Punjabi households preserve on the roof in the sun: mango pickle in mustard oil, lemon, carrot, cauliflower and turnip in winter, chilli, garlic, and mixed achaar in ceramic jars.
Making a year's mango pickle is a household operation done in a specific week in summer, and the recipe is family property. The jar is turned in the sun daily for weeks.
Wadi, sun-dried lentil dumplings spiced with asafoetida, and papad, are made the same way and by the same collective method, on a charpai on the roof in the heat.
Sun and salt and mustard oil are the entire preservation technology and it works in a climate that reaches the high forties.
It is women's work, done in company, on a schedule set by the season, and it is one more of the collective female institutions, along with the trinjan and the chakki, that the household refrigerator ended.
The jar matters. A martban, glazed inside and rough outside, holds the oil without reacting with it and lets a little moisture through the wall, and a household kept the same jars for decades. Plastic and steel each change what happens inside, which is why the old ones were never thrown out.
Mustard oil, salt and the household's own spice mix are the whole method, and the proportions are family knowledge rather than a recipe.
The commercial versions are made with acid and preservative, which is a different food. What a house makes is a preservation technique older than refrigeration, still practised because it tastes better.