If you’re pulling out your old food science reference books to find answers to questions posed by the protein content and quality of the 2007 hard winter wheat crop, you’re not alone. This year’s harvest is shaping up to be as difficult to judge as any in living memory. Protein percentages appear to be average or below average, but even those measurements are open to interpretation when it comes to quality.
First, it’s important to recognize that low protein doesn’t necessarily mean low quality. Second, some basic knowledge about proteins can help guide you through a myriad of choices for protein supplementation.
Amino acids make up all proteins, and of the 150-plus amino acids in nature, 10 are essential — cystine, histidine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan, tyrosine and valine — meaning that they cannot be synthesized by the human body and must be supplied by the diet. The amino acid content of proteins varies by source. While most proteins from animal sources (meat, fish, eggs and milk) contain all the essential amino acids, those from plant sources, including grains, are generally low in one or more of these amino acids. Wheat protein, for example, is low in lysine, but when formulations add soy (which is relatively high in lysine) or whey, the finished product exhibits a better, more complete amino acid profile and, thus, is more nutritious.
It may surprise consumers to learn how much protein they consume when eating baked foods. The level of protein in flour varies from 8 to 14%, and one 28-g slice of whole-wheat bread provides 4 g of protein. While the bread’s carbohydrate content contributes the most energy content, 67% of the caloric value, bread’s protein provides 21%.
In addition to supplying nutritional benefits to consumers, proteins perform a number of other jobs in food systems. These include, but are not limited to, managing moisture, extending shelf life, improving yield and supporting health claims. Also, all enzymes are proteins.
THE GLUTEN MIRACLE
When wheat flour and water are mixed and kneaded, two proteins native to wheat combine to form gluten. This material exhibits plasticity, elasticity and viscosity. Such characteristics help capture and retain leavening gases and allow the dough to be easily handled during processing and forming. By coagulating the proteins, baking sets the structure of the loaf to stabilize the light texture of its interior crumb and help create the stiff exterior crust. Alone, gliaden and glutenin are relatively ineffective.
Wheat is unique; although other seeds or cereal grains contain glutenlike proteins, none is capable of combining or functioning in the same way as the viscoelastic gluten of wheat. Gluten’s functionality even varies among different types of wheat. For example, while durum wheat is very high in protein, its gluten is not very elastic, leading to poor handling qualities and inadequate gas retention.
When bakery formulations require additional strength — to maintain volume, to support particulate or inert ingredients or because of low quality in available flour supplies — the baker usually reaches for vital wheat gluten as a supplement. Vital wheat gluten is generally made by mixing wheat flour and water and kneading it to create a strong gluten network. The dough is washed to remove starch and other nongluten materials, then dried, packaged and shipped. The term "vital" means that it retains its ability to form a cohesive elastic mass when mixed with water.
Vital wheat gluten contains 70 to 76% protein, so every pound of gluten added per cwt flour will make the flour behave as if it has a 0.6 to 0.7% higher protein content. Also, this ingredient will absorb 1.5 to 1.8 times its own weight in water, and it has a tendency to extend dough mixing time. The quality can vary significantly with the wheat source and drying conditions during manufacturer. Suppliers of vital wheat gluten can help optimize usage levels according to need.
Of the many other protein sources available to bakers, eggs, soy and whey compose the most important sources. Eggs long ago earned a respected place in bakery formulas not only for the flavor they add but also for the many functions their protein content performs. The average large egg (1.5 oz) contains 6.29 g of protein, which aids in building crumb structure, foaming ability emulsification power and water binding. And bakers use the film-forming capabilities of egg protein by "washing" a solution of egg whites onto dough surfaces before baking, thus yielding a shiny finished crust.
Soy proteins have also proven their worth to bakers. The soybean itself is 35% protein, on average, but this level is "concentrated" by further processing. Soy flour, for example, contains 50% protein, but soy concentrate carries 65% protein and soy isolate, 90%. One of the chief drawbacks to many soy products, however, is their "beany" flavor. Soy processors have developed new processing and treatment technologies to address this issue, and most new soy ingredients introduced for commercial use claim neutral flavors.
Functional soy powders (FSPs) and soy protein crisps are recent additions to the protein portfolio. FSP will extend or replace nonfat dry milk and eggs. In cookies, for example, FSP can be used with liquid vegetable oil to deliver characteristics that usually require hydrogenated fats or palm oil. The crisps act like rice crisps but contribute higher protein content.
With the notable exception of wheat protein isolate, most protein-based ingredients absorb water, thus controlling moisture migration and lengthening shelf life. Soy protein is so good at this task that it actually improves batch yield. Addition of 1% (flour weight basis) soy flour increases finished moisture levels by 0.3 to 9.5%, thus increasing overall batch yield. Enzyme-activated soy flour, although not as high in protein as other soy ingredients discussed here, helps bleach and whiten bread doughs, improving the appearance of the crumb in the finished product.
Dairy proteins are getting a new look by formulators thanks to hydrolyzed whey protein concentrate. They have less water-binding capacity than ordinary whey proteins, but they still extend shelf life. Many whey proteins also bring a clean, slightly milky flavor to foods, a highly desirable quality for baked products.
Because the cost of using dairybased ingredients has crept up recently, users should consider blending these materials with lower cost ingredients. For example, whey and soy can complement each other functionally and nutritionally. Whey even helps mask the characteristic taste of soy.
Wheat protein isolates are a relatively new addition to the baker’s toolbox of functional ingredients. Made by further processing of vital wheat gluten, the gluten is modified, fractionated, filtered and dried and contains 85 to 90% protein. Like their base material, wheat protein isolates provide high strength and elasticity to formulations. They are highly beneficial in sheeted and laminated items such as pizza crusts, tortillas and laminated doughs for Danish, puff pastry and croissants. They can also be used to extend whole egg powders in cakes and other sweet items.
Because whey protein isolates absorb less water than other protein ingredients, they can be very useful in whole-wheat applications. Wholewheat flours bind more water than conventional enriched white flours, contributing to the dry taste of finished products. Because less water is required, the doughs take less time to bake out, so crusts are no longer undesirably thick and dark.
Also, wheat protein isolate can help carry the inert bran contained by whole-wheat flour, thus lightening the crumb texture. It aids the extensibility of the dough as it goes through the moulders, so the dough degasses better, eliminating the large holes often found in these bread varieties.
Some experts note that wheat protein isolate can partially replace sugar. For example, substituting it for some of the sugar in muffins will reduce calories without affecting textural properties. And it has a tenderizing effect.
Allergenic response concerns bakery formulators, and some are matching the source of added protein to ingredients already in the formula. For example, a wheat protein additive may be a better choice than soy if the formula contains no other ingredients made from soy. A hydrolyzed vegetable protein was recently introduced that is based on sunflower. It acts as a flavor enhancer, but it is also suitable for products that strive for a lower potential allergenic response.
Foods can use their protein content to make health claims but may need supplementation to reach the thresholds required by regulations governing such claims. The soy claim is a good case in point. Nutritional research has long suggested that consuming soy products can reduce the risk of coronary heart disease, so a health claim can be made by foods containing 6.25 g of soy per serving, or one-quarter of the 25-g per day recommended. To reach that level in bread, however, requires use of soy protein, rather than soy flour, in the formula.
The first sports bars relied on carbohydraterich formulations to support athletic performance, but with the advent of "protein diets" such as the Atkins dietary regimen, the makers of sports and nutrition bars flipped their formulas to emphasize protein content.
Boosting the soy or wheat protein content of nutrition bars will also appeal to vegetarians, whose diet can fall short in this nutrient, and to diabetics who must watch their intake of certain carbohydrates.
Among the challenges of making such bars is their tendency to harden undesirably. Isolated soy proteins are known to extend shelf life of such bars, preventing hardening. By tailoring the precise ratios, bar textures can vary from very chewy to more cookie-like.
In bars, wheat protein isolate can replace sugar syrups as the binder, thus reducing sweetness and calories. Thus the baker can replace sugar calories with protein calories, a characteristic that many consumers desire. Experts report that cookies adapt easily to higher protein content to be repositioned as a lower-glycemic choice, minus the sugars and starches when made with alternative sweeteners and protein.
As always, when replacing conventional ingredients with materials such as protein isolates and concentrates, bowl costs will rise. Yet with today’s strong market demand for the qualities these ingredients contribute, the baker can move pricing into premium levels. And that pays dividends to all.