Mango Glut, Humidity and a Self-Help Group's Food-Preservation Decision
A self-help group in Udupi has 12 kg of ripe mangoes left after a festival. The room is humid, about 85% relative humidity at 30°C, there is no refrigerator, and power cuts last four to six hours daily. The group wants to sell something at the village fair in 10 days and keep some for six months. They have glass jars, sugar, salt, mustard oil, spices, a solar dryer, clean water, and ₹1,500; they can borrow a weighing scale and pH strips. Last year's mango jam grew mould on the surface after three weeks, and their pickle became soft and sour. Two members suggest drying the fruit in the sun on the terrace; another wants to make squash and store it in plastic bottles. The group asks you to decide what to make, how to process it, and how to judge whether a batch is safe.
1. Why did last year's jam grow mould and the pickle become soft and sour? Link each fault to a preservation principle.
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Jam mould: mould needs oxygen, moisture, and a favourable pH. Likely causes: too little sugar or too short a boil, so the soluble solids were below about 68–70% and water was available; insufficient acid (mango may be low-acid) so pH was not low enough; underfilled or unsterilised jars, dirty lids, or headspace air; cooling and storing in a humid room. The surface mould does not mean only the top is spoiled-toxins may spread, so the batch should be discarded. Pickle soft and sour: salt concentration was too low or uneven, so spoilage bacteria and yeasts grew; the fruit was probably wet or not dried, and the oil layer did not exclude air; spices may have been contaminated; the jar was opened with wet hands. Preservation principles: jam relies on high osmotic pressure (sugar) plus acidity and heat; pickle relies on salt, acid, oil exclusion of air, and clean anaerobic conditions. Both need hygienic containers and correct measurement.
2. Choose what to make for the 10-day fair and for six months, and give a process flow with critical control points.
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For the 10-day fair: make a small batch of mango jam or murabba, because sugar plus acid plus hot filling gives a shelf-stable product without refrigeration; sell in glass jars. For six months: make a salt-and-oil mango pickle and/or solar-dried mango slices, because the pickle's salt/oil barrier and the dried product's low moisture are more robust in humid Udupi than a bottled squash. Process flow: wash mangoes in clean water → sort, discard bruised fruit → peel and cut on clean boards → for jam, weigh fruit and sugar (about 1:1), add citric acid/lemon juice, cook to about 68–70% TSS, hot-fill into sterilised jars, seal, cool; for pickle, dry the pieces, mix with salt (about 15–20% by weight), turmeric, spices, sun/air-dry, pack under mustard oil, seal; for drying, dip in salt/lemon water, dry in the solar dryer to leathery texture. Critical control points: potable water, hand/utensil hygiene, correct weighing, pH/TSS check, sterilised jars, sealed lids, dry storage, batch labels.
3. Evaluate the terrace sun-drying and plastic-bottle squash suggestions, and list safety indicators the group should use before selling.
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Terrace sun-drying: cheap and uses the solar dryer, but in Udupi's humidity and daily rain, open-terrace drying is risky-dust, insects, birds, uneven drying, and re-wetting can cause mould. If used, use the solar dryer or a raised net with a cover, blanch or salt-dip the slices, turn them, and finish until leathery (about 15–20% moisture); do not dry on bare cement. Plastic-bottle squash: squash needs acidity, sugar, and usually a preservative plus pasteurisation; hot-filling into plastic bottles can deform them and leach, and plastic is not a good oxygen barrier for six months. Use glass bottles, pasteurise, label 'refrigerate after opening', and test pH. Safety indicators: mould (even white surface), off-odour, gas/bulging lids, slime, bitter taste, colour change, and pH rise; any one means discard, not sell. The group should keep a batch record and test a sample before the fair.