Explain the term Chemical Score?
Since egg proteins contain all essential amino acids in adequate amounts and possess the highest nutritive value among dietary proteins, Block and Mitchell (1946) assigned a chemical score of 100 to egg proteins. Since the nutritive value of the proteins depend on the essential amino acid most limiting in the dietary proteins, they evolved a chemical score (based on the most limiting essential amino acid) which can serve as an index of the nutritive value of the proteins. The chemical score is the 'ratio between the content of the most limiting amino acid in the test protein to the content of the same amino acid in the reference protein (egg protein) expressed as a percentage'. The chemical score formula is given herewith. Chemical score of milk proteins is 65 and those of gelatin and zein are 0.
Chemical Score (CS) = (mg of amino acid in lg of test protein / mg of amino acid in lg of reference protein) * 100
Lastly, nutrient-to-energy ratio has attracted wide interest as indices of dietary quality.