Preparation and Cooking of Food

Welcome to the Science of Cooking!

Ever wondered why a raw egg turns solid when heated, or why rice grows bigger when boiled? Cooking is more than just making food taste good—it is actually a fascinating scientific process. In these notes, we will explore why we cook food and how different ingredients (like meat, vegetables, and cereals) change when we prepare them. Let’s dive in!

1. Why do we bother cooking food?

Cooking isn't just about making things hot. There are four main reasons why we put our food through the heat:

A. To make food safe to eat
Raw foods, especially meat and poultry, can carry harmful bacteria (microbes). High temperatures kill these germs, preventing food poisoning.

B. To make food easier to digest
Heat breaks down tough fibers in vegetables and softens starches in cereals (like rice). This makes it easier for our bodies to absorb the nutrients.

C. To keep food for longer (Preservation)
Cooking destroys enzymes and bacteria that cause food to rot, helping it stay fresh for a longer time.

D. To make food more enjoyable
Think of the smell of freshly baked bread! Cooking improves the aroma, flavor, color, and texture of food.

Quick Review Box:
To remember the reasons for cooking, think of the word S.D.P.E.
S - Safety (kills bacteria)
D - Digestibility (easier to eat)
P - Preservation (lasts longer)
E - Enjoyment (better taste/smell)

2. Preparing and Cooking Different Foods

Different types of food react differently to heat. Here is a guide to the most common food groups you need to know for your exam.

(i) & (ii) Meat and Poultry

Nutrients: High in High Biological Value (HBV) protein, iron, and B vitamins.
Uses: Main course (roasting, stewing, frying).
Effects of Cooking:
- Proteins denature and coagulate (the meat firms up).
- Connective tissues (collagen) soften into gelatine, making the meat tender.
- Fat melts, adding flavor.
- The color changes (e.g., red beef turns brown).

(iii) Seafood

Nutrients: High in protein, iodine, and some have healthy Omega-3 fats.
Uses: Steaming, grilling, or in soups.
Effects of Cooking:
- Seafood has very little connective tissue, so it cooks very quickly.
- Overcooking makes seafood (like squid or prawns) tough and rubbery.

(iv) Eggs

Nutrients: HBV protein, Vitamin A, D, and iron.
Uses: Binding (holding burgers together), thickening (custards), or aerating (cakes).
Effects of Cooking:
- Egg whites begin to set (coagulate) at \(60^{\circ}C\).
- Egg yolks set at \(65^{\circ}C\).
- If you cook them too fast or too long, the proteins squeeze out water, making the egg "weep" (this is called syneresis).

(v) Dairy Products (Milk and Cheese)

Nutrients: Calcium, protein, and Vitamin B2 (Riboflavin).
Uses: Sauces, toppings, or drinks.
Effects of Cooking:
- Milk: A "skin" forms on top when heated because the proteins dry out.
- Cheese: Melts when heated but becomes tough and stringy if the heat is too high.

(vi) Cereals (Rice, Wheat, Oats)

Nutrients: High in Starch (Complex Carbohydrates) and B vitamins.
Uses: Staple foods like porridge, rice, and pasta.
Effects of Cooking:
- Starch grains absorb water, swell, and eventually burst. This makes the liquid thicken. This process is called gelatinisation.
- Think of it like a sponge soaking up water until it's soft and full!

(vii) & (viii) Fruits and Vegetables

Nutrients: High in vitamins (C and A), minerals, and dietary fibre.
Uses: Salads, sides, or desserts.
Effects of Cooking:
- Softening: Heat breaks down the cell walls (cellulose), making them softer.
- Vitamin Loss: Water-soluble vitamins (B and C) can be destroyed by heat or leak out into the cooking water.
- Pro-tip: Steam your veggies instead of boiling them to keep the vitamins inside!

(ix) Pulses and Legumes (Beans, Lentils, Peas)

Nutrients: Plant-based protein (Low Biological Value), minerals, and fibre.
Uses: Meat substitutes, dals, or stews.
Effects of Cooking:
- Dried pulses must be soaked and boiled thoroughly.
- This softens the tough outer skin and destroys natural toxins found in some raw beans (like red kidney beans).

3. Summary & Key Takeaways

Don't worry if this seems like a lot of information! Just remember these golden rules:

1. Proteins (Meat, Fish, Eggs) usually firm up when cooked (coagulation).
2. Starches (Cereals, Potatoes) soften and swell with water (gelatinisation).
3. Vitamins (especially Vitamin C) are easily lost in high heat or water.
4. Connective tissue in meat needs slow cooking to become tender.

Did you know?
Adding salt to vegetables while boiling can actually speed up the loss of Vitamin C! It's better to add seasoning at the very end.

Common Mistake to Avoid:
Many students think "denaturation" and "coagulation" are the same. Denaturation is the first step (protein structure unfolds), and Coagulation is the second step (the proteins join together to form a solid mass). Think of it like untangling a ball of yarn (denaturing) and then knotting it back together into a sweater (coagulating)!