Benders'dictionary of nutrition and food technology

391coagulated by heat. So basic that they form salts with mineralacids, e.g. salmine from salmon, sturine from sturgeon, clupeinefrom herring, scombrine from mackerel.proteans Slightly altered proteins that have become insoluble,probably an early stage of denaturation.proteases Alternative name for proteinases.Protecon TM A bone press for preparation of mechanically recoveredmeat (see meat, mechanically recovered).protein All living tissues contain proteins; they are polymers ofamino acids, joined by peptide bonds (see peptides). 21 aminoacids are incorporated into proteins during synthesis, and othersare formed by post-synthetic modification. Any one protein maycontain several hundred or thousand amino acids. The sequenceof the amino acids in a protein determines its overall structureand function: many proteins are enzymes; others are structural(e.g. collagen in connective tissue and keratin in hair and nails);many hormones are polypeptides. Proteins are constituents of allliving cells and are dietary essentials. Chemically distinguishedfrom fats and carbohydrates by containing nitrogen.proteinases Enzymes that hydrolyse proteins, also known aspeptidases.See also chillproofing; endopeptidases; exopeptidases;tenderisers.protein calorie malnutrition See protein–energy malnutrition.protein calories per cent See protein–energy ratio.protein, conjugated Proteins that include a non-protein prostheticgroup,e.g.haemoglobin and cytochromes contain haem;many oxidative enzymes contain a prosthetic group derived fromvitamin b 2 ; glycoproteins proteins are conjugated with carbohydrates;other proteins are conjugated with fatty acids.protein conversion factor See nitrogen conversion factor.protein, crude Total nitrogen multiplied by 6.25.See also kjeldahl determination; nitrogen conversionfactors.protein efficiency ratio (PER) A measure of protein quality.protein–energy malnutrition (PEM) A spectrum of disorders,especially in children, due to inadequate feeding. Marasmus issevere wasting and also occurs in adults; the result of a foodintake inadequate to meet energy expenditure. Emaciation,similar to that seen in marasmus, occurs in patients withadvanced cancer and AIDS; in this case it is known ascachexia.Kwashiorkor affects only young children and includes severeoedema, fatty infiltration of the liver and a sooty dermatitis; it islikely that deficiency of antioxidant nutrients and the stress of