Food additives and chemical preservatives
Additives are added for a technical purpose, not as food. Textbooks group preservatives as Class I (natural: salt, sugar, vinegar, oil, spices) or Class II (chemical: benzoates, sulphites).
Definitions
A food additive is a substance that is not normally eaten as a food by itself and is not a typical ingredient, but is added on purpose for a technological function (to preserve, colour, flavour, thicken, emulsify and so on) during making, processing, packing or storage (Codex Alimentarius, followed by FSSAI). Contaminants, and nutrients added to fortify food, are not counted as additives. A preservative is a substance that, added to food, prevents or slows fermentation, souring or other decomposition by microbes. On labels, additives are declared by class name with the name or INS number (International Numbering System), e.g. 'Preservative (211)'.
Types and functions of food additives
| Type | Function | Examples (INS) |
|---|---|---|
| Preservatives | Stop or slow microbial spoilage | Sodium benzoate (211), potassium sorbate (202) |
| Antioxidants | Prevent rancidity and browning | BHA (320), BHT (321), TBHQ (319), tocopherols, ascorbic acid (300) |
| Acidity regulators (acidulants) | Adjust pH, add sourness, help preservatives work | Citric acid (330), acetic acid (260), lactic acid (270) |
| Colours | Restore or add colour | Turmeric, caramel, annatto; permitted synthetic colours |
| Flavours and flavour enhancers | Add or strengthen taste and aroma | Vanillin; monosodium glutamate (621) |
| Emulsifiers, stabilisers, thickeners | Give smooth texture; stop separation | Lecithin, pectin, gums, CMC |
| Sweeteners | Sweetness with few or no calories | Saccharin, aspartame, sucralose |
| Others | Anti-caking, keeping moist, raising, firming, binding metals | Anti-caking agents in salt; glycerol (humectant); baking soda; calcium chloride; EDTA |
Class I and Class II preservatives (classic textbook grouping)
| Class | Members | How they are used |
|---|---|---|
| Class I (natural, traditional) | Common salt, sugar, dextrose, glucose syrup, spices, vinegar or acetic acid, honey, edible vegetable oils, wood smoke | The old PFA Rules set no limit on amount; current FSSAI rules have no separate Class I clause, so each food's own standard decides. Pickles, jams, murabba |
| Class II (chemical) | Benzoic acid and its salts (sodium benzoate); sulphurous acid and its salts (sulphur dioxide, potassium metabisulphite); sorbic acid and sorbates; propionates; nitrates and nitrites; nisin and others in the FSSAI list | Allowed only in the foods FSSAI lists, each up to a maximum level (mg/kg); check the current regulation for the number |
Common chemical preservatives
| Preservative (INS) | Acts best against | Typical uses | Notes |
|---|---|---|---|
| Sulphur dioxide / potassium metabisulphite, KMS (220 / 224) | Moulds and bacteria more than yeasts | Light-coloured squashes, juices, dried fruits | Also an antioxidant that stops browning; bleaches anthocyanins; corrodes tin cans; destroys thiamine; can trigger asthma in sensitive people |
| Benzoic acid / sodium benzoate (210 / 211) | Yeasts more than moulds; best below about pH 4.5 | Coloured squashes, ketchup, pickles, soft drinks | Active as undissociated benzoic acid; the body excretes it as hippuric acid |
| Sorbic acid / potassium sorbate (200 / 202) | Moulds and yeasts | Cheese, bakery, jams, beverages | Works up to a higher pH than benzoate; little taste |
| Sodium / calcium propionate (281 / 282) | Moulds and rope bacteria | Bread and bakery | Occurs naturally in Swiss cheese |
| Sodium nitrite / nitrate (250 / 251) | Clostridium botulinum | Cured meats: ham, bacon, sausages | Fixes pink colour; can form nitrosamines |
| Nisin (234) | Gram-positive bacteria and spore-formers | Processed cheese, some canned foods | A natural bacteriocin made by Lactococcus lactis |
Safety aspects and permissible limits
- An additive must be technologically needed, safe at its use level, and never used to hide damage, poor quality or bad practice, or to mislead the buyer.
- ADI (acceptable daily intake): the amount per kg of body weight that can be eaten every day for life without appreciable risk. It is set by JECFA (the Joint FAO/WHO Expert Committee on Food Additives), usually as the no-effect level in animal studies divided by a safety factor of 100.
- Permissible limits: FSSAI's food-additive regulations list, for each food category (squash, jam, ketchup, pickles, dehydrated vegetables and so on), which preservatives are allowed and the maximum amount in mg/kg (ppm). Limits differ by product and are revised, so always check the current FSSAI table; this course does not give the numbers.
- Use the lowest amount that works (good manufacturing practice) and declare it on the label.
- KMS arithmetic: in theory KMS releases about 57.6% of its weight as SO2 (2 × 64.07 ÷ 222.3); practical manuals take about half as available.
- Known concerns: sulphites can trigger asthma; nitrites can form cancer-causing nitrosamines; benzoate with ascorbic acid can form traces of benzene; some colours and MSG upset sensitive people. Additives are generally kept out of infant foods.
A dietitian should read the additive list on labels: sulphites can set off asthma, MSG and some colours trouble sensitive people, and foods with many additives are often also high in salt, sugar and fat. Home-made pickles and jams use only Class I preservatives.
2 marks: “What are Class I and Class II preservatives? Give examples.” Class I are natural, traditional agents such as salt, sugar, vinegar, spices, honey and oil; Class II are chemicals such as sodium benzoate and KMS, allowed only in listed foods within FSSAI limits.
5 marks: “Write a note on sulphur dioxide and sodium benzoate as preservatives.” Source (KMS, sodium benzoate); action and best pH; target microbes; uses (light vs coloured juices); limits (bleaching, can corrosion, thiamine loss; benzene with ascorbic acid); used within FSSAI limits.
10 marks: “Define food additives. Explain their types, functions and safety aspects.” Definition; table of types with function and examples; Class I and II preservatives; ADI, JECFA, FSSAI limits and labelling; possible health concerns.
Class I = kitchen shelf (salt, sugar, vinegar, oil, spices, honey). Class II = chemistry lab (benzoate, sulphite, sorbate, propionate, nitrite).