Benders'dictionary of nutrition and food technology

143cyclitols Cyclic sugar alcohols such as inositol, quercitol andtetritol.cyclodextrins Enzyme-modified starch derivatives with ahydrophilic outer surface and a hydrophobic inner cavity, usedfor encapsulation of flavours and other ingredients in food manufacture,and to form stable oil-in-water emulsions. Can also beused to remove cholesterol from dairy products and eggs.Cymogran TM A protein-rich food low in phenylalanine forpatients with phenylketonuria.cystathioninuria A genetic disease due to lack of cystathionase(EC 4.4.1.1) affecting the metabolism of the amino acid methionineand its conversion to cysteine. May result in mental retardationif untreated. Treatment is by feeding a diet low inmethionine and supplemented with cysteine, or, in some cases,by administration of high intakes of vitamin b 6 (about 100–500times the normal requirement).cysteine A non-essential amino acid, abbr Cys (C), M r 121.2, pK a1.92, 8.35, 10.46 (—SH), codons UGPy. Nutritionally importantsince it is synthesised from the essential amino acid methionine.In addition to its role in protein synthesis, cysteine is importantas the precursor of taurine, in formation of coenzyme a fromthe vitamin pantothenic acid and in formation of the tripeptideglutathione. It is used as a dough ‘improver’ in baking.See also cystine.cysticercosis Infection by the larval stage of tapeworms caused byingestion of their eggs in food and water contaminated by humanfaeces. Normally the larval form develops in the animal host, andhuman beings are infected with the adult form by eating undercookedinfected meat.cystic fibrosis A genetic disease due to a failure of the normaltransport of chloride ions across cell membranes. This results inabnormally viscous mucus, affecting especially the lungs andsecretion of pancreatic juice, hence impairing digestion.cystine The dimer of cysteine produced when the sulphydrylgroup (—SH) is oxidised to form a disulphide (—S—S—) bridge.Such disulphide bridges are especially important in maintainingthe structure of proteins, and also in the role of the tripeptideglutathione as an antioxidant. Hair protein (keratin) is especiallyrich in cystine, which accounts for about 12% of its totalamino acid content.cystinuria A genetic disease in which there is abnormally highexcretion of the amino acids cysteine and cystine, resulting inthe formation of kidney stones. Treatment is by feeding a dietlow in the sulphur amino acids methionine, cysteine andcystine.