ISO INTERNATIONAL 763 STANDARD Second edition 2003-12-01 Fruit and vegetable products Determination of ash insoluble in hydrochloric acid Produits derives desfruits etlegumes- Determinationdescendres insolubles dans I'acide chlorhydrique Reference number ISO 763:2003(E) ISO ii Foreword Iso (the International Organization for Standardization) is a worldwide federation of national standards bodies (iSO member bodies). The work of preparing International Standards is normally carried out through IsO technical committees. Each member body interested in a subject for which a technical committee has been non-governmental, in liaison with IsO, also take part in the work. IsoO collaborates closely ywith the InternationalElectrotechnicalCommission(lEC)onallmattersofelectrotechnicalstandardization. International Standards are drafted in accordance with the rules given in the ISO/lEC Directives, Part 2 The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. IsO shall not be held responsible for identifying any or all such patent rights. ISO 763 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 3, Fruit and vegetableproducts. Thissecondeditioncancelsandreplacesthefirstedition(isO763:1982),whichhasbeentechnicallyrevised ii Fruit and vegetable products Determination of ash insoluble inhydrochloricacid Scope This International Standard specifies a method for the determination of the hydrochloric-acid-insoluble ash yielded by fruit and vegetable products. The method serves for the determination of siliceous impurities, together with the silica endogenous to the plant. NOTE A method for the determination of mineral impurities generally originating from the soil is specified in ISO7621) 2 Principle A test portion is incinerated at approximately 525 °C and the mineral matter insoluble in dilute hydrochloric acid is separated. 3 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. 3.1 Hydrochloric acid, 10 % (by mass) solution. 3.2 Silver nitrate, approximately 17 g/l solution. Apparatus Usual laboratory apparatus and, in particular, the following 4.1 Blender. 4.2 Muffle furnace, capable of being maintained at 525°C ±25°C 4.3 Boilingwaterbath. 4.4 Drying oven, capable of being maintained at 103 C ± 2 °C. 4.5 Desiccator, containing an efficient desiccant. 4.6 Incineration dishes, made of quartz orplatinum. 1)Iso762,FruitandvegetableproductsDeterminationofmineralimpuritiescontent. 4.7 Filterpaper,ashless. 4.8 Analytical balance, capable of weighing to the nearest 0,o00 2g Sampling 5 Itisimportantthatthelaboratoryreceiveasamplewhichistrulyrepresentativeandhasnotbeendamagedor changed during transportorstorage. 6 Preparation of test sample Allow frozen or deep-frozen products to thaw in a closed vessel and add the liquid formed during this process to the product before mixing. Before taking the test portion, thoroughly mix the laboratory sample using, if necessary,the blender (4.1). 7Procedure 7.1Preparationof first dish desiccator (4.5) then weigh to the nearest 0,000 2 g. Repeat until a constant mass is achieved. 7.2 Test portion according to the water content of the product. For liquid products, the test portion may be taken by volume (see 8.2). 7.3 Determination 7.3.1 Drying Place the dish and its contents in the boiling water bath (4.3) and evaporate the water present in the product. 7.3.2Incineration 525 °C; the ash may still be grey after incineration. Pre-incinerationat adistinctlylowertemperaturebeforeplacinginthe furnace is sometimesnecessaryfor products