Rancidity is often experienced as a bitter taste or as a burning sensation at the back of the throat. Good salad oils, cooking oils (I don’t know about Mazola) and foods that contain oils, such as nuts and seeds, are subject to rancidity if stored for too long. Best to buy these from a store that turns over its inventory quickly.

This is also true of olive oil, which solidifies when refrigerated and for this reason, seldom is. Many people believe that olive oil does not go rancid. Not true. I bought several different brands of olive oil from various locations and taste-tested them. Really fresh olive oil is wonderfully nuanced in flavour. Rancid olive oil tastes flat and bitter. There is a world of difference. Have you ever bought a good brand of pesto made with olive oil and wondered why your pasta tasted really bitter?...Well, now you know why.

Nuts and seeds are particularly subject to rancidity and should be refrigerated rather than stored in a cupboard. Even bottled freeze-dried nuts have a limited storage life once they are opened. Some peanut butters are mixed with preservatives to prevent rancidity, but even those will go rancid. Kraft peanut butter has an expiry date on the label and it is worth taking the time to check that before buying it.