Food Science & Technology · Product, Health & Industry · also Food Additives, Food Ingredients, Hydrocolloids and Emulsifiers
What each class of additive and ingredient does, how it is chosen and dosed, and how its safety is assessed and regulated: preservatives, antioxidants, emulsifiers, hydrocolloids, colours, sweeteners, flavour enhancers and processing aids.
In the exams: GATE XE-G Section 3 (addition of preservatives and food additives); ICAR AIEEA-PG Code 18 Unit I (food additives); ICAR AICE 35.a Unit 1
Food additives are substances added to food in small amounts for a technological purpose: to preserve it, to stop fats going rancid, to keep emulsions stable, to thicken and gel, to colour, to sweeten, to enhance flavour, to control acidity, to leaven, or to help processing. Together with functional ingredients such as starches, proteins and fibres, they let food technologists make safe, stable, attractive and affordable foods at scale. They are also among the most regulated and most debated components of food, and choosing them well requires knowing both what each one does and how it is controlled.
This subject explains the main classes of additive by function: how each works, which factors such as pH, temperature and other ingredients affect it, how it is chosen and dosed, and what its limitations are. It sets out the international system for naming and numbering additives, the INS numbers of Codex and the E numbers of the European Union, and the principles by which additives are evaluated for safety and permitted. It closes with fat and sugar replacers and with clean-label reformulation, which tries to meet consumer demand for shorter, more familiar ingredient lists without losing safety or quality.
The subject is examined in GATE XE-G Section 3 (addition of preservatives and food additives), ICAR AIEEA-PG Code 18 Unit I (food additives) and ICAR AICE-JRF/SRF 35.a, and in Food Safety Officer and Food Analyst examinations. Examiners ask for definitions, the classes and numbering of additives, mechanisms of preservatives and antioxidants, the effect of pH on weak-acid preservatives, the HLB of emulsifiers, the gelling conditions of pectins, carrageenans and alginates, the relative sweetness of sweeteners, and the distinction between additives and processing aids. Permitted additives and maximum levels differ between countries and change, so this manual names classes and examples and sends the reader to the current law, Codex's General Standard for Food Additives and national regulations such as India's FSS (Food Products Standards and Food Additives) Regulations, for levels. Toxicology of additives is taught in food-toxicology-contaminants-allergens, their legal framework in food-law-regulatory-affairs, and starch and protein chemistry in food-chemistry-major-constituents.
Codex defines a food additive as any substance not normally consumed as a food by itself and not normally used as a typical ingredient of the food, whether or not it has nutritive value, the intentional addition of which to food for a technological purpose in manufacture, processing, preparation, treatment, packing, packaging, transport or holding results, or may reasonably be expected to result, in it or its by-products becoming a component of the food. The definition excludes contaminants and substances added to food for maintaining or improving nutritional qualities, such as vitamins and minerals used in fortification, which are regulated separately.
Three related concepts matter. A processing aid is a substance used in processing for a technological purpose that is not present, or present only as an unavoidable residue without technological function, in the final food; examples are filtration aids, extraction solvents, antifoaming agents in some uses, clarifying agents and many enzymes. Processing aids are generally not declared on labels, though rules vary. Carry-over is the presence of an additive in a food because it was used in an ingredient, such as a preservative in a fruit preparation used in yoghurt; it is allowed if the additive is permitted in the ingredient, its level does not exceed what is justified by the ingredient, and it has no technological function in the final food. Ingredients such as starches, proteins, fibres and fruit concentrates are foods, not additives, unless chemically modified or used purely for a technological function, a line that matters for clean-label products (chapter 12).
Additives are grouped by technological function. Codex lists functional classes that include acidity regulators, anticaking agents, antifoaming agents, antioxidants, bleaching agents, bulking agents, carbonating agents, carriers, colours, colour retention agents, emulsifiers, emulsifying salts, firming agents, flavour enhancers, flour treatment agents, foaming agents, gelling agents, glazing agents, humectants, packaging gases, preservatives, propellants, raising agents, sequestrants, stabilisers, sweeteners and thickeners. One substance may serve several functions: citric acid is an acidity regulator, antioxidant synergist and sequestrant.
The International Numbering System (INS) for food additives, maintained by Codex (CAC/GL 36-1989), gives each additive a number used for identification on labels instead of its long chemical name. The European Union uses the same numbers with the prefix E, applied only to additives approved in the EU. The numbers are grouped broadly by function: the 100s are mainly colours, the 200s preservatives, the 300s antioxidants and acidity regulators, the 400s thickeners, stabilisers, emulsifiers and gelling agents, the 500s acidity regulators, anticaking agents and mineral salts, the 600s flavour enhancers, the 900s glazing agents, gases and sweeteners, and the 1000s other additives including modified starches (1400s). Labels normally state the functional class followed by the specific name or number, for example 'preservative (211)' or 'emulsifier (E322)'. The Codex General Standard for Food Additives (CXS 192-1995) lists additives permitted in each food category with maximum use levels; national lists, such as Appendix A of India's food additive regulations and the EU Union list in Regulation (EC) No 1333/2008, differ and must be checked for each market.
Before an additive is permitted it must be shown to be safe at the proposed levels of use, to have a technological need that cannot reasonably be met by other means, and not to mislead consumers. Internationally, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) evaluates additives using toxicological studies, described in food-toxicology-contaminants-allergens, and establishes an acceptable daily intake (ADI) in mg per kg body weight per day, normally the no-observed-adverse-effect level divided by an uncertainty factor of 100. For substances of very low toxicity whose intake at the levels needed for technological effect poses no health concern, JECFA assigns an ADI 'not specified'. JECFA also prepares specifications of identity and purity, because the safety evaluation applies to a substance of defined composition.
Regional and national authorities make their own decisions. The European Food Safety Authority re-evaluated all additives permitted in the EU before 2009 and continues to review new data, sometimes reaching conclusions that differ from those of JECFA or other authorities, as with titanium dioxide. India's FSSAI Scientific Panel on Food Additives advises on additive standards, generally drawing on Codex and JECFA. In the United States, food additives need FDA approval, while substances generally recognised as safe (GRAS) for their intended use are exempt from the additive approval process.
Permitted levels are set so that intake by consumers, including high consumers and children, stays below the ADI. Maximum levels are expressed in mg per kg of food for each food category. For additives with an ADI 'not specified', use is often allowed at quantum satis, or according to good manufacturing practice (GMP), meaning no numerical limit but only the amount needed to achieve the technological effect, with no use to disguise faulty processing or mislead. Exposure is checked by methods ranging from the conservative budget method, which assumes a fixed share of the diet contains the additive at the maximum level, to refined assessments using actual use levels and consumption surveys. If estimated intake exceeds the ADI for a group, uses or levels are reduced.
Good manufacturing practice for additives means using the lowest level that achieves the effect, using food-grade material meeting specifications, adding it accurately, recording use, and never using additives to hide spoilage, poor hygiene or poor raw materials. A worked check: an additive with an ADI of 5 mg/kg bw/day gives a 20 kg child an acceptable intake of 100 mg per day; if one serving of a drink provides 75 mg, it alone supplies three-quarters of the child's ADI, which is why limits on drinks and foods for children are often stricter. Additive use in infant formula and foods for infants and young children is tightly restricted, because infants' metabolism and exposure differ.
Most chemical preservatives are weak organic acids and their salts. They act mainly in their undissociated form, which is lipid-soluble, crosses the microbial cell membrane, and then dissociates in the near-neutral cytoplasm, releasing protons that the cell must pump out at an energy cost and anions that accumulate and disrupt metabolism. Because the undissociated fraction depends on pH, these preservatives are effective only in acidic foods. By the Henderson-Hasselbalch relationship, the fraction undissociated is 1/(1 + 10^(pH − pKa)): at a pH equal to the pKa, half is undissociated; at one unit above, only about 9 per cent; at one unit below, about 91 per cent.
Benzoic acid and its sodium and potassium salts (INS 210 to 213) have a pKa of about 4.2 and are effective mainly below about pH 4 to 4.5, in soft drinks, fruit juices, pickles, sauces and jams; they act chiefly against yeasts and moulds. Sorbic acid and sorbates (INS 200 to 203) have a pKa of about 4.76, so they remain useful at higher pH, up to about 6 to 6.5, and are widely used against moulds and yeasts in cheese, bakery products, beverages and fruit products; some moulds can degrade sorbate to a compound with a kerosene-like odour. Propionic acid and propionates (INS 280 to 283) are used in bread and bakery products, where they inhibit moulds and rope-forming Bacillus while having little effect on baker's yeast. Acetic acid and lactic acid, as vinegar and in fermented foods, are preservatives as well as flavours. Combinations of preservatives with reduced pH, water activity and heat follow the hurdle principle described in food-microbiology.
Sulphur dioxide and sulphites (INS 220 to 228) inhibit microorganisms, especially bacteria and yeasts in acidic conditions, prevent enzymatic and non-enzymatic browning, and act as antioxidants; they are used in wine, dried fruits, fruit juices and concentrates, and some processed vegetables and seafood. They destroy thiamine, so they are not used in foods that are important sources of it, and they can provoke reactions in some people with asthma, so their presence above 10 mg/kg as SO2 must be declared.
Nitrite and nitrate (INS 249 to 252) are used in cured meats. Nitrite inhibits Clostridium botulinum and some other bacteria, forms nitrosomyoglobin, which gives cured meat its pink colour, and contributes cured flavour and antioxidant protection; nitrate acts after reduction to nitrite by bacteria. Because nitrite can form carcinogenic nitrosamines and causes methaemoglobinaemia at high doses, its levels are strictly limited, and ascorbate or erythorbate is added to inhibit nitrosation.
Natural and biological antimicrobials include nisin (INS 234), a bacteriocin produced by Lactococcus lactis, effective against Gram-positive bacteria and their spores, used in processed cheese, canned foods and some dairy desserts; natamycin (INS 235), an antifungal produced by Streptomyces natalensis, applied to the surfaces of cheese and dry sausages; lysozyme from egg white, used against Clostridium tyrobutyricum in some cheeses; and plant extracts, essential oils, chitosan and fermentates such as cultured dextrose or vinegar, used in clean-label products. Their spectrum, cost, flavour impact and regulatory status vary widely, and permitted uses and levels for all preservatives must be checked in current regulations.
Lipid oxidation, described in food-chemistry-major-constituents, is a free-radical chain reaction that produces rancid flavours, destroys vitamins and essential fatty acids, and shortens shelf life. Antioxidants slow it in two main ways. Primary or chain-breaking antioxidants donate a hydrogen atom to lipid peroxyl radicals, forming a stable antioxidant radical that does not continue the chain; phenolic compounds such as tocopherols, butylated hydroxyanisole and butylated hydroxytoluene act this way. Secondary antioxidants act by other mechanisms: chelating agents such as citric acid, phosphates and EDTA bind iron and copper ions that catalyse peroxide breakdown; oxygen scavengers such as ascorbic acid remove oxygen; and singlet oxygen quenchers such as carotenoids protect against photo-oxidation. Combinations are often more effective than the sum of their parts, a synergy explained by regeneration of primary antioxidants or by chelation of pro-oxidant metals; ascorbyl palmitate with tocopherols, and citric acid with phenolic antioxidants, are classic synergists.
Antioxidants delay but cannot reverse oxidation, so they must be added before oxidation has progressed, ideally to fresh, well-refined oil, and they are not substitutes for good raw materials, low oxygen exposure, protection from light and cool storage. Their effectiveness depends on the food system: in bulk oils, more polar antioxidants such as ascorbyl palmitate and some plant extracts tend to work better, while in emulsions, less polar antioxidants that concentrate at the oil-water interface are often more effective, a pattern described as the polar paradox.
The main synthetic antioxidants are butylated hydroxyanisole (BHA, INS 320), butylated hydroxytoluene (BHT, INS 321), tert-butylhydroquinone (TBHQ, INS 319) and propyl gallate (INS 310). They are effective at low concentrations, cheap and stable. BHA and BHT are relatively volatile and show carry-through, meaning they survive baking and frying to protect the finished product. TBHQ is especially effective in vegetable oils and frying fats; propyl gallate is effective but forms dark complexes with iron and is heat-sensitive. Their permitted uses and levels, and in some cases whether they are permitted at all, differ between jurisdictions.
Natural antioxidants include tocopherols (INS 306 to 309), naturally present in vegetable oils and added as concentrates; ascorbic acid (INS 300) and its salts, and ascorbyl palmitate (INS 304), a fat-soluble ester; rosemary extract (INS 392 in the EU), whose carnosic acid and carnosol are strong antioxidants, used in meat products, oils and snacks; green tea catechins; and other plant extracts. Natural antioxidants are favoured for clean labels, but they are usually more expensive, may add flavour or colour, and are often less effective per gram than synthetic ones, so combinations and higher levels are used. Antioxidant choice is confirmed by accelerated tests such as the Rancimat and by real-time shelf-life studies with peroxide and anisidine values, as described in fats-oils-technology.
Emulsifiers are surface-active molecules with a hydrophilic part and a lipophilic part. They adsorb at oil-water or air-water interfaces, lower interfacial tension so that droplets or bubbles form more easily, and form films that resist coalescence. In foods they also interact with starch and proteins, so they serve as dough strengtheners, crumb softeners and anti-staling agents, and they modify fat crystallisation.
The hydrophilic-lipophilic balance (HLB) scale, introduced by Griffin, rates emulsifiers from about 0 to 20: low HLB values, about 3 to 6, indicate lipophilic emulsifiers that favour water-in-oil emulsions such as margarine; high values, about 8 to 18, indicate hydrophilic emulsifiers that favour oil-in-water emulsions such as dressings and beverages. The HLB of a blend is approximately the weight-averaged HLB of its components: 60 per cent of an emulsifier with HLB 4.3 and 40 per cent of one with HLB 15.0 gives about 0.6 × 4.3 + 0.4 × 15.0 = 8.6. HLB is a guide, not a full description, because emulsifier performance also depends on temperature, the oil phase and interactions.
Important food emulsifiers include lecithin (INS 322), described in fats-oils-technology; mono- and diglycerides of fatty acids (INS 471), the most widely used, in bakery, margarine and ice cream; esters of monoglycerides with acetic, lactic, citric or diacetyl tartaric acids (INS 472a to 472e), of which DATEM (472e) is a strong dough strengthener; sodium and calcium stearoyl lactylates (INS 481, 482); sucrose esters of fatty acids (INS 473); polyglycerol esters (INS 475); polyglycerol polyricinoleate (PGPR, INS 476), which lowers the yield value of chocolate; sorbitan esters (INS 491 to 495), lipophilic; and polysorbates (INS 432 to 436), hydrophilic. Proteins such as caseinates and whey proteins, and gum arabic, are also effective emulsifiers, as natural alternatives.
Stabilisers maintain the physical state of a food, preventing separation of emulsions, sedimentation of particles, syneresis of gels and growth of ice crystals. Most are hydrocolloids, discussed in chapter 6, which work mainly by raising the viscosity of the continuous phase, so that droplets and particles move more slowly according to Stokes' law, or by forming weak gel networks that hold particles in place. In ice cream, stabilisers such as locust bean gum, guar gum and carrageenan bind water, give body and limit ice crystal growth during temperature fluctuations in storage; emulsifiers such as mono- and diglycerides promote partial coalescence of fat globules, giving dryness and stand-up when the mix is frozen.
Emulsifying salts, such as sodium citrates and sodium phosphates, are used in processed cheese. They exchange calcium in the casein network for sodium, making the casein more soluble and able to emulsify the cheese fat when the mixture is heated and sheared, giving a smooth, homogeneous product that melts evenly. Sequestrants such as EDTA and phosphates bind metal ions, improving colour and flavour stability. Firming agents, such as calcium chloride in canned vegetables and fruits, cross-link pectins to keep tissues firm. The choice of emulsifier and stabiliser system is usually made by trials, because interactions among proteins, hydrocolloids, emulsifiers and processing conditions decide the final stability.
Hydrocolloids are hydrophilic polymers, mostly polysaccharides with some proteins, that thicken, gel, stabilise, bind water and control texture at low concentrations. Native and modified starches, described in cereal-science-milling, are the most used and cheapest thickeners. Among the gums, guar gum and locust bean gum are galactomannans from seeds: guar, with a mannose to galactose ratio of about 2:1, dissolves in cold water to give high viscosity; locust bean gum, with about 4:1 and longer unsubstituted regions, needs heating to dissolve and forms gels synergistically with xanthan and κ-carrageenan. Xanthan gum, produced by fermentation with Xanthomonas campestris, gives highly pseudoplastic (shear-thinning) solutions with high viscosity at rest, stable over wide ranges of pH, temperature and salt, ideal for suspending particles in dressings and sauces. Gum arabic, from Acacia trees, gives low viscosity even at high concentrations and is an excellent emulsifier for beverage flavour emulsions and encapsulation. Cellulose derivatives include carboxymethylcellulose, a soluble anionic thickener, and methylcellulose and hydroxypropyl methylcellulose, which unusually form gels on heating and melt on cooling, useful in batters, gluten-free bread and plant-based meat. Other gums include tragacanth, karaya, tara, konjac glucomannan and fenugreek gum.
Pectin, extracted from citrus peel and apple pomace, is a chain of galacturonic acid units, partly esterified with methanol. High-methoxyl pectin, with a degree of esterification above 50 per cent, gels only at high soluble solids, commonly above about 55 per cent sugar, and low pH, about 2.8 to 3.5, as in jams and jellies, through hydrogen bonding and hydrophobic interactions. Low-methoxyl pectin, below 50 per cent esterification, gels with calcium ions across a wider range of sugar and pH, so it is used in low-sugar jams and dairy desserts; amidated low-methoxyl pectins gel with less calcium.
Carrageenans are sulphated galactans from red seaweeds. κ-Carrageenan forms firm, brittle gels with potassium ions; ι-carrageenan forms soft, elastic gels with calcium ions; λ-carrageenan does not gel but thickens. κ-Carrageenan reacts with casein, so very low levels stabilise milk drinks and dairy desserts. Agar, also from red seaweeds, forms strong gels at about 1 per cent that set at around 32 to 40 °C and melt only near 85 °C, a large hysteresis useful in microbiological media and heat-stable confectionery. Alginates, from brown seaweeds, are chains of mannuronic and guluronic acids that form gels at room temperature with calcium ions, binding calcium between guluronic acid blocks in an 'egg-box' structure; they are used in restructured foods, fruit pieces, and spherification. Gellan gum, a fermentation product of Sphingomonas elodea, forms gels at very low concentrations and suspends particles in beverages. Gelatin, derived from animal collagen, forms thermoreversible gels that melt close to body temperature, giving a characteristic melt-in-the-mouth texture in confectionery and desserts; its gel strength is rated in Bloom units, and it is not acceptable for vegetarian, and some religious, diets unless from permitted sources.
Colours are added to restore colour lost in processing, to give uniformity between batches, to intensify natural colour or to colour foods that would otherwise be colourless. Synthetic (artificial) colours are mostly water-soluble dyes of a few chemical classes: azo dyes such as tartrazine (INS 102), sunset yellow FCF (110), carmoisine (122), ponceau 4R (124) and allura red (129); triarylmethane dyes such as brilliant blue FCF (133) and fast green FCF (143); the indigoid dye indigo carmine (132); and the xanthene dye erythrosine (127). They are bright, stable to light, heat and pH, consistent and cheap, and are used at very low levels. Lakes are dyes precipitated onto aluminium hydroxide, making them insoluble so that they colour fat-based and dry products, such as coatings, without bleeding.
Synthetic colours are among the most tightly regulated additives. India permits a short list of synthetic colours, eight in its regulations, only in specified food categories and within a general maximum level, and prohibits colours in many foods such as raw foods, milk and staples; the current regulations should be consulted for the list and levels. Adding non-permitted colours, such as metanil yellow in pulses and sweets or Sudan dyes in chilli, is a classic adulteration offence detected by Food Analysts. The EU requires a warning label on foods containing six synthetic colours associated with hyperactivity in children in the Southampton study, as described in food-toxicology-contaminants-allergens.
Natural colours are pigments extracted from plants, animals, algae or microorganisms, or nature-identical synthetic versions of them. Carotenoids include β-carotene (160a), annatto (bixin and norbixin, 160b) from the seeds of Bixa orellana, paprika extract (160c), lycopene (160d), lutein (161b) and others; they give yellow to red colours, are mostly fat-soluble (with water-dispersible forms), and are sensitive to oxidation and light. Anthocyanins (163), from grapes, purple carrots, berries and red cabbage, are water-soluble and change colour with pH, red in acid, purple near neutral and blue to green in alkali, and are unstable to heat, light and sulphites, so they suit acidic foods such as soft drinks and confectionery. Betanin (beetroot red, 162) gives bright red-pink but is heat-sensitive, suiting chilled and frozen products. Chlorophylls (140) and the more stable copper chlorophyllins (141) give green. Curcumin (100) from turmeric gives bright yellow but fades in light. Carmine and cochineal (120), from insects, give stable red but are not vegetarian and are occasionally allergenic. Phycocyanin from spirulina gives blue, a colour hard to obtain naturally. Caramels (150a to 150d) are the most widely used colours by volume, in four classes made with or without ammonium and sulphite compounds; classes III and IV can contain 4-methylimidazole, which is limited.
Natural colours generally cost more, are less stable, may carry flavour, and vary between batches, so their use requires matching the pigment to the food's pH, processing, light exposure and shelf life. Colouring foods, concentrates of fruits and vegetables such as carrot, beetroot or spirulina used for colour, are treated in some jurisdictions as ingredients rather than additives, provided the extraction is not selective for the pigment, which makes them attractive for clean labels (chapter 12).
Sucrose is the reference sweetener, with a relative sweetness of 1. Other nutritive sugars include glucose (about 0.7), fructose (about 1.2 to 1.7, depending on temperature and concentration), invert sugar, honey, glucose syrups and high-fructose syrups, described in cereal-science-milling. Sugars do much more than sweeten: they provide bulk, lower water activity, depress freezing point in ice cream, raise boiling point in confectionery, take part in browning, feed yeast, and give texture and mouthfeel, so replacing them is difficult (chapter 11).
Polyols (sugar alcohols) are made by hydrogenating sugars. They include sorbitol (420), mannitol (421), maltitol (965), lactitol (966), xylitol (967), erythritol (968) and isomalt (953). They are less sweet than sucrose, from about 0.4 to 1.0, except xylitol at about 1.0, provide less energy because they are incompletely absorbed (the EU uses 2.4 kcal/g for most polyols and 0 for erythritol), do not cause tooth decay, and raise blood glucose less than sugar. Excessive intake causes laxative effects because unabsorbed polyols draw water into the gut, so labelling of products high in polyols commonly requires a warning, and erythritol is better tolerated. Xylitol and erythritol give a cooling effect from their negative heat of solution. Polyols act as bulk replacers for sugar in sugar-free confectionery, chewing gum and chocolate.
High-intensity sweeteners are used at very low levels because they are many times sweeter than sucrose; values below are approximate and depend on concentration and food. Saccharin (954), discovered in 1879, is about 300 to 500 times as sweet, with a bitter aftertaste at high levels. Cyclamate (952) is about 30 to 50 times as sweet; it was banned in the United States in 1970 but is permitted in many other countries. Aspartame (951), a dipeptide methyl ester of aspartic acid and phenylalanine, is about 200 times as sweet, breaks down on prolonged heating and in neutral solution, and must be labelled as a source of phenylalanine for people with phenylketonuria. Acesulfame potassium (950) is about 200 times as sweet and heat-stable, often blended with aspartame for synergy. Sucralose (955), a chlorinated derivative of sucrose, is about 600 times as sweet and heat-stable. Neotame (961) and advantame (969) are thousands of times as sweet. Steviol glycosides (960) from Stevia rebaudiana, about 200 to 300 times as sweet, and mogrosides from monk fruit are plant-derived; thaumatin (957), a protein from the katemfe fruit, is about 2,000 to 3,000 times as sweet.
Sweetness equivalence is calculated from relative sweetness: replacing the sweetness of 100 g of sucrose needs about 100/600, or 0.17 g, of sucralose, or about 0.5 g of aspartame. Because high-intensity sweeteners supply no bulk, sugar replacement in solid foods also needs bulking agents (chapter 11). Blends reduce off-tastes and improve the temporal profile, since many sweeteners have delayed onset or lingering sweetness. Safety evaluation, ADIs and debates such as the 2023 IARC classification of aspartame are covered in food-toxicology-contaminants-allergens; permitted food categories, maximum levels and label statements, such as warnings that a product contains artificial sweeteners, vary by country and must be checked in current law.
Flavour enhancers have little flavour of their own at use levels but intensify or round out existing flavours. The most important are monosodium glutamate (MSG, INS 621), the sodium salt of glutamic acid, and the 5'-ribonucleotides disodium inosinate (631) and disodium guanylate (627), often used together as disodium 5'-ribonucleotides (635). They stimulate the umami taste, the savoury taste of meat broths, cheese, tomatoes, mushrooms and seaweed, identified by Kikunae Ikeda in Japan in 1908 from kombu stock. Glutamate and the nucleotides act synergistically: a small amount of nucleotide greatly increases the umami intensity of glutamate, which is why they are combined in seasonings, soups, snacks and instant noodles.
MSG is made mainly by bacterial fermentation, using Corynebacterium glutamicum. JECFA has given glutamate an ADI 'not specified', and controlled studies have not consistently reproduced the symptoms once attributed to it, as noted in food-toxicology-contaminants-allergens. Other sources of umami used in clean-label products include yeast extracts, rich in glutamate and nucleotides, hydrolysed vegetable proteins, tomato and mushroom concentrates, fish sauces and fermented soy products. Flavour enhancers are also tools in salt reduction, because umami can compensate partly for the lower savoury impact of reduced-salt foods.
Acidulants give sour taste, lower pH for microbial safety and preservative effectiveness, act as synergists for antioxidants by chelating metals, control pectin gelation and Maillard browning, invert sucrose in heated syrups, and serve as leavening acids. Citric acid (330), produced by fermentation with Aspergillus niger, is the most widely used, with a clean, fruity sourness. Malic acid (296), the acid of apples, has a smoother, lingering sourness and blends well with high-intensity sweeteners. Tartaric acid (334), from grapes and wine by-products, has a sharp taste and is used in grape-flavoured products and baking powders. Lactic acid (270) has a mild taste and is used in dairy, meat and fermented products. Acetic acid (260), as vinegar, is used in pickles and sauces. Phosphoric acid (338) gives the sharp acidity of cola drinks. Fumaric acid (297) is strong and slightly soluble, used in powdered drinks. Glucono-delta-lactone (575) hydrolyses slowly to gluconic acid, giving gradual acidification in tofu, dairy and leavening, as described in pulses-oilseeds-plant-proteins and bakery-pasta-snacks.
Acidity regulators and buffers, such as sodium citrate and potassium phosphates, keep pH within a range during processing and storage, moderate sourness and help stabilise proteins. In acidified foods, the target pH, often at or below 4.6 for safety in shelf-stable products, as described in thermal-processing-canning, must be reached reliably, so formulation includes enough acid to overcome the food's own buffering capacity. Titratable acidity, expressed as the predominant acid, and pH are measured in quality control.
Chemical leavening releases carbon dioxide to aerate baked goods, as described in bakery-pasta-snacks. Sodium bicarbonate (500) is the gas source; leavening acids react with it at different rates: fast-acting monocalcium phosphate (341) reacts mostly during mixing, while sodium acid pyrophosphate (450), sodium aluminium phosphate (541) and glucono-delta-lactone react more slowly or when heated. Baking powders combine bicarbonate with one or more acids and a starch filler to keep the components dry. Ammonium bicarbonate (503), which decomposes completely to ammonia, carbon dioxide and water on heating, is used in thin, low-moisture products such as biscuits and crackers, where the ammonia can escape; in thicker, moister products it would leave an ammoniacal taste. Potassium bicarbonate is used in sodium-reduced formulations. The balance of acid and bicarbonate is set by the neutralising value, so that no excess alkali or acid remains. Yeast, a biological leavening agent, is an ingredient rather than an additive. Leavening choice also affects colour, flavour and texture: excess bicarbonate raises pH, darkens crumb and gives a soapy taste, while the rate of gas release must match the setting of the structure so that gas is retained rather than lost.
Enzymes are proteins that catalyse specific reactions, and are used widely in food processing; most are produced by microbial fermentation, increasingly using genetically modified production strains, and regulated as additives, processing aids or under specific enzyme regulations depending on the jurisdiction. Examples include amylases and glucoamylase in starch conversion and baking; maltogenic amylase as an anti-staling agent; proteases such as papain from papaya and bromelain from pineapple for meat tenderising and beer chill-proofing; chymosin (rennet), now largely produced by fermentation, for cheese making; pectinases for juice extraction and clarification; lactase for lactose-free milk; glucose isomerase for high-fructose syrup; glucose oxidase to remove oxygen or glucose; lipases for flavour development in cheese and for interesterification; transglutaminase to cross-link proteins in restructured meat, fish and dairy; phospholipases in oil degumming; and asparaginase to reduce acrylamide. Enzymes are effective at low levels and under mild conditions, but their activity depends on temperature, pH and the presence of inhibitors, and residual activity must be controlled, usually by heat inactivation.
Processing aids include filtration aids such as diatomaceous earth, clarifying agents such as bentonite and gelatin in wine and juices, extraction solvents such as hexane in oil extraction, antifoaming agents such as dimethylpolysiloxane in fermentations and frying, release agents in baking, catalysts such as nickel in hydrogenation, and many enzymes. Their residues must be technically unavoidable and safe, with limits set for some, such as solvent residues in oils and meals. Whether a substance is an additive or a processing aid depends on whether it has a technological function in the final food, which determines labelling requirements and is a common examination question.
Fat contributes energy (9 kcal/g), flavour, flavour release, creaminess, lubrication, tenderness, aeration in creamed products and heat transfer in frying, so reducing it changes much more than energy content. Fat replacers are grouped by origin. Carbohydrate-based replacers, such as modified starches, maltodextrins, gums, pectin, inulin, cellulose gels and fibres, bind water and build viscosity and body to mimic creaminess; they supply 0 to 4 kcal/g and suit dressings, sauces, dairy products, meat products and bakery fillings, but cannot be used for frying. Protein-based replacers, such as microparticulated whey protein, in which protein is heated and sheared into tiny spherical particles that roll over the tongue like fat droplets, give creaminess in dairy products and spreads but are heat-sensitive.
Fat-based replacers are fat-like molecules modified to give fewer calories. Olestra, a sucrose polyester with six to eight fatty acids, is not hydrolysed or absorbed, and was approved in the United States in 1996 for savoury snacks, though it can cause gastrointestinal effects and reduce absorption of fat-soluble vitamins; it was not approved in many other countries. Structured lipids with short- and long-chain fatty acids (such as salatrim) or with medium-chain fatty acids provide fewer calories per gram. More common in practice are fat-reduction strategies: emulsions with smaller fat phases, aeration, fat crystal engineering and oleogels (fats-oils-technology), and flavour compensation. Each approach must be assessed for texture, flavour, stability, shelf life and labelling.
Replacing sugar requires replacing both sweetness and the functions of sugar. High-intensity sweeteners (chapter 8) supply sweetness at negligible weight, so bulk must be replaced by other ingredients. Polyols supply bulk and some sweetness with fewer calories and are used in sugar-free confectionery and chocolate, with limits from laxative effects. Soluble fibres such as polydextrose (1200), inulin and fructo-oligosaccharides, resistant maltodextrins and soluble corn fibre add bulk and fibre with low energy, and inulin and oligofructose are prebiotic; high levels cause flatulence. Rare sugars such as allulose (psicose), about 70 per cent as sweet as sucrose with very little energy, and tagatose, and slowly digested sugars such as isomaltulose, are newer options; their regulatory status differs between countries, and in some, such as the EU, allulose has not been approved.
Sugar reduction also changes processing and shelf life. Without sugar, water activity rises, so preservation must be reconsidered; freezing point rises in ice cream, so texture becomes harder; Maillard browning and caramelisation fall, changing colour and flavour; and biscuits and cakes lose spread and tenderness. Successful reformulation therefore combines sweeteners, bulking agents, fibres, flavours and process changes, tested systematically as described in food-product-development. Nutrition labelling and claims for reduced-sugar or no-added-sugar products must follow the rules in food-law-regulatory-affairs, which often require a minimum reduction compared with a reference product.
'Clean label' has no legal definition. It describes products with short ingredient lists of familiar, kitchen-like ingredients, without E numbers or names that consumers perceive as artificial or chemical. Surveys in many countries show that consumers prefer such labels, and retailers and manufacturers have responded by removing or replacing synthetic colours, preservatives, flavour enhancers, chemically modified starches, hydrogenated fats and some emulsifiers. The drivers are perception and marketing more than safety, since permitted additives have been evaluated as safe at permitted levels; but the trend is strong enough to shape much of product development.
The technologist's task is to keep the functions that additives performed, safety, stability, texture, colour and flavour, using ingredients that consumers accept. Typical substitutions include vinegar, cultured dextrose and other fermentates, and plant extracts instead of benzoates and sorbates; rosemary extract and tocopherols instead of BHA and BHT; colouring foods such as carrot, beetroot, spirulina and paprika concentrates instead of synthetic colours; physically modified or 'functional native' starches, citrus fibre and pulse flours instead of chemically modified starches and gums; yeast extracts and vegetable concentrates instead of MSG; and natural flavours.
Clean-label reformulation has real costs and limits. Natural alternatives are often more expensive, less potent, more variable, and may add flavour or colour; preservation by fermentates and extracts may be less robust, requiring tighter process and cold chain control and shelf-life validation. Some substitutions change little in substance: celery powder or other vegetable concentrates rich in nitrate, used to cure 'nitrite-free' meat, generate nitrite in the product just as added nitrite does, and authorities and consumer groups have questioned such labelling. Colouring foods must be produced without selective extraction of the pigment to be labelled as foods rather than colours, according to EU guidance. Claims such as 'natural', 'no preservatives' or 'no artificial colours' are regulated in many countries, including by FSSAI's advertising and claims regulations, and must be truthful; 'no added' claims are not allowed where the substance is not permitted in the food anyway, or where a functional equivalent is used.
A responsible approach starts from a clear brief: which functions are needed, what safety margin is required, what cost and shelf life are acceptable, and what claims will be made. Options are screened in the laboratory, optimised systematically, validated by challenge tests and shelf-life studies, and checked against current regulations in every target market before launch. Removing an additive must never reduce safety: for example, removing nitrite from cured meats without an equivalent control of Clostridium botulinum, or removing preservatives from a high-water-activity product without changing its process or storage, creates real hazards. Clean label at its best means fewer, better-understood ingredients; at its worst, it means relabelling the same chemistry or accepting more risk.
A student uses this subject to build a map of additive functions and examples, linked to mechanisms: why benzoate fails at neutral pH, why HM pectin needs sugar and acid, why κ-carrageenan stabilises chocolate milk. The calculations are short: undissociated fraction from pH and pKa, blend HLB, sweetener equivalence, intake against ADI. Learning the INS number ranges and a few key numbers in each class makes label reading and exam questions straightforward.
Five years into product development or quality, a technologist chooses preservative, antioxidant, emulsifier and hydrocolloid systems for new products, checks every additive against the permitted list and levels for each market, writes compliant ingredient declarations, troubleshoots separation, syneresis or colour fading, reformulates for clean label or reduced sugar and fat, and works with suppliers on specifications and documentation.
A senior R&D or regulatory leader with twenty-five years' experience sets the company's additive policy, decides how far to pursue clean label against cost and risk, anticipates regulatory changes such as bans or re-evaluations, manages global harmonisation of formulations across markets, and communicates honestly with customers and consumers about why additives are used.
A researcher at this level works on mechanisms and alternatives: structure-function of hydrocolloids and emulsifiers, natural antimicrobials and antioxidants with proven efficacy, stable natural colours, sweetener blends with sugar-like temporal profiles, fat and sugar replacement with minimal processing change, and exposure and health effects of additive use. Such work combines physical chemistry, microbiology, sensory science and regulation.
This manual names classes, mechanisms and examples but deliberately does not give permitted maximum levels or full permitted lists, which differ between Codex, India, the EU and other jurisdictions and change through amendment; the current regulation must be read for each market. Relative sweetness and other values are approximate. Flavourings, nutrients for fortification and packaging additives are only touched on and are covered in spices-flavours-essential-oils, human-nutrition and food-packaging. Toxicology is in food-toxicology-contaminants-allergens and legal frameworks in food-law-regulatory-affairs.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions. Permitted additives and levels change: check current regulations.
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