Food Test Experiments.
This requires
a broader scope of knowledge, not only on nutrition and food substances, but
also skills in report writing. It also requires integration of knowledge from
other topics from Form I to IV Biology course.
However, the topics of Digestion, Excretion, Growth, and Enzymes need to be emphasized.
The areas of consideration.
Chemical reagents used in different food tests.
i.
Iodine
Solution for testing Starch
ii.
Fehling’s
Solution or Benedict’s Solution for testing Reducing Sugar.
iii. Fehling’s Solution or Benedict’s Solution
plus Dil. HCl, and Sodium Hydroxide for testing Non-Reducing Sugar.
iv. Sodium Hydroxide plus Copper Sulphate
Solution for testing Protein.
v.
Sudan
III Solution Or Ethyl Alcohol Or filter paper for testing Lipids and Fats.
Note. If you do not
see the changes you expect, that shows that the food sample does not contain
the food you are testing.
For each food tested and found present
in the sample or specimen, students should be able to know and explain the
following:-
-The natural
source of the food.
-The
regions of the alimentary canal where the food is digested and the enzymes
involved.
-The end product
of digestion and its functions in the body.
-The age group of
human that need the food mostly and the reasons for that.
-Malnutritional
deficiency of the food.
How to make a report
on food test experiments.
Food Tested
|
Procedure |
Observation
|
Inference
|
Starch. i.e. Cassava, yam,
cereals, potatoes
|
Put a sample in a test
tube, then add few drops of iodine solution.
|
Colour of the mixture
change to blue-black
|
Starch is present
|
Reducing
Sugar-Glucose,
(monosaccharide) i.e. Onion, carrot, germinating maize
|
Put sample in a test tube,
add few drops of Fehling’s solution or Benedict’s solution. Mixture is heated to
boiling point.
|
Mixture change colours
from blue to green to yellow to brown and brick red on cooling.
|
Reducing Sugar is present.
|
Non Reducing
Sugar-Sucrose, (polysaccharides),
i.e. Sugar cane, beet toot, fresh milk
|
Put sample in a test tube
add few drops of dil. HCl. Heat the
mixture then allow to cool. Add few drops of NaOH followed by
few drops of Fehling’s solution or Benedict’s solution, then heat the
mixture to boiling point.
|
Mixture change colours
from blue to green to yellow to brown and brick red on cooling.
|
Non Reducing Sugar is
present.
|
Protein, i.e. Egg white,
groundnut, beans, milk.
|
Put a sample in a test
tube, add few drops of NaOH, shake gently then add few drops of Copper sulphate and shake again. (Biuret Test)
|
Colour of the mixture
change from blue to Violet
|
Protein is present
|
Lipids or Fat, i.e. Cooking oil,
Groundnuts, sunflower, castor oil seed, egg yolk.
|
Put a sample in a test
tube, add few drops of Sudan III solution.
|
The mixture was left to
settle. distinct red ring was formed.
|
Lipid or Fat is present
|
Lipids
or Fat
|
Put 2 drops of the sample
in a test tube then add 5 drops of Ethyl alcohol. Shake the
mixture. Then pour the mixture into another test tube containing little
water.
|
A cloudy white emulsion is
formed.
|
Lipid or fat is present.
|
Lipids
or Fat
|
Smear or rub a warmed
sample on a filter paper and leave it to dry.
|
A permanent translucent
mark is formed on the paper
|
Lipid or fat is present.
|
NOTE:
1. The report should
be in the past tense. i.e. I put ... or I added … or Few drops of … was added.
2. Inference should
be a definite statement, i.e. Starch is present; not; Starch may
be present.
SPECIMENS
Specimens from NECTA Past papers
2001.
A = Cactus twig
B = Sisal plant
C = Bread mould
D = Moss plant
*Beans: solution for the
food test.
2002.
Q1 = Onion leaf Foliage.
Q2 = Ripe Banana
T1 = Mushroom
T2 = young Fern plant
Z = Tendril
Y = Leaf of onion storage
2003
2004
L = Humerus Bone
M1 = Cockroach
M2 = Acacia twig
M3 = Frog/Toad
M4 = Bean Seed
M5 = Pistia (Water weed)
M6 = Irish potato
2005
A = Yeast
B = Sprouting Irish Potato
C = Vegetating Sugar Cane
D = Germinating Maize Grain
X = Pawpaw Leaf Petiole
2006
Q = Cassava Root
R = Ginger
S = Acacia Twig
T = Cactus Plant/Twig
V = Cockroach
2007
J = Grasshopper
K = Earth worm
L = Centipede
M = Cocoyam
N = Simple leaf
S = Groundnuts solution.
2008
S1 = Moss plant
S2 = Bread moulds
S3 = Grasshopper
S4 = Millipede
*Variegated leaf for food
test (Chlorophyll and Starch)
CLASSIFICATION
On
the Classification of living organisms, students should study the following;
Kingdom Fungi
-Be
able to describe the features of Fungi.
-Be
able to explain variety of fungi members, e.g. Bread moulds, yeast, mushroom,
puffballs, etc. Consider their growth conditions, body forms and their economic
importance to human, other living organism and to the environment.
Kingdom Plantae
Students
should be able to identify and describe plants in their sub-groups, starting
with the lowest (primitive) plant to the higher plants, as follows
-Features
-Habitats
-Adaptation
-Nutrition
-Reproduction
-Economic
importance
-Diagram
(Showing body morphology)
-Classification.
-Kingdom
-Division
-Class
-Common name
-Species
Division Bryophyta:
a.
Mosses
b.
Liverworts
Be
able to explain why Bryophytes are lower forms (primitive Plants) by basing on
their body forms (structures) and adaptation to terrestrial life, i.e. rhizoids
instead of roots, no true roots, no true stem and no true leaves.
Division pteridophyta
-Fern plant
How
are they different from higher plants?
Division Gymnospermatophyta
-Pines
Division Angiospermatophyta
Class: -Monocotyledon, i.e.
Maize
-Dicotyledon, i.e. Beans
Kingdom Animalia
Students
should be able to identify and describe features of the members of the kingdom.
Important points are:
-Features
-Habitats
-Adaptation
-Nutrition
-Reproduction
-Economic
importance
-Diagram
(Showing body morphology)
-Classification.
-Kingdom
-Phylum
-Class
-Common name
-Species
Examples are: Roundworms (ascaris and earthworm), tapeworms, liver fluke, housefly,
bees, scorpion, crab, millipede, centipede, cockroach, frog/toad, fish, grasshopper/locust,
etc.
Note: Details on the mentioned points
(i.e. Features, Habitats, Adaptation, Nutrition, Reproduction, Economic
importance and Diagrams) please refer Biology Notes on Classification.