SOYBEAN AS PROTEIN SOURCE

Soybeans are valued for their high protein content as the protein content in dried soybean seeds ranges from 30-50% of the total weight. Protein compounds are composed of amino acid. There are 20 types of amino acids that are physiologically needed by the human body, but not all of these amino acids can be synthesized in the body so they must be obtained from a daily diet. Amino acids that cannot be synthesized by the body are called essential amino acids. There are 8 (eight) essential amino acids needed by the human body, namely Leucine, Isoleucine, Valine, Phenylalanine, Threonine, Methionine, Triptophan, and Lysine. Soybean contain all 8 essential amino acids.

Foods that have high protein content contain high amino acids as well. But that does not mean that these foods have a high content of essential amino acids. Therefore, the protein quality of a food is determined by the ability of the food to provide essential amino acids in an amount that is in accordance with the body’s requirements. The recommended method to assess the quality of protein in food is the PDCAAS (Protein Digestibility Corrected Amino Acid Score) method which measures protein digestibility based on the amino acid content. Based on the PDCAAS value, the soybeans have a value of 0.91 (91%); close to that of the beef  which is 0.92 (92%). Eggs and cow’s milk have a perfect PDCAAS value because they have a value of 1.00 (100%) (PDCAAS has a maximum value of 1.00 (100%). Among plant protein sources, soybeans have the highest PDCAAS value, compared to other foods such as wheat and peas.

The United Nations Food and Agriculture (FAO) now also proposes to measure the quality of protein in foodstuffs based on the DIAAS (Digestible Indispensable Amino Acid Score) method. Based on calculations, the value of DIAAS for soy protein for adults is expected not to differ greatly from the value of PDCAAS. However, for infants and children aged <2 years, soy protein will have a lower DIAAS value than milk and eggs.