Chapter 2 — Components Of Food

What is food? Food is any substance eaten to provide energy, build and repair body parts, and regulate body processes. Nutrition is the process by which living beings obtain and use food for these purposes.

Why do we need food? (Main functions)

• Energy: Fuels activities and body warmth.
• Growth and repair: Builds new tissues and fixes worn-out parts.
• Regulation: Controls body processes (e.g., digestion, immunity).
• Protection: Nutrients help resist infections and illnesses.

Major components of food and their roles

• Carbohydrates — main source of energy. Found in rice, wheat, potatoes, bread, fruits. Deficiency: tiredness, low energy.
• Proteins — needed for growth and repair. Found in pulses, eggs, meat, milk, soy. Deficiency: stunted growth, weakness, slow healing.
• Fats — concentrated energy source, helps absorb vitamins and protect organs. Found in oils, butter, nuts, seeds. Excess: weight gain; deficiency: dry skin, poor vitamin absorption.
• Vitamins — small amounts needed for body regulation. e.g., vitamin C (fruits) prevents scurvy; vitamin D (sun, milk) helps bones.
• Minerals — e.g., calcium for strong bones (milk), iron for blood (green leafy vegetables, meat). Deficiencies cause problems like anemia or weak bones.
• Dietary fibre (roughage) — from vegetables, fruits, whole grains; helps digestion and prevents constipation.
• Water — essential for nearly all body functions; transports nutrients and removes wastes.

Balanced diet

A balanced diet gives the right amounts of all the nutrients — carbohydrates, proteins, fats, vitamins, minerals, fibre and water — in the right proportions. For children a simple guideline is: eat a variety of foods from different groups every day, keep portions moderate, and include fruits and vegetables.

Simple digestion overview

• Ingestion: Taking food into the mouth.
• Digestion: Breaking down food into smaller parts (mechanical and chemical).
• Absorption: Nutrients pass into blood from the intestine.
• Assimilation: Cells use nutrients for energy, growth, repair.
• Egestion: Removal of undigested waste.

Simple calorie example

Use energy values (kcal per gram): carbohydrates 4 kcal/g, proteins 4 kcal/g, fats 9 kcal/g. Example: 50 g rice (mainly carbs) ≈ 50 × 4 = 200 kcal; 30 g cooked lentils (protein & carbs) ≈ 30 × 4 = 120 kcal; 10 g ghee (fat) ≈ 10 × 9 = 90 kcal. Total ≈ 410 kcal.

Practical tips: eat fresh, clean food; include fruits and vegetables daily; limit very oily and sugary foods; drink enough water; and vary food to get all nutrients.

What are nutrients? Nutrients are substances in food that provide energy, build and repair the body, and regulate body processes. The main components of food are carbohydrates, proteins, fats, vitamins, minerals, water and dietary fiber.

Carbohydrates: Main source of energy. Found in rice, wheat, potatoes, sugar, fruits and bread. Carbohydrates give quick energy for daily activities. Excess may be stored as fat.

Proteins: Used for growth, repair and making enzymes and hormones. Good sources: eggs, milk, pulses (dal), meat, fish, paneer and nuts. Protein deficiency in children leads to poor growth and weakness.

Fats (Lipids): Concentrated source of energy and help absorb fat‑soluble vitamins. Found in oils, ghee, butter, nuts, fatty fish and cheese. Fats also protect organs and keep the body warm. Too much fat can lead to weight gain.

Vitamins: Small amounts are needed for normal functioning and to prevent diseases. Examples: vitamin C (citrus fruits) helps wound healing and prevents scurvy; vitamin A (carrots, milk) is important for vision; vitamin D (sunlight, fortified milk) helps calcium absorption.

Minerals: Inorganic nutrients needed for many functions. Important ones include calcium (milk, helps strong bones and teeth), iron (green vegetables, pulses, helps make blood) and iodine (iodised salt, needed for proper thyroid function). Deficiency examples: iron deficiency can cause anaemia; lack of calcium can cause weak bones.

Water: Essential for life. It helps transport nutrients and wastes, keeps body temperature stable and is needed for almost every body process. Drink enough clean water every day.

Dietary Fiber: Found in whole grains, fruits, vegetables and pulses. It helps in digestion and prevents constipation. Fiber does not give energy but keeps the digestive system healthy.

Balanced diet: A diet containing the right proportions of all nutrients is called a balanced diet. A balanced meal usually includes a cereal or staple (carbohydrates), a protein source (dal, egg, meat or paneer), vegetables (vitamins, minerals, fiber), some fat (a little oil or ghee) and fruit or milk.

Quick summary of roles: Energy providers (carbohydrates, fats), body builders and repairers (proteins), regulators and protectors (vitamins, minerals, water, fiber).

Practical tips: Eat a variety of foods, include colorful fruits and vegetables, prefer whole grains for fiber, use iodised salt and drink safe water.

What are carbohydrates?
Carbohydrates are organic compounds made of carbon (C), hydrogen (H) and oxygen (O). Their general formula is Cn(H2O)n — which is why they are often referred to as hydrates of carbon. They are one of the three main macronutrients and are the primary source of energy for the body.

Classification

• Monosaccharides (simple sugars): Single sugar units. Examples: glucose and fructose. They are sweet and soluble in water.
• Disaccharides: Two monosaccharide units joined together. Example: sucrose (table sugar) = glucose + fructose; lactose = glucose + galactose.
• Polysaccharides (complex carbohydrates): Long chains of monosaccharide units. Examples: starch (plant storage), glycogen (animal storage), cellulose (plant cell walls and dietary fibre).

Biological roles and importance

• Energy source: Carbohydrates are broken down to release energy. Glucose is the main fuel for cells and the brain.
• Energy storage: Excess glucose is stored as glycogen in liver and muscles (animals) or as starch in plants.
• Structural role: Cellulose forms plant cell walls; it is dietary fibre for humans (indigestible but important for digestion).
• Spares proteins: If enough carbohydrates are available, the body uses them for energy so proteins can be used for growth and repair.

Digestion
Starch in food is broken down by saliva (enzyme amylase) and further by enzymes in the intestine to produce glucose, which is absorbed into the blood.

Common tests

• Benedict's test (reducing sugars): Heat the sample with Benedict's solution. A positive test gives a colour change from blue to green/yellow/orange/red depending on amount of reducing sugar (red indicates high concentration).
• Iodine test (starch): Add a few drops of iodine solution to the sample. A blue-black colour indicates presence of starch; brownish-yellow means starch is absent.

Important notes for Class 6

• Foods like rice, wheat, potatoes and sugar are rich sources of carbohydrates.
• Simple sugars cause a quicker rise in blood sugar, while complex carbohydrates (starch, fibre) are digested more slowly and give sustained energy.
• Dietary fibre (cellulose) helps in digestion but is not a source of energy for humans.

Everyday relevance
Carbohydrates are present in almost all staple foods. Understanding simple vs complex carbohydrates helps make better food choices — e.g., choosing whole grains and fruits for steady energy and fibre rather than too much refined sugar.

What are proteins?
Proteins are large, complex molecules made of building blocks called amino acids. They are one of the three main components (macronutrients) of food, along with carbohydrates and fats. Proteins are essential for the structure, function and regulation of the body’s cells, tissues and organs.

Building blocks — amino acids
All proteins are made from about 20 common amino acids. These amino acids join together by peptide bonds to form long chains called polypeptides; one or more polypeptide chains fold into a functional protein.

Main functions of proteins

• Growth and repair of body tissues (muscles, skin, bones).
• Make enzymes that speed up chemical reactions in the body.
• Form hormones (for example insulin) that regulate body processes.
• Make antibodies that help fight infections.
• Transport substances in the blood (for example, haemoglobin carries oxygen).

Sources of proteins
Proteins come from both animal and plant foods. Animal sources (milk, eggs, fish, meat, poultry) usually provide all essential amino acids and are called "complete" proteins. Many plant sources (pulses, beans, nuts, seeds, some grains) provide proteins but may lack one or more essential amino acids; combining plant foods (for example rice + dal) gives a balanced mix.

Digestion of proteins (simple)
When we eat protein foods, digestion breaks proteins into amino acids. This happens mainly in the stomach (enzyme pepsin) and small intestine (enzymes like trypsin). The amino acids are then absorbed into the blood and used by the body to build new proteins.

What happens if we do not get enough protein?
Protein deficiency can cause poor growth, weakness, frequent infections and in severe cases diseases such as kwashiorkor (swelling, thin muscles, hair changes). Balanced intake of proteins is especially important for growing children.

Useful facts
1 gram of protein provides about 4 kilocalories (kcal) of energy. For a healthy diet, proteins should make up a part of daily calorie intake (commonly around 10–15% of total energy, depending on age and activity).

What are fats (lipids)?
Fats, also called lipids, are one of the main components of food. They are substances made of glycerol and fatty acids and are insoluble in water but soluble in organic solvents. Fats store energy and perform several important functions in the body.

Composition

• Basic building block: a triglyceride — one glycerol molecule joined to three fatty acid molecules (by ester bonds).
• Fatty acids have a long hydrocarbon chain and an acid group (written as R–COOH).

Functions of fats

• Provide concentrated energy: fats give more energy per gram than carbohydrates or proteins.
• Insulation: help keep the body warm by providing a layer under the skin.
• Protection: cushion and protect internal organs.
• Absorption of vitamins: help absorb fat‑soluble vitamins A, D, E and K.
• Stored energy: excess energy is stored as fat in the body for later use.

Types of fats (simple explanation)

• Saturated fats — usually solid at room temperature (e.g., butter, ghee, animal fats). Eat in limited amounts.
• Unsaturated fats — usually liquid oils at room temperature (e.g., olive oil, mustard oil, sunflower oil). Considered healthier.
• Trans fats — formed during hydrogenation of oils; found in some processed foods and are unhealthy.

Sources of fats
Common sources include butter, ghee, vegetable oils (olive, mustard, sunflower), milk, cheese, nuts, seeds, egg yolk, fatty fish (like salmon), avocado and meat.

How to detect fats (simple tests)

• Grease-spot test: Rub food on a paper; oily foods leave a translucent (greasy) spot that does not dry — indicates presence of fat.
• Sudan III stain (lab): fat shows red-stained droplets with Sudan dye.
• Solubility test: fats dissolve in alcohol but not in water.

Health note
Fats are essential but should be eaten in moderation. Excessive intake, especially of saturated and trans fats, can lead to health problems like obesity and heart disease.

Simple digestion idea
Fats are emulsified by bile in the small intestine and then broken down by enzymes (lipases) into fatty acids and glycerol, which are absorbed and used or stored by the body.

What are vitamins? Vitamins are organic (carbon-containing) nutrients required in very small amounts for normal growth, development and functioning of the body. They do not provide energy like carbohydrates, proteins or fats, but help the body use those nutrients and carry out chemical reactions.

Types of vitamins

• Fat-soluble vitamins: A, D, E and K. These dissolve in fats and are stored in the body (mainly in the liver and fatty tissues).
• Water-soluble vitamins: Vitamin C and the B-complex vitamins (such as B1, B2, B3, B6, B12 and folic acid). These dissolve in water and are not stored much; excess is usually excreted in urine.

Main functions of vitamins

• Help in growth and development (e.g., Vitamin A for vision and growth).
• Help in energy release from food by assisting enzymes (many B vitamins).
• Protect the body from infections and help wound healing (e.g., Vitamin C).
• Help in blood clotting (Vitamin K) and bone health (Vitamin D).

Sources — Vitamins are found in a variety of foods: fruits, vegetables, milk, eggs, fish, meat, nuts and whole grains. Some foods are fortified (extra vitamins added), and the body can make Vitamin D with the help of sunlight.

Deficiency and symptoms

• Vitamin A deficiency: poor night vision, dryness of eyes, slow growth.
• Vitamin C deficiency: scurvy—bleeding gums, weak immunity, slow healing.
• Vitamin D deficiency: rickets in children (soft bones), bone pain.
• Vitamin K deficiency: bleeding and slow clotting.
• B vitamin deficiencies: tiredness, poor appetite, nerve problems, anaemia (some B vitamins).

Too much (excess) — Fat-soluble vitamins can build up and cause problems if taken in very large amounts (hypervitaminosis). Water-soluble vitamins are usually excreted when taken in excess, but very large doses can still cause harm.

Tips to keep vitamins in food

• Eat a variety of foods every day (fruits, vegetables, dairy, grains, proteins).
• Do not overcook vegetables; use less water and shorter cooking times to preserve water-soluble vitamins (especially Vitamin C and B).
• Include a small amount of fat with meals to absorb fat-soluble vitamins (A, D, E, K).
• Get safe sunlight exposure for Vitamin D synthesis.

Summary: Vitamins are vital micronutrients needed in small amounts. A balanced diet with a variety of foods is the best way to get the vitamins the body needs.

What are minerals? Minerals are inorganic nutrients required in small amounts by the body for growth, development and proper functioning of organs. Unlike carbohydrates, fats and proteins, minerals are elements or simple compounds (they do not provide energy) but are essential for body structure and physiological processes.

Types of minerals

• Major (macrominerals) — needed in larger amounts: calcium (Ca), phosphorus (P), sodium (Na), potassium (K), magnesium (Mg).
• Trace (microminerals) — needed in tiny amounts: iron (Fe), iodine (I), zinc (Zn), fluoride (F), copper (Cu).

Main functions

• Calcium and phosphorus: form bones and teeth and keep them strong.
• Iron: important for forming haemoglobin in blood; carries oxygen to cells.
• Iodine: needed to make thyroid hormones that control growth and metabolism.
• Sodium and potassium: help maintain water balance and nerve/muscle function.
• Magnesium and zinc: act as cofactors for many enzymes (help chemical reactions).
• Fluoride: strengthens teeth and helps prevent dental cavities.

Sources

• Calcium: milk, curd, cheese, paneer, ragi, sesame seeds, leafy green vegetables.
• Iron: green leafy vegetables (spinach), jaggery, beans, peas, meat (non-vegetarian source).
• Iodine: iodised salt, seafood.
• Potassium: bananas, potatoes, tomatoes, beans.
• Sodium: common salt (table salt — use in moderation).

Deficiency effects

• Calcium deficiency: weak bones, rickets in children, tooth problems.
• Iron deficiency: anaemia — tiredness, pale skin, lack of energy.
• Iodine deficiency: goitre (swelling in neck), slow growth, learning problems.
• Fluoride deficiency: more tooth decay; excess fluoride causes mottling of teeth.
• Imbalance of sodium and potassium: cramps, weakness, problems with nerve signals.

How to get enough minerals

• Eat a balanced diet with milk, pulses, vegetables, fruits, nuts and iodised salt.
• Include a variety of foods so you get both major and trace minerals.
• Avoid excessive salt (sodium) and highly processed foods.

Quick classroom note: Minerals are required in very small amounts but their absence or excess affects health. They are inorganic (do not contain carbon) and are different from vitamins and energy-providing nutrients.

What is Roughage (Dietary Fibre)?
Roughage, or dietary fibre, is the part of plant foods that the human digestive system cannot fully digest. Unlike carbohydrates, proteins or fats, fibre passes mostly unchanged through the stomach and intestines. It is essential for healthy digestion and overall well-being.

Types of Fibre

• Insoluble fibre: Does not dissolve in water. Adds bulk to the stool, helps food pass quickly through the stomach and intestines, and prevents constipation. Found in whole grains, wheat bran, vegetables and skins of fruits.
• Soluble fibre: Dissolves in water to form a gel-like substance. Slows digestion, helps lower blood cholesterol and controls blood sugar levels. Found in oats, peas, beans, apples, citrus fruits and flaxseeds.

Functions and Benefits

• Prevents and relieves constipation by increasing stool bulk and softening stools.
• Helps maintain healthy bowel movements and prevents disorders like diverticulosis.
• Soluble fibre helps lower blood cholesterol and can regulate blood sugar levels.
• Increases satiety (feeling full), which can help maintain a healthy weight.
• Promotes growth of healthy gut bacteria (prebiotic effect).

Sources (common everyday foods): Whole grains (whole wheat, brown rice, oats), fruits with skins (apple, pear), vegetables (carrots, spinach, broccoli), legumes (lentils, chickpeas, beans), nuts, seeds and bran.

When there is too little or too much fibre

• Too little: Can cause constipation, irregular bowel movements and discomfort.
• Too much (especially sudden large increase): May cause bloating, gas and reduced absorption of some minerals; increase fibre gradually and drink sufficient water.

How to include enough roughage

• Choose whole fruits rather than juices.
• Use whole-grain breads, rotis and cereals instead of refined ones.
• Add vegetables to every meal and include legumes regularly.
• Include a small serving of nuts, seeds or bran occasionally.

Simple classroom note: Roughage is not a nutrient that gives energy directly, but it is very important for the digestive system and helps other nutrients work properly.

What is Water?

Water is a simple chemical substance made of two hydrogen atoms and one oxygen atom (H2O). It is a colourless, tasteless, odourless liquid at room temperature and is essential for all known forms of life. In the context of 'Components of Food', water is one of the major components present in foods and is vital for the body to use other nutrients.

Physical Properties (simple points)

• State at room temperature: Liquid.
• Freezing point: 0°C (at 1 atm). Boiling point: 100°C (at 1 atm).
• Density: ~1 g/cm³ at 4°C.
• High specific heat: it stores and releases heat slowly, helping regulate temperature.

Why is Water Important in Food and for the Body?

• Solvent: Many food components (salts, sugars, some vitamins) dissolve in water so they can be digested and absorbed.
• Digestion and transport: Water helps in breaking down food and transporting nutrients and waste in blood and lymph.
• Chemical reactions: Most metabolic reactions in cells occur in watery solutions.
• Temperature regulation: Sweat and evaporation cool the body.
• Structural role: Keeps cells turgid (plants) and maintains blood volume (animals).

Water Content in Foods (simple examples)

Different foods contain different amounts of water. Fruits and vegetables usually have very high water content (e.g., watermelon >90%), while dry foods such as biscuits, nuts and cereals have low water content. Milk and curd also contain a high amount of water.

Daily Requirement

Humans need water every day. A typical recommendation for children and adults is about 1.5–3 litres per day depending on activity, climate and age. Water also comes from foods (fruits, vegetables, milk).

Simple Classroom Activities

• Weigh a fruit, dry it (sun or oven) and weigh again to estimate water loss and calculate water percentage.
• Demonstrate dissolution: dissolve salt/sugar in water to show water as a solvent.

Safety and Conservation

Drinking safe, clean water is essential to prevent disease. Conserving water (fixing leaks, using water wisely) is important for the environment.

What is a Balanced Diet?

A balanced diet provides all the nutrients — carbohydrates, proteins, fats, vitamins, minerals, dietary fibre and water — in the right quantities and proportions to keep the body healthy and active. It meets energy needs, supports growth, protects against disease and helps repair tissues.

Main Components and Their Functions

• Carbohydrates: Main source of energy (eg, rice, wheat, potatoes).
• Proteins: Build and repair body tissues; essential for growth (eg, pulses, dals, eggs, milk, meat, paneer).
• Fats: Concentrated energy source, help absorb some vitamins (eg, ghee, oils, nuts).
• Vitamins and Minerals: Regulate body processes (eg, vitamin C in citrus, calcium in milk, iron in leafy greens).
• Dietary Fibre: Aids digestion and prevents constipation (eg, fruits, vegetables, whole grains).
• Water: Needed for all body reactions, temperature control and transport of nutrients.

Characteristics of a Balanced Diet

• Variety: Includes foods from all groups.
• Right quantity: Enough calories for age and activity but not too many.
• Proper proportions: Correct mix of nutrients (carbohydrates, proteins, fats, etc.).
• Safe and clean: Hygienically prepared, fresh and safe to eat.

Why It Matters for Class 6 Students

Children need a balanced diet for physical growth, mental development, concentration in school and resistance to infections. Poor diet can cause tiredness, slow growth, repeated illnesses and difficulty learning.

How to Plan a Balanced Meal

• Use a plate with half filled with vegetables and fruits, one quarter with cereals or staples (rice/roti), and one quarter with proteins (dal, paneer, egg or meat).
• Include a small amount of healthy fats and a glass of milk or curd for calcium.
• Eat regular meals and healthy snacks like fruit, nuts or yogurt.

Definition: Deficiency diseases are illnesses caused by the lack of one or more essential nutrients (vitamins, minerals, proteins, fats, carbohydrates, or water) in the diet. They occur when the body does not get enough of a nutrient it needs to grow, repair tissues, or carry out normal functions.

Causes: Poor or unbalanced diet, poverty, lack of knowledge about nutrition, digestive or absorption problems, long‑term illness, or living in areas with food shortages.

Common deficiency diseases, their causes and prevention:

• Scurvy — caused by deficiency of vitamin C. Symptoms: bleeding gums, swollen joints, weakness, slow healing of wounds. Prevention: eat citrus fruits, guava, amla, tomatoes, green leafy vegetables.
• Rickets — caused by lack of vitamin D and/or calcium in growing children. Symptoms: soft, weak bones, bowed legs, delayed growth. Prevention: sunlight exposure, milk, eggs, fish, fortified foods, adequate calcium intake.
• Night blindness / Xerophthalmia — caused by deficiency of vitamin A. Symptoms: poor vision in dim light, dry eyes, increased risk of eye infections. Prevention: carrots, sweet potatoes, green leafy vegetables, mangoes, liver.
• Beriberi — caused by deficiency of vitamin B1 (thiamine). Symptoms: weakness, nerve and heart problems, swelling in legs. Prevention: whole grains, pulses, nuts, meat.
• Goitre — caused by iodine deficiency. Symptoms: swelling in the neck (enlarged thyroid). Prevention: iodised salt, seafood, milk.
• Iron deficiency anaemia — caused by lack of iron. Symptoms: tiredness, pale skin, shortness of breath, reduced concentration. Prevention: green leafy vegetables, meat, legumes, iron‑fortified cereals, combine with vitamin C for better absorption.
• Kwashiorkor — severe protein deficiency (often with some calorie intake). Symptoms: swollen belly, thin limbs, hair changes, delayed growth. Prevention: adequate protein from milk, eggs, pulses, meat.
• Marasmus — severe deficiency of calories and proteins. Symptoms: extreme thinness, wasting, very low weight for age. Prevention: sufficient balanced calories and proteins.

Prevention — general rules: Eat a balanced diet including cereals, pulses, vegetables, fruits, milk, eggs or meat (if non‑vegetarian), use iodised salt, get regular sun exposure for vitamin D, use fortified foods when available, maintain good hygiene to avoid infections that reduce nutrient absorption.

When to seek help: If a child shows growth failure, persistent fatigue, swelling, bone deformities, or vision problems, consult a healthcare provider for diagnosis and treatment (dietary correction, supplements or medical care).

Overview: Foods are grouped according to the main nutrients they provide. The major food groups (nutrients) are carbohydrates, proteins, fats, vitamins, minerals, roughage (fiber) and water. Each group has specific roles in the body and comes from particular foods (sources).

Food groups, their functions and common sources:

• Carbohydrates – Main source of energy. Sources: rice, wheat, maize, potatoes, bread, sugar, chapati. (Function: quick energy for daily activities.)
• Proteins – For growth, repair and body building. Sources: pulses (dal), legumes, beans, peas, milk, paneer, eggs, fish, meat, soy.
• Fats – Concentrated energy, insulation and protection of organs. Sources: ghee, butter, cooking oils, nuts, seeds, oily fish, cheese.
• Vitamins – Help in body regulation and preventing diseases. Sources: fruits (citrus, mango), vegetables (carrot, spinach), milk (vitamin D often fortified), eggs.
• Minerals – Important for bones, teeth, blood and enzymes. Examples: calcium (milk, curd, cheese), iron (spinach, jaggery, pulses), iodine (iodised salt).
• Roughage (Dietary fibre) – Aids digestion and prevents constipation. Sources: whole grains, fruits with skin, vegetables, nuts, bran.
• Water – Essential for all life processes, digestion, transport of nutrients and temperature regulation.

Deficiency effects (short list): Protein deficiency → stunted growth; Iron deficiency → anemia (tiredness, pale skin); Vitamin C deficiency → scurvy (bleeding gums); Calcium deficiency → weak bones/teeth.

Balanced diet: A healthy meal contains a mix of these groups — enough carbohydrates and fats for energy, adequate protein for growth/repair, fruits and vegetables for vitamins and minerals, fibre for digestion and plenty of water. A simple balanced plate example: a portion of cereal (rice/chapati), a portion of dal or paneer (protein), vegetables (vitamins/minerals), a small amount of fat (dal tadka/oil) and a fruit or milk for dessert.

How to use this knowledge: When you choose foods, think which nutrient you need. For growth phases (children/teens), include more protein and calcium-rich foods. For energy before sports, include carbohydrates. To avoid constipation include enough fiber and water.

Overview: Food tests are simple, safe chemical or staining reactions used to detect major components of food — starch, reducing sugars, proteins and fats — in everyday samples (fruits, vegetables, milk, oil, etc.). These tests are qualitative (show presence/absence) and with care can be made semi‑quantitative by comparing color intensity.

Common tests and procedure (materials: test tubes, water bath/boiling tube, dropper, Benedict's solution, iodine solution, Biuret reagent, Sudan III or oil test paper, distilled water):

1. Test for starch (Iodine test)
   1. Place a small piece or extract of the food in a watch glass or test tube.
   2. Add 2–3 drops of iodine solution (iodine in potassium iodide).
   3. Observation: blue-black colour indicates presence of starch; yellow-brown indicates absence.
2. Test for reducing sugars (Benedict's test)
   1. Mix a little food extract with Benedict's solution in a test tube.
   2. Heat the mixture in a boiling water bath for 2–5 minutes.
   3. Observation: a colour change from blue to green/yellow/orange/red or formation of a red precipitate (Cu2O) indicates presence of reducing sugars. Colour intensity roughly increases with sugar concentration.
3. Test for proteins (Biuret test)
   1. Add a few drops of Biuret reagent (alkaline copper sulfate) to the food extract.
   2. Observation: violet or purple colour indicates presence of proteins (peptide bonds). Blue means protein absent.
4. Test for fats/lipids
   1. Paper (grease spot) test: Rub sample on brown paper and allow to dry — a translucent greasy spot that does not disappear on drying indicates fat.
   2. Sudan III (or Sudan IV) test: Add Sudan dye to the extract; the dye dissolves in lipids and stains them red/orange in the top layer — appearance of red‑stained oil droplets indicates fats.

Controls and interpretation: Always use a positive control (known sample that contains the component, e.g., potato for starch) and a negative control (water). Run tests on small, properly prepared extracts (crush solid food and mix with small amount of water). If a test is ambiguous, repeat or use alternative test.

Safety & tips:

• Wear safety glasses and gloves when handling reagents and heating.
• Do not taste reagents. Handle hot tubes carefully.
• Perform tests in small volumes to reduce waste and risk.
• Some coloured foods (e.g., beetroot) may interfere with visual results — use controls or dilute sample.

What is unhealthy eating and junk food?

Junk food means foods that are high in sugar, salt and unhealthy fats but low in essential nutrients such as vitamins, minerals, protein and fibre. Examples are chips, sugary soft drinks, candies, pizzas with little vegetable, deep fried snacks and many packaged ready-to-eat items.

Why are they harmful?

• High energy but low nutrients: Junk foods supply many calories but few useful nutrients, so the body gets energy but not the vitamins and minerals needed for growth and health.
• Too much sugar and fat: Excess sugar and unhealthy fats can cause weight gain and affect organs like the liver and heart.
• Too much salt: High salt can raise blood pressure over time and harm the heart.

Immediate (short-term) effects

• Stomach ache, acidity and indigestion after heavy fried or spicy junk food.
• Tooth decay from frequent sugary snacks and drinks.
• Temporary energy spikes followed by tiredness and poor concentration (sugar crash).

Long-term effects

• Obesity and overweight if calorie intake regularly exceeds energy used.
• Increased risk of type 2 diabetes due to frequent high sugar intake.
• High blood pressure and heart disease risk from excess salt and unhealthy fats.
• Nutrient deficiencies (for example anaemia, weak bones) if junk food replaces nutritious meals.
• Poor immunity, frequent infections and slower healing.

Effects on school life and growth

• Poor concentration, low attention span and poor academic performance after heavy junk food intake.
• Slower and unbalanced growth if essential nutrients are missing from the diet.

How to reduce harm

• Limit junk food to occasional treats and keep portion sizes small.
• Choose healthier snacks: fruits, nuts (in moderation), yoghurt, roasted chana, homemade sandwiches and salads.
• Read food labels and pick options with less sugar, salt and trans fat.
• Eat a balanced diet with cereals, pulses, milk, fruits, vegetables and some fat and sugar in small amounts.

Simple classroom activity: Compare the nutrient labels of a packet of chips and an apple. List calories, sugar, fat and vitamins to see the difference.

What are food habits? Food habits are the usual ways in which people choose, prepare and eat food. These habits are shaped by many influences and affect our health, growth and nutrition.

Why culture and society matter: Cultural and social factors determine what foods are considered acceptable, how they are cooked, when they are eaten and who prepares or serves them. These factors often pass from one generation to the next and form an important part of identity.

Main cultural and social factors that affect food habits:

• Religion and beliefs: Religious rules may permit or forbid certain foods (for example, many Hindus avoid beef; Muslims avoid pork; Jains practice strict vegetarianism and avoid root vegetables).
• Traditions and festivals: Special foods are prepared for festivals, weddings and ceremonies (e.g., sweets during Diwali, dates during Ramadan).
• Region and climate: Local climate and geography influence staple foods—rice is common in warm, wet regions while wheat is common in drier, temperate regions.
• Availability and seasonality: Fresh fruits, vegetables and fish depend on seasons and local markets.
• Family and peer influence: Family preferences and peers (friends, classmates) shape daily eating habits, snacks and meal timing.
• Economic factors: Income and food prices influence which foods a family can regularly buy (cheaper staples vs. expensive protein-rich foods).
• Occupation and lifestyle: Physical work may require high-energy diets; sedentary jobs may need lighter meals. Urbanization changes meal patterns (more ready-to-eat and fast foods).
• Media and advertising: TV, internet and advertisements influence tastes, often increasing demand for packaged and fast foods.

Effect on nutrition and health: Cultural preferences can be healthy (plant-rich diets) or risky (over-reliance on fried or sugary foods). Social practices like fasting can be beneficial if planned, but may be harmful for growing children without proper substitutes. Understanding these factors helps promote balanced diets that respect culture.

How to balance culture and nutrition: Respect cultural practices while ensuring a variety of foods. For example, vegetarian diets should include pulses, dairy, nuts and seeds for protein and iron; seasonal fruits and vegetables add vitamins; using healthier cooking methods (steaming, grilling) can reduce excess fat.

Overview: Practical activities and simple projects help you check for major components of food (carbohydrates/starch, fats, proteins and sugars) and learn how to plan a balanced diet. Revision skills help you remember concepts, use results, and link experiments to everyday life.

Common practicals (what, why and how):

• Starch test (Iodine test): Materials: food samples (potato, bread, rice), iodine solution, dropper, white tile/paper. Procedure: put a small portion of the food on the tile, add a drop of iodine. Observation: blue-black colour = starch present. Why: iodine fits into the spiral structure of starch and gives a blue-black complex.
• Fat test (Grease/Brown-paper test): Materials: brown paper or filter paper, food samples (butter, ghee, cheese, nuts). Procedure: rub a little food on brown paper and leave to dry. Observation: a translucent (greasy) spot that remains after drying indicates fat. Why: fats leave an oil stain that does not evaporate.
• Sugar test (Benedict’s test) — teacher/demonstration: Materials: Benedict’s reagent, test tube, water bath, food sample extract. Procedure: mix sample with Benedict’s and heat. Observation: change from blue to green/yellow/orange/red depending on amount of reducing sugar. Note: requires heating and teacher supervision.
• Protein test (Biuret test) — optional/supervised: Materials: dilute NaOH and copper sulfate (Biuret reagent). Procedure: add reagents to a protein-containing sample. Observation: violet/pink colour indicates protein. Note: chemical handling should be supervised by teacher.

Simple project ideas:

• Make a balanced-diet chart for a week for a student, showing portions from cereals, pulses, vegetables, fruits, dairy and fats.
• Collect common snacks and test for starch and fat; present results in a table and recommend healthier options.
• Study how cooking affects starch: test raw vs cooked potato or rice for starch (iodine test) and record results.
• Design a poster or model showing food sources of carbohydrates, proteins and fats with pictures and short notes.

Recording and interpreting results:

• Keep a lab notebook: date, aim, materials, method, observations (write colours or ‘‘+’’/‘‘–’’), conclusion and safety notes.
• Compare samples: e.g., score intensity of iodine reaction (0 = no change, 1 = faint, 2 = moderate, 3 = strong) to make a simple comparative chart.
• Relate results to diet: if a food tests strongly for starch but weak for protein, it is mainly an energy source, not a protein source.

Revision skills (how to remember and apply topics):

• Make concept maps linking foods → nutrients → functions (e.g., rice/bread → carbohydrates → provide energy).
• Create flashcards: one side name of test (Iodine) or nutrient (Fats), other side procedure/observation/function/source.
• Practice by writing short answers: give two tests for food components and explain one real-life example.
• Use past question papers and turn practical steps into short sentences you can recall quickly.

Safety and good practice: Always use safe amounts of reagents, wear gloves/eye protection when needed, never taste chemicals, and conduct heating/tests under teacher supervision.

How this connects to daily life: You can test material at home (bread, potato, cooking oil) to see what they contain; make a weekly meal plan to include cereal (carbs), pulses/dairy (proteins), vegetables/fruits (vitamins/minerals/fibre) and small portion of fats for energy.