Paulsen suggests working with whey protein concentrates (WPCs) in yogurt because, at around 34% to 80% protein, they contain enough lipid matter to add mouthfeel, as well as gelation. “It’s designed to be a nice, full-body-creating ingredient,” she says. Some sta-bilization of the gel is still advisable, though. “As long as there are any free linkages” between proteins, she says, “bonds will keep try-ing to form, and the network will just keep squeezing tighter and tighter,” expelling more water, and crying out for a stabilizer to hold it in.
One characteristic of whey protein gels is their irreversibility. This isn’t the case with gelatin, which forms thermoreversible gels. Unlike many other hydrocolloids, a colloidal solution of gelatin, once gelled, can “melt back down” with subsequent heating, McKibbin says.
And, because it melts at around 86°F—right near body temperature—“that gives it a special mouthfeel and texture that’s a little bit different from other hydrocolloids, like your pectins and carrageenans,” Kaufmann says.
The meat of the matter
Gelatin frequently appears in sausages and meat products, where it binds water and builds texture. Just as frequently, you’ll see soy proteins doing the same. “From sausage and ground meats to whole-muscle meats, soy proteins can increase succulence, improve taste and texture, increase yields, and decrease costs,” says Courtney Kingery, marketing and customer development manager, ADM Spe-cialty Food Ingredients, Decatur, IL.
Minhthy Nguyen, associate director of technology and innovation, Solae LLC, St. Louis, credits soy’s globular structure for its gel-ling prowess. “What happens with the globular protein,” he explains, “is that it can swell up and develop a large hydration layer. It has many side chains that are not ‘friendly’ to water, and they’re in the globule core. But it’s on the outside of the globule where you have the contact with the hydrophilic amino acids, and that’s where you’re able to have a lot of water adhering to the surface of the mole-cule.”
Paulsen notes that whey protein also works “amazingly well” at binding water in meat applications. Whether WPCs or isolates work best “really depends on what you’re trying to get out of it,” she says. “I would say the most commonly used is WPCs because manufac-turers are looking for a combination of emulsification, water binding and gelation.”
Rolling in dough
Emulsification, water binding and gelation all come into play in the formation of dough. The proteins responsible are the glutens in wheat’s endosperm. While gluten proteins are present in virtually all grains, the ones that form the strongest dough network belong to wheat.
The two gluten fractions most active in dough formation are the high-molecular-weight glutenins and lower-weight gliadins. Both exhibit poor water solubility because their amino acid composition is only sparingly ionizable. But their high concentration of hydroxyl amino acids make them quick to hydrogen-bond and surround themselves in an adsorbed layer of water. Kneading of the hydrated gluten mass mechanically unfolds and realigns the proteins, encouraging disulfide bonding and interactions among hydrophobic amino acids. The result is a three-dimensional, viscoelastic network of membranes that captures fermentation gases and stretches as the dough rises. During baking, soluble albumin and globulin protein fractions denature and aggregate, setting the bread’s finished structure.
Studies show that glutenins give dough its strength, elasticity, cohesiveness and mix tolerance, while gliadins promote extensibility and expansion for greater volume. Too much of either makes for an inferior loaf, and manufacturers manipulate gluten protein interac-tions to strike a functional balance. “Disulfide bonds are especially important to the creation of the gluten network that provides strength and structure in baked applications,” says Brook Carson, technical product manager, specialty products, ADM Milling, Decatur, IL. By cleaving those bonds with reducing agents like cysteine, bakers can weaken the dough for better stretch and extensibility (handy in pizza crusts and wheat tortillas), while oxidizing agents like bromate tighten the dough and make it more elastic.
Such manipulations also allow wheat-protein processors to produce functional modified wheat proteins, like isolated wheat gluten, which is an increasingly popular adjunct. In its production, Carson explains, “disulfide bonds are broken, relaxing the functionality of the protein. These proteins have a broad range in functionality and can be used in a wider variety of applications.”