Do you really need to preheat the oven before cooking?

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Your mention of preheating an oven recently reminded me of a statement made by my brother-in-law. "Don't waste electricity by preheating to cook your scones. Put them in cold and they'll be cooked by the time the oven is hot," he said. Not being an adventurous cook, indeed not caring much for scones, I have never tested his theory, so is my brother-in-law correct? T. Frost

Well, T. Frost, we offer a great service here at the Brainfood Institute*. We have a test kitchen** in which we can conduct research. We, in which I mean me, made a batch of lemonade scones from the Phillippa's Home Baking cookbook on your behalf, placing them in a cold oven, which I turned on to 220C, the recommended baking temperature. Instead of taking the recommend 12-15 minutes to bake, at which stage they were still very doughy, they took 25 minutes to cook through. I then made another identical batch of scones and baked them in a preheated oven and they took the prescribed 15 minutes to cook through. They were almost identical in appearance, flavour and texture.

Assuming it takes 20 minutes to preheat an oven, the method your brother-in-law suggests to cook scones saves 10 minutes' worth of gas or electricity. This is fine for scones but don't try this with lighter cakes or bread, where the burst of heat expands the gas trapped in the batter or dough respectively to make the product rise before the gluten hardens to form the crust.

If I cook a curry or a casserole on the stovetop, is it safe to cover it and leave it out of the fridge for two to three hours until it's time to eat, to improve its flavour? A. Creswick

Curry is always better the next day. Overnight in the fridge the aromas of the spices meld and the curry changes to become more than the sum of its parts. If you did this on the kitchen bench overnight, you'd risk ending up giving the household food poisoning. Risky foods such as meat, fish, poultry, rice, dairy need to be stored under 5C and cooked foods should remain heated above 60C or cooled then chilled. Cooked foods, such as your curry, can be taken off the heat and left unrefrigerated and consumed, preferably within two hours, four maximum. After four hours it is recommended that unrefrigerated cooked food be discarded.

Letters

A few weeks back we gave instructions for pickling olives. B. Mitchell offers another way of preserving them. "I am an Australian who has lived on the Mediterranean for 10 years. I have 12 200-year-old olive trees. Now I have tried every method going back to Roman times to cure them. These methods are time-consuming and can fail if you make one miscalculation. Here is a failsafe, easy way to get olives to a state where they can be enjoyed with wine and in food. Place ripe olives on a baking dish lined with foil. Sprinkle with olive oil and plenty of sea salt. Place in a preheated oven at 180C for 25 minutes. Allow to cool. Store in the refrigerator."

*Like the Pond's Institute, it's a bit made up.

**Actually my kitchen at home.

Send your vexing culinary conundrums to brainfood@richardcornish.com.au or tweet to @Realbrainfood.

Brain Food by Richard Cornish is out now from MUP (RRP $19.99, eBook $11.99).