Food additives

Food Science and Technology (B.Sc) · Food science · free study notes for exams, placements and interviews

In short

A food additive is any substance deliberately added to food in small quantities to improve its keeping quality, texture, colour, flavour or nutritive value, without being consumed as a food by itself. Additives make modern processed food possible — bread stays soft, oil does not go rancid, ice cream stays smooth, jam sets — but each one is permitted only up to a legally fixed limit in named food categories. In India they are governed by the Food Safety and Standards Act, 2006 and the FSS (Food Products Standards and Food Additives) Regulations, 2011, with FSSAI as the regulator and the Codex GSFA/INS numbering system as the international reference. The topic is examined in B.Sc. Food Science, food technology entrance and GATE-XL/Food Technology papers, and is the single most-asked area in QA/QC, R&D and regulatory-affairs interviews at Indian food companies.

Explained

Definition, classification and numbering

Legal definition (FSS Act, 2006): a substance not normally consumed as a food by itself and not normally used as a typical ingredient of food, added intentionally for a technological purpose in manufacture, processing, packing or storage, and which becomes a component of the food. Nutrients added for fortification and processing aids are handled separately.
Not additives: processing aids (filter aids, enzymes used and then removed/inactivated, release agents), contaminants (pesticide residues, heavy metals), and incidental migrants from packaging.
Intentional vs incidental: intentional additives are added knowingly for a function; incidental additives enter unintentionally (tin from cans, lubricants) and are controlled as contaminants.
INS numbers: the International Numbering System of Codex Alimentarius gives each additive a number — e.g. INS 102 tartrazine, INS 211 sodium benzoate, INS 300 ascorbic acid, INS 322 lecithin, INS 621 monosodium glutamate. In the EU the same number is prefixed "E"; Indian labels use INS numbers (the FSSAI Labelling and Display Regulations, 2020 require the class name plus the additive's name or INS number).
Functional classes commonly examined: preservatives (antimicrobial), antioxidants, emulsifiers, stabilisers and thickeners, colours, flavours and flavour enhancers, sweeteners, acidulants and buffering agents, anticaking agents, humectants, leavening/raising agents, firming agents, flour treatment agents, sequestrants/chelating agents, clarifying agents, glazing agents, propellants and packaging gases, enzymes.

Preservatives and antimicrobial agents

Class I preservatives (FSSAI): common household substances allowed without quantitative limit — common salt, sugar, dextrose, spices, vinegar or acetic acid, honey, edible vegetable oils, wood smoke. Chemical preservation by Class I substances relies on lowering water activity or pH.
Class II preservatives: specified chemicals permitted only in named foods at stated maximum levels. Key families:
- Benzoates (benzoic acid, sodium benzoate INS 211) — active as undissociated benzoic acid, so effective only below about pH 4.5; used in squashes, sauces, pickles. Typical FSSAI limits are of the order of 120–750 mg/kg depending on the product — always quote the current Regulations table rather than a remembered figure.
- Sorbates (sorbic acid, potassium sorbate INS 202) — effective up to about pH 6.5, strongest against yeasts and moulds; used in cheese, bread, bakery fillings, fruit juices.
- Sulphites (SO₂, sodium metabisulphite INS 223) — antimicrobial plus antioxidant and anti-browning; used in dried fruit, fruit pulp, sugar, maida (limited), wines. Must be declared on the label; a known trigger for asthmatics, and sulphites destroy thiamine.
- Nitrite and nitrate (INS 250/251) — cure meats, develop the pink nitrosomyoglobin colour and specifically inhibit *Clostridium botulinum*; limits are low (tens of mg/kg, expressed as residual nitrite) because nitrites can form nitrosamines on high-temperature cooking. Ascorbate is added as a nitrosamine blocker.
- Propionates (calcium propionate INS 282) — mould and rope (*Bacillus subtilis*) inhibitor in bread; does not interfere with yeast at use levels.
- Natamycin and nisin — microbial-origin preservatives for cheese surface and canned/heat-treated products respectively.
Mechanism: weak-acid preservatives cross the cell membrane in the undissociated form, dissociate inside at near-neutral cytoplasmic pH, acidify the cytoplasm and drain energy from proton pumping — hence the strong pH dependence given by the Henderson–Hasselbalch relation.
Only one Class II preservative is generally allowed in a food unless the Regulations specifically permit a combination; mixing permitted preservatives arbitrarily is a violation.

Antioxidants, sequestrants and acidity regulators

Why: fats and oils undergo autoxidation — initiation (free radical R•), propagation (R• + O₂ → ROO•; ROO• + RH → ROOH + R•), termination. Hydroperoxides break down to aldehydes and ketones giving rancid odour.
Primary (chain-breaking) antioxidants: donate hydrogen to the peroxy radical — BHA (INS 320), BHT (INS 321), TBHQ (INS 319), propyl/octyl/dodecyl gallate (INS 310–312), tocopherols (INS 307), ascorbyl palmitate. Permitted at low levels — typically 100–200 mg/kg of fat in India; TBHQ is the usual choice for Indian frying oils and snacks because of its stability at frying temperature.
Secondary antioxidants/synergists: citric acid, ascorbic acid, EDTA, phosphates, tartrates act as oxygen scavengers or sequestrants, chelating pro-oxidant trace metals (Cu²⁺, Fe³⁺).
Carry-through: BHA survives baking/frying into the finished product; BHT and gallates are less stable; gallates discolour with iron.
Acidulants and buffers: citric (INS 330), malic, tartaric, lactic, acetic, phosphoric, fumaric acids control pH for setting pectin gels, flavour tartness, microbial safety (acidified foods to pH < 4.6) and colour retention. Buffer salts (sodium citrate, phosphates) hold pH in processed cheese and beverages.
Anti-browning: sulphites and ascorbic acid prevent enzymatic browning (polyphenol oxidase) in cut fruit and potato; ascorbic acid reduces o-quinones back to phenols.

Emulsifiers, stabilisers, thickeners and texture agents

Emulsifier: a surface-active molecule with a hydrophilic head and lipophilic tail that lowers interfacial tension and stabilises an oil-in-water (milk, mayonnaise) or water-in-oil (butter, margarine) emulsion. Examples — lecithin (INS 322, from soy), mono- and diglycerides (INS 471), DATEM (INS 472e), polysorbates (INS 432–436), SSL/CSL (INS 481/482), polyglycerol esters (INS 475).
HLB (hydrophilic–lipophilic balance): a 0–20 scale; HLB 3–6 favours w/o emulsions, 8–18 favours o/w; HLB 13–15 suits detergency/solubilisation. Blends are designed by averaging HLB on a weight basis.
Stabilisers and thickeners (hydrocolloids): increase viscosity or form gels and so slow creaming, sedimentation and ice-crystal growth — guar gum (INS 412), locust bean gum (410), xanthan (415), carrageenan (407), alginates (401–405), pectin (440), CMC (466), gelatin, starches and modified starches (INS 1400 series). Guar and xanthan are workhorses in Indian ice cream, ketchup and bakery.
Pectin gelation: high-methoxyl pectin (DE > 50%) needs sugar above about 55–65% and pH 2.8–3.5 (hydrogen bonding and hydrophobic interaction); low-methoxyl pectin gels with Ca²⁺ and little sugar — the basis of low-sugar jams.
Other texture agents: firming agents (calcium chloride in canned vegetables, alum in pickles), anticaking agents (silicon dioxide INS 551, tricalcium phosphate, magnesium carbonate in salt and powders), humectants (glycerol, sorbitol, propylene glycol — hold moisture, lower water activity), raising agents (sodium bicarbonate with acid salts such as SAPP, MCP, SALP; ammonium bicarbonate in biscuits), flour treatment agents (ascorbic acid as an oxidising improver; potassium bromate was banned in India in 2016 by FSSAI, while potassium iodate remains permitted as a bread improver), dough conditioners and anti-foaming agents (silicone in frying oil).

Colours, flavours and sweeteners

Permitted synthetic colours in India — eight only: tartrazine (INS 102), sunset yellow FCF (110), carmoisine (122), erythrosine (127), ponceau 4R (124), brilliant blue FCF (133), indigo carmine (132), fast green FCF (143). The general limit is 100 mg/kg of the finished food for most products (200 mg/kg for a few categories), and blends must stay within the overall limit.
Natural colours: annatto/bixin, curcumin, chlorophyll, caramel, carotenes, beet red, anthocyanins, cochineal/carmine, paprika oleoresin, iron oxides (limited).
Not permitted: colouring of staple foods — a food cannot be coloured unless the Regulations allow it for that product; non-permitted colours such as metanil yellow, rhodamine B, malachite green, Sudan dyes and lead chromate in turmeric are common adulterants and are offences (unsafe food) under the FSS Act with severe penalties.
Flavours: classified by FSSAI as natural flavouring substances, nature-identical flavouring substances and artificial flavouring substances; flavours are exempt from INS numbering and are declared by class on the label, with artificial flavours requiring a specific declaration. Diacetyl (a diketone), vanillin and benzaldehyde (aldehydes) and ethyl butyrate (an ester) are typical flavouring substances used.
Flavour enhancers: MSG (INS 621), disodium inosinate (631) and guanylate (627) — umami, strongly synergistic with glutamate; FSSAI requires the declaration "not recommended for infants below 12 months" and MSG is not permitted in foods for infants or in certain standardised products.
Sweeteners (high-intensity, non-nutritive): saccharin (INS 954), aspartame (951, must carry "contains a source of phenylalanine" — unsuitable for phenylketonurics and not heat-stable), acesulfame-K (950), sucralose (955), neotame (961), steviol glycosides (960), and polyols/bulk sweeteners (sorbitol, mannitol, maltitol, xylitol — laxative above about 20 g/day, non-cariogenic, lower calorie). Relative sweetness: sucrose 1, saccharin ~300, aspartame ~200, sucralose ~600, neotame ~7,000–13,000, steviol glycosides ~200–300.
Table-top sweetener packs and foods with added sweeteners carry mandatory statutory warnings.

Safety evaluation and Indian regulation

Toxicological testing: acute (LD₅₀), short-term (90-day), long-term/chronic and carcinogenicity, reproductive and teratogenicity, mutagenicity (Ames), metabolism and ADME studies, usually in two species.
NOAEL → ADI: JECFA (the FAO/WHO Joint Expert Committee on Food Additives) sets the Acceptable Daily Intake in mg per kg body weight per day by dividing the NOAEL (no-observed-adverse-effect level) by a safety factor of 100 (10× animal-to-human × 10× human variability). "ADI not specified" means the additive is of such low concern that no numerical limit is needed.
GRAS: the US FDA's "generally recognised as safe" list; Codex GSFA (General Standard for Food Additives) is the global reference table of additive/food-category/limit combinations that FSSAI largely harmonises with.
Indian framework:
- Food Safety and Standards Act, 2006 — single law replacing the PFA Act, 1954; FSSAI is the regulator; defines unsafe, misbranded and sub-standard food.
- FSS (Food Products Standards and Food Additives) Regulations, 2011 — the operative additive tables, amended frequently; additives are listed by food category with maximum permitted levels, and an additive not listed for a category is not permitted in it (positive-list approach).
- FSS (Labelling and Display) Regulations, 2020 — class name plus name/INS number, allergen declaration, the green/brown veg–non-veg mark, and mandatory warnings for MSG, aspartame, caffeine and added sweeteners.
- FSS (Approval of Non-Specified Food and Food Ingredients) Regulations, 2017 — route for a new additive not already permitted.
- Other relevant: FSS (Contaminants, Toxins and Residues) Regulations, 2011, FSS (Fortification of Foods) Regulations, 2018 (+F logo), Legal Metrology (Packaged Commodities) Rules, 2011 for declarations.
- GST on most processed/packaged foods falls in the 5% or 18% slabs under the structure effective 22 September 2025; additives and premixes are taxed as chemicals/food preparations per their HSN.
Quality specifications: additive-grade purity is specified by JECFA monographs / FCC and, in India, by the Regulations' own purity criteria; relevant BIS standards exist for substances such as food-grade common salt, sodium bicarbonate and citric acid — quote an IS number only after checking the current edition, as many have been revised or withdrawn.
Misuse and enforcement: excess or non-permitted additive use attracts penalties under the FSS Act — monetary penalties for sub-standard and misbranded food and imprisonment for unsafe food; FSSAI's surveillance surveys and state food-safety officers draw samples tested by notified labs.

Key points

Food additive - intentionally added, non-food substance serving a technological function and remaining in the food.
Processing aid - used during processing but removed or inactivated, so not an additive.
INS number - Codex International Numbering System code for an additive; "E" prefix is the EU form of the same number.
Class I preservative - salt, sugar, vinegar, spices, honey, edible oil, wood smoke; no quantitative limit.
Class II preservative - specified chemicals (benzoates, sorbates, sulphites, nitrites, propionates) with food-wise maximum limits; normally only one per food.
Weak-acid preservative action - effective only below its pKa-linked pH range; benzoate needs pH < 4.5, sorbate works to about pH 6.5.
Nitrite - cures meat colour and is the only practical inhibitor of *C. botulinum*; risk is nitrosamine formation, countered by ascorbate.
Primary antioxidant - donates H to peroxy radicals (BHA, BHT, TBHQ, gallates, tocopherols); synergist/sequestrant chelates pro-oxidant metals (citric acid, EDTA).
HLB - 0–20 scale for emulsifiers; low HLB → w/o, high HLB → o/w emulsions.
Hydrocolloid stabiliser - raises viscosity or gels to prevent creaming, syneresis and ice-crystal growth (guar, xanthan, carrageenan, CMC, pectin).
HM vs LM pectin - HM needs high sugar and low pH; LM gels with calcium, enabling low-sugar jams.
Eight synthetic colours permitted in India, generally at 100 mg/kg of finished food; staple foods may not be coloured.
Non-permitted colours - metanil yellow, rhodamine B, malachite green; their use makes the food unsafe under the FSS Act.
MSG and 5'-ribonucleotides - umami enhancers, strongly synergistic; mandatory infant-feeding declaration.
Aspartame - ~200× sucrose, heat-labile, needs a phenylalanine source declaration.
ADI = NOAEL ÷ 100 - safety factor 100 = 10 (species) × 10 (individual variation); set by JECFA.
Positive list - if an additive is not listed for that food category in the 2011 Regulations, it is not allowed.
Potassium bromate - banned as a flour treatment agent in India since 2016.

Formulas and examples

Water activity a_w = p/p₀ = ERH/100 — p = vapour pressure of water in food, p₀ = that of pure water at the same temperature; dimensionless, 0–1.
Raoult's law (ideal solute): a_w = n_w/(n_w + n_s) — n_w = moles of water, n_s = moles of solute.
Henderson–Hasselbalch: pH = pKa + log₁₀([A⁻]/[HA]); undissociated fraction = 1/(1 + 10^{pH − pKa}) — gives the active share of a weak-acid preservative.
Additive dosing: mass of additive = (permitted level in mg/kg × batch mass in kg) ÷ 1000, in grams.
ADI (mg/kg bw/day) = NOAEL ÷ safety factor (usually 100); allowable intake = ADI × body mass (kg).
Blend HLB = Σ(wᵢ × HLBᵢ)/Σwᵢ — wᵢ = weight fraction of emulsifier i.
Peroxide value (meq O₂/kg) = (V_s − V_b) × N × 1000 / W — V in mL thiosulphate, N = normality, W = sample mass in g.

1. Preservative dosing in a squash batch. A fruit squash is to be preserved with sodium benzoate at the permitted level of 600 mg/kg. Batch = 250 kg.

Mass needed = 600 × 250 / 1000 = 150 g of sodium benzoate.
Dissolve in a little warm water and add at the end of boiling; a 150 g charge in 250 kg is 0.06% w/w.

2. Active fraction of benzoic acid versus pH. pKa of benzoic acid = 4.20. Undissociated fraction = 1/(1 + 10^{pH − 4.20}).

At pH 3.0: 10^−1.2 = 0.0631 → fraction = 1/1.0631 = 0.941 (94.1% active).
At pH 4.2: 10⁰ = 1 → fraction = 1/2 = 0.500 (50%).
At pH 6.0: 10^1.8 = 63.1 → fraction = 1/64.1 = 0.0156 (1.56%).
At pH 6.0 roughly 60 times less of the dose is in the active form than at pH 3.0 — which is why benzoate is useless in near-neutral foods and sorbate (pKa 4.76, used up to pH 6.5) is chosen instead.

3. ADI and actual intake of a sweetener. Aspartame ADI = 40 mg/kg body weight/day. A 60 kg adult drinks 2 cans of diet cola per day; each 300 mL can contains 180 mg aspartame.

Allowable intake = 40 × 60 = 2,400 mg/day.
Actual intake = 2 × 180 = 360 mg/day → 15% of the ADI.
Cans needed to reach the ADI = 2,400/180 = 13.3 cans/day — the margin is large, which is the point of the safety factor.

4. NOAEL to ADI. A 90-day and chronic study set the NOAEL of a new antioxidant at 250 mg/kg bw/day in rats.

ADI = 250/100 = 2.5 mg/kg bw/day.
For a 25 kg child, allowable = 2.5 × 25 = 62.5 mg/day.
If the additive is used at 200 mg/kg in a snack, the child reaches the ADI at 62.5/200 × 1000 = 312.5 g of snack per day.

5. Emulsifier blend HLB. Required HLB for an o/w salad dressing = 11.0. Available: Tween 80 (HLB 15.0) and Span 80 (HLB 4.3).

Let x = weight fraction of Tween 80: 15.0x + 4.3(1 − x) = 11.0 → 10.7x = 6.7 → x = 0.626.
For a 2.0 kg emulsifier charge: Tween 80 = 1.253 kg, Span 80 = 0.747 kg.
Check: 0.626 × 15.0 + 0.374 × 4.3 = 9.39 + 1.61 = 11.0 ✓

Preservative	INS	Effective pH	Chiefly inhibits	Typical Indian use
Sodium benzoate	211	< 4.5	Yeasts, bacteria	Squashes, sauces, pickles
Potassium sorbate	202	up to 6.5	Moulds, yeasts	Cheese, bakery, juices
Sodium metabisulphite	223	< 4.5	Bacteria, moulds; also antioxidant	Dried fruit, fruit pulp, wine
Sodium nitrite	250	5.5–6.5	C. botulinum	Cured meats
Calcium propionate	282	< 5.5	Moulds, rope bacilli	Bread

Antioxidant	INS	Heat/fry stability	Note
BHA	320	Good carry-through	Often blended with BHT
BHT	321	Moderate	Volatile; lost in frying
TBHQ	319	Best for frying oils	Common in Indian snack oils
Propyl gallate	310	Poor above 150 °C	Blue-black with iron
Tocopherols	307	Natural, moderate	"Clean label" choice

Where it is used

Beverages and squashes (Dabur, Parle Agro, Coca-Cola India, Hector Beverages): benzoate/sorbate dosing, citric-acid acidification, colour and sweetener blending, label compliance.
Bakery and biscuits (Britannia, Parle, ITC, Modern Foods): calcium propionate, SSL/DATEM dough conditioners, ascorbic acid improver, raising-agent systems — and bromate-free formulations since the 2016 ban.
Dairy and frozen desserts (Amul, Mother Dairy, Hatsun, Vadilal): stabiliser–emulsifier blends (guar, LBG, carrageenan, mono-diglycerides) to control overrun and ice-crystal growth; emulsifying salts in processed cheese.
Edible oils and snacks (Adani Wilmar, Marico, Haldiram's, Bikaji): TBHQ/BHA antioxidant dosing, peroxide-value monitoring, anti-foaming agents in frying.
Job roles: QA/QC chemist, product development and R&D executive, regulatory affairs/labelling specialist, food-safety auditor (FSSAI FoSTaC, HACCP, ISO 22000, BRC), and state Food Safety Officer and notified-lab analyst roles.
Ingredient suppliers and distributors (Roquette, IFF, Givaudan, Sonarome, Keva, Ingredion, local gum houses) employ application technologists who design additive systems to customer specification and within FSSAI limits.

Interview questions

Q: How does a food additive differ from a processing aid? A: An additive performs a function in the finished food and remains in it; a processing aid acts only during manufacture and is removed or inactivated, so it need not be declared as an ingredient.
Q: Why is sodium benzoate ineffective in a neutral product like milk? A: Only the undissociated benzoic acid is antimicrobial, and at pH near 7 almost all of it is ionised — at pH 6.0 only about 1.6% is active, against 94% at pH 3.
Q: What are Class I and Class II preservatives under Indian regulations? A: Class I are common substances such as salt, sugar, vinegar, spices, honey and edible oils with no quantitative limit; Class II are specified chemicals such as benzoates, sorbates and nitrites permitted only in named foods at stated maximum levels, normally one per product.
Q: Why is nitrite still used in cured meat despite the nitrosamine concern? A: It is the only practical agent that both fixes the cured pink colour and reliably inhibits *Clostridium botulinum*; residual levels are kept low and ascorbate is added to block nitrosamine formation.
Q: Which antioxidant would you choose for an oil used in continuous frying, and why? A: TBHQ, because it is the most heat-stable of the permitted phenolic antioxidants and carries through into the fried product, whereas BHT is volatile and gallates degrade and discolour with iron.
Q: What does HLB tell you, and what HLB would you need for mayonnaise? A: HLB ranks an emulsifier's hydrophilic–lipophilic balance on a 0–20 scale; mayonnaise is oil-in-water, so a high-HLB emulsifier system of roughly 9–12 is required, usually achieved by blending.
Q: How is an ADI established? A: JECFA takes the NOAEL from animal toxicity studies and divides by a safety factor of 100 (10× for species difference and 10× for human variability) to give mg per kg body weight per day.
Q: How many synthetic colours are permitted in India and at what general level? A: Eight — tartrazine, sunset yellow FCF, carmoisine, erythrosine, ponceau 4R, brilliant blue FCF, indigo carmine and fast green FCF — generally up to 100 mg/kg of the finished food, and only in food categories where colouring is allowed.
Q: A supplier offers a cheap turmeric powder with a very bright colour. What do you suspect and how do you check? A: Possible metanil yellow or lead chromate adulteration; screen with the standard FSSAI rapid tests (HCl spot test for metanil yellow, water-settling test for lead chromate) and confirm by HPLC/AAS at a notified lab.
Q: Why was potassium bromate banned in India? A: FSSAI removed it from the permitted flour treatment agents in 2016 on carcinogenicity concerns after residues were found in bread; ascorbic acid and enzyme-based improvers replaced it.
Q: Which labelling declarations are triggered by additives? A: The functional class name with the additive's name or INS number, "contains a source of phenylalanine" for aspartame, the MSG statement that it is not recommended for infants below 12 months, added-sweetener and caffeine warnings, and allergen declarations where relevant.
Q: If an additive is not listed in the 2011 Regulations for your product category, can you still use it? A: No — India follows a positive list, so it is not permitted; approval must be sought through the FSS (Approval of Non-Specified Food and Food Ingredients) Regulations, 2017.

Common mistakes

Treating "permitted" as "permitted everywhere" — a limit applies to a specific food category, and absence from that category means prohibition.
Quoting benzoate for neutral-pH foods, or omitting the pH condition when explaining weak-acid preservatives.
Confusing primary antioxidants (radical scavengers) with synergists/sequestrants (metal chelators), or calling citric acid a preservative.
Mixing up mg/kg of finished food with mg/kg of fat basis for antioxidants, and losing the factor of 1000 when converting mg/kg to g per batch.
Writing ADI as a per-day absolute amount instead of per kg body weight per day, or forgetting to apply the safety factor of 100 to the NOAEL.
Calling emulsifiers and stabilisers the same thing — emulsifiers act at the interface, stabilisers act in the continuous phase by raising viscosity or gelling.
Citing the PFA Act, 1954 or outdated INS lists and limits; the FSS Act, 2006 and the frequently amended 2011 Regulations govern, so the current amendment must be checked before any limit is quoted.