Thursday, August 14, 2014

Sous-Vide Series: Beginnings and Definitions

The nomenclature for sous-vide is confusing, if not outright misleading. So before we go on, let’s discuss the definitions.

Sous-vide literally means “under vacuum.” Traditionally, all food cooked by this method was sealed in plastic, with air evacuated by a chamber vacuum sealer. This keeps the food fresh (no oxidation), and eliminates air bubbles that could insulate the food or float the bag on top of the water bath.

Not your Grandma's commercial chamber vacuum sealer.

However, vacuum packing is not of central importance to sous-vide cooking. Most of what we care about is precise temperature control and a high-humidity environment. These are the only conditions needed for true low-temperature cooking.

It is this—low-temperature cooking—that is most often associated with sous-vide. It means cooking in an environment that is as hot, or only slightly hotter, than the final temperature of the food. To cook a piece of fish to 54°C, you cook in a humid environment (like a sous-vide bag) that’s 54° to 55°C. Conventional, high heat cooking would use an oven or skillet that’s above 200°C.

The differences are two-fold. With low-temperature cooking, you’re no longer dependant on precise timing to get the food cooked perfectly. Within reason, a little extra time in the cooker makes no difference. The food can wait until you and your guests are ready. And the food can be cooked truly perfectly, without any temperature gradient. No more undercooked food at the center and overcooked food at the edge. You no longer have to suffer the gray, dried-out ring of beef that has traditionally imprisoned a perfectly pink middle. For more details on low-temperature cooking, please see the excellent Cooking Issues primer.

Low-temperature cooking is the most common use of sous-vide, but not the only one. In Europe, especially, it’s common to cook in a water bath that’s significantly hotter than the final temperature. This introduces a deliberate temperature gradient (like, if you enjoy both rare salmon and medium-rare salmon, and want both in the same piece of fish). Sous-vide can give the same kinds of temperature gradients as high-temperature cooking, but with more control. This is called cooking with a temperature gradient (or Delta-T, if you want to annoy impress your friends).

We can achieve all these effects without a vacuum machine, packaging the food in Ziploc bags. We can even achieve them without a water bath: modern ovens like combi and c-vap ovens cook in approximately the same way, but with steam. These ovens create their own high-humidity environment, so no food packaging is required.

To complicate things further, vacuum-packing is used for culinary techniques that have nothing to do with cooking. The most common examples are high-speed pickling, marinating,  and texture modifications. Techically, these are sous-vide methods. But they’re not what we’re talking about most of the time.

In this blog, when we say sous-vide, we are using a definition that is innacurate but that has become more or less conventional. We mean: cooking in a sealed container placed in a water bath, heated with precise temperature control.

The sealed container could be a vacuum bag or a ziploc (I use ziplocs almost exclusively), a Food Saver bag, a few layers of plastic wrap, or a canning jar. The water bath could be heated by an immersion circulator, or a rice cooker with a jerry-rigged PID controler. It could even be a beer cooler filled from the kitchen tap with help from a thermometer.

A Poly-Science immersion circulator in a polycarbonate Cambro container.

Sous-Vide Supreme non-circulating water oven (the first product for consumers)
Franken-rice-cooker with PID controller. A popular option before circulators got cheap. From

Considering the low cost of circulators today, there’s little reason not to get one. But you absolutely don’t need a vacuum machine. They offer advantages, especially in a commercial, high-volume operation. For small-volume use, the disadvantages can be deal-breakers. The machines are large and expensive. Food needs to be cold before vacuum-packing. And the machines may need additional attachments if your bags contain liquids. Ziploc bags don’t suffer these particular limitations. (See this post for details on sous-vide with Ziplocs.)

So why do we stick with such a misleading term? Partly because it’s become entrenched. And partly because the suggested alternatives have been clunky or equally misleading (and sometimes both). Until further notice, we’ll be calling it sous-vide, and apologizing in advance for the confusion.

1 comment:

  1. Very useful info about sous vide cooking for a beginer like me. Thanks.