|Locust bean pods|
What Are They?
Stabilizers are any ingredients used to thicken the water in ice cream. They make ice cream smoother, by slowing the growth of ice crystals. And they can improve the texture generally, by adjusting the body, the speed of melt, and the finish.
Custard viscosity varies with the concentration of yolks and cooking temperature. For thickening and stabilization, ice cream requires at least 3% egg yolk by weight, which is between 1.5 and 2 egg yolks per liter. 4 to 6 yolks per liter is more common, and some people go higher, making a dessert that’s more a frozen custard than an ice cream, with egg flavors and textures dominating.
Cooked egg flavor, like viscosity, increases with concentrationand cooking temperature, and possibly also with cooking time. With yolk concentrations below 4%, eggy hydrogen sulfide compounds will probably be undetectable except after extreme cooking. For more egg-rich recipes, it may be beneficial to keep the cooking temperature between 70°C and 72°C for longer cooking, or below 82°C for shorter cooking.
Refined Starches, like cornstarch and tapioca, are a staple in many ice cream traditions. Cornstarch is most famously used in Southern Italian gelatos, which are often made without eggs or even cream. It’s become popular in many home recipes because it’s easy to find and easy to use, and gives reasonably good texture and stability. Tapioca works similarly. Starches generally give better flavor release than custard, but not as good as gums
I’ve seen some recipes that use arrowroot starch, which is possibly the best of the refined starches for savory applications, but should be avoided in ice cream. Arrowroot reacts with dairy ingredients to create unpleasant, snot-like textures.
We’re going to look at a small selection of gums individually, although much of the strength of gums comes from their synergies; they work best in combinations. The synergies are often such that the gums reinforce one another, and offer capabilities in combination that they did not offer individually. 1 + 1 = 3, etc.
The challenge in creating a gum blend lies is balancing the qualities of the individual gums with each other, as well as with the rest of the recipe, while taking into account the various synergies between those individual gums.
Locust Bean Gum, also called carrob bean gum, is made by milling the seeds of the locust tree. It’s been used as a thickener since at least 79 AD, and possibly much longer (look up traditional Indian recipes for cluster beans, another name for guar. They eat it by the bowl. We’ll be using it by the milligram). LBG has the most powerful ice crystal suppression of all the conventional gums. It favors a smooth, creamy, natural texture that does not draw attention to itself. It manages this by forming a weak gel that is stable while frozen, but that is highly shear-thinning, so once the ice cream melts and starts moving, most of the added viscosity vanishes. These characteristics make it the most important of the gums in ice cream.
LBG needs to be heated to hydrate. Most varieties require heating above 80°C, which is higher than ideal for many ice cream processes. Varieties sold by TIC gums and Willpowder hydrate at much lower temperatures.
Guar’s main use, besides strengthening the effect of LBG, is to add body. In high concentrations, it can make ice cream that’s chewy and elastic—either a flaw or a benefit, depending on your point of view. In New England, they like a lot of guar.
|Irish Moss / Carrageenan|
Carrageenan’s secondary role is to prevent wheying-off, a phenomenon of milk proteins preciptating out of suspension, aggregating, and creating grainy textures. Locust bean gum and carboxymethylcellulose can induce whey-off, so when these stabilizers are used you’ll usually see at least a minute amount of carrageenan.
|Giant kelp / brown algae. Where we get the alginate.|
Sodium Alginate is another seaweed extract, made from a brown seaweed grown in cold water areas. It’s a popular stabilizer, especially in low-fat and fat-free ice creams, because it forms a gel in the presence of calcium ions in the dairy. Its gelling quality makes it less useful in standard recipes (see the note on gels, below). The gel breaks into a fluid gel when the ice cream is spun, creating a unique body and viscosity. It’s quite effective at ice crystal suppression.
Sodium Carboxymethyl Cellulose: a big-ass molecule
There are low-viscosity varieties of CMC that suppress ice crystal formation with very little increase in base viscosity, if they’re used in a non-gelling blend. These theoretically allow you to control iciness and texture completely independently. Examples include TIC Gums CMC PH-15.
|You can get xanthan at the supermarket these days.|
Xanthan is often called the “wonder gum,” because it’s easy to dissolve at any temperature, it thickens at any temperature, works at a wide range of acidities, can tolerate alcohol, freezing, thawing, and just about anything else.
While most gum recipes require a scale that reads to 0.01g and careful dispersion and heating, cooks find xanthan pretty friendly in an old-fashioned-ingredient way. Need to stabilize a vinnaigrette? Toss in a pinch of xanthan and whisk until it’s dispersed. Want to add a bit of body to a sauce? Make a slurry with a pinch of xanthan, and whisk in just as you would with cornstarch or arrowroot.
|Dondurma vendor offering a cold chew.|
Salep, Mastic, Gum Arabic, and Konjac Flour are specialty stabilizers used in Dondurma, a traditional taffy-like ice cream popular in Turkey and Azerbaijan. Also called Maraş, this ice cream is both chewy and resistant to melting. Salep (flour made from the root of the Early Purple Orchid), and Mastic (hardened sap the Mastic Tree) are traditional. Gum arabic (hardened sap of the Acacia Tree) and Japanese konjac flour (starch from the Konjac, aka Elephant Yam) are more readily available substitutes. A combination of gellan gum (a microbial gum like xanthan, which forms gels) and guar can also substitute.
Blends and Variations
This is the same as the standard formula, but with the guar and carrageenan increased, and with soy lecithin added. Egg custard has thickening and stabilizing benefits, so its elimination requires a higher concentration of gums. The eggs also act as emulsfiers (see the next post).
The lecithin content of this blend is equal to a large egg yolk. You could theoretically use less—as little as 1/3 this much.
This is similar to the standard formula, but with iota carrageenan added, and total gum quantity doubled. Sorbets have no cream, and are low on solids. They have little to no inherent creaminess, and a lot of water to stabliize. The iota carrageenan forms a weak gel in combination with the locust bean gum, adding viscosity and body. The gel breaks easily into a fluid gel under shear and then re-forms. It’s freeze-stable and helps give a creamy texture.
Most sorbets have no fat content and so have no need for emulsifiers. If you wish to make a sorbet with chocolate, nut butters, olive oil or other fatty ingredients, you may get smoother results by adding some lecithin (maybe start with 1.5g / Liter).
We’ll look at all this in greater depth in a future post on sorbets.
Notes on Using Gums
If you experiment, pay special attention to the finish—the flavors and textures left behind in your mouth after swallowing. A successful stabilizer blend won’t be detectable. The ice cream flavors should linger and continue to develop, but shouldn’t be indelible. The feeling of creaminess should gradually dissipate. It should not devolve into pastiness or stickiness. These kinds of textural flaws point to over-stabilization, or to poor choices in stabilizing ingredients. I like the locust-guar-lambda blend as much for its transparency as for its effectiveness.
Note on Gels
Some common stabilizer ingredients form a gel in ice cream. Examples include Sodium Alginate and Kappa Carrageenan (which gel in the presence of the dairy’s calcium). Other ingredients form gels in combination with each other. Examples include xanthan gum with locust bean gum, locust bean gum with kappa or iota carrageenan, and carboxymethylcellose with locust bean gum, guar gum, or any carrageenans.
Gels are solids that exhibit properties of a liquid. Technically they are colloidal dispersions in which the solid forms the continuous phase, while the liquid (we’re always talking about water in the ice cream world) forms the dispersed phase. The solids create a network, with either physical or chemical bonds, and typically work in very small quantities—often less than 1% the weight of the water.
Gels can be strong or weak, yielding or elastic, brittle or tough, high or low viscosity. Under shear, some gels exhibit brittleness and crumble (like flan), others stretch and bounce back (like gel-o), others deform (like clay), others form a fluid gel that after sheer reforms into a gel (like iota carrageenan), others form a fluid gel that after sheer stays fluid (like agar).
To gel or no to gel? For most ice creams, I prefer non-gelling stabilizers. They tend to have a less intrusive texture, and to work more predictably, and to be easier to handle. Often with gelling stabilizers, the mix will be too thick after aging to spin efficiently in the ice cream machine. It will have to be thinned with a blender first, turning it into a fluid gel. If possible, I like to avoid this added step.
If you’re making low-fat or fat-free ice creams, or sorbets, gelling stabilizers become useful. They can add body and creaminess that’s often lacking in these recipes.
I hope this post has made a case for the usefulness of stabilizers—of custard, at least, but preferably something with a bit more effectiveness and flexibility. The questions should be about how deeply involved you want to get.
Hydrocolloids—Competent Ice Cream Stabilizers
Foods Under the Microscope—Effects of Stabilizers
The Role of Gelatin in Ice Cream
TIC Gum Gurus: (800) 899-3953
1“Microscopic investigation revealed that stabilized ice cream (locust bean gum and carrageenan) had significantly smaller mean ice crystal diameters both initially and as a result of heat shock and storage (24 weeks) compared to those of ice cream without stabilizer. However, the differences grew larger over time.”
—Caldwell, K. B.; Goff, H. D.; and Stanley, D. W. (1992) “A Low-Temperature Scanning Electron Microscopy Study of Ice Cream. II. Influence of Selected Ingredients and Processes,” Food Structure: Vol. 11: No. 1, Article 2.
Available at: digitalcommons.usu.edu/foodmicrostructure/vol11/ iss1/2