Forty bottles of chutney and four white patches
Rekha runs a home-scale catering business and supplies tomato-chilli chutney to two shops. Each batch uses 10 kg tomatoes, 700 g sugar, 60 g salt and the juice of four lemons, cooked 40 minutes in a large aluminium vessel and stirred with an iron ladle. She cools it overnight, uncovered, on the kitchen platform and fills it next morning into empty mineral-water bottles rinsed in tap water and dried in the sun. The bottles are capped and stored on a shelf beside the window. This week three of forty bottles have leaked gassy liquid, one cap has bulged, and a white patch has appeared on the surface of four more. A shopkeeper has returned a bottle and asked for a replacement. A neighbour advises her to 'just add sodium benzoate' and to 'boil it again, it will be fine'. Her cost is ₹22 a bottle and she sells at ₹35; the spoiled batch costs ₹880 in ingredients plus the shops' trust.
1. Diagnose why the batch spoiled, identifying at least four specific lapses and linking each to a principle of food preservation.
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1. Cooling uncovered overnight. The product was sterile after 40 minutes of boiling and was then re-contaminated from air, dust, insects and airborne mould spores. Principle: heat treatment is useless if the product is exposed to recontamination before sealing.
2. Filling cold into unsterilised bottles. A tap rinse does not kill spores; the narrow neck makes cleaning impossible. Principle: containers must be sterile and the product filled hot, so that the residual heat both sterilises the surface and creates a vacuum on cooling.
3. Insufficient acid/sugar hurdle. 700 g sugar in 10 kg is about 7% - far below the 60–65% needed for preservation by sugar alone; tomatoes sit at pH 4.3–4.6 and four lemons may not push the batch below pH 4.0. Principle: the acidity hurdle was assumed, not measured.
4. Aluminium vessel and iron ladle. Acid reacts with these metals and gives darkening, metallic off-flavour and corrosion pitting; stainless steel or glass is required. Principle: equipment must be non-reactive with food acids.
5. Storage by the window. Light and heat accelerate lipid oxidation, colour loss and mould growth. Principle: cool, dark storage extends shelf life.
The evidence matches microbial fermentation: gas and leakage indicate yeasts or heterofermentative bacteria producing CO₂; the bulged cap is a pressure sign; the white surface patch is aerobic mould growing in the headspace.
2. Rewrite her process step by step, with the reason for each step.
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- Select and wash sound, ripe tomatoes; discard bruised fruit. Reason: one mouldy tomato seeds the whole batch.
- Cook in stainless steel with a stainless ladle; add 15–20% sugar, 2–3% salt and lemon juice until pH is below 4.0, checked with pH paper. Reason: measurable acidity is the main hurdle for a tomato product.
- Cook to a thick consistency (about 65–68 °Brix if a preserve-style chutney) so water activity falls. Reason: less free water, fewer spoilage organisms.
- Sterilise glass jars by boiling 15 minutes, and keep them hot. Reason: the jar, not the chutney, is the usual source of contamination.
- Fill hot (≥85 °C), leaving 1 cm headspace, and cap immediately; invert 2 minutes. Reason: hot fill plus vacuum excludes air and collapses surviving vegetative cells.
- Pasteurise filled jars in a water bath at 85–90 °C for 20–25 minutes. Reason: kills heat-sensitive organisms that entered during filling.
- Cool, label with date, store in a dark cupboard; check that the lid is concave. Reason: a flat or domed lid signals gas and a failed batch.
- Hold back one bottle per batch for 3 days' observation. Reason: cheap quality control at her scale.
3. Evaluate the two pieces of advice - 'add sodium benzoate' and 'boil it again'. What is true, what is unsafe, and what does the law require?
Read the worked answer
'Add sodium benzoate.' Partly true: benzoic acid is a permitted chemical preservative for tomato sauce and ketchup under the FSSAI Food Products Standards and Food Additives Regulations, but only up to a specified maximum (historically around 750 mg/kg for this category - check the current schedule before advising). It works only in acid foods, it prevents growth rather than sterilising a contaminated batch, and it must be declared on the label. A preservative cannot rescue a product made with poor hygiene; it merely slows what is already happening. Used above the permitted level or undeclared, it is a food-safety offence.
'Boil it again.' This is the more dangerous advice. Reheating kills vegetative cells but not heat-stable mould toxins, so the toxin is still in the bottle, and the colour, flavour and texture are damaged. An already-spoiled batch must be discarded, never re-sold.
Correct action: withdraw and refund the returned bottle, discard the affected jars, trace which step failed, keep a simple batch record, and if she supplies shops regularly, obtain FSSAI basic registration or licence and label with ingredients, net weight, date and the FSSAI mark.