The CVap oven (CV stands for controlled vapor) was originally created for Colonel Sanders (Kentucky Fried Chicken) over thirty years ago by Winston Shelton to keep chicken moist and warm for long periods of time. While with a conventional oven, moisture evaporates as food is heated, drying it out, the CVap oven produces a humid, rain forest-like environment that surrounds the food with vapor, preventing it from losing or gaining any moisture. For a restaurant like KFC, chicken that was fried in the morning and placed in a CVap stayed crisp and tasted the same no matter when it was served. At the time however the CVap was only used as a holding oven.
Today CVap ovens are used by many chefs to cook food at low temperatures in a manner similar to sous vide cooking. The CVap allows cooking either with vapor or no vapor at low temperatures. The presence of vapor speeds up the cooking time. The advantage here is no vacuum bag is required. Most major restaurant have one or more CVap's in their kitchen. chef Jean-Georges (3 star Michelin chef in NYC), use it almost exclusively.
Since Cvap ovens having the ability to sous vide food when vacuum packed some chefs believe that over time CVap ovens may replace the current sous vide tools.
CVap ovens do have a limit at the higher range of cooking. Their temperature range is usually between 90° - 200°F. With a browning control of 1-10 which is determined by the humidity of the chamber.-
CVap vs. Sous Vide --and-- Combi Ovens vs Sous Vide
While sous vide is rather easy to use considering only temperature is a factor, CVap has two variables -- temperature and humidity. Understanding wet bulb and dry bulb temperatures makes for a learning curve for CVap oven which is minimal when using the sous vide technique.
With both CVap and sous vide you don't have to figure out how long or at what temperature is needed to cook something. One major advantage with CVap cooking is that you don't have to put the food inside a vacuum packed plastic container; you can actually cook food that looks as though it came out of a conventional oven. This is also extremely important when considering that some foods e.g., fish can be texturally altered under vacuum.
Neither sous vide cookers or CVap ovens have the ability to brown food since the temperature is below that required by the Maillard Reaction. Foods that require browning need to be seared or grilled after removing them from either Sous Vide or CVap appliances. This is usually done just prior to serving still making these methods of cooking desirable.
Combi means "combination" which is a mix of the hot, dry air of an oven and the wet heat of a steamer. Combi ovens can cook with ambient air (as an ordinary convection oven does), with injected steam, or with a combination of both. A combi oven is an oven with three functions: convection, steam and combination cooking. In the convection mode, the oven circulates dry heat - ideal for pastries and breads. The steam mode injects water into the oven to poach fish, rice and vegetables. This allows something like a Crème brûlée to be tackled without using a bain-marie.
A combi oven is not cheap. It costs roughly $15,000 for an oven the size of a half sheet pan and several times that for larger configurations. Miniature combi ovens designed for commercial kitchens have recently come on the market for as little as $2,000, but these use very small pans. And the technology is starting to come into the home kitchen.
Downside of Combi Ovens
Combi ovens are not able to hold low temperatures well at low temperatures (below 140o F). And, this becomes a problem when cooking fish and meat where more exact temperatures are needed. At these temperatures there can be a variation of 4-9oF whereas in sous vide the temperature will not vary more than 1-2 oF (ref. Modernist Cuisine at Home pg. 38). A few degrees can drastically alter taste and texture. See Cooking Chicken Sous Vide.
Thermador and Wolf have recently launched products joining the German Miele and Gaggenauin the area of steam ovens or combi ovens. Cuisinart (photo below) also launched a very affordable version. Alto-Shaams and Cambros have also been in the business many years.