The potential advantages of sous-vide (a French term meaning "under vacuum") cooking are great: you get great flavor, better texture and can lower your energy consumption and reduce waster, all while you enjoy chef-prepared foods. And because sous-vide foods are prepackaged under vacuum seal, they enjoy a particularly long shelf life— as in canned foods, there's no oxygen in the package to catalyze an aerobic decay process.
We really believe that the sous-vide renaissance underway now will revolutionize American cooking both in the home kitchen and in the restaurant industry. But we do get asked a lot of questions.
In particular, some cooks find it challenging to achieve a consistent texture when cooking sous-vide vegetables. We'll address those concerns here and show you how you can get the best from your veggies.
It's all about chemistry.
For those of you who haven’t experimented with new cooking methods, let's recap a bit of the background science, shall we?
As you might imagine, cooking is essentially a chemical reaction. when you mix ingredients, you are placing substances with different properties in close proximity and precipitating a reaction process. The same is true when you cook or chill your food: the addition or subtraction of heat causes the structure of the food to change.
A commonly observed reaction is the way meats change consistency and color when heated. When you throw a burger on the grill, you can see the color change from bright red or pink, to a nice, sizzling brown. The heat from the flame causes a Maillard reaction, in which amino acids (the building blocks of proteins, which are in turn the primary building blocks of the meat) and residual sugars in the meat begin to react with one another.
The sugars in the meat break down and rearrange (caramelize) to give you the brown color. The amino acids rearrange into tightly-folded protein chains, which give cooked meat its springier texture relative to raw meat. These processes take place even as the sugars and amino acids react with one another to produce cooked meat's smooth, savory flavor.
Understand the difference between cooking vegetables and cooking meat.
Again, it goes back to chemistry. Meat proteins typically reach their maximum physical change (short of carbonization, or "burning") somewhere between 140-165 degrees Fahrenheit.
Vegetables contain a substance called pectin, a polysaccharide (substance made up of simple sugar molecules linked together into a larger, more complex molecule— essentially the sugar-based equivalent of a protein chain) that holds plant cells together. It's also used in cooking as a thickening agent; pectin is what makes jelly have jelly-like consistence. But unlike meat proteins, pectin must reach a temperature of 183 degrees Fahrenheit to begin breaking down— which explains why jelly-making is accomplished under high temperatures.
If you're cooking meat and vegetables together sous-vide, and your water bath never gets to 183°F, your vegetables aren't going to fully cook. Likewise, if you are trying to cook meat sous-vide in a 183°F bath along with your vegetables, your veggies will do just fine, but the meat probably won’t be as perfectly pink as it would be cooked at a lower temperature.
The answer? Cook vegetables and meats separately.
Just like you wouldn't attempt to bake a cake and a meatloaf in the same oven at the same temperature at the same time, you probably don’t want to package your sous-vide meats and vegetables in the same bag when you’re designing a new ready-to-eat meal.
With that in mind, there are plenty of vegetables that do exceedingly well in sous-vide recipes.
Carrots are one tasty example: with just a little butter, sugar, salt and pepper, and herbs to taste, you can get a nice, tender, flavorful carrot that will melt in your mouth without first going to mush.
Parsnips, an oft-overlooked carrot relative, and vegetables in the onion family, like leeks and turnips, are also especially good for sous-vide cooking. You could also try beets, radishes or artichokes; sous-vide preparation can take an overly-tough, crunchy vegetable and turn it into a completely delectable meal component that is sure to please.