Welcome to Food Preparation Technology!

Hey everyone! Ready to dive into the amazing world of cooking? This chapter is all about the science and skills behind preparing delicious and safe food. We'll explore everything from the basic ingredients (food commodities) to the high-tech ways we cook and preserve them. Understanding this isn't just for passing exams – it’s a life skill that will help you eat healthier, cook with confidence, and keep your family safe. Let's get started!


1. Food Commodities: The Building Blocks of Our Meals

Think of food commodities as the main characters in our cooking story. Each one has a unique personality – its own nutrients, properties, and role to play in a dish. Knowing them well is the first step to becoming a great cook.

Milk and Dairy Products

Examples: Fresh milk, cheese, yoghurt, butter.

  • Nutritive Value: Packed with calcium for strong bones and teeth, high-quality protein for growth, and vitamins like A and D.
  • Properties in Cooking: Milk can add moisture and richness. Cheese melts to create a creamy texture and adds flavour. Yoghurt can be used to tenderise meat or as a base for sauces.
  • Uses: Cereal, cheese toast, pasta sauces, marinades.

Eggs

  • Nutritive Value: An amazing source of protein, vitamins D and B12, and iron.
  • Properties in Cooking: Eggs are super versatile! They can:
    • Bind ingredients together (like in meatballs).
    • Thicken sauces and custards.
    • Leaven (add air) to cakes and soufflés when whisked.
    • Emulsify, helping to mix oil and water (like in mayonnaise).
  • Uses: Scrambled eggs, cakes, quiches, coatings for fried food.

Meat and Poultry

Examples: Pork, beef, lamb, chicken, duck.

  • Nutritive Value: Excellent source of protein, iron (especially red meat) to prevent anaemia, and B vitamins.
  • Properties in Cooking: The texture changes with cooking. Tougher cuts with more connective tissue need slow, moist cooking (like stewing) to become tender. Leaner cuts can be cooked quickly (like grilling).
  • Uses: Stir-fries, roasts, soups, curries.

Fish and Seafood

Examples: Salmon, cod, shrimp, mussels.

  • Nutritive Value: Great source of lean protein. Oily fish (like salmon) are rich in Omega-3 fatty acids, which are fantastic for brain and heart health.
  • Properties in Cooking: Cooks very quickly! It's easy to overcook, which makes it dry and tough. The flesh should be opaque and flake easily when done.
  • Uses: Steamed fish, grilled fish fillets, seafood pasta.

Vegetables and Fruits

  • Nutritive Value: Our main source of vitamins (like Vitamin C), minerals, and dietary fibre, which is essential for a healthy digestive system.
  • Properties in Cooking: Heat softens the cellulose (fibre) in vegetables, making them easier to digest. Different cooking methods can change their colour, texture, and flavour.
  • Uses: Everywhere! Salads, stir-fries, soups, snacks, desserts.

Cereals and Grains

Examples: Rice, wheat (flour, pasta, bread), oats, corn.

  • Nutritive Value: The primary source of carbohydrates for energy. Whole grains also provide dietary fibre and B vitamins.
  • Properties in Cooking: They often absorb water and swell up. Starch in cereals can be used to thicken sauces (e.g., cornflour). Gluten in wheat flour gives bread its structure.
  • Uses: Steamed rice, pasta dishes, bread, breakfast porridge.
Quick Review: Fresh vs. Processed

Fresh/Raw: Foods in their natural state. (e.g., a fresh apple, raw chicken breast). They often have higher nutrient content but spoil quickly.
Processed/Preserved: Foods that have been altered to make them last longer or to create a new product. (e.g., canned applesauce, frozen chicken nuggets). They are convenient but can sometimes have added salt, sugar, or preservatives.

Key Takeaway

Understanding what each food commodity offers in terms of nutrition and cooking properties allows you to plan balanced, delicious, and interesting meals.


2. Personal Food Hygiene: Your First Line of Defence

This is one of the most important topics! Poor hygiene can lead to food poisoning. The goal is to prevent harmful micro-organisms from getting into our food. A great way to remember the key principles is the "4 Cs of Food Safety".

The 4 Cs of Food Safety
  1. Clean:
    • Wash your hands thoroughly with soap and water before and after handling food, especially raw meat.
    • Keep work surfaces, chopping boards, and utensils clean. Use separate chopping boards for raw and cooked food if possible.
  2. Cook:
    • Cook food to the correct temperature to kill harmful bacteria. For most foods, this means reaching at least 75°C in the centre.
    • When reheating food, make sure it is piping hot all the way through.
  3. Chill:
    • Chill perishable foods (like dairy, meat, and leftovers) promptly. Don't leave them out for more than 2 hours.
    • Your fridge should be set at or below 4°C.
  4. Cross-Contamination (Prevent it!):
    • This is when bacteria spread from a source (usually raw food) to other foods.
    • Never let raw meat, poultry, or seafood touch or drip onto other foods. Store raw meat on the bottom shelf of the fridge.
    • Use separate utensils for raw and cooked foods.
Did you know?

You shouldn't wash raw chicken! Rinsing it can splash bacteria like Salmonella all over your sink, countertops, and nearby utensils. The heat from proper cooking is what safely kills the bacteria.

Key Takeaway

Good food hygiene is a habit, not a one-time action. Following the 4 Cs every time you cook is the best way to keep your food safe for everyone to enjoy.


3. Food Cooking Processes: The Science of Heat

Cooking is essentially applying heat to food. But how that heat gets to the food makes a huge difference! This is called heat transfer.

Types of Heat Transfer

  • Conduction: Heat transfer through direct contact.
    Analogy: Imagine a line of people passing a hot potato. The heat moves from one person to the next.
    Example: Frying an egg in a pan. The stove heats the pan, and the pan heats the egg.

  • Convection: Heat transfer through the movement of liquids or gases (like air). Hotter, less dense fluids rise, and cooler, denser fluids sink, creating a circular flow called a convection current.
    Analogy: A lava lamp. The heated wax rises, cools at the top, and sinks again.
    Example: Boiling water in a pot or baking a cake in an oven. The hot air or water circulates around the food.

  • Radiation: Heat transfer through energy waves, like light or radio waves. No direct contact is needed.
    Analogy: Feeling the warmth of the sun on your face, even though you're not touching it.
    Example: Toasting bread in a toaster or grilling sausages. The glowing hot elements radiate heat onto the food.

Modern Cooking Technologies

  • Microwave: Uses radiation (microwaves) that cause water molecules in the food to vibrate rapidly, generating heat from the inside.
  • Induction: Uses a magnetic field to directly heat the pot itself (which must be made of a magnetic material). This is a form of conduction, but the heat source is the pot, not the stovetop.

Cooking Methods: Choosing Your Technique

We can group cooking methods into two main types:

Moist Heat Methods (using water or steam)

These methods are great for making tougher foods tender.

  • Boiling: Cooking in water at 100°C.
  • Steaming: Cooking with the steam from boiling water. This is very gentle and helps preserve nutrients.
  • Stewing/Braising: Cooking food slowly in a small amount of liquid in a covered pot.
  • Pressure Cooking: Cooking in a sealed pot that builds up steam pressure, raising the boiling point of water and cooking food much faster.
Dry Heat Methods (using air or fat)

These methods create browning and a rich flavour through a chemical reaction called the Maillard reaction.

  • Baking/Roasting: Cooking with hot, dry air in an oven.
  • Grilling: Cooking with radiant heat from below or above.
  • Frying: Cooking in hot fat or oil.
Effect of Heat on Digestibility

Why do we cook food? Besides making it safe and tasty, cooking breaks down tough cell walls and connective tissues. This makes the food softer and allows our digestive system to access and absorb the nutrients more easily. Think of the difference between a raw potato and a baked potato!

Key Takeaway

The cooking method you choose is a powerful tool. It changes the food's texture, flavour, appearance, and even how nutritious it is. Matching the right method to the right food is key!


4. Food Spoilage and Food Poisoning: When Food Goes Wrong

It's important to know the difference between food that is spoiled and food that can cause poisoning. They are not the same thing!

Food Spoilage: The quality of the food gets worse. It might look, smell, or feel unpleasant (e.g., mouldy bread, slimy vegetables). It's a sign that the food is no longer good to eat, but it won't necessarily make you sick.

Food Poisoning: Caused by eating food contaminated with harmful (pathogenic) micro-organisms or toxins. The food might look, smell, and taste completely normal, but it can make you very ill.

Causes of Food Spoilage

  • Natural Decay:
    • Enzymatic Activity: Enzymes are natural substances in food that cause ripening and eventually decay. (e.g., A banana turning brown and mushy).
    • Chemical Degradation (Oxidation): Reaction with oxygen in the air. (e.g., A cut apple turning brown).
  • Contamination by Micro-organisms:
    • Bacteria, Yeast, and Mould are tiny living things that feed on the food, breaking it down and causing spoilage.

Causes of Food Poisoning

  • Poisonous Food: Some foods are naturally poisonous. (e.g., certain wild mushrooms or herbs).
  • Chemicals: Contamination with harmful chemicals. (e.g., vegetables with too much pesticide residue).
  • Pathogenic Micro-organisms: This is the most common cause! These are the "bad guys" that cause illness.
    Common culprits to know:

    Salmonellae:
    Common Foods: Raw chicken, raw eggs, milk.
    Symptoms: Diarrhoea, fever, stomach cramps.

    Escherichia coli (E. coli):
    Common Foods: Undercooked minced beef, contaminated water.
    Symptoms: Severe stomach cramps, diarrhoea (often bloody).

    Vibrio cholerae:
    Common Foods: Contaminated water, raw or undercooked seafood.
    Symptoms: Severe watery diarrhoea, dehydration.

Key Takeaway

Always trust your senses for spoilage—if it looks or smells bad, don't eat it ("When in doubt, throw it out!"). For food poisoning, you can't see, smell, or taste the danger, which is why practicing good food hygiene is your only protection.


5. Food Preservation: Making Food Last Longer

For centuries, people have found clever ways to stop food from spoiling. This is food preservation. The goal is to create an environment where spoilage micro-organisms can't grow or survive.

Why Preserve Food? (Purposes)

  • To prevent waste and save surplus food.
  • To enjoy seasonal foods all year round.
  • To make food safe to eat for longer.
  • For convenience (e.g., canned soup).

The Principles of Preservation

Think of this as making your food a very unwelcoming place for microbes. You can do this by:

  1. Controlling Temperature: Making it too cold for them to grow (chilling/freezing) or hot enough to kill them (heating).
  2. Removing Moisture: Microbes need water to survive. No water, no growth!
  3. Adding Chemicals: Using natural preservatives like salt, sugar, or acid to make the environment hostile for microbes.

Common Preservation Methods

Based on Temperature Control:
  • Chilling & Freezing: Slows down the growth of microbes. Freezing stops them almost completely.
  • Pasteurisation: Heating liquids to a specific temperature (e.g., 72°C for 15 seconds for milk) to kill most harmful bacteria.
  • Sterilisation & Canning: Heating food to a very high temperature (above 100°C) to kill ALL microbes and their spores, then sealing it in an airtight can or jar.
Based on Moisture Removal:
  • Drying: Removing water from food. (e.g., dried fruit, beef jerky).
Based on Adding Chemicals:
  • Adding Sugar: High sugar concentrations draw water out of microbes, killing them. (e.g., making jam).
  • Adding Salt: Works just like sugar by drawing out water. (e.g., curing meat).
  • Adding Acid (Pickling): Most microbes cannot survive in a highly acidic environment. (e.g., pickled cucumbers using vinegar).
Other Modern Methods:
  • Irradiation: Using ionising radiation to kill bacteria without significantly raising the food's temperature.
Key Takeaway

Food preservation is a practical application of science. By controlling temperature, moisture, and acidity, we can safely extend the life of our food, reducing waste and increasing availability.