How to Calculate the Biological Value of Protein?

A method for determining the biological value of proteins was developed by Mitchell in 1925. It measures the quantity of dietary proteins utilized by the animal for meeting its protein needs for maintenance and growth. Groups of albino rats (28 days old) are fed successively on the following diets for a period of 10 days:

(1) protein-free diet, and

(2) Diet containing 10 percent protein to be tested.

Urine and faeces are collected by keeping them .in metabolism cages. Records of food intake are maintained. The diet, urine and faeces are analyzed for nitrogen. Biological value is then calculated using the following formula:

Thus, BV is a measurement of protein quality expressing the rate of efficiency with which the protein is used for growth. On a scale with 100 representing top efficiency, Table presents the biological values of proteins in several foods.

Table: Biological values of proteins in several foods