How do I get my sweet potatoes sweet? V. McIlroy

Sweet potatoes are like the Hemsworth boys. They start off all bland and starchy but put a little heat under them and they start to become more palatable. The cell walls in sweet potatoes, like all veg, are carbohydrate molecules made up of smaller sugar (glucose) molecules. When you heat sweet potatoes an enzyme is released that breaks down the carbohydrate into maltose (two glucose molecules).

This happens between 60C-70C. If you put sweet potato slices straight into a hot oven they won't spend a lot of time at this temperature. Instead, peel and cut the sweet potato. Place in a saucepan of water and heat until the water is hot but not boiling. Keep on a low heat for an hour. Drain. Roast as usual. You can place sweet potatoes in a cold oven then turn the oven on to give a sweeter potato.

What is cryo-blanching? P. Huggart

Sounds like a method for preserving a PM's intimate biographer but it is in fact a term coined by US modernist chefs to describe a method of using the freezer to help cook veg. Most vegetables are  about 90-95 per cent water. Freeze water and it expands. Ice crystals inside cells can break them apart. Freeze a raspberry the wrong way and it turns to puree.

Cryo-blanching uses freezing's destructive powers for good. Skinny green vegetables such as beans and asparagus are quickly frozen in a single layer, often in a vacuum bag. The vegetables are then thawed, drained and dried then sauteed.

The bright flavour and colour are quite remarkable, yet with a soft texture. It's a technique that is so easy to do at home. Cryo-blanching differs from the frozen peas from the supermarket. These are individually quick frozen (IQF), a process that maintains the structure and texture.

Treat boiled eggs like fresh meat. Photo: Marina Oliphant

How long do hard-boiled eggs last after cooking? R. Reid

When I was young I used to do the gardening for a pair of spinster sisters who lived on a farm. They had an expansive root cellar, kept their apples in a thick bed of beach sand over winter and coated their eggs in warm mineral oil to keep them longer.

This helped the natural cuticle, or waxy layer, on the outside of the shell that is a natural barrier stopping air getting in through the pores of the eggshell. When you boil an egg you remove this natural cuticle, rendering the boiled insides open to the air. Bacteria can then enter the egg. Treat boiled eggs like fresh meat. Once cooked refrigerate boiled eggs within two hours. Keep in the fridge and use within a week.

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