Richard Cornish

La Gina canned tomatoes
Approach with caution ... ring-pull tin cans can be tricky.

I often snap off the ring-pull on tins of tomatoes before I get the lid off. How can I safely get the lid off?

I am nervous around ring-pull tin cans. The combination of razor-sharp steel, bare-knuckle flesh and application of brute force has me thinking about the quickest route to hospital casualty. Next time you find yourself with the ring detached from the lid, turn the tin upside down and use a can opener to open the bottom. If you have broken the seal, complete the task over a bowl, otherwise you could be covered in red liquid - hopefully not blood.

I read recently where you recommend substituting pure icing sugar for sugar in dessert baking. Should I use a cup measure or the scales? J. Warth

Cup measures in baking are great for simplicity but diametrically opposed to precision. For example, a quick experiment saw a cup of hard, lumpy icing sugar weigh in at 150 grams, while a cup of nice, fluffy icing sugar from a fresh packet weighed in at 125 grams. I weighed three different types of sugar, with one weighing 175 grams a cup while the others weighed 200 grams. To add further confusion, an imperial cup of sugar weighs 230 grams and a customary US cup of sugar weighs 190 grams. Because of this, I am a big fan of using digital scales in baking - a gram is a gram is a gram. (I bought a pair of scales with one-gram increments used for weighing post for about $100 from Officeworks.) However, as a rule, a metric cup of sugar weighs 200 grams and a metric cup of icing sugar weighs 125 grams. You do the math.

When buying organic food at the farmers' market, some farmers say ''we are organic but not certified''. What is the difference between certified organic and not? M. Rathbone

I remember visiting a farm and the farmer saying, ''We're basically organic. We don't use any sprays.'' Under his feet, however, was a great line of bare earth covered in dead bugs where he had sprayed weed killer. Out of his familiarity with weed killer being sprayed on the ground and not on his fruit trees, he didn't consider it a chemical spray. Certified organic and bio-dynamic farmers are audited and inspected by one of seven certifying bodies, such as Australian Certified Organic and the Bio-Dynamic Research Institute, which are authorised by the Australian Quarantine and Inspection Service. They make sure the standards set out by their organisations, which demand the eschewing of many man-made fertilisers and pesticides, are maintained. It has been proved that pesticide residue in certified organic food is lower than in conventional food. A co-founder of Slow Food in Australia, James Broadway, warns on buying food by any label alone and encourages people to trust their senses. See daff.gov.au /aqis/about/contact/aco

My husband is allergic to all seafood, including Thai fish sauce. What could I use in its place? H. Ross

If you saw them make Thai fish sauce, you'd never eat it again. Entire little fish are salted in great concrete vats for about a year. During the process, salt-loving bugs transform the protein in the fish into amino acids, which give it that incredible mouth-filling sensation. So you're looking for something full of amino acids and salt - you could try Vegemite, but it takes a great chef to make Vegemite taste good in a dish. You could try Maggi Seasoning, available in supermarkets and popular on Vietnamese pork rolls, but it's not dirty enough. Or head to an Asian grocer and try some mushroom soy sauce. It's salty and full of amino acids. To add that mysterious back note of decay, soak a few grams of porcini mushrooms in a little hot water, pulverise these, and add them to a few tablespoons of mushroom soy.

Send your queries to brainfood@richardcornish.com.au