of energy.

❖ They provide more energy than all other food substances. Each

gram of lipid provides nine calories of energy.

❖ They are important components of cell membranes.

❖ Fat deposits surround and protect body Organs such as the heart

and kidneys.

❖ Storage of fat in the adipose tissue under the skin help to regulate

body temperature by insulating the body against loss of heat,

❖ Fat-soluble vitamins are also stored in fatly tissues.

❖ Essential fatty acids are important for the formation of substances

that help to control blood pressure and activate the body's immune

response.

Note:

There are two forms of lipid which are fats and oils.

✓ Fats are solid at room temperature and are usually extracted from

animals.

✓ Oils are liquid at room temperature and usually extracted from

plant seeds. fats are stored under skin

Note: Excess lipid in the human body leads to obesity

Obesity increases the likelihood of conditions such as;

✓ High blood pressure

✓ Heart diseases

✓ Diabetes

✓ Stroke

✓ Respiratory problems

Parts of alimentary canal

1 Digestion in the mouth

a. Mechanical and chemical digestion of food starts in the mouth.

Mechanical digestion is achieved by teeth through mastication

(chewing). During mastication, the food is mixed with saliva, a

watery mixture of mucus and amylase secreted by the salivary

glands in response to thought, smell, taste or sight of food. Saliva is

a neutral or very weak alkali with the pH ranging between 6.5 and

7.5.

Saliva has the following functions with regard to digestion:

❖ It lubricates food so that it can move through the oesophagus

easily;

❖ It catalyses the hydrolysis of starch into maltose using the

enzyme called salivary α-amylase;

❖

It maintains pH of the mouth between 6.5 and 7.5. This level is

optimum for the action of salivary amylase to function which is

accomplished by its constituent mineral salts (example

NaHCO

b. Chemically, the digestion of food in the mouth involves converting

starch into maltose by salivary α-amylase. The tongue which is

located at the back of the buccal cavity rolls the food into a ball-

like structure called bolus and forces it against the soft palate

during swallowing, thereby closing the nasal cavity. The opening

in the larynx (voice box) called glottis, is also closed by a flap like

structure called epiglottis. Then, the bolus enters the oesophagus.

2 The stomach

The stomach is a highly elastic muscular organ. It has two valve-

like rings of smooth muscles called sphincters that can open and

close. One sphincter is called cardiac sphincter. It is located

between the oesophagus and the stomach. The second sphincter is

called pyloric sphincter. It is positioned between the small intestine

and the stomach. The stomach wall consists of a layer of mucous

membrane called gastric mucosa, it is highly folded and is

equipped with small pits (gastric pits) leading to gastric glands in

which gastric juice is secreted.

Gastric juice has the following components:

❖ Water. This is a solvent involved in hydrolysis by which food

substances are broken down.

❖ Hydrochloric acid (HCl).

This is an acid produced by parietal cells of the gastric mucosa.

Hydrochloric acid activates prorennin and pepsinogen into

rennin and pepsin respectively, also kills any bacteria that

might have entered the stomach through food.

❖ Mucus.

This protects the stomach from its own digestive enzymes and

lubricates the wall for easy passage of food to the small

intestine.

❖ Pepsinogen.

❖ It is produced by the chief cells of the stomach wall. It is a

precursor or inactive form of pepsin. Pepsinogen is activated

by hydrochloric acid in the stomach to form pepsin; an

enzyme responsible for the breaking down of polypeptides

into peptides.

❖ Prorennin: This is a precursor of rennin, the enzyme that

catalyses the conversion of soluble milk protein into an

insoluble milk protein. In other words, rennin is an important

enzyme in coagulation or curdling of milk in the stomach.

The coagulated milk is semi solid and it can be retained in

the stomach for a relatively long time for proper digestion.

This is very important in lactating young mammals.

Note

Digestion of food in the stomach may take about 4 to 6

hours.

3 Duodenum.

Duodenum is the first part of the small intestine. When chyme

reaches the duodenum, it stimulates the pancreas to release

pancreatic juice that is transported into the duodenum through the

pancreatic duct.

Pancreatic juice contains sodium bicarbonate that provides an

alkaline medium in the duodenum. This helps to neutralise the

acidic condition of the chyme from the stomach. Pancreatic juice

also contains digestive enzymes for the breakdown of proteins,

carbohydrates, fats and oils. Such enzymes include the following:

❖ Lipase enzyme

❖ This catalyses the conversion of fats and oils into fatty

acids and glycerol.

❖ Pancreatic amylase enzyme

❖ It catalyses the breakdown of starch which was not digested

in the mouth into maltose.

❖ Trypsin enzyme

❖ It catalyses the conversion of proteins which were not

digested in the stomach into peptides and amino acids.

Trypsin is produced in an inactive form known as

trypsinogen, this is converted into an active form known as

trypsin by an enzyme called enterokinase, that is produced

by the duodenal walls.

Also, there is bile which facilitates the digestion of fats and Oils by

breaking them into tiny droplets through a process called

emulsification. This helps to increase the surface area for digestive

enzymes to act on fats and Oils. The bile is made in the liver and

stored in the gall bladder. The gall bladder releases bile through the

bile duct that joins the pancreatic duct before 0Jxning into the

duodenum. Bile is a greenish-yellow juice containing a large

amount of water and small amounts of greenish yellow pigment,

salts, mucin, and other substances.

4 Ileum.

Digestion in the ileum the ileum is the final part of the small

intestine. The process of digestion ends in the ileum. When chyme

enters the ileum, it stimulates the intestinal wall of the ileum to

secrete an intestinal juice known as sucus entericus. This contains

digestive enzymes for finalisation of the digestion of proteins,

carbohydrates and lipids (fats and oils). The digestive enzymes

found in the ileum include the following:

❖ Lipase

This enzyme catalyses the conversion of the remaining fats

and Oils into fatty acid and glycerol

❖ Maltase

It catalyses the conversion of maltose into glucose.

❖ Sucrase

❖ It catalyses the conversion of sucrose into glucose and

fructose.

❖ Lactase

It catalyses the conversion of lactose into glucose and

galactose

❖ Peptidase

❖ It catalyses the conversion of the remaining peptides into

amino acids

Part of

alimentary

canal

Medium

Secretion

Enzymes

secreted

Substance

digested

Product of

digestion

Mouth

Alkaline

saliva

Salivary amylase

Carbohydrate

(starch)

Maltose

Stomach

Acidic

Gastric

juice

Pepsin

Protein

Peptides

Renin

Soluble milk

protein

Casein

Duodenum

Alkaline

Pancreatic

juice

Trypsin

Protein

Peptides

Pancreatic

amylase

Starch

Maltose

Pancreatic lipase

Lipid

Fatty acids

and

glycerol

Ileum

Alkaline

Intestinal

Maltase

Maltose

Glucose

juice

Sucrase

Sucrose

Glucose

and

fructose

Lactase

Lactose

Glucose

and

galactose

Peptidase

(erepsin)

Peptides

Amino

acids

Lipase

lipid

Fatty acids

and

glycerol

FOOD TEST REPORT

Food tested

PROCEDURE

OBSERVATION

INFERENCE

STARCH

To 2cm

of solution X in a test

tube, 3drops of Iodine

solution were added and then

shaken well.

Blue-black colour was

observed in the mixture

solution

Starch was present

REDUCING

SUGAR

To 2cm

of solution X in a test

tube,2ml of Benedict’s

solution was added then

heated.

Series of colour changes

were observed from blue to

green to yellow to orange to

brick red precipitates

Reducing sugar

was present

NON-

REDUCING

SUGAR

To 2cm

of solution X in a test

tube,1ml of dilute

hydrochloric acid was added

followed by heating and then

left to cool, 1ml of sodium

hydroxide solution followed

by addition of 2ml of

Benedict’s solution and then

heated again.

Series of colour changes

were observed from blue to

green to yellow to orange to

brick red precipitate

Non-reducing

sugar was present

PROTEIN

To 2cm

of solution X in a test

tube, 1cm

of sodium

hydroxide solution was added

followed 2drops of 1% copper

II sulphate solution and the

mixture was shaken well then

allowed to settle.

Purple or violate colour

observed.

Protein was

present

FATS/OILS

To 2cm

of solution X in a test

tube, 3drops of Sudan III

solution were added and the

mixture was shaken well then

allowed to settle for 1miute.

A red- stained oil layer

separates on the surface of

solution.

Fats/oils was

present

Note: On the case of testing reducing sugar and non- reducing sugar, you

must start with reducing sugar. If reducing sugar present, there is no need

to test non- reducing sugar.

Preparation of Sample solution from Irish potato

(i)

Irish potato was peeled and then sliced into small pieces.

(ii)

Sliced pieces of Irish potato were put into mortar and then grinded

or crushed.

(iii)

Little amount of water was added and then filtered to get potato

solution.

(iv)

The solution was filtered in a beaker and labeled.

Preparation of sample solution from sugarcane

(i)

A piece of fresh sugarcane was peeled and then sliced into small

pieces.

(ii)

Sliced small pieces of sugarcane were put in the mortar and then

crushed.

(iii)

Little amount of water was added in the mortar then fibers of

sugarcane was squeezed to get sugarcane juice(solution).

(iv)

The solution was filtered in a beaker and labeled.

Preparation of sample solution from onion bulb

(i)

Onion bulb was peeled and cut into two halves by using a knife.

(ii)

Halves of onion was sliced into small pieces.

(iii)

Sliced of onions were put in the mortar and crushed using pestle

and mortar.

(iv)

Little amount of water was added and then filtered to get solution.

(v)

The solution was filtered in a beaker and labeled.

Preparation of sample solution from cassava root

(i) A piece of cassava was peeled and then sliced into small pieces.

(ii) Small pieces of cassava were put in the mortar and grinded or

crushed using pestle.

(iii) Little amount of water was added and then filtered to get solution.

(iv) The solution was filtered in a beaker and labeled.

WORKED EXAMPLE

1. You have been provided with four test tubes labeled 1,2,3 and 4; a

beaker, sieve measuring cylinder, test tube rack, specimen P and

table reagents. Use them to carry out the experiments instructed in

item (i)-(ix), then answer the questions that follow.

(i)

Take specimen P, peel it to remove the outer cover and cut it

into four pieces.

(ii)

Grind two pieces of specimen P by using a mortar and pestle

to obtain the paste

(iii)

Put the paste in a beaker and the add 30ml of water and steer

the mixture

(iv)

Filter by using a sieve to obtain solution P.

(v)

Put 2ml of solution P into each of the test tube 1,2,3, and 4

(vi)

Add 2 drops of iodine solution into the test tube 1

(vii)

Add 2 ml of Benedict’s solution into test tube 2 and boil the

content.

(viii)

Add 1 ml of dilute hydrochloric acid into the test tube 3 and

boil the mixture. After cooling, add 2 ml of sodium

hydroxide solution slowly until the fizzing stops followed

by 2 ml of Benedict’s solution and boil the mixture again

(ix)

Add 1 ml of sodium hydroxide solution into the test tube 4,

followed by 2-3 drops of copper sulphate solution.

Questions

a) What is the aim of experiment?

b) Based on observations made in the test tubes 1, 2, 3 and 4, what

are the types of food substances contained in the specimen P? Give

reasons to justify your answers.

c) Why sodium hydroxide solution and dilute hydrochloric acid was

used in this experiment?

d) Why boiling and cooling is important in procedure (viii)?

e) What will be the end product of digestion of digestion of food

substances contained in specimen P to the human body?

f) What is the importance of the food substances identified in

specimen P food substances identified in specimen P to the human

body?

g) Why the skills used in this experiment useful for preparation of

balanced diet in your daily life?

ANSWERS

a) The aim of experiment was to determine which food nutrients were

present in food specimen P.

b) The food nutrients contained in specimen p was starch in a test

tube 1 since the colour of the mixture solution changed to blue-

black.

c) Sodium hydroxide solution: –Its function is to neutralize dilute

hydrochloric acid solution added in the mixture solution

Dilute hydrochloric acid: -

Function of dilute hydrochloric acid, is to break the bonds of

complex sugars to simple sugar (reducing sugar).

d) boiling is important in order to hydrolyse any polysaccharide and

disaccharide into monosaccharide.

e) The end product of digestion of food substance starch is glucose

f) Functions of starch are;

❖ To provide energy to the body.

❖ It is important component of cell membrane.

g) There are several reasons why food testing is important

This

aspect is part of routine quality control, which in addition to

evaluating the food component, further helps determine the state of

the raw materials, which controls various stages of processing

a food from the moment it arrives, until it exits.

PRACTICAL ACTIVITY

1. You have been provided with specimen P (Groundnuts seeds) and

a piece of white paper

Procedure

(i)

Peel the specimen P.

(ii)

Rub the peeled specimen P on a piece of white paper

(iii)

Expose the paper to light,

(iv)

Compare the part of the paper rubbed with seeds with the part

that was not rubbed.

(v)

Record what you see.

Questions

a) What is the aim of experiment?

b) Based on observations made on a piece of white paper what

is the type of food substances contained in the specimen P?

Give reasons to justify your answers.

c) What will be the end product of digestion of digestion of

food substances contained in specimen P to the human

body?

d) What is the importance of the food substances identified in

specimen P to the human body?

e) What other seeds can you use to perform the grease spot test

ANSWERS

a) The aim of experiment was to test for the presence of, lipids

in specimen P by the grease spot.

b) The food nutrients contained in specimen p was lipids on a

piece of white paper since the paper becomes translucent

c) the end product of digestion of digestion is fatty acids and

glycerol

d) Functions of lipids are;

❖ Used as energy source in the body

❖ Fat deposits protect organs such as heart and kidney

❖ Insulate the body against heat loss

❖ Activate the body’s immune response

e) Other seeds can you use to perform the grease spot test

❖ Avocado

❖ Sunflower Seeds

❖ Coconuts.

❖ Castor seeds

1. You are provided with specimen X

(a) write the procedures you will follow to prepare a solution X for

investigation

(b) Using chemical reagents provided, carry out experiments to

identify food substance(s) present in specimen x. Record your

experimental work as shown in table 1 below.

Table 1

Food tested

Procedure

Observations

inference

(d) Name four other sources which contain the same food substance

as that identified in specimen X

(e) mention the parts of the human alimentally canal in which the

digestion of the food substance in specimen X takes place

(f) Explain how the body stores excess food substance(s) identified in

solution x

(g) Why the food substance(s) identified in solution X important in

human body?

ANSWERS

(a) Preparation of sample solution from orange fruit

(i)

Orange fruit was peeled and then sliced into small pieces.

(ii)

Small pieces of orange fruit were put into mortar and then grinded

or crushed.

(iii)

Little amount of water was added and then filtered to get orange

fruit solution (juice).

(iv)

The solution was filtered in a beaker and labeled X.

(b) Table 1

FOOD TESTED

PROCEDURE

OBSERVATION

INFERENCE

STARCH

To 2cm

of solution X

in a test tube,2drops

of iodine solution

were added and then

shaken well.

The mixture solution

retained reddish-brown

colour of iodine solution

Starch was not present

REDUCING

SUGAR

To 2cm

of solution X

in a test tube,2ml of

Benedict’s solution

was

added

then

heated.

Series of colour changes

were observed from blue to

green to yellow to orange

to brick red precipitates

Reducing sugar was

present

Protein

To 2cm

ofsolution X

in a test tube, 1cm

sodium hydroxide

solution

was

added

The mixture solution

retained the blue colour of

1% of copper II sulphate

solution

Protein was not

present