Benders'dictionary of nutrition and food technology

393Biological value (BV) is the proportion of absorbed proteinretained in the body (i.e. taking no account of digestibility). Aprotein that is completely usable (e.g. egg and human milk) hasa BV = 0.9–1; meat and fish have BV = 0.75–0.8; wheat protein0.5; gelatine 0.Net protein utilisation (NPU) is the proportion of dietaryprotein that is retained in the body under specified experimentalconditions (i.e. it takes account of digestibility; NPU = BV ×digestibility). By convention NPU is measured at 10% dietaryprotein (NPU 10 ) at which level the protein synthetic mechanismof the animal can utilise all of the protein so long as the balanceof essential amino acids is correct. When fed at 4% dietaryprotein, the result is NPU standardised. If the food or diet is fedas it is normally eaten, the result is NPU operative (NPU op ).Protein efficiency ratio (PER) is the gain in weight of growinganimals per gram of protein eaten.Net protein retention (NPR) is the weight gain of animals fedthe test protein, minus the weight loss of a group fed a proteinfreediet, divided by the amount of protein consumed.Protein retention efficiency (PRE) is the NPR converted intoa percentage scale by multiplying by 16; it then becomes numericallythe same as net protein utilisation.Relative protein value (RPV) is the ability of a test protein,fed at various levels of intake, to support nitrogen balance, relativeto a standard protein.Chemical score is based on chemical analysis of the protein; itis the amount of the limiting amino acid compared with theamount of the same amino acid in egg protein.Amino acid score (protein score) is similar to chemical score,but uses an amino acid mixture as the standard.Protein digestibility corrected amino acid score (PDCAAS) isthe amino acid score × digestibilityEssential amino acid index is the sum of all the essential aminoacids compared with those in egg protein or the amino acidtarget mixture.protein rating Used in Canadian food regulations to assess theoverall protein quality of a food. It is protein efficiency ratio ×per cent protein content of food × the amount of food that is reasonablyconsumed. Foods with a rating above 40 may be designatedexcellent dietary sources; foods with rating below 20 areconsidered to be insignificant sources; 20–40 may be describedas good sources.protein, reference A theoretical concept of the perfect proteinwhich is used with 100% efficiency at whatever level it is fed inthe diet. The nearest approach to this theoretical protein are egg