Toxic constituents in food and new trends in adulteration
Some foods carry natural toxicants (BOAA in khesari dal, aflatoxin, solanine) and some adulterants are poisons (argemone, lead chromate). Economically motivated adulteration keeps finding new tricks.
Natural toxicants in foods
| Toxicant | Found in | Effect | How to reduce |
|---|---|---|---|
| BOAA (β-N-oxalyl amino alanine, also called β-ODAP) | Khesari dal (Lathyrus sativus), a hardy pulse eaten in drought years in parts of central and eastern India | Neurolathyrism: stiff, spastic paralysis of the legs when the dal is a large part of the diet for months | Steep in hot water or parboil and discard the water; low-toxin varieties; never make it the staple |
| Aflatoxins (B1 the most toxic) | Damp, mouldy groundnuts, maize, chillies and copra; milk (as aflatoxin M1) when cattle eat mouldy feed | Liver damage (aflatoxicosis) and liver cancer | Dry crops quickly; store dry and cool; discard mouldy or shrivelled nuts; normal cooking does not destroy it |
| Goitrogens (glucosinolates, thiocyanates) | Cabbage, cauliflower, mustard, radish; cassava; soybean | Block iodine uptake by the thyroid; can worsen goitre when iodine intake is low | Cooking reduces them; use iodised salt |
| Trypsin (protease) inhibitors | Raw soybean and other raw pulses; raw egg white | Block protein digestion; poor growth in animal studies | Destroyed by moist heat; soaking, sprouting and proper cooking |
| Solanine (glycoalkaloid) | Green or sprouted potatoes and potato skin | Nausea, vomiting, diarrhoea, headache; nerve effects in large amounts | Store potatoes in the dark; cut away green parts and sprouts |
| Haemagglutinins (lectins) | Raw or undercooked rajma (red kidney beans) and other legumes | Vomiting and diarrhoea; red blood cells clump | Soak and boil well; slow cooking at low heat is not enough |
| Cyanogenic glycosides | Cassava (tapioca), bitter almonds | Release hydrogen cyanide: headache, dizziness, breathing failure in large doses | Peel, soak, grate, ferment and cook cassava well |
Toxic adulterants and contaminants
| Substance | Where it is found | Harm |
|---|---|---|
| Argemone oil (alkaloids sanguinarine and dihydrosanguinarine) | Mustard oil, when look-alike argemone seeds are mixed with mustard seed | Epidemic dropsy: swelling of the legs, diarrhoea, breathlessness, heart failure, glaucoma; a large outbreak occurred in Delhi in 1998 |
| Khesari dal | Mixed into toor dal, chana dal or besan | Lathyrism with long use |
| Metanil yellow (non-permitted azo dye) | Turmeric, dals, sweets and laddoos | Animal studies show damage to the nervous system, liver and reproductive organs |
| Lead chromate | Used to polish turmeric fingers and brighten spices and dals | Lead poisoning: anaemia, abdominal colic, nerve and brain damage, worst in children |
| Other non-permitted colours (Sudan dyes, rhodamine B, malachite green) | Chilli powder, sweets, green peas and chillies | Suspected to cause cancer; not allowed in food |
| Calcium carbide | Used to ripen mangoes, bananas and papayas | Banned for ripening; the industrial grade carries traces of arsenic and phosphorus compounds |
| Urea, detergent, formalin | Urea and detergent in 'synthetic milk'; formalin sprayed on fish to keep it looking fresh | Stomach upset and organ strain; formaldehyde is toxic and a known cancer-causing chemical |
Recent trends in adulteration
- Economically motivated adulteration (EMA): deliberate substitution or addition purely for profit, e.g. cheaper oils in costly ones, vanaspati or animal fat in ghee, sugar syrups in honey.
- Smarter adulterants made to pass routine tests: a 2020 study by the Centre for Science and Environment reported sugar syrups in honey that passed most standard Indian tests but were caught by advanced NMR testing.
- Synthetic milk and milk products: water, urea, detergent, starch and cheap fat mixed to imitate milk, khoa and paneer, especially before festivals.
- Chemical ripening and colouring: calcium carbide on fruit, malachite green on vegetables, formalin on fish.
- Fraud in premium foods: non-basmati rice mixed into basmati, cheap fish sold as costly fish, false 'organic' or 'pure' claims (misbranding).
- Loose and online sales: unbranded, unlabelled spices and oils, and online sellers that are hard to trace.
New detection methods and consumer awareness
- Rapid test kits and strips for milk, oil and spices, and hand-held milk analysers at collection centres.
- Food Safety on Wheels: FSSAI's mobile testing vans that run quick tests, train vendors and spread awareness.
- Laboratory methods: chromatography (HPLC, GC), mass spectrometry, NMR (used for honey), near-infrared spectroscopy, and DNA-based tests to identify species and varieties (meat, fish, basmati rice).
- Consumer awareness: FSSAI's DART booklet and videos, the Eat Right India movement, and campaigns in schools and colleges.
- Training and labels: FoSTaC training for food handlers; the FSSAI licence or registration number on labels, which consumers can check.
Challenges in controlling adulteration
- A huge unorganised sector of street vendors, small shops and loose sales that is hard to inspect.
- Too few food safety officers and accredited labs for the number of food businesses; slow testing and prosecution.
- Adulterants designed to escape standard tests, so methods must keep changing.
- Home tests catch only gross adulteration; low levels need costly instruments.
- Low consumer awareness, a preference for the cheapest price, and few complaints made.
- Long supply chains, imports and e-commerce make traceability difficult.
A dietitian working with low-income families should warn against khesari dal as the main pulse, advise throwing away mouldy groundnuts, and make sure iodised salt is used where cabbage and cauliflower are eaten often. Food businesses should buy oils and spices only from licensed suppliers to keep toxic adulterants out.
2 marks: “What is lathyrism?” A paralytic disease (spastic paralysis of the legs) caused by eating khesari dal (Lathyrus sativus) as a staple for months; the toxin is BOAA (β-ODAP).
5 marks: “Write a short note on epidemic dropsy.” Cause: argemone oil in mustard oil; toxins sanguinarine and dihydrosanguinarine; signs: leg swelling, diarrhoea, breathlessness, heart failure, glaucoma; detection: nitric acid test; prevention: licensed oil, clean seed.
10 marks: “Discuss the toxic constituents in foods and the recent trends and challenges in food adulteration.” Table of natural toxicants; table of toxic adulterants; trends (EMA, synthetic milk, honey syrups, chemical ripening); new detection methods; consumer awareness; challenges; close.
Natural toxicants are K-A-G-T-S: Khesari (BOAA, legs), Aflatoxin (liver), Goitrogens (thyroid), Trypsin inhibitors (protein digestion), Solanine (green potato). Argemone oil causes epidemic dropsy.