Benders'dictionary of nutrition and food technology

92carbohydrate by difference It is relatively difficult to determinethe various carbohydrates present in foods, and an approximationis often made by subtracting the measured protein, fat, ashand water from the total weight. It is the sum of nutritionallyavailable carbohydrates (dextrins, starches and sugars); nutritionallyunavailable carbohydrate (pentosans, pectins, hemicellulosesand cellulose) and non-carbohydrates such as organicacids and lignins.carbohydrate loading Practice of some endurance athletes(e.g. marathon runners) in training for a major event; it consistsof exercising to exhaustion, so depleting muscle glycogen, theneating a large carbohydrate-rich meal so as to replenish glycogenreserves with a higher than normal proportion of straightchain glycogen.carbohydrate metabolism See glucose metabolism.carbohydrate, unavailable A general term for those carbohydratespresent in foods that are not digested, and are thereforeexcluded from calculations of energy intake, although they maybe fermented by intestinal bacteria and yield some energy. Theterm includes both indigestible oligosaccharides and the variousnon-starch polysaccharides.See also fatty acids, volatile; starch, resistant.carbon dioxide, available See baking powder; flour, selfraising.carbon dioxide storage See packaging, modified atmosphere.g-carboxyglutamate A derivative of the amino acid glutamate(abbr Gla, M r 191.1) which is found in prothrombin and othercalcium-binding proteins involved in blood clotting. Its formationrequires vitamin k. Also occurs in the protein osteocalcin inbone, where it has a function in ensuring the correct crystallisationof bone mineral.carboxymethylcellulose See cellulose derivatives.carboxypeptidase E Enzyme (EC 3.4.17.10) that catalysescleavage of pro-insulin to insulin, and post-syntheticmodification of pro-opiomelanocortin and other peptidehormones.carboxypeptidases Enzymes (EC 3.4.17.1 and 2) secreted in thepancreatic juice that remove amino acids sequentially from thefree carboxyl end of a peptide or protein, i.e. exopeptidases.carcinogen Any compound that is capable of inducing cancer.carcinoid syndrome Condition in which there are metastases tothe liver of a carcinoid tumour of the enterochromaffin cells ofthe small intestine. The tumour produces a variety of physiologicallyactive amines, including histamine (which causes flushingreactions) and 5-hydroxytryptamine. The depletion of trypto-