Notes: Food | Science & Pedagogy Paper 2 for CTET & TET Exams - CTET & State TET PDF Download

Food fuels the daily activities of living beings, with its various components playing distinct roles, from supplying energy to supporting growth. For our body and mind to function properly, we need clean, balanced, and healthy food.

Food is the fundamental source of energy for all living organisms, providing the nourishment necessary for survival. It supplies the chemical substances needed for:

• Building new cells and tissues
• Providing energy to the body
• Repairing old and worn-out cells
• Resisting diseases and protecting against infections

Sources of Food

Living organisms obtain their food from various sources, primarily from plants and animals.

• Plant sources include cereals, pulses, vegetables, fruits, oil seeds, tea, coffee, spices, etc.
• Animal sources include milk, butter, cheese, eggs, meat, fish, honey, etc.

Components of Food

The components of food are essential for maintaining various life processes in living organisms. Each nutrient has specific functions but must work together harmoniously. The main components of food, known as nutrients, include:

• Carbohydrates
• Fats
• Proteins
• Vitamins
• Minerals

In addition to these, dietary fibers and water are also crucial for maintaining life processes in humans.

Types of Nutrients

• Macronutrients: Required in large amounts and form the bulk of the diet. They provide calories or energy. Examples include carbohydrates, proteins, fats, and macro minerals like calcium.
• Micronutrients: Needed in small amounts but are equally important. They work with macronutrients to maintain body functions and energy levels. Examples include vitamins and trace minerals.

Various Components of Food and Their Functions

Carbohydrates

Carbohydrates are compounds of carbon, hydrogen, and oxygen, formed in plants during photosynthesis. Common carbohydrates include glucose (C₆H₁₂O₆), sugar (C₁₂H₂₂O₁₁), and starch (C₆H₁₀O₅n).

They are categorized as energy-giving foods, with 1g of carbohydrates yielding approximately 4 kcal (16.8 KJ) of energy. Key types of carbohydrates include:

• Sugars: Glucose, fructose, sucrose, etc.
• Starch: Found in rice, wheat, potatoes, maize, etc.
• Cellulose: Known as roughage

Glucose enters the bloodstream directly, providing immediate energy through respiration. Excess intake of carbohydrates can lead to weight gain as they are stored as fats, a process called lipogenesis. Continuous fat deposition can result in obesity. Excess glucose is stored in the liver and muscles as glycogen through a process called glycogenesis. Insulin converts extra glucose in the blood into glycogen, and its deficiency can lead to diabetes.

Test for Starch: Starch presence can be tested by applying 2-3 drops of dilute iodine solution to the food item. If it turns blue-black, the food contains starch, commonly found in potatoes, bread, rice, etc.

Fats

Fats, derived from animals (like butter and ghee) and plants (such as groundnut oil, mustard oil, soybean oil), are consumed by humans. One gram of fat provides double the energy of one gram of carbohydrates, with an adult requiring about 35g of fat per day.

Fats are classified as:

• Saturated fats: Obtained from animals
• Unsaturated fats: Obtained from plants

Fats are concentrated energy sources, carrying essential fatty acids and fat-soluble vitamins (A, D, E, and K) within the body. They also protect delicate organs. However, excessive fat intake can lead to obesity, high blood pressure, cardiac problems, and increased blood cholesterol. A deficiency in fats can result in body weakness and loss of stamina.

Proteins

Proteins are complex organic compounds composed of carbon, hydrogen, oxygen, and nitrogen. Some proteins also contain sulfur, phosphorus, and iron. A protein molecule is made up of many smaller molecules called amino acids (RCHNH₂COOH). There are 20 different amino acids in our body.

Proteins are sourced from both plants and animals. While all plants contain some proteins, groundnuts, beans, cereals (such as maize and wheat), and pulses are particularly rich in vegetable proteins. Milk, fish, meat, and eggs are primary sources of animal proteins.

Proteins play crucial roles in digestion, body growth, tissue repair, and catalyzing certain biochemical processes. The protein requirement for adults is 1 gram per kilogram of body weight, with growing children and pregnant women needing more for growth.

Blood contains a protein called hemoglobin, which transports oxygen from the lungs to the cells and carbon dioxide from the cells to the lungs.

Protein Energy Malnutrition (PEM) results from a deficiency of proteins and carbohydrates, leading to diseases such as:

• Kwashiorkor: Affects children aged 1-5 years who are not fed protein-rich mother’s milk. Symptoms include irritability, pathetic facial expressions, cracked skin, swollen abdomen, weak legs, and reddish hair.
• Marasmus: Displays symptoms similar to Kwashiorkor. The child becomes extremely thin with loose folds of skin visible all over the body.

Test for Protein: If the food item is solid, make a paste or powder and add 10 drops of water. Then add two drops of copper sulfate (CuSO₄) followed by 10 drops of caustic soda (NaOH). The appearance of a violet color indicates the presence of proteins.

Vitamins

The term ‘vitamin’ was coined by Polish-born biochemist Casimir Funk. Vitamins are essential for the growth and maintenance of our body, aiding in the proper utilization of other nutrients. They are classified based on their solubility:

• Fat-soluble vitamins: Vitamins A and D
• Water-soluble vitamins: B complex and C

The human body can synthesize only two vitamins, D and K, making it essential to obtain other vitamins from food. Excess intake of fat-soluble vitamins can cause hypervitaminosis; for example, too much vitamin A can lead to liver disorders, while excess vitamin D can result in kidney stones. Deficiency diseases, indicated by the term hypovitaminosis, arise from the lack of essential vitamins, with a steady absence of a single vitamin in an otherwise complete diet leading to such conditions.

Minerals

Minerals are salts of certain metals and non-metals required by our body for normal functioning. They are needed in very small quantities.

Roughage

Roughage consists of plant fibres, mainly found in the cell walls of plants. Major sources of roughage in our diet include salads, corn cobs, whole grains, vegetables, and fruits.

Roughage helps retain water in the body, adds bulk to the food, and provides a feeling of fullness after meals. It prevents constipation, aids in regular bowel movements, assists in removing undigested waste, massages gums, and prevents tooth decay.

Water

Water is essential for life, making up about two-thirds of our body weight. Some important functions of water include:

• Transporting nutrients and chemicals to and from cells
• Maintaining body temperature
• Excreting body wastes
• Serving as a medium for biochemical reactions

Water loss from the body can cause dehydration, leading to thicker blood and severe muscle pain and cramps. To rehydrate, Oral Rehydration Solution (ORS) is given, which is prepared with 200 ml of water, a teaspoon of sugar, and a pinch of salt. ORS is also administered to patients suffering from diarrhoea.

Balanced Diet

A balanced diet contains all the nutrients our body needs in the right quantities, along with roughage and water. The composition of a balanced diet depends on factors such as sex, age group, and occupation.

A typical balanced diet should include:

• Carbohydrates (60%)
• Fats (15%)
• Proteins (25%)
• Minerals
• Vitamins
• Roughage
• Water

Maintenance of Food Quality

Maintaining food quality involves protecting food from spoilage and contamination. Food can spoil at any stage from production to consumption. By keeping food clean, we can avoid food poisoning. Cleanliness should be a priority during production, management, storage, distribution, cooking, and serving.

Cleaning of Food

We consume many foods raw, while others are cooked. It's important to maintain cleanliness even during cooking. Additionally, overcooking food can destroy its nutrients, so care should be taken to avoid this.

Food Preservation

During storage and distribution, food can undergo undesirable changes in flavor, color, texture, and appeal. To prevent these changes, certain chemicals, known as preservatives, are added to food. These chemicals protect food from microbial actions, such as fermentation, acidification, and decomposition.

Food preservatives work in two main ways:

• Bactericidal process: Preservatives kill germs.
• Bacteriostatic process: Preservatives restrict the growth of germs.

Examples of Food Preservatives

• Carboxylates: Sodium benzoate is used as a preservative in soft drinks and acidic foods. It is metabolized by conversion to hippuric acid (C₆H₅CONHCH₂COOH) and excreted in urine. Sodium and calcium propionates are used as preservatives in breads and cakes.
• Vitamin E: A naturally occurring preservative found in vegetable oils.
• Sodium Metabisulphite (Na₂S₂O₅) or Potassium Metabisulphite (K₂S₂O₅): Used to preserve jams, squashes, and pickles. The sulphurous acid present inhibits microbial growth.
• Sorbic Acid and Its Salts: Used as preservatives in cheese, baked goods, pickles, and meat.
• Epoxides and Ethyl Formates: Used for preserving spices, nuts, and dried fruits.