Understanding Protein as A Functional Ingredient
Ingredient technology advances are providing a growing array of uniquely functional proteins.
By Claudia O'Donnell, Contributing Editor | 01/25/2013
Consumers are increasingly aware of the health benefits that protein consumption can offer, such as weight management and muscle loss prevention. However protein additives also have long been valued by food formulators for properties such as their ability to gel, foam, emulsify and form films and dough structure. Research is providing a better understanding of protein functionality and how to best utilize these ingredients even as technical advances are also providing product developers new ingredients with unique capabilities.
Protein ingredients range from gelatin to plant-derived proteins — such as from wheat, soy, rice and pea — and even more recently to protein from cultivated algae. Cutting-edge processes for separation and purification of specific protein components from their original native sources have been the driver behind many of these ingredients. So the march of innovative options making an effort to enter the marketplace continues.
Regardless of their source, all proteins are composed of a sequence of amino acids. The specific order of amino acids in the sequence and their ratio determines a protein's physical properties — such as molecular size (i.e., shape) and charge, solubility and isoelectric point (IEP). A protein's IEP is the pH at which the molecule's charge is neutral and is generally no longer soluble in water-based solutions.
While these physical properties are useful in separating out and concentrating specific proteins, the properties also determine a protein's functionality as a food ingredient. Thus, by controlling the various parameters used to manufacturer a protein, the protein's final functionality as an ingredient is influenced.
Gelatin, for example, can be manufactured through an acidic (Type A), alkaline (Type B) or enzymatic process. Acidic processing results in gelatins with IEPs in a pH range of about 7 to 9. Alkaline processing produces proteins with IEPs of 4.7 to 5.4. [Source]
A characteristic such as a protein's IEP is important when formulating a product. The pHs of flavored waters or soymilk are about 7.0 (neutral), yogurt tends to be in the 4-5 range and tofu is slightly alkaline (7.2). Juice drinks can have pHs down to 2.5. In the simplest example, if the pH of a protein-based solution such as milk is lowered through its proteins' IEPs, they will no longer be soluble and will precipitate out of solution.
Even as product formulators are becoming more familiar with such formula and processing challenges for finished products, vendors are offering ingredients adapted for specific uses.
Wheying new developments
Whey protein concentrates and isolates, for example, are added to foods and beverages for both nutritional and functional purposes. Whey protein itself is composed of a variety of fractions differing in characteristics, including weight (molecular mass) and IEP. About half of whey proteins are beta-lactoglobulins with IEPs of about 5.4; some 20 percent are alpha-lactalbumin (IEP 4.4) and a little more than 10 percent are GMPs or glycomacropeptides (IEP <3.8).
These whey fractions vary greatly in how or whether they are used as food additives. For example, industrially GMPs are generally used for their health benefits, but not for their gelling, foaming or emulsifying abilities.
Beta-lactoglobulin, on the other hand, performs generally well in these areas. Performance also can vary depending on the characteristics of the application in which the whey fraction is used. Some fractions will gel at a neutral pH while others won't. Some are more heat-stable than others.
Commercially, separation methods for these individual components are being developed that take advantage of their differences as much as possible. Used alone or in combination, processes include ultra- and microfiltration, chromatography and ion exchange.
It is difficult to decipher from a product's ingredient statement when such innovative components are being used. In the U.S., the standard of identity for whey protein concentrate (WPC) broadly requires the product to have 25 percent or more protein, 1-10 percent fat and 2-15 percent minerals (ash). See CFR Title 21, Sec. 184.1979c. It does not detail the type of whey protein fractions that must be present. Thus, WPCs can be composed of differing fractions that have different characteristics and provide differing functions, but all are labeled as WPC.
Physical Properties of Whey Protein
Molecular mass (kg/mol)¹
Percent of whey protein³
| Serum albumin
| Immunoglobulin G
¹²Derived from Etzel, M. 2004. Manufacture and Use of Dairy Protein Fractions. J Nutr. 134(4):996S-1002S (http://jn.nutrition.org/content/134/4/996S.full)