igcse food and nutrition

- for igcse 0648 food and nutrition students | topics covered: micronutrients, macronutrients, life stages, energy, digestion, bake goods (bread, pastry, cake), healthy balanced diet, nutrition key terms, cereals

nutrition

The study of food and how the body uses it for growth, repair, energy, and maintenance

nutrients

Chemical substances found in food that are essential to life, health, and proper bodily function

macronutrients

Macronutrients: Essential nutrients required by the body in large amounts (measured in grams), namely carbohydrates, proteins, and fats

micronutrients

Micronutrients: Essential nutrients required by the body in small/minute amounts (measured in milligrams or micrograms), namely vitamins and minerals

balanced diet

Balanced Diet: A diet containing all the essential nutrients (carbohydrates, proteins, fats, vitamins, minerals, water, and fiber) in the correct proportions and amounts to suit the individual's needs

malnutrition

Malnutrition: A state resulting from an unbalanced or incorrect intake of nutrients. (Can mean over-nutrition or under-nutrition)

under-nutrition

Under-nutrition: A form of malnutrition caused by an insufficient intake of essential nutrients or energy

over-nutriton

Over-nutrition: A form of malnutrition caused by an excessive intake of nutrients or energy (often leading to obesity)

dietary references values

Dietary Reference Values (DRVs): Estimates of the amounts of nutrients needed by different groups of healthy people in the population

basal metaolic rate

Basal Metabolic Rate (BMR): The minimum amount of energy required by the body to maintain vital involuntary life functions (breathing, heartbeat, temperature control) when completely at rest

energy balance

Energy Balance: When the total energy intake from food equals the total energy expended through metabolism and physical activity

fat relationship

fats (lipid) —-(lipase)—> fatty acids +glycerol

site: small intestine (duodenum)

carbohydrate relationship

starch —(amylase)—> maltose

maltose —(maltase)—> glucose

sucrose —(sucrase)—> glucose+fructose

lactose —(lactase)—> glucose + galactose

site: small intestine

protein relationships

proteins —(pepsin/trypsin) —> tiny fat droplets

glucose+amino acids —(absorption)—> blood capillaries

site: villi in the ileum (small intestine)

fatty acids + glycerol —(absorption)—> lacteal

site: centre of the villi in the ileum

infant needs

• high energy and protein → cell division, growth, weight gain

• high calcium and vitamin d → lengthening of bones and teethes

• high iron→ prevent anemia

• high vitamin c → enhance non-heme iron absorption

• no added sugar or salt → immature kidneys cannot precess salt, sugar causes tooth decay

toddlers and young children

• high energy density→ need small frequent meals packed with energy

• high calcium and vitamin d→ essential for growth and maintaining strong bones

• high hbv protein→ muscle tissue growth and repair

• less saturated fat→ protects cardiovascular health

• less sugar → causes tooth decay

adolescents

• high hbv protein → building new muscles tissue

• high calcium and vitamin d→ strong bones

• high iron (esp women) → replace regular blood loss

adults

• hbv protein → cellular repair and tissue maintenance

• less saturated fat → reduces CHD

• less free sugar → prevent weight gain, obesity and type 2 diabeted

pregnant women

• high vitamin b9 (folic acid) → preventing neural tube defects

• high iron → build extra hemoglobin

• high calcium and vitamin d→ construct bones and teethes

lactating/breastfeeding women

• high fluids and water→ maintain consistent volume of milk production

• high protein and calcium → preserve own bone density

• high vitamin c→ immune quality of breast milk passed to infant

elderly

• high nsp→ prevent constipation

• high calcium and vitamin d→ slows down rate of bone thinning

• low saturated sugar → reduce strokes, heart attacks

amount of carbohydrates needed

4kcal/g

amount of fats (lipids) needed

9kcal/g

amount of proteins needed

4kcal

chemical energy

Energy stored within the chemical bonds of food molecules

mechanical / kinetic energy

Energy used by muscles for movement and physical activity

thermal / heat energy

Energy used to maintain a constant internal body temperature (37°C)

involuntary processes funded by BMR

• Heartbeat and blood circulation.

• Breathing and respiration

• Brain function and nerve impulses

• Cellular repair and chemical reactions

• Maintenance of body temperature.

voluntary physical activity

Energy expended through deliberate movement and work
eg. walking, running

factors affecting energy requirements

1. ave

2. gender

3. occupation

4. body size

5. climate

energy balance

energy intake = energy expenditure

positive energy balance

energy intake > energy expenditure

negative energy balance

energy intake < energy expenditure

mechanical digestion

physical breakdown of food into smaller pieces without altering its chemical structure (e.g., chewing, churning)

chemical digestion

The breakdown of large, insoluble molecules into small, soluble molecules through the action of enzymes, water, and digestive juices

mouth

• Mastication (Chewing): Teeth mechanically break down food.

• Saliva: Lubricates food into a smooth mass (bolus) for easy swallowing.

• Salivary Amylase: Begins chemical digestion of starch into maltose.

esophagus

• Peristalsis: Rhythmic, wave-like muscle contractions that push the bolus down to the stomach. No digestion happens here.

stomach

• Churning: Muscular walls mechanically mix food into a semi-liquid state called chyme.

• Hydrochloric Acid (HCl): Kills harmful bacteria consumed with food and provides the optimum acidic pH (around pH 2) for stomach enzymes.

• Pepsin: Begins chemical digestion of proteins into shorter peptide chains.

small intestine (duodenum and ileum)

• Bile: Produced in the liver, stored in the gall bladder, and secreted into the duodenum.

• Function 1: Neutralizes acidic chyme leaving the stomach to create an alkaline environment for enzymes.

• Function 2: Emulsifies fats (breaks large fat drops into tiny droplets) to increase surface area for lipase.

• Pancreatic Juice & Intestinal Juice: Contain amylase, trypsin, and lipase to fully complete the chemical breakdown of carbohydrates, proteins, and fats

absorption (ileum)

• Definition: The passage of small, soluble digested nutrients through the walls of the alimentary canal into the blood or lymphatic system.

• The Villi: Tiny, finger-like projections lining the ileum that maximize absorption efficiency

adaptions of villi for rapid absorption

• Large Surface Area: Millions of villi (and microvilli) expand the contact area with digested food

• Thin Walls: Only one cell thick, creating a very short pathway for nutrients to diffuse through

• Rich Blood Supply: A dense network of blood capillaries rapidly carries away glucose, amino acids, water-soluble vitamins, and minerals.

the large intestine (colon and rectum)

• Water Absorption: Absorbs remaining water, vitamins, and mineral salts from undigested food residue.

• NSP (Dietary Fiber) Role: Cannot be digested, so it adds bulk to the waste material, stimulating peristalsis to move it along smoothly.

• Egestion: The removal of undigested, solid waste material (feces) from the body through the anus

why is fat used in baking

• shortening → prevents water from mixing with flour proteins

• aeration →creates a light fluffy texture

• flaking in

• flavor and color →adds rich creaming flavor (golden brown color)

shortcrust fat to flour ratio

1:2

short crust method

rubbing in →fat is rubbed into plain flour using fingertips

rules for rubbing in

• use finger tip →palm (internal heat)

• use cold water and keep everything chilled

• do not over-knead

flaky pastry fat to flour ratio

2:3

rough puff pastry fat to flour ratio

2:3

creaming method dish eg

victoria sponge cake

creaming method

• Fat and sugar are beaten thoroughly until pale and fluffy → traps air. Eggs are added gradually, followed by self-raising flour folded in gently

proportions of creaming method

• Proportions: Equal weights of flour, fat, sugar, and eggs.

whisking method dish eg

swiss rolls, sponge fingers

rubbing in method dish eg

rock cakes, scones

whisking method

•  Whole eggs and sugar are whisked together over warm water until thick and at the "ribbon stage" → traps massive volumes of air. No fat is used in a traditional whisked sponge.

melting method dish eg

gingerbread, brownies

melting method

• fat, syrup/sugar, and spices are melted together in a pan before being added to dry ingredients.

bread making key ingredients

1. strong flour → high in gluten

2. yeast

3. warm water → 37C

4. sugar

5. salt

bread making steps

1. Kneading: Stretching the dough → develops the gluten network into an elastic web.

2. Proving (Fermentation): Leaving dough in a warm place → yeast digests sugar and produces carbon dioxide (CO₂) gas and alcohol → gas expands the gluten web, causing the dough to double in size.

3. Baking: Hot oven expands the CO₂ gas → yeast is killed → alcohol evaporates → gluten coagulates (hardens) to set the permanent shape of the bread loaf.

strong flour (bread flour) characteristics

high gluten content

strong flour used in

• yeast bread and rolls

• choux pastry

• pizza dough

plain flour (all purpose/soft) characteristics

low gluten content

plain flour used in

• shortcrust pastry

• flaky

• rough puff

• sauces

• biscuits and cookies

self raising flour characteristics

plain flour that has been pre-blended with a chemical raising agent

self raising flour used in

sponge cakes, scones, muffins

wholemeal flour (whole wheat flour) characteristics

 Made by grinding the entire cereal grain, meaning it retains 100% of the bran (outer layer) and germ

wholemeal flour usage

wholemeal bread, digestive biscuits

cornflour (cornstarch) characteristics

fine white flour made strictly from the pure starch endosperm of the mzise grain

• zero gluten

cornflour used in

• thickening custard, fruit pies filling

dietary guidelines

1. reduce total fat

2. reduce free sugar

3. reduce sodium (salt) intake

4. increase NSP

5. increase fresh fruits and vegetables

6. increase carbohydrates

7. increase water intake

reduce fat intake

• grill, bake, steam or poach food instead of deep drying

• trim off excess fat

• used plant based oil

• choose low fat dairy options

reduce sugar intake

• drink plain water

• use fresh fruits to naturally sweeten desserts

• avoid high fructose corn syrup

reduce salt intake

• use herbs, spices, lemon juice, garlic to flavor meals

• avoid high processed canned food

• avoid salt shaker

increase nsp

• choose whole grain products

• leave the skins off vegetables and fruits

• incorporate beans, pulses into soups and salads

planning for vegetarians

• combine LBV foods to form complementary proteins that provide all amino acids

• find alternative sources of vitamin b12 and d

planning for diabetics

• avoid simple sugar

• focus on nsp and starch for slow energy release

planning for lactose intolerant

• swap cows milk for plant based alternatives (soya, almond, oat)

planning for the obeased

• low fat

• low sugar

• high water

• high fiber to promote fullness

why do people malfunction structurally

• Obesity: Caused by a consistent positive energy balance (too much fat/sugar, too little exercise).

• Coronary Heart Disease (CHD): Caused by excess saturated fat clogging the coronary arteries with cholesterol plaques.

• Hypertension (High Blood Pressure): Caused by excessive salt intake forcing the heart to pump harder against restricted blood vessels.

• Constipation: Caused by a lack of NSP and water, making feces dry and hard to pass

types of cereals

wheat, rice, maize (corn), oats, barey oats

nutritional values of cereal

• high in carbohydrate

• low biological value

• rich in vitamin b group

• low water content

storage of cereals

• keep dry (room temp)

• pest control (airtight container)

• wholemeal care

gelatinization (Moist heat)

When cereal starches (like flour or rice) are heated in a liquid (60°C–100°C), the starch granules absorb water, swell, burst, and thicken the liquid (e.g., making a white sauce or porridge)

dextrinization (dry heat)

When dry heat is applied directly to cereal products (like baking bread or making toast), the starch molecules on the surface split into simpler sugars called dextrins, causing a color change to golden brown and a sweeter flavor

water soluble vitamins

vitamin b,c

fat soluble

vitamin a,d,e,k

vitamin a functions

• The maintenance of healthy skin and mucous membranes (in eyes, lungs and the digestive system)

• The normal function of the immune system

• Production of visual purple in retina of eye

• Helps vision in dim light

• Prevents night blindness

• Required for growth in children

retionol

from animal source, ready-made

carotenoids

from plant

vitamin a food source

retinol: liver, whole meal

carotenoid: carrot, vegetables, fruits

vitamin a deficiency disease

night blindness, dry skin

excess vitamin a

toxic

vitamin d functions

• Promotes absorption of calcium and phosphorus

• Formation and maintenance of bones and teeth

• Antioxidant

• Maintenance of normal muscle function

vitamin d food source

• Mushroom

• oily fish

• fortified cereals

• dairy products (milk, yoghurt, cheese etc)

• fish liver oil

• sunshine/ sun light

• eggs

• margarine

vitamin d deficiency

rickets in children, osteomalacia in adults

vitamin e functions

• Healthy skin

• Antioxidant

• Destroys free radicals

• Helps to prevent heart disease

• Formation of new blood vessels around damaged areas

• Maintenance of cell membranes

• Reduces risk of developing certain cancers

vitamin e food source

• Plant oils and their spreads(e.g. Sunflower oil/ margarine, olive oil/ margarine)

• Nuts (e.g. peanut, almond etc)

• Seeds (e.g. sunflower seeds, pumpkin seeds etc)

• Wheatgerm

vitamin k functions

• Clotting of blood

• Normal liver functioning

• Aids the absorption of calcium in bone structure

• Important in maintaining vitality and longevity

• Protects against osteoporosis

vitamin k food source

• Green leafy vegetables

• Dairy products

• Eggs

• Meats

vitamin b1 thiamin functions

• The release of energy from carbohydrate

• Normal function of the nervous system and heart