Benders'dictionary of nutrition and food technology

255invertase Also known as sucrase or saccharase; either of twoenzymes, glucohydrolase (EC 3.2.1.20) or fructohydrolase (EC3.2.1.26), with differing specificity, that hydrolyse sucrose toyield glucose and fructose. Used in the manufacture of invertsugar (see sugar, invert) and in chocolate confectionery tohydrolyse crystalline sucrose to a liquid syrup. The bifunctionalsucrase–isomaltase of the intestinal mucosa is glucohydrolase.invert sugar See sugar, invert.in vitro Literally ‘in glass’; used to indicate an observation madeexperimentally in the test tube, as distinct from the natural livingconditions, IN VIVO.in vivo In the living state, as distinct from IN VITRO.iodine An essential mineral, a trace element; reference intakesare about 140 µg per day. Iodine is required for synthesis ofthe thyroid hormones, which are iodotyrosine derivatives. Aprolonged deficiency of iodine in the diet leads to goitre. It isplentifully supplied by sea foods and by vegetables grown in soilcontaining iodide. In areas where the soil is deficient in iodide,locally grown vegetables are iodine deficient, and hence goitreoccurs in defined geographical regions, especially inland uplandareas over limestone soil.Where deficiency is a problem, salt maybe iodised (see iodised salt) to increase iodide intake.iodine number (iodine value) Measurement of the degree ofunsaturation of fatty acids by iodination of the carbon–carbondouble bonds. The Wijs method uses iodine chloride, Hanusiodine bromide, and Rosenmund–Kuhnhenn a pyridine sulphate/brominereagent.iodine, protein-bound The thyroid hormones, tri-iodothyronineand thyroxine, are transported in the bloodstream bound to proteins;measurement of protein-bound iodine, as opposed to totalplasma iodine, was used as an index of thyroid gland activitybefore more specific methods of measuring the hormones weredeveloped.iodised oil Oil intended for administration either by injection ororally in regions of severe iodine deficiency; prepared by treatingvegetable oils with iodine, which adds across double bonds.Oils used include poppyseed, peanut and rape seed oils; injectionsprovide protection for 2–4 years, oral administration about1 year.iodised salt In areas of mild iodine deficiency, salt is oftenenriched with iodate at levels of 10–25 mg iodate/kg; in areas ofmoderate deficiency to levels of 25–40 mg/kg. Where there issevere deficiency, iodised oil is used. In some areas all salt isenriched, in others it is optional. In some countries bread mustbe made with iodised salt.