Freezing coffee beans can affect the taste of the end product.

Freezing coffee beans can affect the taste of the end product.

TRUE or false? Bad eggs float. Coffee is best stored in the freezer. Steaks should only be flipped once.

Kitchen lore, tips and tricks are passed from generation to generation and often accepted without question.

Advances in technology, food research and knowledge have exposed some long-held beliefs as myths, while others still ring true. We asked asked chefs, scientists and industry experts to sort fact from fiction.

Bad eggs do float.

Bad eggs do float.

'Bad eggs will float in a bowl of cold water, fresh eggs will sink'

TRUE The sink-or-float test sounds too simple to be true but it works, according to Tim Elwin, of Urban Food Market at Marrickville. ''There's a membrane between the egg white and the shell and as the egg gets older, the membrane pulls away from the shell, creating an air pocket,'' he says. ''As the air pocket expands, the egg will rise in water and eventually float.'' Another quick test for freshness is to look at the expiry date. ''An egg has an approximate six-week shelf life and is at its optimum in the first one-to-two weeks,'' Elwin says. ''So if you see a use-by date that's five weeks away, you know they're pretty damn fresh.''

'Food cooks faster in salted boiling water'

True ... food cooks faster in salted boiled water.

True ... food cooks faster in salted boiled water.

TRUE ''Adding salt to water raises its boiling point and so speeds cooking,'' says Harold McGee in his encyclopaedia, On Food & Cooking. ''When salt, sugar or any other water-soluble substance is added to pure water, the boiling point of the resulting solution becomes higher,'' he says. However, it takes about 30 grams of salt in a litre of water - the salinity of the ocean - to raise the boiling point by less than one degree Celsius. Rather, salt helps improve flavour. Pasta cooked in unsalted water tastes bland, McGee says, and cooking green vegetables in salted water reduces flavour loss.

'Storing coffee in the freezer helps it stay fresh longer'

FALSE The chief executive of Vittoria Coffee, Les Schirato, says while it's true coffee goes stale quickly, freezing it affects the viscocity of essential oils in the beans. ''When you make coffee, you are trying to extract all the essential oils,'' he says. If the coffee has been frozen ''you're not getting all the benefits of the crema''. Paul Geshos of Mecca Espresso in Sydney's central business district and Ultimo agrees. ''I would never freeze beans,'' he says. ''In my opinion, it defeats the purpose of buying fresh coffee.'' It's best to buy small amounts at a time and store in a vacuum package or airtight container in a cool, dark place.

False ... spoons don't preserve the fizz.

False ... spoons don't preserve the fizz in champagne.

'Placing a spoon in the neck of an open champagne bottle helps the wine stay bubbly'

FALSE French folk wisdom prescribes if you hang a silver spoon (handle down) in the neck of a champagne bottle, the contents will still be bubbly the following day. Thomas Hogan from the Lake House in Daylesford, Victoria - who recently completed the prestigious Court of Masters Sommeliers exam in London - disagrees. ''In an unopened bottle of champagne, the carbon dioxide which gives rise to the bubbles remains dissolved under pressure. The moment you open the bottle, the pressure and the carbon dioxide begin to dissipate. A professional champagne stopper slows the rate of pressure dissipation by recreating a seal, albeit imperfectly. A spoon can't possibly do the same job,'' he says. Hogan isn't alone - numerous studies including one by the French industry body for champagne have concluded the spoon's influence seems to be non-existent.

'Mushrooms continue to grow after they're picked'

True ... mushrooms continue to grow after they're picked.

True ... mushrooms keep growing after they've been picked.

TRUE A microbiologist and founder of Li-Sun Exotic Mushrooms in Bowral, Dr Noel Arrold, says compared to most produce, mushrooms remain active after they are picked and can continue to grow for up to four days. Arrold says common varieties such as button and field mushrooms are best stored in paper bags to avoid condensation and spoilage. However exotic mushrooms such as shiitake, enoki, and oyster are best stored in plastic covered pre-packs, ''because if you put them into paper bags they will desiccate''.

All alcohol burns off when you cook with wine or spirits

FALSE Coq au vin, beef bourguignon, flambes and Christmas puddings are classic dishes with alcohol as a central ingredient. But does the alcohol burn off completely when used in recipes like these? The answer is no, according to Ryan Flaherty from Estelle Bar & Kitchen in Northcote, Melbourne, who has also spent time at ElBulli in north-east Spain and Heston Blumenthal's The Fat Duck. ''Alcohol burns off on a scale of time versus temperature, but some alcohol always remains, regardless of the cooking technique,'' Flaherty says. Food author Harold McGee's guide to cooking with alcohol: long-simmered stews retain about 5 per cent of the alcohol added; briefly cooked dishes, from 10 per cent to 50 per cent; and flambes can retain as much as 75 per cent.

Mussels

Don't throw unopened mussels away without checking they're edible.

'If a mussel doesn't open during cooking, it should be thrown out'

FALSE Mussels that don't open during cooking can still be edible and it's easy to check, says the manager of the Sydney Seafood School at Pyrmont, Roberta Muir. ''Pry them open with a blunt knife, like a butter knife, over the sink,'' she says. ''If they smell and look good, they're fine to eat. If they're bad, they'll have a distinctly 'off' aroma. This applies to all bivalves such as mussels, pipis, vongole and surf clams.'' Unlike most seafood, bivalves should be bought when still alive. Before cooking, it's important to check all the shells are closed – a live bivalve will close with a gentle tap on the shell. ''If the shells don't close they're not alive, so discard them,'' Muir says.

'Store a ripe banana with other fruit to help it ripen faster'

True ... bananas can ripen other fruit.

True ... bananas can ripen other fruit.

TRUE This is due to the ethylene gas emitted by the banana as it ripens, says the produce buyer for Harris Farm Markets, Carlo Ceravolo. ''If you're trying to ripen [other] things, put them in there together,'' he says. ''If you don't want to, keep them out of the fruit bowl and on the kitchen bench.'' 

Avocado is another fruit that releases a high amount of ethylene gas. Ceravolo says a ripe banana can be situated next to a hard avocado to encourage it to ripen. This also works in reverse. ‘‘That ripe banana will speed up the ripening process of the avocado and vice versa,’’ he says. Some other fruits for which this applies are tomatoes, mangoes and papayas.

'When cooking pasta, drizzle olive oil in the water to stop the pasta from sticking'

Undecided ... cooking wine cork with octupus to tenderise the tentacles.

Undecided ... cooking wine cork with octopus to tenderise the tentacles.

FALSE Never put oil in the water, only salt, is the advice of the chef-owner of Ormeggio at the Spit and Spiedo at Westfield Sydney, Alessandro Pavoni. The trick to stopping those strands of pasta from sticking together is to get the water to a vigorous boil. ‘‘A lot of people think pasta has to simmer, it has to boil hard when you cook it. The boiling of the water keeps the pasta moving so it doesn’t stick.’’ Moving the pasta around in the pot while it is cooking is his other suggestion. ‘‘You also needs heaps of water,’’ he says.

What about when the pasta is strained, should olive oil be drizzled on then? No - this could make the pasta slippery and prevent the sauce from sticking, he says. Instead, drain the pasta and keep some of the cooking liquid aside. ‘‘So you want to drain the pasta, two to three minutes before it is cooked and then you want to finish the pasta cooking in the sauce. The pasta will release the starch and this will make the sauce stick together with the pasta. That’s the secret.’’ Add some of the pasta water to the pot if needed while the cooking process finishes.

'Cooking octopus with a wine cork helps tenderise the tentacles'

ON THE FENCE ''Nobody knows if this really works because nobody dares to cook without it,'' says the owner of Lucio's in Paddington, Lucio Galletto, when quizzed on the Italian tradition of cooking octopus with a wine cork. Common in kitchens across Italy, particularly in Liguria, it is claimed that an enzyme in the cork causes a chemical reaction that softens the fibres. A partner in New York's sprawling Italian marketplace Eataly, Mario Batali, also swears by the trick. But American food author Harold McGee says ''forget the wine cork'' and instead recommends brining or simmering as the best way to tenderise octopus.

'Steak should only be flipped once'

ON THE FENCE often overheard at backyard barbecues, this rule of thumb is hotly contested. Many home cooks and professional chefs subscribe to the flip-it-once theory, but chef and owner of British restaurant The Fat Duck, Heston Blumenthal, proposes an alternative. After extensive research, the British chef recommends flipping steak every 15 seconds (a two-centimetre-thick steak should take about two minutes to reach medium rare). ''This effectively gives the steak continual pulses of heat, which prevents it from overcooking,'' Blumenthal says. David Blackmore of Blackmore Wagyu Beef in Alexandra, Victoria, believes steak cuts such as rib-eye, rump, sirloin, scotch fillet, striploin and chuck should be cooked on the barbecue and can be turned up to three times. ''You want the surface to caramelise and form a crust,'' he says. ''Once the moisture starts to come through, flip them once and repeat on the other side. You don't want the juices to come out. Then flip the meat back and serve. Flip three times at the most.'' To avoid wagyu tasting overly fatty, Blackmore says the meat should be cooked long enough so the marbling (fine deposits of fat) is reabsorbed back into the meat and isn't noticeable when sliced.

'Searing a piece of meat seals in the juices'

FALSE This is one of the more widespread misconceptions in the kitchen. While the idea has been disproved by scientists, it still lives on, even among professional chefs. American author and chemist, Harold McGee writes: ''The crust that forms around the surface of the meat is not waterproof, as any cook has experienced. The continuing sizzle of meat in the pan or grill is the sound of moisture continually escaping and vaporising.'' Instead, when meat is seared, the surface browns (the Maillard reaction) producing new, intense flavours.

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