Soy Protein V Hemp Protein

Not all vegetable proteins are created equal, in fact soy proteins are the only plant-based proteins with a protein quality equal to that of meat, milk and eggs. This high-quality protein comes in three major forms for maximum flexibility in food applications: soy flours, soy protein concentrates, soy protein isolates. Hemp protein, in spite of the misleading marketing hype, is a poor quality protein when compared to soy, egg, and milk proteins.

Protein Quality: Protein is a macronutrient with many functions. Proteins supply amino acids. Amino acids are the building blocks of protein. They are used for the formation of muscle and other protein-containing components in the body including immunoglobulins, albumin, enzymes and hormones. The body synthesizes non-essential amino acids, while others are essential and must be supplied by food sources. Proteins and other nitrogen-containing compounds are continuously degraded and rebuilt. All of these losses must be replaced by a continuous supply of amino acids, provided through the diet.

All plant and animal proteins have approximately the same 20 amino acids. The proportion of the amino acids varies as a characteristic of the protein source. The nutritional quality of any protein relates to its amino acid composition, digestibility, and ability to supply the essential amino acids in the amounts required by the species consuming the protein. The ability of Soy Proteins to supply the essential amino acids in the amounts required by humans has been examined in several protein quality studies. These studies have involved infants, pre-school children and adults.

Traditionally, Protein Efficiency Ratio (PER) was used to evaluate the quality of proteins. The PER method reflects the amino acid requirements of young growing rats, and not humans. A report was published in 1991, by the Food and Agricultural Organization/World Health Organization (FAO/ WHO) Joint Expert Consultation which called for a more acceptable and validated procedure for protein quality evaluation. The recommended method, called Protein Digestibility-Corrected Amino Acid Score (PDCAAS), was adopted by regulatory bodies in most countries including the US Food and Drug Administration (FDA) for protein quality evaluation and nutrition labeling purposes for products intended for children over the age of two and adults.

The PDCAAS method is based on an amino acid scoring method, comparing the amino acid profile of the test protein food to the FAO/WHO two- to five-year-old amino acid pattern. The two- to five-year-old pattern is used because it exceeds the amino acid requirement patterns of older children and adults. The most limiting amino acid is used to determine the uncorrected amino acid score and that number multiplied by the food's digestibility is the PDCAAS. Using this method, Isolated Soy Proteins have the highest obtainable score (1.0) for calculating the corrected protein value. No protein can have a PDCAAS greater than 1.0. Soy Proteins are highly digestible, complete proteins containing all the essential amino acids in the reference pattern in the correct proportion. By contrast, Hemp protein scores very low on the PDCAAS with a value of less than .5 and with 5 essential amino acids below the minimum reference pattern.

The calculated PDCAAS (for soy protein isolate):

Digestibility = 97%
Uncorrected Amino Acid Score = 26 divided by 25 = 1.04
Protein Digestibility Corrected Amino Acid Score = 0.972 x 1.04 = 1.00

The following list shows soy proteins and hemp proteins compared to the FAO/WHO reference pattern for the essential amino acids: Hemp protein is deficient in 5 of the essential amino acids as compared to the FAO/WHO with tryptophan being the limiting amino acid. Hemp will not meet the minimum protein requirements for 2-5 year olds.

 

Hemp Proteins
Soy Proteins
FAO/WHO 2-5 Yr Old Pattern

 

mg/g protein
mg/g protein
mg/g protein

Histidine

25
26
19
Isoleucine
15
49
28
Leucine
71
82
66

Lysine

43
63
58

Methionine + Cystine

24
26
25

Phenylalanine + Tyrosine

93
90
63

Threonine

37
38
34

Tryptophan

6
13
11

Valine

30
50
35

Soy Protein Forms:

Three Major Processed Soy Products

  • Soy Flours are made by grinding dehulled, defatted soybean flakes. Soy flour is approximately 50 percent protein by weight and contains the carbohydrate components of the soybean sugars, oligosaccharides and fiber.
  • Soy Protein Concentrates are made by removing a portion of the carbohydrates from defatted and dehulled soybeans. Soy protein concentrates retain most of the fiber in the original soybeans and must contain at least 65% protein on a moisture-free basis.

Soy Protein Isolates are prepared through a process using water extraction and minimum heat on soy flakes. The product is nearly carbohydrate and fat-free, with no characteristic "beany" flavor. Soy protein isolates prepared this way are 90 percent protein by dry-weight.

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