Category: Baking Ingredients

Arrowroot

Arrowroot has been gaining popularity as a general-purpose thickener for at least a decade, and indeed many cooks prefer it over cornstarch. The reason: because it does just about everything cornstarch does only better. Sauces thickened with arrowroot are clearer than those thickened with cornstarch. They also have less of an aftertaste which is nice if your sauce has very delicate flavor notes. Arrowroot also thickens at a lower temperature (about 180 F) and is a good deal more tolerant of acid and long boiling. Arrowroot gels can also be frozen and thawed, making them great for baked frozen fruit pies.

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Regarding Hydrocolloids

With the rise of molecular gastronomy the term hydrocolloid has become, shall we say, hot. But what exactly is a hydrocolloid? “Colloid” is a science-y sounding term that simply means one thing dispersed in another. They’re all around us, colloids. There are solid-in-liquid colloids like, say, paint. There are gas-in-liquid colloids (whipped cream), gas-in-solid colloids (styrofoam), liquid-in-liquid colloids (salad dressing), liquid-in-gas colloids (hair spray), the list goes on. A kitchen hydrocolloid, as the name implies, is a colloid that’s based on water or some other mostly-water liquid like juice or broth. Which is to say it’s a colloid where water is the medium that something else is being dispersed in — the “continuous phase” as it’s technically called — and the something else that’s being dispersed (the “dispersed phase”) is a gum or starch or a protein.

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Eggs

Eggs are without a doubt the most common thickener used in the pastry kitchen. Long, tangly proteins are the source of their thickening power, which can bring the water flow around them to pretty much a complete stop. Though egg proteins naturally occur in small clumps, they can be convinced to un-clump with the application of a little heat or with some agitation. Once they’re unfolded they can be further convinced to bond at which point all manner of textures are possible depending on the degree of protein coagulation: a thick liquid crème Anglaise, a semi-flowing pastry cream, a fully gelled crème brûlée or a crisp baked meringue. All the cook must guard against is over-heating or over-agitating those egg proteins which causes them to completely coagulate, squeeze out the moisture that’s between them and form tough curds.

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Pectin

Pectins are long-chain sugars that are found in the cell walls of plants, most especially in the walls of fruit cells. There they create a sort of elastic, moisture-retaining barrier and also function as a glue that holds the cells together. Pectins are especially abundant just before fruits are at peak ripeness. When fruit is cut up and/or mashed and then immersed in hot water the pectins come loose, dissolve and disperse. Under the right conditions those sugars can be brought back together into a flow-preventing network, but it takes a little coaxing since pectins repel each other in pure water. Acid generally does the trick as it changes the molecules’ polarity and encourages them to bond.

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Xanthan Gum

It’s hard to know where to start with an ingredient as incredibly versatile as xanthan gum. Yes, it’s a thickener, but really it’s much, much more than that. Add water and it becomes an elastic goo that works as a thickener, an emulsifier, a gluten replacer for gluten-free breads, a foaming agent, a fat replacer, a moisture enhancer, the list goes on. Notice I said “add water” and not “heat” for xanthan gum will thicken a liquid of any temperature, hot or cold. It doesn’t clump, so it can simply be whisked into a cold salad dressing or a hot sauce. A few seconds later — presto chango — you have an increase in viscosity.

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Potato Starch

The Joe Pastry All-Star Tour of Thickeners continues with potato starch. Boy. After a while all these white powders really start to look the same don’t they? And they’re awfully hard to photograph without overexposing them. Poor, poor blogger me. Anyway, where was I? Ah yes, potato starch. Potato starch is another pure starch like cornstarch and tapioca. In other words: pure thickening power in powdered form. Potato starch performs much like other thickening starches, and is good for a wide variety of applications, especially soups. It thickens at below-boiling temperatures and in fact should never actually be boiled, as it un-thickens quite rapidly at that point. Potato starch is especially useful during Passover for those who adhere to Jewish dietary rules, as it’s a non-grain thickener.

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Tapioca

Like cornstarch tapioca is a “pure starch” which means that compared to wheat flour it has no protein, bran or germ in it and as such packs more of a thickening punch. Tapioca comes in “pearls”, in granules (pieces of pearls) and in flour form. All can be used as thickeners, though the smaller the pieces the more readily they dissolve and the faster they act. Tapioca flour, my preference, dissolves almost instantaneously and because it gels at a lower temperature than cornstarch you can see the results immediately if the mixture is above 140 or so degrees Fahrenheit. Like other starch gels, however it also “un-thickens” when overcooked.

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Air

Please excuse the lack of photo. Air is a thickener we commonly take for granted, but bubbles slow the flow of water as well as any other type of thickener. Where would our egg white foams be without it? Of course the trouble with bubble thickening is that bubbles tend to pop. That’s largely a […]

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Fat

Melted fats or liquid oils make very effective thickeners in watery mediums. Oil and water won’t dissolve in each other, so when you combine them the result is a mutual disaffection that runs all the way down to the molecular level. Cooks can force the two to mix by a liberal application of the whip, which has the effect of breaking up large blobs of fat into many smaller ones. The thing is that no matter how small the blobs get they’re still many times larger than water molecules, and so do a very effective job at slowing down their flow.

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Cornstarch (Corn Flour)

Cornstarch is, obviously, a starch thickener which means it thickens much the same way wheat flour does: with tangles of long-chain sugars that slow down the flow of the water around them. However there are several important differences between wheat flour and corn starch. One of those is particle size. Cornstarch is milled much finer than wheat flour, which means when those particles come in contact with hot water, they begin to shed starch molecules much faster. So cornstarch thickening happens faster than wheat flour thickening, but then also “un-thickens” that much faster.

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