The PolyScience thermal immersion heater clamped to a pan of warm water in Chef Duncan Ly's kitchen at Calgary's Raw Bar looks innocuous enough.
In the stainless steel world behind this award-winning restaurant, it's just another piece of professional equipment. But ever since this little $1,500 machine - designed for precise temperature control in a lab setting - morphed into the latest cutting edge kitchen tool, it has caused a revolution in top restaurants and consternation for the food safety experts who police them.
The equipment is used for cooking sous vide or "under vacuum" - food vacuum-packed in plastic and slowly cooked in hot water, for up to 36 hours. It's a professional trick of the trade that top chefs are increasingly using to get that extra layer of flavour and texture in food, one that results in fork-tender proteins and intensely flavoured vegetables with all of their colour and vitamins intact.
But the technique can be risky. Without careful temperature control throughout the process there is a risk of deadly food poisoning. Since last year, New York chefs have been ordered by city health inspectors to cease using vacuum sealers and immersion heaters like Chef Ly's until they have an approved food-safety plan in place.
"There is a significant health risk - namely botulism - that can be associated with this process if it is not done correctly," says Sara Markt, press secretary for the New York City Department of Health and Mental Hygiene, who confirms that four New York restaurants have been fined for continuing to use sous vide equipment after being ordered to stop.
Even Chef Thomas Keller, the father of sous vide in North America, had to refrain from making his tender butter-poached lobster, squab and foie gras in the portable temperature-controlled tanks scattered throughout Per Se's kitchen until the city's food police approved his safety plan, now the standard for the food-processing industry. Since New York cracked down on sous vide, only a handful of restaurants, including Per Se, have qualified to resume sous vide cooking, while a few others are awaiting approval.
But in many other cities across North America, it's a growing, and largely unregulated, practice.
In Vancouver, chefs like Rob Feenie of Lumiere and Brian Fowkes of Rare consistently turn out their critically acclaimed cuisine with the help of sous vide. Chef Justin Labossiere says it was likely his lobster, artichoke and poached escabeche of shellfish - all prepared sous vide - that won him the top $10,000 prize at last year's Prince Edward Island International Shellfish Chefs Challenge. He now uses the technique to turn out up to 3,500 plates during playoff games at the Calgary Flames' massive new sports bar and restaurant complex, Flames Central and Wildfire Grill.
Cuisine Technology, the company that sells the PolyScience immersion heaters has a long list of customers on its website - and it reads like a who's who of top American chefs, from Jean-Georges Vongerichten to Charlie Trotter.
Sous vide cooking was first developed in the 1970s in France to preserve the delicate texture of foie gras, but chefs soon applied it to other foods. Portions of meat, fish, poultry or vegetables are vacuum-packed in a plastic pouch with flavourings such as herbs, spices and olive oil, then gently poached in hot water (usually below 62°C - about the temperature of hot tap water) for extended periods. The computerized thermal circulator keeps the water in the pan gently moving and warmed to a precise pre-set temperature, regulated to within one-tenth of a degree, often for many hours.
The science of sous vide cooking is straightforward: The ideal internal temperature is reached without ever overheating the food, so a medium rare steak retains its pink colour and juicy texture throughout.
