NUTRITION -2 .2

Glucose – is used in respiration to release energy. Some is stored as starch or oils during exchange.

Oxygen – Some oxygen is used during respiration while the rest is released into the atmosphere during exchange.

Water – some water is used in various chemical reactions within the cells, some water is released to the atmosphere during transpiration

The overall chemical equation representing the process of photosynthesis

ADAPTATION OF THE LEAF IN THE PROCESS OF PHOTOSYNTHESIS

(i) Cuticle and epidermis are transparent to allow easy penetration of light

(ii) Presence of stomata on the leaf allows easy diffusion of carbon dioxide

(iii)The network of veins allows movement of materials in and out of the leaf

(iv)The air spaces in the spongy mesophyll layer allow gases to circulate easily.

(v) Presence of large numbers of chloroplasts in the palisade layer enables maximum sunlight absorption.

(vi) The leaves are well arranged to avoid overlapping and overshadowing

(vii) Broad and flat lamina allows maximum absorption of sunlight and carbon dioxide.

            FACTORS AFFECTING THE RATE OF PHOTOSYNTHESIS PROCESS

1. LIGHT INTENSITY: A good quality of light enhances the rate of photosynthesis.

                        - Very bright light damages the plant due to strong sun rays

                        - Plants under shade receive poor quality of light

2. CARBON – DIOXIDE CONCENTRATION: An increase in carbon dioxide concentration results to an increase in the rate of photosynthesis up to a certain level

- Any further increase in the carbon dioxide concentration after the maximum point induce the stomata to close and therefore cutoff the supply of carbon dioxide.

3. TEMPERATURE: Photosynthesis is controlled by enzymes. Enzymes are affected by changes in temperature.

- High temperature destroys the enzymes, very low temperature inactivate them.

- The rate of photosynthesis increase as the temperature increase up to maximum point i.e. 40⁰c.

4. WATER: Plants require water for the various chemical reactions of the cells.

-Water is also a raw material for photosynthesis.

5. MINERAL SALTS: Some minerals such as magnesium and iron are responsible in the formation of chlorophyll.

- The availability of these minerals results in the chlorophyll synthesis and the rate of photosynthesis increases.

6. LEAF AGE: As the leaf ages chlorophyll breaks down hence the rate of photosynthesis is reduced.
7. PRESENCE OF MANUFACTURED CARBOHYDRATES: This will reduce the rate of photosynthesis since carbohydrates are product of photosynthesis

            IMPORTANCE OF PHOTOSYNTHESIS

(i) Food substance like glucose is formed. Plants and animals use these food substances.

(ii) Release oxygen in the atmosphere for respiration of organisms

(iii) Purify the atmosphere by removing carbon dioxide.

(iv) Light energy is converted into a form that can be used by all other organisms. This energy is known as ATP.

            STORAGE ORGANS

Plants store food for future use

Foods in plants can be stored in:

(a) Leaves e.g. Onions, cabbage                        

(b) Fruits e.g. Mango, pineapple, pawpaw

(c) Seeds e.g. Beans, peas, rice, maize

(d) Stems e.g. Irish potato, ginger, sugar cane

(e) Roots e.g. Sweet potato, cassava, carrots

ADVANTAGE OF FOOD STORAGE ORGANS                                          

i) Some organs give rise to new plants e.g. Seeds, stem, tubes

ii) Permits the survival of plants over dry seasons.

iii) Some are used as source of food by man and other animals e.g. Rice, wheat, potatoes etc.

iv) The stored food is used during germination before the leaves form.

v) Some are used for commercial purpose by man e.g. Sugar cane

MINERAL REQUIREMENTS IN PLANTS

• The mineral elements required by plants are grouped into two;

1. Macro elements or Macro nutrients

These are elements required in large quantities by the plants.

They include; manganese, carbon, calcium, oxygen, phosphorus, sulphur, hydrogen, potassium and nitrogen.

     2. Micro element or micro nutrients
         These are elements required in small quantities by the plants.

They include; manganese, zinc, sodium, boron, chlorine, copper, cobalt and silicon.

NOTE: Nitrogen, iron and magnesium are used to synthesize carbohydrates

• Lacking of these elements cause yellowing of leaves
• Carbon, Hydrogen and oxygen are used to synthesize carbohydrates
• Lack of these elements show stunted growth in plants.

  

FOOD PROCESSING, PRESERVING AND STORAGE

Food processing: This refers to all the ways in which food is treated in order to make it edible, appetizing and safe to eat or keep it fresh for a long time

• Some of the activities involved in food processing are:

(i) Picking, sorting and washing fruits and vegetables

(ii) Converting raw material into other products

Examples – Making cheese from milk                                                                                        

               - Making sugar from sugar cane

FOOD PROCESSING TECHNIQUES

Common food processing techniques include

i) Removing unwanted outer layers e.g. peeling potato

ii) Chopping or slicing e.g. Bananas, mangoes and cassava

iii) Liquefaction e.g. producing juice by squeezing fruits

iv) Fermentation e.g. making wine from banana and grapes and beer brewing

v) Cooking e.g. boiling, frying, steaming or grilling

vi) Deep freezing

vii) Baking

            FOOD PRESERVING

This is a method that involve special methods of food processing that are used to prevent food from getting spoiled or going bad. These methods include:

1. Canning or bottling; this is used for getting rid of micro – organisms.

2. Pasteurization and boiling; this involves using high temperature to kill micro – organisms that cause spoilage

3. Refrigeration – using very low temperature to slow down the growth of micro – organisms

4. Irradiation – this involves using radiations to kill micro – organism that might make food go bad.

5. Drying salting, applying honey or smoking eliminate the moisture that is needed for growth of micro organisms.

6. Adding chemicals such as salt, sugar and carbon monoxide to prevent physical changes in food.

IMPORTANCE OF FOOD PROCESSING, PRESERVING AND STORAGE

1) Prevents wastage of food

2) Saves money by preventing spoilage of food

3) Maintains the quality of food.

4) Prevents growth of micro – organisms that can cause illness and improves the flavor of food.

5) Removes harmful toxins and micro – organisms from food

6) Makes food available even when they are not in season

7) Enables transportation of delicate and perishable food such as milk and fruits over long distance

TRADITIONAL METHODS OF FOOD PROCESSING AND PRESERVING

1. CURING: This involves the addition of substances such as sugar, salt, spices and vinegar to animal foods e.g. Meat and fish.

- Curing binds or removes water making it unsuitable for the growth of micro – organism

- It also improves the taste of food. Example sausage and canned beef are made by curing meat.

2. DRYING IN THE SUN

The food is left in the sun for long periods of time in order to reduce its moisture content.

• Removing the amount of water in the food discourage the growth of micro – organism This method is used to reserve rice, maize, cloves, bananas, beans, peas, meat, fish, cassava and green vegetables.

NOTE: Dried grain or cassava can be pounded or ground into flour and dry cloves are used for making spices.

3. SMOKING

Smoke reduce the moisture content of food to prevent the growth of micro – organisms

Example: Grains, meat and fish can be dried slowly over a smoking wood fire.

4. COOKING: This includes boiling, steaming, baking in hot ash, grilling and roasting.

- These processes help to soften food, improve flavor and preserve food. Examples: potatoes, banana, and maize can be boiled before being dried

- Meat can be grilled or deep fried.

5. SALTING: Salt removes water from the food and kills micro – organisms that would otherwise spoil the food.

6. FERMENTATION

Fermentation is the conversion of carbohydrates such as sugars into acids and alcohol

Fermentation can occur naturally or can be induced

Example: Milk can be fermented into yoghurt by keeping in a container for some time.

Picking foods such as cucumbers and mangoes can be fermented by putting them in salty water for some time, bacteria produce lactic acid that gives the food its distinctive flavor and helps to preserve it.

MODERN METHODS OF FOOD PRESERVATION AND PROCESSING

1. PASTEURIZATION: This is the method of heating food to very high temperature for a short while in order to kill micro – organism that can cause food spoilage

Pasteurizations maintain the nutrients content and flavor of food. Example: Food which can be pasteurized is milk and fruit juice

2. LIQUEFICATION; this is the making of liquids from solid food

- It is mostly applied to fruits where by juice is made out of them.

- The juice is then pasteurized and post into cans or containers.

3. CANNING AND BOTTLING

This is the method where by food is preserved by heating it in air tight vacuum – sealed bottles or cans.

• First the container is filled with food then the air is pumped out to form a vacuum.
• The container is sealed and heated to kill micro – organisms and enzymes fruits and fruits juices, beef, fish and baked beans.

NOTE: Bottled and canned foods can be kept for months or even years.

4. USING ADDITIVES – This is the addition of chemicals such as sodium benzoate, sodium chloride and vinegar to slow down the growth of micro – organisms. Examples the food can be preserved by this process are fish and meat.

5. DRYING OR DEHYDRATION: This is where food is dried by using either hot blasts of air from vacuum dryer or a freezer (freeze drying).

- After drying, the food is then sealed in moisture proof containers

6. IRRADIATION – This is the use of ray’s energy to stop growth of micro – organism in stored food stuff.

- This makes food last longer

- Also prevents spoiling.

Examples: the foods that can be preserved by this method are onions, beans and potatoes

FOOD STORAGE

Food storage is a method used to keep reserves of food for future use

• Food storage can be done on a small side at the family level. Examples in the food storage, or on a large scale for populations. Example in government sides for grains

TRADITIONAL METHODS OF FOOD STORAGE

1) Storage in granaries and pits

- Dry grains are stored in granaries which are usually raised above the ground.

The gains are sometimes mixed with neem leaf ash or groundnuts to further prevent attack by micro – organisms.

• Granaries keep grains safe from insects, rodents and birds
• Harvested yams, potatoes and cassava can be stored in large the ground after drying.

2) Storage in pots and tins

- Preserved foods such as flour, dried vegetables and cassava can be in large dry puts or tightly covered for future use.

- Foods can be stored for months by using this method.

ADVANTAGE OF TRADITIONAL METHODS OF FOOD PROCESSING, PRESERVATION STORAGE

i) They are simple and can be done by most people

ii) They use locally available materials and simple technology, the keeping costs low.

iii) No harmful chemicals are added to the food.

iv) Curing and smoking add a distinctive flavor to the food

v) Most methods do not destroy nutrients

DISADVANTAGES OF TRADITIONAL METHODS OF FOOD STORAGE, PROCESSING AND PRESERVATION

i) Food can be preserved and stored for only limited periods of time

ii) Traditional method is difficult to do on a large scale.Traditional methods are highly limited in the variety of foods that can be processed, preserved and stored

MODERN METHODS OF FOOD STORAGE

1. Refrigeration

- This is the temporary storage of food at temperature of up to 4⁰c in order to slow down the growth of micro – organism

- Refrigeration can be done in refrigerators or cold rooms

Example: The foods that can be refrigerated are milk, fresh fruit, fresh vegetable, juice and bottler.

2. Freezing: This is the strong food at very low temperature i.e. below -10⁰c in order to stop the growth of micro – organisms

Food is frozen in freezers. Example the foods that can be frozen are: poultry, fish and meat.

ADVANTAGES OF MODERN METHODS OF FOOD PROCESSING, PRESERVATION AND STORAGE

(i). Food can last for many months or even years

(ii). Modern methods can process, preserve and store a large variety of foods.

(iii). The advanced technology used is fast and can handle large quantities of food

DISADVANTAGES OF MODERN METHOD OF FOOD PROCESSING, PRESERVATION AND STORAGE

• The chemicals used can be harmful if eaten in excess.
• These methods can only be used in a certain area. Example – refrigeration and freezing require electricity.
• The process used for example radiation; canning and pasteurizing require special skills.
• Sometimes nutrients are lost thus lowering the nutritional value of food.

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