Science and Cooking: From Haute Cuisine to Soft Matter Science - Emulsions and Foams

As I posted in my October 13th blog entry, I've enrolled in an on-line course about the relationship between science and cooking. I'm still plugging away at this, good thing I decided to do this for the knowledge.

Here's what went down on the eighth week.

• The focus of this week's lecture was on emulsions and foams. Ever since seeing that Marcel guy from "Top Chef" using them as a crutch, I respect the science behind foams a lot more than I do his use of them - that preening prat makes them look as pretentious as he is.
• An emulsion is drops of a fluid in a second fluid. A foam is the same thing, except instead of a fluid in a fluid, it's drops of air in a fluid. Mayonnaise is an edible example of an emulsion (oil and water). An obvious example of a foam is the stuff on top of your fancy coffee at the coffeehouse - your whipped cream is also a foam.
• Aioli is like a garlic mayonnaise. Below, Nandu Jubany, chef and owner of restaurant Can Jubany in Vic, Spain, shows how to make some:
• You might be asking how can an emulsion exist since oil and water don't mix. Emulsifying is done by slowly adding one ingredient to another while simultaneously mixing rapidly. This disperses and suspends tiny droplets of one liquid through another.The two liquids would quickly separate again, however, if an emulsifier, a stabilizer between the two liquids, wasn't added. In mayonnaise, the emulsifier is egg yolk, which contains lecithin, a fat emulsifier. Another food that contain emulsifiers is gelatin.
• Chemically, emulsions are colloids, heterogeneous mixtures composed of tiny particles suspended in another unmixable material. Though less than one one-thousandth of a millimeter, these particles are larger than molecules, and do not settle out and will pass right through filter paper. The particles in a colloid can be solid, liquid or bubbles of gas, and can be suspended a solid, liquid or gas, although gas colloids cannot be suspended in a gas.
• It's the tiny air bubbles in foams like meringues, soufflés, and mousses their texture and mouth-feel. In most of these foods, proteins are the main surface active agents that help in the formation and stabilization of the dispersed gas phase. To create a protein-stabilized foam, it usually involves bubbling, whipping or shaking a protein solution and its foaming properties refers to its capacity to form a thin tenacious film at the gas-liquid interface for large amounts of gas bubbles to become incorporated and stabilized.
• When protein concentrations are increased to their maximum value the foaming powers and foam formation are generally increased. A protein will always have certain stresses that it must over come, such as gravitational and mechanical, it’s the proteins ability to stabilize foam against these stresses that determines the foams stability. The foams stability is usually expressed as the time required for 50% of the liquid to drain from foam (a 50% reduction in foam volume).
• Here once again is Nandu Jubany to demonstrate how he makes a carrot foam:
  
• Two of the recipes used in this week's lesson were for hollandaise sauce and for a chocolate soufflé, taken from Julia Child's "Julia and Jacques Cooking at Home", and the Food Network website, respectively. Try them out to conduct your own emulsion and foam experiments.

Ingredients - Hollandaise sauce

1 Tbsp. (15 mL) water
1 Tbsp. (15 mL) fresh lemon juice
3  large egg yolks
6-8 oz. (177-236 mL) very soft unsalted butter
1 dash cayenne pepper
salt and ground white pepper to taste

1. Whisk the yolks, water, and lemon juice in the saucepan until thick and pale.
2. Set the pan over moderately low heat and continue to whisk at reasonable speed, reaching all over the bottom and insides of the pan, where the eggs tend to overcook.
3. Frequently move the pan off the burner for a few seconds, and then back on. (If, by chance, the eggs seem to be cooking too fast, set the pan in the bowl of cold water to cool the bottom, then continue).
4. As they cook, the eggs will become frothy and increase in volume. When you can see the pan bottom through the streaks of the whisk, remove from the heat.
5. By spoonfuls, add the soft butter, whisking constantly to incorporate each addition. As the emulsion forms, you may add the butter in slightly larger amounts, always whisking until fully absorbed. Continue adding butter until the sauce has thickened to the desired consistency.
6. Season lightly with salt, pepper, and a dash of cayenne pepper, whisking in well. Taste and adjust the seasoning, adding droplets of lemon juice if needed. Serve lukewarm with fish or vegetables.

---

Ingredients - Chocolate soufflé

7 oz. (198 g.) finely chopped bittersweet or semisweet chocolate
4 Tbsp. (59 g.) unsalted butter (+ extra for greasing the molds)
1.5 tsp. (7.4 mL) pure vanilla extract
3  large egg yolks
3 Tbsp. (45 mL)  warm water
1/2 cup  (65 g.) sugar (+ extra for lining the molds)
8  large egg whites
1/2 tsp.  (2.4 mL) fresh lemon juice
confectioners' sugar for garnish

1. Brush 6 (6-ounce (177 mL)) ramekins with butter and coat with sugar. Preheat oven to 400 degrees °F (204 °C).
2. Melt and combine chocolate and butter in a double-boiler until smooth. Remove from heat and stir in vanilla extract.
3. Beat egg yolks and warm water until frothy. Add 2 Tbsp. sugar and beat till ribbons form. Fold into chocolate mixture.
4. Beat egg whites and lemon juice on medium until frothy. Gradually add the sugar, beating until stiff (but not dry) peaks form.
5. Fold about 1/4 of the egg whites into the chocolate to lighten; then fold in remaining whites until blended. Gently ladle or spoon the soufflé mixture into the ramekins and place on a baking sheet.
6. Immediately bake until the souffle rises about 1.5 inches above the ramekins and the tops brown, approximately 18-20 minutes. Remove from oven, dust with confectioners' sugar and serve immediately.