ABSTRACT
The quality of dietary protein should meet the physiological needs of the consumer. Protein with a high nutrient value is digestible and provides a full complement of the essential amino acids. Protein nutrient value (PNV) raises issues beyond the normal terms of reference for chemical analysis. A great deal of progress was made in this field recently and a consensus was reached about procedures for assessing protein quality. This chapter considers PNV and its evaluation. Sec. 1 describes some of the most important indicators of protein quality, factors affecting these indicators, and an outline of the literature. Human bioassays for protein quality are discussed in Sec. 2. Investigations using human subjects are slow and expensive. Alternative tests involve rats, chicks, and other small animals (Sec. 3). A number of chemical tests for protein quality are also available (Secs. 4 and 5) that are fast and inexpensive but have yet to undergo rigorous interlaboratory evaluation. The range of in vitro tests for protein quality includes measurements of reactive lysine, dye binding, and the rate of hydrolysis by proteolytic enzymes.
