The Pickle With a White Skin and a Thirty-Rupee Menu
An aided residential school for 30 students has a food budget of ₹30 per student per day. The cook's standard day is tea and two slices of bread at 7 a.m.; rice, thin dal and potato sabzi at 1 p.m.; and rice with pickle at 8 p.m. Two students are anaemic, one has type 2 diabetes, and no student eats eggs on Tuesdays and Thursdays. Prices: rice ₹30/kg, toor dal ₹120/kg, wheat flour ₹35/kg, potatoes ₹25/kg, spinach ₹20 per 250 g bunch, groundnuts ₹80/kg, milk ₹50/L, oil ₹140/L, and salt and spices about ₹2 per head per day. Separately, a 5 kg jar of mango pickle made three weeks ago with 8% salt and a mustard-oil layer has a white surface growth; the cook wants to scoop it off and serve the rest.
1. Decide whether the pickle can be salvaged, and justify the decision using what is known about its salt level, oil layer and storage.
Read the worked answer
Decision: discard the whole jar. Do not scoop and serve.
Why the salt level is the key fact
- Traditional oil-based mango pickle relies on roughly 15–20% salt by weight (or a lower salt with measured acid plus oil) to hold water activity low enough to stop mould and yeast.
- At 8% salt, enough water remains available for surface yeasts and moulds to grow, especially where pieces float above the oil.
Why the oil layer is not a guarantee
- Oil excludes air only where it forms an unbroken layer above the food. Mango pieces that poke above the oil, or a jar that was opened and reclosed with a wet spoon, create the moist, aerated surface that mould needs.
- Condensation on the lid drips back and dilutes the surface salt.
Why scooping is unsafe
- Visible growth is only the fruiting body. Mould hyphae and mycotoxins can extend well below the surface and into the oil, and most mycotoxins are not destroyed by heat.
- White growth might be Kahm yeast (which can be relatively harmless) or a mould; without a laboratory test, and with 30 children to feed, you assume the worse case.
- Any fuzzy or coloured growth, off-odour or gas bubbles confirm spoilage outright.
Judgement: the cost of 5 kg of pickle is far smaller than the cost of a food-poisoning outbreak, and a school cannot take that risk on an uncertain batch.
2. Redesign one full day's menu for this school within ₹30 per head, addressing the anaemia and diabetes, and show your arithmetic.
Read the worked answer
Budget: ₹30 × 30 students = ₹900 per day.
Breakfast
- Poha (rice flakes) 50 g - ₹2.00
- Groundnuts 15 g - ₹1.20
- Jaggery 5 g - ₹0.23
- Milk 100 ml - ₹5.00
- Subtotal: ₹8.43
Lunch
- Rice 70 g - ₹2.10
- Toor dal 30 g - ₹3.60
- Spinach 50 g - ₹4.00
- Oil 8 g - ₹1.12
- Subtotal: ₹10.82
Dinner
- Wheat flour 60 g - ₹2.10
- Potato 100 g - ₹2.50
- Groundnut 10 g - ₹0.80
- Oil 7 g - ₹0.98
- Subtotal: ₹6.38
Spices and salt: ₹2.00
Total: ₹27.63 per head - within ₹30, leaving about ₹2.37 as buffer.
Why this menu addresses the problems
- Anaemia: spinach, groundnut, dal and jaggery supply iron; groundnut and dal supply protein. Adding a lemon wedge or tomato to the dal gives vitamin C, which improves absorption of non-haem iron. Tea with meals should be avoided because tannins block iron absorption.
- Diabetes: for that student, reduce rice to 50 g, double the spinach, omit the jaggery, and use groundnut instead. Whole wheat roti at dinner has a lower glycaemic response than the previous plain rice.
- No eggs on Tuesday/Thursday: the menu contains no eggs, so no substitution is needed; dal, milk and groundnut carry the protein.
- Variety and fibre: the old menu was rice–potato–pickle twice a day, which is high in refined carbohydrate and low in protein and iron. The new menu replaces one rice meal with wheat and adds a green leafy vegetable.
3. State how the next pickle batch should be made and stored so that this failure does not repeat.
Read the worked answer
The failure came from too little salt, surface exposure to air, and probably moisture on the pieces or the spoon. Fix all three.
Before packing
- Use fully dry, firm mango pieces; spread them in sun for 3–4 days, turning daily, until the surface is dry to touch.
- Use about 18–20% salt by weight of the fruit for the first stage, or 12% salt plus 2% acid (lemon juice or vinegar) and a measured oil layer. Weigh the salt; do not estimate by eye.
- Sterilise the jar with boiling water and dry it completely; any water left in the jar dilutes the surface brine.
Packing
- Pack tightly so that pieces stay below the oil or brine level.
- Keep an oil layer at least 1 cm above the food; add oil whenever the level drops after a spoon has been taken.
- Use a dry, clean spoon every time; never a wet or used spoon.
Storage and checking
- Store in a cool, dark place away from the window; heat and sunlight drive condensation on the lid.
- Check weekly for bubbles, off-odour, colour change or surface growth.
- Label the jar with the date and salt percentage.
- Discard the whole jar at the first sign of growth - do not top up with oil and hope.
Teaching point: salt percentage is a safety control and must be recorded, exactly like a cooking time or a fridge temperature.