Ingredients added in small quantities during processing for specific purposes: preventing chemical and microbial spoilage, enhancing flavour or colour, improving nutritional value, or aiding manufacture. The major classes include preservatives, colourings, sweeteners, flavourings, emulsifiers, thickeners and stabilisers — from ancient salt and vinegar to modern ascorbates and steviol glycosides. Each permitted additive carries an identity number, such as an E number in Europe, and a regulated maximum level grounded in toxicological review. The system balances technological need against consumer safety through safety assessment, labelling transparency and periodic re-evaluation.