Cooking for Geeks: Real Science, Great Hacks, and Good Food (62 page)

Making Foams: Lecithin

Foams are another area of play in modernist cuisine. If you ever happen to be served a dish that has a “foam” component — say, cod served on a bed of rice with a “carrot” foam or
uni
(sea urchin) in a shell with green apple foam, it was probably created by adding a stabilizer such as lecithin or methylcellulose to a liquid and then whipping or puréeing it. (Foams can also be created using cream whippers as described in
Cream Whippers (a.k.a. “iSi Whippers”)
in
Chapter 7
.) While perhaps a little too trendy, it’s a clever way to introduce a flavor to a dish without adding much body.

Instructions for use.
Add about 1% to 2% lecithin to your liquid (by weight, i.e., 1g lecithin per 100g liquid) and use an immersion blender to froth the liquid. Hold the immersion blender up and at a slight angle so that the blades are in contact with both the liquid and air.

Uses.
As an emulsifier, lecithin can be used to create stable flavored foams. It’s also used as an antispattering agent in margarines, an emulsifier in chocolate (to reduce the viscosity of the melted chocolate during manufacturing), and as an active ingredient in nonstick food sprays.

Origin and chemistry.
Lecithin is typically derived from soya beans as a byproduct of creating soy-based vegetable oil. Lecithin is extracted from hulled, cooked soya beans by crushing the beans and then mechanically separating out (via extraction, filtration, and washing) crude lecithin. The crude lecithin is then either enzymatically modified or extracted with solvents (e.g., de-oiling with acetone or fractionating via alcohol). Lecithin can also be derived from animal sources, such as eggs and animal proteins, but animal-derived lecithin is much more expensive than plant-derived lecithin, so it is less common.

Lecithin molecules have polar and nonpolar regions that are most stable when one side is exposed to a polar substance and the other side to a nonpolar substance. See the sidebar
The Chemistry of Emulsifiers
for a description of how lecithin stabilizes foams.

Fruit Juice Foam

In a large mixing bowl or other similarly large and flat container, blend with an immersion blender:

½ cup (100g) water
½ cup (100g) juice, such as carrot, lime, or cranberry
1 teaspoon (3g) lecithin (powder)

Notes

Hold the immersion blender such that it is partly out of the liquid. You want to allow it to siphon air into the mixture.
Allow foam to rest for a minute after blending, so that the resulting foam that you spoon off is more stable.
Try other liquids, such as coffee or beet juice. Lecithin works best at around a 1–2% concentration (2g lecithin per 100g of liquid).

Lecithin can be used to make a large-bubble foam that is surprisingly stable for long periods of time.

The Chemistry of Emulsifiers

You might be wondering why oil and water are able to “mix” in the presence of an emulsifying agent, after the earlier discussion about polar (e.g., water) versus nonpolar (e.g., oil) molecules not being able to mix. An emulsifier has a hydrophilic/lipophilic structure: part of the molecule is polar and thus “likes” the water, and part of the molecule is nonpolar and “likes” the oil. Emulsifiers concentrate at the boundary between water and oil because of the charge structure of the molecules.

Adding an emulsifier keeps foods from separating by providing a barrier between droplets of oil. Think of it like a skin around the oil droplets that prevents different droplets from touching and coalescing. Emulsifiers reduce the chance that oil droplets will aggregate by increasing what chemists call
interfacial tension
. The oil and water don’t actually mix; they’re just held apart at the microscopic level.

Emulsifiers stabilize foams by increasing their kinetic stability — i.e., the amount of energy needed to get the foam to transition from one state to another is higher. Take the foam of a bubble bath as an example: the soap acts as an emulsifier, creating a foam of air and water. Water doesn’t normally hold on to air bubbles, but with the soap (the emulsifier), the interfacial tension between the air and water goes way, way up, so it takes more energy to disrupt the system. The more energy it takes, the more kinetically stable the foam is, and the longer it’ll last.

Take a look at the following two photographs to see what a difference an emulsifier can make (and see
http://www.cookingforgeeks.com/book/lecithin/
for a video demonstration).

A photo under a light microscope of a half-water, half-oil solution. (The slide is pressing the oil droplets flat.)

The same mixture with 1% lecithin added. The droplets are stable and do not coalesce into larger drops.

Anti-Sugar: Lactisole

This one is unusual. Unlike the modern additives covered so far, which have essentially focused on either trapping liquids in a gel structure or changing the physical state of food, “anti-sugar” is an additive used to modify a flavor sensation: it reduces the sensation of sweetness. (And no, mixing sugar and anti-sugar does not result in more energy being released than eating just plain sugar.)

One of the challenges facing the food industry is the need to maximize shelf stability and storage potential while maintaining acceptable flavor and texture. Sugar is used in confections and sweets not just for its sweetness, but also as a preservative: because sugar “latches” on to water, it reduces the amount of water available in a food product for bacterial growth. Think back to the FAT TOM rule from
Chapter 4
: bacterial growth is inhibited by reducing the water activity (the “M” in FAT TOM is for moisture), and because sugar is hygroscopic, adding sugar reduces the freely available water. But more sugar means increased sweetness, so the other flavors in foods can end up being masked with a cloying, overly sweet taste.

In the mid-1990s, Domino Sugar researched chemical modifiers that would reduce the perception of sweetness. The compound lactisole — a carboxylic acid salt — happens to do just that: add it to your foods at a concentration of around 100 parts per million (ppm), and goodbye sweet sensation, as it interferes with your taste buds (the TAS1R3 sweet protein receptor, for you bio geeks). Unlike traditional methods of dampening sweetness in a dish (i.e., adding bitter or sour ingredients), lactisole works by inhibiting the sensation of sweetness on the tongue, so it does not impact perception of saltiness, bitterness, or sourness. Sadly, you can’t add it to foods to remove the calories from sugar.

Domino sells a product called Super Envision
^®that is a blend of mostly sucrose, some maltodextrin, and “artificial flavor” at 10,000 ppm. It’s meant to be used at around a 1% concentration in the final product, so the 10,000 ppm becomes 100 ppm. (Gee, I wonder if that “artificial flavor” could be lactisole?)

Try tasting “anti-sugar” in caramel sauce (see
Caramel Sauce
in
Chapter 4
). Add a small quantity of Domino Super Envision to one bowl of caramel sauce, leaving a second bowl of caramel unmodified for comparison’s sake. The taste of the burnt compounds in the caramel sauce will be stronger in the adulterated bowl, because the sweet sensations won’t be masking them.

With lactisole, what was once perishable can be mass manufactured without the same worries about spoilage by increasing the amount of sugar and then canceling out the additional perceived sweetness. Some jams and jellies, for example, need a certain level of sugar to remain shelf-stable. Super Envision also shows up in products such as salad dressings, in which sweetness from stabilizers or thickeners would be undesirable, and in some mass-manufactured breads. Pizza dough, when baked, is more visually appealing if it turns golden brown. Adding sugar is an easy way to get a browning reaction, but sweet pizza dough isn’t so appealing.

For a list of industrial-style recipes — cereal coatings, instant chocolate milk mix, marshmallows, meringue toppings — see Domino’s Envision Applications page at
http://www.dominospecialtyingredients.com/recipes/envision_more.html
.

Savory French Meringues

Without sugar, meringues — well, egg whites — bake into a dry brittle foam that resembles Cheetos (but without the flavor): it’s extremely crunchy and, without any flavorings, not particularly pleasant. When sugar is added, the meringue turns into something light, slightly chewy, and delightful.

Try the following experiment to understand how sugar helps stabilize meringues and how lactisole masks the sweetness.

Start by separating six egg whites into a bowl and whipping to stiff peaks. Using a scale, weigh out into three small glass or metal bowls:

Standard meringues

50g whisked egg white
20g granulated sugar

Meringues sans sugar

50g whisked egg white

Meringues with “anti-sugar”

50g whisked egg white
20g granulated sugar
1g Domino Super Envision

Transfer each batch into a piping bag. (A plastic bag with a small cut in the corner works well.) Pipe onto a Silpat or a cookie sheet lined with parchment paper.

Note

Add in chopped nuts, dried fruit, and/or chocolate chips to extend it. Try dipping the baked meringue in tempered chocolate as well.

Bake the meringues in an oven set to 200°F / 95°C for several hours, until dry. (Trying this in the evening? You can set your oven to ~300°F / 150°C, pop the cookies in, and then turn the oven off and come back the next morning.)

Note

Don’t try baking meringues directly on the cookie sheet. Proteins are very sticky and will bind to it, making it hard to remove them without breaking them. Because it’s flexible, the Silpat or parchment paper can easily be peeled off the back of the cooked meringues.

You can see the difference instantly in the “meringue” made without sugar: the egg white doesn’t flow as smoothly out of the piping bag. The standard and anti-sugar meringues have the same texture, but the taste of the standard one is, as expected, sweet. The anti-sugar one tastes pretty much like nothing, as egg white doesn’t carry a strong flavor of its own.