Benders'dictionary of nutrition and food technology

487rylation, so permitting more or less uncontrolled oxidation ofmetabolic fuels, with production of heat. An important part ofmaintenance of body temperature by non-shivering thermogenesis,and maintenance of energy balance; they are stimulated byleptin.UCP-1 (thermogenin) is the best studied. It occurs in brownadipose tissue (see adipose tissue, brown), and is activated byfree fatty acids produced in response to β-adrenergic stimulation.UCP-2 occurs in a variety of tissues, including skeletal muscleand lung; UCP-3 occurs only in skeletal muscle.uncrystallisable syrup See syrup.unesterified fatty acids (UFA) See fatty acids, non-esterified.UNICEF United Nations Children’s fund; web sitehttp://www.unicef.org/.universal product codes (UPC) Standard multidigit numbers thatrepresent product, size, manufacturer and nature of contents, onfood and other labels as machine-readable bar codes.unsaponifiable See non-saponified.unsaturated fatty acids See fatty acids.UNU United Nations University; web site http://www.unu.edu/.UPC See universal product codes.uperisation A method of sterilising milk by injecting steam underpressure to raise the temperature to 150 °C. The added water isevaporated off.uracil A pyrimidine; see nucleic acids.urataemia High blood concentration of uric acid and its salts, asin gout.uraturia Urinary excretion of high concentrations of uric acidand its salts.urd bean See grams, indian.urea CO(NH 2 ) 2 , the end-product of nitrogen metabolism in mostmammals, excreted in the urine. Synthesised in the liver fromammonia (arising from the deamination of amino acids) and theamino acid aspartic acid. It is the major nitrogenous compoundin urine, and the major component of the non-protein nitrogenin blood plasma.urease Intestinal bacterial enzyme (EC 3.5.1.5) that hydrolysesurea to ammonia and carbon dioxide. Important in the enterohepaticcycling of urea. Also found in some beans.urethane Ethyl carbamate, used as intermediate in organic syntheses,as a solubiliser and as the precursor for polyurethanefoam. Found in small amounts in liqueurs made from stone fruits,wines and some distilled spirits where it is formed by reactionbetween alcohol and nitrogenous compounds; cause for concernsince it is genotoxic, and hence a potential carcinogen.