Enzymes & Signs of Food Spoilage

High-Risk Foods

We classify ready-to-eat foods as high-risk foods if they can cultivate dangerous bacteria from being stored incorrectly.

High-risk foods

Cooked fish, poultry and meat.
Gravies, sauces and stocks.
Shellfish.
Cooked rice.
Dairy products, such as cheese, milk and eggs.

Storing and classifying high-risk foods

These foods contain lots of protein and water.
Because there's a risk of bacteria multiplying rapidly, these foods cannot be kept safely for long (short shelf life).
We don't classify certain uncooked foods as high-risk foods because we don't consume them uncooked. Eggs are a good example.

Identifying 'off' food

Common signs that food is going off include:
- Mould growing - on things like bread.
- A sour smell - for things like yoghurt.
- A slimy texture - for things like chicken.
But sometimes there are no signs that food has been spoiled, so we have to be careful.

Identifying spoil-free food

Common signs include:
- Fresh meat - smelling fresh, feeling firm and appearing bright.
- Fresh fish - smelling clean or a little salty, with red-coloured gills, shiny skin and clear eyes.

Enzymes

Enzymes are biological catalysts that increase the rate of chemical reactions. They are proteins that cause fruits to either ripen or brown.

Ripening

Fruits ripen because of the enzymes they contain.
Ripeness determines a fruit's colour, texture and sweetness.
Enzymes in bananas cause them to soften and sweeten by breaking down the starch they contain.

Browning

Slicing fruits and vegetables like pears and potatoes expose their insides to oxygen. The oxygen causes the fruit to brown and the enzymes in the fruit make this process happen faster.
Fruits also start to brown as they start to overripen.

Contolling enzyme activity

Enzymes function best at an optimal pH. So, introducing an acid can stop enzymes from working properly.
- E.g. pouring orange or lemon juice (acidic) over fruits will stop the fruits browning.
Enzymes ripen vegetables, causing them to gradually lose flavour, nutrients, colour and texture. Although freezing vegetables will slow enzyme activity, it won't end enzyme activity. Therefore, we must blanch foods to kill ripening enzymes and make sure vegetables are suitably colourful and nutritious for freezing.

1Food Preparation Skills

1.1Food Preparation Skills

1.1.1General Practical Skills

1.1.2Knife Skills

1.1.3Preparing Fruit, Vegetables & Using Equipment

1.1.4Cooking Methods: Prepare, Shape & Combine

1.1.5Sauce Making, Tenderising & Marinating

1.1.6Dough & Pastry

1.1.7Shaping & Finishing Dough

1.1.8Raising Agents & Mixtures

1.1.9End of Topic Test - Food Preparation Skills 1

2Food, Nutrition & Health

2.1Macronutrients

2.1.1Proteins

2.1.2Proteins 2

2.1.3Fats

2.1.4Carbohydrates

2.1.5Carbohydrates 2

2.2Micronutrients

2.2.1Fat-Soluble Vitamins

2.2.2Water-Soluble Vitamins

2.2.3Minerals & Water

2.2.4Minerals & Water 2

2.2.5End of Topic Test - Macro & Micronutrients

2.3Nutritional Needs & Health

2.3.1Informed Choices for a Balanced Diet

2.3.2Informed Choices for a Balanced Diet 2

2.3.3Energy Needs

2.3.4Nutritional Analysis

2.3.5Diet Modifications

2.3.6Diet-Related Problems

2.3.7Diet-Related Problems 2

2.3.8End of Topic Test - Nutritional Needs & Health

3Food Science

3.1Cooking of Food & Heat Transfer

3.1.1Reasons for Cooking & Heat Transfer

3.1.2Water-Based Cooking Methods

3.1.3Fat-Based Cooking Methods

3.1.4Dry Cooking Methods

3.1.5Dry Cooking Methods 2

3.2Functional & Chemical Properties of Food

3.2.1Proteins & Carbohydrates

3.2.2Fats & Oils

3.2.3Raising Agents

3.2.4End of Topic Test - Food Science

4Food Safety

4.1Food Spoilage & Contamination

4.1.1Microorganisms & Signs of Food Spoilage

4.1.2Enzymes & Signs of Food Spoilage

4.1.3Food Poisoning

4.1.4Bacterial Contamination

4.1.5Microorganisms in Food Production

4.2Principles of Food Safety

4.2.1Temperature Control

4.2.2Ambient Foods & Food Labels

4.2.3Preparing, Cooking & Serving Food

4.2.4End of Topic Test - Food Safety

5Food Choice

5.1Factors Affecting Food Choice

5.1.1Factors Which Influence Food Choice

5.1.2Food Choices

5.1.3Religious Food Choices

5.1.4Food Labels

5.1.5Mandatory Food Labels

5.1.6Optional Food Labels

5.1.7Marketing Influences

5.1.8End of Topic Test - Food Choice

5.2British & International Cuisines

5.2.1British Cuisine

5.2.2Japanese Cuisine

5.2.3Japanese Ingredients & Dishes

5.2.4Spanish Cuisine

5.2.5Spanish Ingredients & Dishes

5.3Sensory Evaluation

5.3.1Taste Receptors & Olfactory Systems

5.3.2Sensory Testing Methods

5.3.3Sensory Testing Methods 2

5.3.4End of Topic Test - Cuisines & Senses

6Food Provenance

6.1Environmental Impact & Sustainability of Food

6.1.1Food Sources - Intensive & Organic Farming

6.1.2Food Sources - Genetically Modified Crops

6.1.3Food Sources - Reared Food

6.1.4Food Sources - Caught Food

6.1.5Food & The Environment

6.1.6Food & The Environment 2

6.1.7Sustainability of Food

6.1.8Sustainability of Food 2

6.1.9End of Topic Test - Environmental Impacts

6.2Food Processing & Production

6.2.1Primary Food Processing

6.2.2Primary Food Processing 2

6.2.3Secondary Food Processing

6.2.4Fortification

6.2.5Additives

6.2.6End of Topic Test - Food Processing & Production

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