Abstract
To get a brief estimation of the deterioration of cooking oil, we measured the extension of a bubbling series of foam from around a slice of potato (2cm2; 3mm thick) one minute after it was dropped in the boiling oil.
And we found the foam extension grew longer in proportion to the oil rancidity. In case we used oil of the same rancidity, its extension proved to be constant and free from the quantities of oil, the kind of vessels, and the temperatures (160°C-200°C) when measured.
It might be said that the foam extension would be a measurement of the rancidity of oil.
When we continued to heat non-rancid oil at 160°C, 180°C, 200°C and 220°C, respestively, the higher was the oil heated, the longer did its extension grew in a short minute.
The properties of whale meats, onion and potato fried at 180°C for 4 minutes at an interval of 10 minutes, the extension grew longer in a short minute.
