What is FAT in milk?
The cream in the milk, as a percentage. In most Indian dairies it is the single biggest thing deciding what a litre is worth.
Fat is measured by a milk analyser or by the older Gerber method, and written as a percentage — 4.2, 6.5, 7.1. Buffalo milk typically reads higher than cow milk, which is why most dairies keep separate rates for the two.
Every pricing method used in India leans on it. In a fat-point rate, the whole price is fat multiplied by a rate per point. In the 52/48 and 60/40 formulas, fat carries the larger share. In the 100/0 formula, fat is the only thing measured at all.
Dairywala accepts fat between 2 and 12 per cent. A reading typed as 65 is corrected to 6.5 and one typed as 120 to 12.0, because those are the mistakes that actually happen at a counter — but a reading that could not be real is refused rather than guessed at.