Wednesday, October 29, 2008
Xanthan Gum, Demystified
If you read the ingredients label on gluten-free baked goods, check our recipe for a gluten-free flour blend, or otherwise spend time with gluten-free baking, you're almost certainly bound to come across xanthan gum, one of the secrets to successful GF baking. But what is it, and how does it work?
Xanthan gum is named for the bacteria, Xanthomonas campestris, which plays a crucial role in this description. Technically speaking, xanthan gum is a polysaccharide, which is just a fancy way to say "a string of multiple sugars." (Starch, in its myriad forms, is a polysaccharide.) To create xanthan gum, the Xanthomonas campestris bacterium is allowed to ferment on a sugar. In the United States, corn sugar is typically used as the base for the fermentation. The result is a "slime" (there's no other way to put it) that is then dried and milled to create the powder xanthan gum you buy at the store. It's expensive, but thankfully, a very little bit goes a long way!
Xanthan gum has a number of powerful properties. First, it works as an emulsifier, encouraging liquids that normally don't like one another to mix together. For this reason, xanthan gum is often used in salad dressings to prevent the oil and vinegar from separating. Second, it works as thickener, increasing the viscosity of liquids and batters. Third, it can create a creamy texture. For this reason, it's sometimes added to ice creams and dairy-free recipes that want to emulate the creaminess of milk.
Thanks to those reasons - outside the world of gluten-free baking - xanthan gum has found a devoted following in the realm of molecular gastronomy, in which chefs do unconventional things with conventional ingredients. For example, imagine expecting to bite into an egg yolk, but instead getting the flavor of mango! Chefs can use xanthan gum to increase the viscosity (thickness) of a mango puree to help it to mimic an egg yolk. Or, if you've ever watched Iron Chef America on the Food Network, you know that the chefs are often fond of making flavored foams. Those foams are often not possible without the addition of xanthan gum, which gives the base liquid enough viscosity to be able to hold the form of the foam bubbles without popping and releasing the air inside.
In the world of gluten-free baking, on the other hand, xanthan gum plays the crucial role of imitating gluten. How? In baking, gluten is what makes dough "doughy." It gives the dough elasticity, as well as viscosity. Those properties help to hold a cookie together while it bakes on a sheet in the oven, and they enable cakes and breads to hold onto the gas bubbles that form inside them - this allows them to rise and take shape. If gluten didn't help the dough to retain those air bubbles, they'd escape and the cake (its gas bubbles based on baking soda or baking powder) or the bread (based on yeast) would fall.
Prior to the use of xanthan gum, these were the primary problems with GF flours and baking recipes. Without the gluten, how do you prevent those problems from happening? Xanthan gum provided the solution - by increasing the viscosity of a GF dough, xanthan gum enables the dough to hold together while baking, and to retain the all-important gas bubbles that form during the process.
The gluten-free flour blend we've developed has a baseline level of xanthan gum that makes it a great all-around flour mix. It's perfect to use in pancake and waffle recipes. But we've discovered that other recipes - such as cookies - require an additional quantity of xanthan gum.
The photo above shows two identical chocolate chip cookies, both made with identical recipes and both made using our gluten-free flour blend. The only difference is that the cookie on the left has no additional xanthan gum, while the cookie on the right has a small amount added to the dough prior to baking. You can see how dramatic the results are. Without the additional xanthan gum, the cookie on the left spread paper-thin while baking. With the additional xanthan gum, the dough for the cookie on the right maintained enough viscosity to withstand the baking process, resulting in a cookie that had great thickness and texture.
For sure, xanthan gum isn't the only gluten substitute you'll find in GF baking. Guar gum is another common ingredient, and there are others. But we've found xanthan gum to be a powerful ingredient in our flour mix and recipes, and have been more than happy with the results!
Finally, a reminder: tonight Kelli and I are teaching a GF cooking class at the Whole Foods in Littleton, Colorado. It starts at 6:30pm. Please come by and say hello!