Benders'dictionary of nutrition and food technology

86acid ingredient of baking powder and self-raising flour, sinceit reacts with bicarbonate to liberate carbon dioxide. Calciumphosphates are permitted food additives (E-341).calculi (calculus) Stones formed in tissues such as the gall bladder(biliary calculus or gallstone), kidney (renal calculus) orureters. Renal calculi may consist of uric acid and its salts(especially in gout) or of oxalic acid salts. Oxalate calculi maybe of metabolic or dietary origin and people at metabolic risk offorming oxalate renal calculi are advised to avoid dietary sourcesof oxalic acid and its precursors. Rarely, renal calculi may consistof the amino acid cystine.See also tartar.calf’s foot jelly gelatine, stock made by boiling calves’ feet inwater; it sets to a stiff jelly on cooling.calmodulin Small intracellular calcium-binding protein that actsto regulate adenylate cyclase (EC 4.6.1.1) and protein kinases inresponse to changes in intracellular calcium concentrations.calorie A unit of energy used to express the energy yield of foodsand energy expenditure by the body. One calorie (cal) is theamount of heat required to raise the temperature of 1g of waterthrough 1 °C (from 14.5 to 15.5 °C).Nutritionally the kilocalorie (1000 calories) is used, theamount of heat required to raise the temperature of 1 kg of waterthrough 1 °C, and is abbreviated as either kcal or Cal.The calorie is not an SI unit, and correctly the joule isused as the unit of energy, although kcal are widely used.1kcal = 4.18 kJ; 1 kJ = 0.24 kcal.See also energy; energy conversion factors.calorimeter (bomb calorimeter) An instrument for measuring theamount of oxidisable energy in a substance, by burning it inoxygen and measuring the heat produced.The energy yield of a foodstuff in the body is equal to thatobtained in a bomb calorimeter only when the metabolicend-products are the same as those obtained by combustion.Thus, proteins liberate 23.64 kJ (5.65 kcal)/g in a calorimeter,when the nitrogen is oxidised to the dioxide, but only 18.4 kJ(4.4 kcal)/g in the body, when the nitrogen is excreted as urea(which has a heat of combustion equal to the ‘missing’ 5.23 kJ(1.25 kcal)).See also energy conversion factors.calorimetry The measurement of energy expenditure by the body.Direct calorimetry is the measurement of heat output from thebody as an index of energy expenditure, and hence energyrequirement. The subject is placed inside a small thermally insulatedroom, and the heat produced is measured. Few such diffi-