While all oils have a limited shelf life, nut and seed oils, like hazelnut, almond, sesame, and walnut, are more likely than others to turn rancid. The main reason is that they’ve sat too long on the shelf, either at home or in the market. We’ve purchased nut oils that had gone bad before they were opened. The lesson: Be sure to taste your oil before every use. An oil can be rancid without smelling bad, so don’t just take a whiff— try it. If its flavor is the slightest bit unpleasant, discard it.
How to protect those pricey oils
Rancid oil is inevitable, but you can do a couple of things to delay it. Air, light, and temperature are the enemies, so…
1. Purchase from a store that has high turnover; chances are the oil will be fresher when you buy it.
2. Transfer the oil to a metal or dark-glass container if it didn’t come in one, in order to block light.
3. Tightly close the container to keep air out.
4. Store the oil in the refrigerator to keep it cool.