🧪 Food Additives and Preservation

This lesson builds core elective concepts in BSc Agriculture with practical applications and exam-oriented clarity.

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Food Additives and Preservation

Food Additives

Food additives are substances added to food intentionally for a technological purpose (not consumed as food itself) in the manufacture, processing, treatment, packaging, transport, or storage of food. They must be permitted under FSSAI/Codex regulations and used at the minimum effective level.

INS numbers: International Numbering System for food additives (Codex Alimentarius); equivalent to E numbers in the European Union.

Safety evaluation: ADI (Acceptable Daily Intake) — amount of food additive that can be ingested daily over a lifetime without appreciable health risk; expressed as mg/kg body weight/day; established by JECFA (Joint FAO/WHO Expert Committee on Food Additives).

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Categories of Food Additives

Preservatives

Preservatives prevent or retard microbial spoilage, extending shelf life.

Preservative	INS Number	Application	Mechanism
Sodium benzoate	E211	Acidic foods: jams, ketchup, soft drinks	Inhibits enzymes; effective at pH <4.5
Potassium sorbate	E202	Bread, cheese, fruit juices, wine	Inhibits yeast and moulds; broad spectrum
Nisin	—	Dairy products, processed cheese	Bacteriocin; inhibits Gram-positive bacteria (Clostridium, Listeria)
Sulphur dioxide	E220	Dried fruits, wines, fruit juices	Antioxidant + antimicrobial; inhibits browning
Sodium nitrite	E250	Cured meats (bacon, ham, sausage)	Inhibits C. botulinum; imparts pink colour (nitrosomyoglobin)
Propionic acid/Na propionate	E280/E281	Bread, bakery products	Inhibits moulds, rope-forming Bacillus; does not affect yeast

Antioxidants

Antioxidants prevent oxidative rancidity of fats and oils — delay the chain reaction of lipid oxidation.

Antioxidant	INS	Application	Notes
BHA (butylated hydroxyanisole)	320	Edible oils, snacks	Synthetic; heat-stable; GRAS (USA); restricted in some countries
BHT (butylated hydroxytoluene)	321	Edible oils, breakfast cereals	Synthetic; similar to BHA
TBHQ (tertiary butylhydroquinone)	319	Frying oils, poultry fat	Very effective for frying oils
Vitamin C (Ascorbic acid)	300	Fruit products, bread, meat	Also nutritional; prevents browning
Vitamin E (Tocopherols)	307	Vegetable oils, baby food	Natural; especially alpha-tocopherol
Propyl gallate	310	Animal fats, edible oils	Gallate ester; used with BHA/BHT

Colours

Colours restore colour lost during processing or add colour for visual appeal.

• Natural colours: beta-carotene (E160a — orange/yellow; provitamin A), anthocyanins (E163 — red/purple; grapes, red cabbage), chlorophylls (E140 — green), curcumin (E100 — yellow; turmeric; also anti-inflammatory), caramel (E150 — brown; from sugar)
• Synthetic colours: Sunset Yellow FCF (E110 — orange), Tartrazine (E102 — yellow), Carmoisine (E122 — red), Brilliant Blue FCF (E133 — blue)
  • FSSAI restricts several synthetic dyes; metanil yellow and Sudan red are prohibited in India (used to adulterate turmeric and chilli)
  • Southampton study (2007): linked some synthetic dyes to hyperactivity in children → EU added warning labels

Flavours and Flavour Enhancers

• Natural flavours: vanilla (vanillin from Vanilla planifolia), citral (lemon grass), diacetyl (butter flavour), essential oils
• Artificial flavours: chemically identical but synthetically produced; cheaper; consistent quality
• MSG (Monosodium Glutamate) (E621): umami (5th taste — savoury, meaty); naturally in tomatoes, mushrooms, parmesan; added to Chinese food, instant noodles, soups; controversial (Chinese Restaurant Syndrome — headache, flushing — not consistently proven in controlled studies); FSSAI permits at GMP level

Emulsifiers

Emulsifiers keep immiscible phases (oil and water) mixed by reducing interfacial tension; amphiphilic molecules (hydrophilic + lipophilic ends).

• Lecithin (E322): from soy or egg yolk; widely used in chocolate, margarine, mayonnaise, bread
• Mono- and di-glycerides (E471): from glycerol + fatty acids; bread, ice cream, margarine
• Polysorbates (E432–E436): oil-in-water emulsions; ice cream, salad dressings
• HLB (Hydrophilic-Lipophilic Balance): value 3–6 → water-in-oil emulsions; value 8–18 → oil-in-water emulsions

Stabilisers, Thickeners, and Gelling Agents

Used to improve texture, consistency, and mouthfeel:

Additive	INS	Source	Application
Guar gum	E412	Cyamopsis (cluster bean) seeds	Thickener in sauces, ice cream, bakery
Xanthan gum	E415	Xanthomonas campestris (bacterial fermentation)	Thickener, stabiliser; gluten-free baking
Pectin	E440	Apple pomace, citrus peels	Gelling agent; jams, jellies; requires sugar + acid
CMC (Carboxymethyl cellulose)	E466	Cellulose derivative	Thickener, stabiliser; ice cream, sauces
Carrageenan	E407	Red seaweed	Gelling, thickening; dairy desserts, infant formula (controversial)
Locust bean gum	E410	Carob tree seeds	Synergistic gelling with xanthan and carrageenan

Sweeteners

• Bulk (caloric) sweeteners: sucrose, glucose, fructose, lactose, maltose; nutritive; cariogenic
• Polyols (sugar alcohols): sorbitol, xylitol, mannitol; lower caloric value; not fully absorbed; laxative effect at high doses; non-cariogenic; used in sugar-free gum, diabetic foods
• Intense (non-nutritive) sweeteners: very high sweetness relative to sucrose

Sweetener	Sweetness vs. Sucrose	INS	ADI	Use
Saccharin	300×	954	5 mg/kg	Oldest; slightly bitter aftertaste; heat-stable
Aspartame	200×	951	40 mg/kg	Heat-labile (not for baking); avoid in PKU (phenylalanine source)
Sucralose	600×	955	15 mg/kg	Heat-stable; made from sucrose; no bitter aftertaste
Stevia (steviol glycosides)	200–300×	960	4 mg/kg	Natural (Stevia rebaudiana leaf); popular "natural" option
Acesulfame-K	200×	950	9 mg/kg	Heat-stable; often combined with aspartame

Other Additives

• Acidity regulators: citric acid (E330), acetic acid (E260), lactic acid (E270); control pH, flavour, and microbial growth
• Anti-caking agents: silicon dioxide (E551), calcium silicate (E552); prevent powder clumping in salt, icing sugar, powdered milk
• Leavening agents: sodium bicarbonate + acid (cream of tartar, lactic acid) → CO2 → baked goods rise
• Humectants: sorbitol (E420), glycerol (E422); retain moisture; soft bakery goods, candies

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Food Preservation Principles — Hurdle Technology

Hurdle Technology (Leistner, 1995): multiple mild preservation hurdles applied simultaneously are more effective and less damaging to quality than a single severe treatment. Hurdles: temperature, Aw, pH, Eh, preservatives, competitive flora.

Heat Treatment

Method	Temperature/Time	Target	Application
Pasteurisation (LTLT)	63°C for 30 min	Vegetative pathogens; extends shelf life	Milk, fruit juices, beer
Pasteurisation (HTST)	72°C for 15 sec	Same	High-volume milk processing
UHT (Ultra High Temperature)	135–150°C for 2–5 sec	All microorganisms; shelf-stable	Tetra Pak milk, juices, soups
Sterilisation (retort)	121°C for 15 min (or equivalent F₀)	All pathogens including C. botulinum spores	Canned foods
Blanching	85–100°C for 1–5 min	Enzyme inactivation	Before freezing/drying

F₀ value: thermal process equivalent to 1 minute at 121.1°C with z = 10°C; used to calculate sterilization adequacy for canned foods.

Cold Preservation

• Refrigeration (0–4°C): slows microbial growth and enzymatic reactions; does not kill organisms; shelf life 1–3 weeks
• Freezing (−18°C or below): stops microbial growth; slows chemical reactions; shelf life months to years
  • IQF (Individually Quick Frozen): blast freezing; small ice crystals; better texture; peas, corn, fish fillets
  • Freezer burn: surface dehydration in improperly packaged frozen food → off-texture, colour loss

Drying / Dehydration

Reduces water activity (Aw) to levels that inhibit microbial growth:

Aw Value	Inhibition
<0.85	Most bacteria inhibited
<0.70	Most yeasts inhibited
<0.60	Most moulds inhibited; safe for long storage

Drying Method	Quality	Application	Notes
Sun drying	Poor (nutrient loss, contamination)	Traditional; raisins, chillies, fish	Low cost; weather-dependent
Hot air (cabinet/tunnel) drying	Moderate	Vegetables, spices, snacks	Common; some nutrient loss
Spray drying	Good	Milk powder, coffee, egg powder	Atomised droplets; rapid; heat-sensitive products
Freeze drying (lyophilisation)	Excellent	Coffee, space food, probiotics, herbs	Sublimation (ice → vapour); best rehydration, nutrition, aroma

Modified Atmosphere Packaging (MAP)

• Replaces air in package with mixture of reduced O2 + elevated CO2 + nitrogen
• CO2: antimicrobial, inhibits respiration
• N2: inert, prevents pack collapse
• Extends shelf life of fresh produce, meat, bakery by 3–5×
• CA (Controlled Atmosphere) storage: rooms with continuously maintained O2/CO2 ratio; apples, kiwi — 9–12 months

Irradiation

• Uses ionising radiation: gamma rays (Cobalt-60), X-rays, or electron beams
• Destroys DNA of microorganisms; no radioactivity remains in food
• India: approved for spices (BARC developed), onions (prevents sprouting), pulses, potato, mango
• Radura symbol: internationally recognised symbol on irradiated foods
• Doses: low (<1 kGy — inhibit sprouting, insect disinfestation), medium (1–10 kGy — pasteurisation), high (>10 kGy — sterilisation)

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Water Activity (Aw)

Water activity = the ratio of vapour pressure of water in food to that of pure water at same temperature (0 to 1.0 scale).

• Pure water: Aw = 1.0
• Fresh meat/fish: Aw ≈ 0.99
• Bread: Aw ≈ 0.96
• Jam (high sugar): Aw ≈ 0.82
• Intermediate moisture foods (dried fruit, jerky): Aw 0.60–0.90
• Dried crackers, biscuits: Aw ≈ 0.30
• Freeze-dried products: Aw < 0.20

Controlling Aw: adding solutes (salt, sugar) reduces Aw via osmosis; removing water by drying.

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Preservation Methods — Comparison Table

Method	Aw Achieved	Temperature	Key Advantage	Limitation
Refrigeration	No change	0–4°C	Simple; retains quality	Short shelf life; no spore kill
Freezing	Lowers (ice formation)	≤−18°C	Long shelf life	Texture changes; freezer burn; energy
Sun drying	<0.70	Ambient	Low cost	Slow; contamination risk; nutrient loss
Spray drying	<0.30	150–250°C inlet	Rapid; scalable	High energy; heat-sensitive may degrade
Freeze drying	<0.10	Sub-zero	Best quality/nutrition	Very expensive; slow
Canning (retort)	No change	121°C	Very long shelf life (2–5 yr)	High heat; nutrient loss; capital cost
UHT	No change	135–150°C	6-month shelf life; minimal heat damage	Requires aseptic packaging
MAP	No change	Refrigeration	Extends fresh shelf life	Packaging cost; gas cost
Irradiation	No change	Ambient	Kills pathogens; no heat	Consumer acceptance; regulatory
Fermentation	Lowers to ~0.92	Ambient	Probiotic; flavour; natural	Limited shelf life without refrigeration

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	Categories of food additives (preservatives, antioxidants, colours, emulsifiers, sweeteners), food preservation principles (heat, cold, drying, MAP, irradiation), water activity, and hurdle technology.
Section context	Revise this lesson with the rest of Food Processing for stronger conceptual continuity.