ZT - Cooking oils and their smoke points - how hot is too hot?

In the kitchens where I grew up in the English Midlands, chip pans were standard issue. Blackened with years of constant use, they were half filled with solid fat that was reheated whenever families made chips (often). Those were the days when fat was just fat - neither good nor bad - and if the chip pan billowed smoke, we\'d just open the window.

In my own kitchen (a chip pan-free zone) I cook with olive oil because I know it\'s heart healthy and high in antioxidants. But on the few occasions I do deep fry (pappadams, these days, not chips), I\'m careful not to let the oil get so hot that it smokes - besides affecting the food\'s flavour, the smoke produces toxic fumes (not good to inhale), and may mean the fat is oxidising and releasing potentially harmful substances into the food. But what I wasn\'t sure about was which oils are best for cooking at high temperatures - could I use the same extra virgin olive oil for deep frying that I use on salads and for sauteeing vegetables?

This, it turns out, isn\'t a simple question. Although there\'s no shortage of references on the web giving the smoke points of different oils, it\'s hard to know how accurate they are. When I checked with Dr Chakra Wijesundera, a lipid chemist with CSIRO Food Science Australia in Adelaide, his advice was to avoid extra virgin oil for high temperature cooking because - like all unrefined oils - it usually has a lower smoke point than refined oils. A typical temperature for deep frying is 195 degrees C, he explains, and his own tests found that extra virgin olive oil had a smoke point of about 205 degrees C, which might not leave enough margin for error. Light olive oil, which he found to have a higher smoke point of 210 degrees C in his own tests, is a better choice, he says. While canola oil is quite good for deep frying because of its higher smoke point of 240 degrees C, he adds, it can also start to oxidise before reaching its smoke point.

Dr Wijesundra\'s advice is to avoid reheating oil - once oil has been heated, food sediments remaining in it can lower its smoke point, he says.

He\'s also cautious about relying on information on the smoke points of different oils on the web - like me, he could find little information that had real authority. And when he ran a few tests on different oils himself he found their smoke points differed from those he\'d seen published on the web.

So for now, I\'m sticking with the extra virgin olive oil for salads and sauteeing, and light olive oil for cooking at higher temperatures (light, of course, doesn\'t mean lower in kilojoules - just that the colour and flavour are lighter). And instead of cooking chips, I use my mum\'s recipe for oven baked fries that she adopted when she finally dumped the deep fryer. It goes something like this:

- steam sliced or chipped unpeeled potatoes until they start to soften, but are still firm.
- toss in 1-2 tablespoons olive oil with pepper, chopped parsley and a little salt (if you use it).
- spread in a baking dish lined with foil and bake at about 190 degrees C for about 30 minutes, turning occasionally.