The taste of the oil depends on the growing region, olive type, soil, blend, how it was produced and even whether the fruit was facing sun, explains Toronto food writer Malcolm Jolley. Californian oils tend to be softer and sweeter. Mediterraneans are more aromatic and grassy. Spain is particularly famous for its quality and variety of olive oils, he adds.
The price of an oil varies greatly, from $10 to nearly $200 a litre. But the cheaper ones aren't necessarily a bargain: According to a 2007 study by the Canadian Food Inspection Agency, about 33 per cent of olive oils are contaminated with other ingredients. They might claim to be 100 per cent pure, but they have been mixed with sunflower, canola, olive-pomace (a cheap grade made from the remnants of the fruit) or another oil.