These are all properties of egg white, or albumin, proteins. Able to foam both at their “natural” pH of 8 to 9 and near their pI of 4 to 5, egg albumin proteins are models of foaming functionality. Ovalbumin is the fraction most responsible for goosing foam capacity, while ovomucin contributes stabilization, making for a rapidly formed foam that retains its volume, even when heated. (Careful, though: Egg white proteins denature and lose their foaming capacity above 136.5°F.) Whipping increases the number and decreases the size of the foam’s air bubbles, “growing” the foam and aggregating the proteins at the surface. However, beating for more than 6 to 8 minutes, or at shear pressures above 5,000 psi, can denature the proteins so much that they no longer adsorb adequately.
Other factors affecting egg-white foams include salt, which decreases stability, and sugar, which delays foam formation. Perhaps most important is the injunction against lipid contamination; levels as low as 0.05% can significantly impair foaming performance. This applies not only to egg white foams, but to soy- and dairy-based foams, too. That’s why straight whey protein isolates, with their high concentration of protein, form the best foams among whey proteins. “The more protein, the better the foam,” says Paulsen.
Canola proteins also show foaming potential, Segall says, although “much of the research we have conducted on foam properties has been done in the laboratory with model systems.” While his company is just now focusing on applied work, they’ve observed that foams made with a canola albumin product achieve both greater volume—perhaps because of the constituent proteins’ low molecular weight—and greater stability over time than those made with the globulin ingredient.
Kimberly J. Decker, a California-based technical writer, has a B.S. in consumer food science with a minor in Eng-lish from the University of California, Davis. She lives in the San Francisco Bay Area, where she enjoys eating and writing about food. You can reach her at
kim@decker.net
.
In Bloom
Chemists quantify gelatin’s gel strength using Bloom, defined as the weight in grams required to de-press a half-inch plunger 4 mm into a standard gelatin solution. Different gelatin ingredients exhibit dif-ferent Bloom strengths, depending on the conditions of their extraction. “The first extraction we do on the raw material”—usually porcine skin, less commonly bovine hide and bone—“is usually your highest Bloom, because it’s processed at a lower temperature,” says Mindi McKibbin, associate chemist, Gelita USA, Sioux City, IA. “The more extractions you do from the raw material, the lower the Bloom gets.”
Bloom values range from around 50 to 300 Bloom grams. As a benchmark, a gummy candy might use 7% to 9% gelatin at a strength of 200 to 275 Bloom grams; a marshmallow 1.7% to 2.5% at 225 to 275 Bloom; and a dairy product like yogurt 0.2% to 1.0% at 150 to 250 Bloom. “Usually, the higher the Bloom, the better the color, clarity and taste that you’ll get,” McKibbin adds. Lower-Bloom gelatins are better suited to applications that don’t need the gel strength, such as cereal or protein bars that use the gelatin as a binder.
“You can get the equivalent of a higher Bloom strength with a 100 Bloom gelatin just by using more,” adds Jeremey Kaufmann, senior sales manager, edible and specialty gelatins, Gelita USA.
Cheat-Meat, Version 2.0—The Latest in Meat Analogues
Anyone even passingly familiar with the “fakin’ bacon” crumbles and not-dogs of the past will agree: The less said about these first-generation vegetarian meat analogues, the better. Whether the products were dry and cottony or dense and gummy, they left little doubt as to what you were eating, and it wasn’t meat.
Yet, while early texturized soy and vegetable proteins had their weaknesses, the technologies used to make them demonstrate principles of protein science and engineering that bear review today. Take the thermoplastic extrusion of textured vegetable chunks. The process begins with a mixture of hy-drated soy protein flours or concentrates—ranging in protein from 45% to 70%—that moves through a cylinder where it encounters extremes of heat, pressure and shear force. Once it reaches the proper viscosity, rapid extrusion into the ambient environment causes internal moisture to flash off and creates an expansion of the mass. Cooling transforms the protein mass into a dry, porous matrix that can ab-sorb as much as four times its weight in water, developing a chewy, elastic texture not unlike that of meat. The process relies on good protein solubility, and involves thermal aggregation and coagulation.