When you heat oil …
It starts to break down and can result in the production of harmful oxidative and polar compounds linked to diseases such as Alzheimer’s and Parkinson’s.
While heating any oil to smoke point is unwise, new research suggests this marker should not be the only benchmark for determining the safety of cooking oils.
Which oil is most stable?
An Australian study compared the performance of nine supermarket oils when heated to domestic cooking temperatures—extra virgin and refined olive oils, canola, rice bran, grapeseed, coconut, peanut, sunflower and avocado.
The researchers concluded that smoke point alone is not the best predictor of stability and safety when heating cooking oils. The most stable and healthiest oil to cook with was extra virgin olive oil (EVOO). This is likely due to its lower content of polyunsaturated fatty acids (so less prone to oxidation), lack of refining and higher antioxidants compared to other oils.
The least stable oils when heated were canola, grapeseed and rice bran.
Tips for cooking with oils
- Choose a high quality, fresh EVOO. Check label for less than 0.8 per cent free fatty acids, although the lower the better as this indicates quality.
- Never heat any oil to smoke point and use lower temperature cooking methods.
- Avoid refined oils (such as those listed above). These have been chemically treated—eg, bleached, deodorised—and contain higher levels of oxidative products even before you start heating them!
- While coconut oil appears fairly stable, it contains significantly less antioxidants compared to EVOO, so limit its use to special occasions.
Baked eggplant halves with Mediterranean topping
Succulent eggplant flavoured with plenty of sofrito, an antioxidant-rich sauce made of extra virgin olive oil, onions and tomato.
Preparation: 15 mins | Cooking: 80 mins | Serves: 8
- 2 tsp salt
- 1 ½ cups extra virgin olive oil
- 4 medium eggplants
- 2 medium onions, sliced
- 3 cloves garlic, chopped
- 2 cups passata
- 2 tbsp tomato paste
- 5 tbsp chopped parsley
- Halve eggplants lengthwise. Cut a strip of skin from the bottom (so they sit flat) and make a slit in the centre of the flesh halfway down. Transfer to a bowl and rub in half the salt. Set aside for 30 minutes to extract juices. Rinse with water and pat dry with towelling.
- Heat 1 cup of oil in a medium saucepan and fry 2 eggplant halves at a time for about 5 minutes on each side until golden. Transfer to a large baking dish, skin side down. Position eggplants close together so there are no gaps. Gently open up the slits with a fork.
- Heat oven to 220°C.
- To prepare topping, heat remaining oil in a pan and sauté the onions with the remaining salt for 10 minutes until soft. Add the garlic, tomato purée, tomato paste, parsley and half a cup of boiling water. Simmer for 10 minutes.
- Pile topping onto each eggplant half. Drizzle 1 cup of boiling water around the edges of the dish so the liquid comes halfway up the eggplants. Bake for 35–40 minutes until browned. Juices will continue to be absorbed while cooling.
Serve hot or at room temperature. (Store in the fridge for up to five days.)
- Swap passata with 4 grated medium-sized tomatoes (no skin).
- Sprinkle with crumbled feta prior to baking, if desired.
- Leftover extra virgin olive oil from frying can be re-used on another occasion.