Study Notes
Overview
This study guide provides a comprehensive analysis of food additives, a core component of the OCR J309 GCSE specification. Understanding additives is not merely about listing E-numbers; it requires a scientific appreciation of their function. Examiners expect candidates to explain how these substances modify the properties of food, from extending shelf-life to improving texture and appearance. This guide will break down the four principal categories of additives: preservatives, antioxidants, emulsifiers, and stabilisers. We will explore their chemical mechanisms, provide specific examples (both natural and artificial) that you must memorise, and analyse the technological benefits versus consumer health concerns. By engaging with the content, worked examples, and exam tips provided, you will be equipped to answer questions with the precision and analytical depth required to achieve the highest marks.
The Four Key Types of Food Additives
Examiners require you to be able to distinguish clearly between the four main functional groups of additives. Credit is awarded for using precise scientific language to describe their purpose.
1. Preservatives
Function: To inhibit the growth of pathogenic microorganisms such as bacteria, yeasts, and moulds, thereby extending the shelf-life of food and preventing foodborne illness.
Mechanism: Preservatives work by creating an environment that is hostile to microbial life. This can be through various means, such as altering the pH of the food or interfering with the microbe's cell membrane or enzymes.
Specific Knowledge: You must be able to name both natural and artificial examples.
- Natural: Salt (sodium chloride) used in curing meats like bacon; Vinegar (acetic acid) used in pickling.
- Artificial: Sodium Benzoate (E211) found in acidic foods like soft drinks and jams; Sulphites (E220-E228) used in wine and dried fruits to prevent microbial spoilage.
2. Antioxidants
Function: To prevent the chemical process of oxidation, which causes fats and oils to become rancid and cut fruit surfaces to brown.
Mechanism: Antioxidants are substances that are easily oxidised themselves. They 'sacrifice' themselves to react with oxygen before it can damage the food components. This is a crucial distinction from preservatives; antioxidants prevent chemical spoilage, not microbial spoilage.
Specific Knowledge:
- Natural: Ascorbic Acid (Vitamin C, E300) is added to fruit juices and cut fruits to prevent enzymatic browning. Tocopherols (Vitamin E, E306-E309) are added to fatty products.
- Artificial: Butylated Hydroxyanisole (BHA, E320) and Butylated Hydroxytoluene (BHT, E321) are used in products containing fats, such as cereals, chewing gum, and vegetable oils.
3. Emulsifiers
Function: To enable the mixing of two immiscible liquids, such as oil and water, to form a stable mixture called an emulsion.
Mechanism: Emulsifier molecules have a dual structure: a hydrophilic (water-loving) head and a hydrophobic (water-hating/oil-loving) tail. The hydrophobic tail dissolves in the oil droplets, while the hydrophilic head dissolves in the surrounding water, creating a stable bridge between them and preventing them from separating.
Specific Knowledge:
- Natural: Lecithin (E322), found in egg yolk and soya beans, is the classic example used to stabilise mayonnaise.
- Artificial: Mono- and di-glycerides of fatty acids (E471) are widely used in ice cream, margarine, and baked goods to create a smooth, uniform texture.
4. Stabilisers
Function: To help maintain a uniform dispersion of substances in a food. They are used to give food a firm, consistent body and texture, and to prevent the separation of ingredients (like in an emulsion).
Mechanism: Stabilisers are large molecules that form a three-dimensional network within the food, trapping water molecules. This increases the viscosity of the product and provides structural support, preventing ingredients from settling out.
Specific Knowledge:
- Natural: Pectin (E440), extracted from citrus peel and apples, is the gelling agent responsible for setting jam and marmalade. Gelatine, from animal collagen, is used in jellies and mousses.
- Artificial: Xanthan Gum (E415) is used to thicken sauces, salad dressings, and is common in gluten-free products to provide texture.
Natural vs. Artificial Additives
It is a common misconception that all additives are synthetic 'chemicals'. Examiners award credit for recognising that many additives are derived from natural sources. However, you must also be able to evaluate the use of both natural and artificial additives, considering their technological necessity against consumer perceptions and health concerns.
