What is Protein?
Protein is an essential part of our diet. It is composed of amino acids. There are 22 amino acids, and each is essential to health and well being for the human body to properly function. Amino acids can be classified in three distinct categories. 1) essential; 2)non-essential, and 3)conditional amino acids.
Essential amino acids must be derived from the consumption of food because the body cannot produce essential amino acids. Leucine, isoleucine, lysine, threonine, valine, tryptophan, methionine, histidine, and phenylalanine are essential amino acids.
On the other hand the human body, from the consumption of essential amino acids or the breakdown of proteins, produces non-essential amino acids. Non-essential amino acids include glutamic acid, aspartic acid, asparagine, and alanine. Conditional amino acids are nonessential and only are needed in individuals with life long medical illness or special circumstances of requirement and are serine, glycine, proline, tyrosine, cysteine, glutamine, and arginine.
Protein is the building block of nature. In the body, it is the function of strength provided by the muscles that require proteins. In food, it provides structure that gives the food its characteristic texture.
Vital nutrient composed of polymer chains of amino acids, linked via peptide bonds. Daily, protein should comprise 10-15% of total caloric intake by consuming 2-3 servings of dairy as well as 2-3 servings of meat, poultry, fish, or other protein source. In the human body, consumption of protein provides 4 kcal per gram of energy and during digestion is broken down into polypeptides courtesy of the protease enzyme, to ultimately be utilized by the body in amino acid form.
Amino acids are found in animal sources such as eggs, poultry, red meats, and fish. Whole grains, fruits, nuts, seeds, and soy are additional sources of protein. In baking, protein mainly comes from wheat, eggs, whole grains, fruits, nuts, seeds, and soy products. Foods that contain essential amino acids necessary to bind with nonessential amino acids to form a ʻcompleteʼ protein are from animal sources while an ʻincompleteʼ protein lacks essential amino acids and are found in fruits, vegetables, seeds, or nuts. By combining incomplete proteins with other incomplete proteins, a complete protein is formed.
The major protein in the baking industry is gluten, a protein found in flour. Gluten plays a very important role in the world of baking. When mixing begins, the protein takes in water and swells under the absorption of the moisture. Next, gluten forms a protein matrix that comprises the structure and support within the dough, giving dough its elastic and extensible properties. Gluten can be found in any product utilizing flour, which leads to a diverse range of items in the baking industry, including breads, muffins, bagels, tortillas, crackers, cakes, pastries, cookies, etc. Breads have the greater amount of protein because a more dense, tough, chewy bite is desired, while on the opposite end of the spectrum, a cake or sweet dough baked item has less protein because a light, airy product is desired.
Proteins are extremely functional in the industry and aid in a variety of ways. Viscosity, binding, foam formation, emulsification, strengthening and dough formation are purposes of protein in baking. Below touches upon the most frequent types of protein used in baking.
- Wheat Protein: Functionally and applicably diverse protein source used in baking. Very viscoelastic due to gliadin and glutenin, with the gluten protein derived from wheat. Gliadin denotes extensible properties to dough while glutenin gives dough elastic properties. Increased protein content of flour leads to increased water absorption, also increasing moisture content and softness in the final product attributes. Bakers can adjust the protein content of flour by utilizing wheat flour isolates. Increasing the glutenin content increases the elastic properties of the dough, while increasing the gliadin content of the flour increases the extensible properties of dough. Crackers require more extensible dough to achieve desired crispness. In frozen or refrigerated doughs, wheat proteins have film-forming capabilities. Film-forming capabilities are useful in baking, for instance, because fat absorption is consequently decreased in fried goods whose dough forms film because of wheat proteins.
- Whey Protein: Whey is the liquid by-product from making cheese. Bakers turn to whey proteins because of the flavor, function, and nutritional aspects. Quick breads, cakes, muffins, bars, cookies, and other delicate baked goods may contain whey protein because it provides a neutral flavoring, not adding any undesirable tastes to the baked item. Whey proteins are very heat stable, have emulsifying capabilities, can form a gel, and bind water, making the protein a great egg product or powdered milk substitute.
- Soy Protein: Bakers who desire to boost nutrition and increase functionality utilize soy. In addition, using soy proteins can increase white coloring in the crumb of baked goods. This is because soy proteins contain the active enzyme lipoxidase, which bleaches the cartenoid fractions of wheat flour. However, in baked products utilizing soy for nutritional aspects most often, combine with wheat flour to counteract the poor loaf volume resulting from soy flour.
Proteins are classified here based on their solubility1:
- Albumins are the most soluble in water. Most often, this type of protein is ovalbumin (egg white).
- Globulins are not soluble in our water, but are soluble in salt solutions. Milk proteins (β-lactoglobulin) are high in globulins.
- Prolamins are soluble in 70% ethyl alcohol. Gliadin (from wheat) is a prolamin. Most often, this protein is found at higher levels in zein (corn) and wheat.
- Glutelin are hydrophobic, and are soluble only in dilute acids or bases. Glutenin is a glutelin.
1. Hoseney, R. Carl. “Proteins.” Principles of Cereal Science and Technology. St. Paul, MN, USA: American Association of Cereal Chemists, (1986): 68.