Benders'dictionary of nutrition and food technology

392infection may be involved. The name kwashiorkor is derivedfrom the Ga language of Ghana to describe the illness of the firstchild when it is weaned (on to an inadequate diet) on the arrivalof the second child.See also gomez classification; marasmic kwashiorkor; waterlowclassification; wellcome classification.protein–energy ratio The protein content of a food or dietexpressed as the proportion of the total energy provided byprotein (17 kJ, 4 kcal/g). The average requirement for protein isabout 7% of total energy intake; western diets provide about14%.protein equivalent A measure of the digestible nitrogen of ananimal feedingstuff in terms of protein. It is measured by directfeeding or calculated from the digestible pure protein plus halfthe digestible non-protein nitrogen.protein, first class An obsolete system of classifying proteins intofirst and second class, to indicate their relative nutritional valueor protein quality. Generally, but not invariably, animal proteinswere considered ‘first class’ and plant proteins ‘second class’, butthis classification has no validity in the diet as a whole.protein hydrolysate Mixture of amino acids and polypeptidesprepared by hydrolysis of proteins with acid, alkali or proteases,used in enteral and parenteral nutrition and in supplements.protein intolerance An adverse reaction to one or more specificproteins in foods, commonly the result of an allergy. Generalprotein intolerance may be due to a variety of genetic diseasesaffecting amino acid metabolism. Treatment is normally bysevere restriction of protein intake.See also adverse reactions to foods; amino acid disorders;hyperammonaemia.protein kinases Enzymes that catalyse phosphorylation of targetenzymes in cells in response to the action of hormones and neurotransmitters.Protein kinase A is activated by 5′-AMP, proteinkinase B by the activated insulin receptor substrate, proteinkinase C by cyclic AMP; map kinases are activated by a varietyof mitogenic hormones.protein quality A measure of the usefulness of a protein food formaintenance and repair of tissue, growth and formation of newtissues and, in animals, production of meat, eggs, wool and milk.It is important only if the total intake of protein barely meets therequirement. Furthermore, the quality of individual proteins isrelatively unimportant in mixed diets, because of complementationbetween different proteins. Two types of measurement areused to estimate protein quality: biological assays and chemicalanalysis.