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: