A measurement of protein quality expressing the rate of efficiency with which protein is used for growth.
Egg contains the highest quality food protein known.
It is so nearly perfect, in fact, that egg protein is often the standard by which all other proteins are judged. Based on the essential amino acids it provides, egg protein is second only to mother's milk for human nutrition. On a scale with 100 representing top efficiency, these are the biological values of proteins in several foods. The Amino Acid Content of Foods and Biological Data on Proteins.