Lesson Notes By Weeks and Term - Senior Secondary 2
Food storage and preservation
Food storage and preservation
Term: 2nd Term
Week: 5
Class: Senior Secondary School 2
Age: 16 years
Duration: 40 minutes of 2 periods each
Date:
Subject: Home management
Topic:- Food storage and preservation
SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to:
INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source
INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures
INSTRUCTIONAL PROCEDURES
PERIOD 1-2
|
PRESENTATION |
TEACHER’S ACTIVITY |
STUDENT’S ACTIVITY |
|
STEP 1 INTRODUCTION |
The teacher reviews the previous lesson on scientific study of food nutrients |
Students pay attention |
|
STEP 2 EXPLANATION |
She explains the meaning of food preservation and storage. She outlines the guidelines for buying food |
Students pay attention and participates |
|
STEP 3 DEMONSTRATION |
She highlights various food preservation methods and discusses some principles of wise buying |
Students pay attention and participate |
|
STEP 4 NOTE TAKING |
The teacher writes a summarized note on the board |
The students copy the note in their books |
NOTE
FOOD PRESERVATION AND STORAGE
Food preservation is the act of keeping food in good condition to prevent decay and be made readily available for consumption when needed. Decay is caused by the growth of microorganisms such as yeast, moulds and bacteria which are present in most fruits and vegetables. All foods decay sooner or later, but some do so much faster than other.
The art of food preservation is based on the following:
(i) Destruction of microorganisms
(ii) Prevention of their entry into the food.
(iii) Arrest of the action of food enzymes
(iv) Arrest or prevention of purely chemical reactions.
The above principles can be achieved by employing different preservation methods
REASONS FOR FOOD PRESERVATION
Foods are preserved for the following reasons:
(i) To have varieties of food available, in case an emergency situation
(ii) To conserve food and prevent wastage in time of plenty
(iii) To avoid waste of money by purchasing food when they are expensive (iv) To allow us to buy and eat foods that are not in season.
(v) To prevent spoilage
(vi) To prolong its shelf life
(vii) To avoid wastage, especially when they are in season
(viii) To be able to take care of emergency situations
CAUSES OF FOOD SPOILAGE
TYPES OF FOODS TO BE PRESERVED
(a) Local foods:
i. Cereals e.g. rice, maize, millet etc
ii. Legumes e.g. cowpeas, beans, groundnut etc.
iii. Fish e.g. mackerels, stock fish, cat fish etc
iv. Meat e.g. beef, chevron, chicken, rabbit, partridge etc
v. Tubers and roots e.g. yam, potatoes, cocoyam, cassava etc
vi. Fruits and vegetables e.g. “okra”, pepper, tomatoes, pineapple, orange etc
(b) Foreign foods
i. Cereals e.g. corn flakes, biscuits, cakes, wheat meal etc
ii. Legumes e.g. flour, soy sauce etc
iii. Roots and tubers e.g. potato flakes, yam flakes etc
iv. Fish e.g. whole fish, fish fillets, fish cutlets, canned sardines etc.
v. Meat e.g. beef burger, corned beef, etc.
vi. Fruits and vegetables e.g. tomato purees and paste, etc.
Food suitable for preservation can be classified into three major groups
(a) Perishable foods or high moisture foods
(b) Semi-perishable foods or intermediate moisture foods.
(c) Stable foods or low moisture foods.
PREPARATION OF FOOD FOR PRESERVATION
It must be emphasized that only wholesome foods should be preserved as preservation methods will not improve the quality of the food. We should therefore ensure that any food to be preserved must be of good quality. Also, to achieve the maximum effect of any preservation method employed, the food must be prepared accordingly.
Some of the preparations that should be embarked upon before preserving our foods are:
i. Foods to be preserved by freezing should be well packaged to prevent absorption of odour from other food stuffs in the fridge or freezer.
ii. Foods like onion; garlic etc should not be refrigerated with other food stuffs to prevent odour transfer.
iii. Expose as much surface areas as possible to facilitate drying.
iv. Examine drying equipment routinely to make sure they are in good condition.
v. Use good quality chemicals for drying; always look out for expiry dates. vi. Foods to be preserved should be properly cleaned or washed before preservation.
vii. Canned or bottled foods should first be heat treated to make them sterile.
viii. Care should be taken and precautions observed while preserving foods by irradiation.
ix. If possible, avoid the use of antibiotics as a preservative to prevent resistance to these drugs.
x. Ensure that the food is of good quality i.e. wholesomeness of the food.
xi. Package food appropriately and label if need be.
Methods of food preservation
There are different methods of preserving foods. However, the type of methods used depends on the nature of the food, length of preservation required, the facilities available and the type of dish to be prepared.
The different methods of food preservation are:
This is the process by which the water content (moisture content of the food) is reduced to create an unfavourable environment for the action of food enzymes and microorganisms, hence preventing spoilage
TYPES OF DRYING
The rate of drying of food stuffs can be affected by the following factors;
This is keeping the food at low temperature by freezing below 00C in the freezer and chilling at higher temperature in the refrigerator e.g. fish, meat, milk, fruit, vegetables.
This is the application of heat to food stuff to destroy the food enzymes and microorganism. It could be by;
i. Pasteurization – to destroy only the pathogenic microorganism with minimum effect on the nutritional properties of the food. Usually at a temperature below 1000C e.g. milk.
ii. Sterilization – to destroy all the microorganisms present in the food stuff at a very high temperature e.g. tomato puree, canned meat and fish etc.
iii. Blanching – to kill insects and their eggs, pathogenic microorganism inactivate the food enzymes. The process involves dipping food stuff into boiling water for 3 to 5 minutes e.g. vegetables. It is used with other preservative methods like freezing.
This is the addition of chemicals to food to;
i. Inhibit the action of food enzymes
ii. Create an unfavourable environment for the growth of the microorganisms
iii. To prevent chemical reactions from taking place in the food.
iv. Tieing up the moisture present in the food.
Examples of natural chemical preservatives are vinegar, salt, sugar, phenols and aldeheydes.
This is keeping food especially in cans or bottles. The food is sterilized, sealed in vacuum or in the presence of inert gases and then put in cans or bottles e.g. fruit juices, meat, fish, fruit purees, beverages, etc.
This involves the use of radioactive elements like cobalt to destroy microorganisms and food enzymes e.g. potato, yam tubers and onion.
This involves the decomposition of some of the food components to produce acid that makes the food unfavourable to microorganism e.g. locust bean seeds (iru), melon seeds (ogiri) and wines.
This is the drying of food stuff over a fire for different reasons. Some of these reasons may be that the food is not needed immediately, excess is knowingly or unknowingly purchased or food prepared cannot be completely consumed. The nature of the food will determine the storage method to adopt. However, most leftover cooked foods are stored in the refrigerator (where available) or in the food cupboard. Cereals and legumes are usually stored in containers with tight fitting covers, in dry and airy places. Onions are usually stored in open, dry airy place. Tubers e.g. yam are also stored in open, airy places on raised platform. The perishable foods are not usually stored in the home except where facilities for their preservation are available.
METHODS OF FOOD STORAGE
There are two (2) main methods of food storage.
a) Traditional method
b) Modern Method
a) Traditional Method
This can be grouped into two (2):
Large Scale storage & Small scale or Domestic storage.
Cereals/Grains are stored in such a way that their moisture· content will be reduced gradually to a safe level. They can be stored in the following ways: i) They can be stored in a dry air-tight container that is rodentproof e.g. tins, plastic containers
ii) They can be stored in local silos or cribs.
iii) They can be placed on platforms built over a hearth & the heat generated from the fire dries and keeps the cereal warm and free from insects/pests.
iv) Maize & millet can be stored in a rhumbus.
v) Sheds with galvanized sides can be used to store grains.
vi) Some cereals can be suspended on trees to promote good air circulation.
Legumes such as cowpeas, groundnuts etc.
It can be stored in bags
It can be sprayed with insecticides/fungicides & arranged in a dry airy place/store.
Fruits and Vegetables
- Can be sun-dried to remove the moisture. Okro, pepper, leafy vegetables can be chopped to quicken drying.
- Vegetables can be washed, blanched and kept in salt/sugar solutions.
- Some vegetables and tubers are stored in barns in the farm and on raised platforms in the house.
Poultry, Fish· & Meat
-Can be put in a wire cage & hung over a fire place.
- Can be washed, cut & salted and left to sun dry.
- Can be salted & spread on a wire gauze over a fire or heated charcoal. Smoking imparts flavour to them.
b) Modern method
Different types of food can be kept in small containers with fitting lids e.g. jars, tins, plastic containers etc. which are stored in cupboards, on racks or shelves. Perishable foods with high moisture content are better stored in the refrigerator.
Meat & sea foods can be stored in the freezer compartment of a refrigerator for a long time while fruits and vegetables are stored in the chilling compartment.
Cereals and grains can be stored in silos where the temperature and humidity are not affected.
Roots and tubers can be sprayed with anti-sprouting chemicals that prevent tubers from germinating. Irradiation & controlled atmosphere storage can also be used for roots & tubers.
FACTORS THAT AFFECT METHOD OF FOOD STORAGE
The choice or method of storage depends on the following factors:
i) Facilities available in the house.
ii) Length of storage required.
iii) Ultimate use of foodstuff.
EVALUATION: 1. Describe and perform a test for the presence of
a. carbohydrates
b. proteins
c. fats and oils
(write out the result of the tests)
a. carbohydrates
b. proteins
c. fats and oils
CLASSWORK: As in evaluation
CONCLUSION: The teacher commends the students positively