UGANDA STANDARD 
       US ISO 763
First Edition
2009-mm-dd
 
 Reference numbe r 
    US ISO 763:2003
© UNBS 2009
  
Fruit and vegetable products — Determination of ash insoluble 
in hydrochloric acid 
 US ISO 763:2003 
 
© UNBS  2009 – All rights reserved Compliance with this standard does not, of itself confer immunity from legal obligations 
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2009  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, in cluding photocopying and microfilm, without prior written 
permission from UNBS. 
Requests for permission to reproduce this document should be addressed to 
The Executive Director 
Uganda National Bureau of Standards 
P.O. Box 6329 
Kampala  
Uganda 
Tel: 256 41 505 995 
Fax: 256 41 286 123 
E-mail: unbs@infocom.co.ug  
      US ISO 763:2003  
© UNBS  2009 - All rights reserved National foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry  of Tourism, Trade and 
Industry established under Cap 327, of the Laws of Uganda.  UNBS is mandated to co-ordinate the 
elaboration of standards and is  
(a)
 a member of International Organisation for Standardisation (ISO) and  
(b)
 a contact point for the WHO/FAO Codex A limentarius Commission on Food Standards, and  
(c)
 the National Enquiry Point on TBT/SPS Agr eements of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a gi ven field or area and consists of representatives of 
consumers, traders, academician s, manufacturers, governme nt and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committ ee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council. 
This Uganda Standard, US ISO 763:2003, Fruit and vegetable products — Determination of ash insoluble in
 hydrochloric acid, is identical with and  has been reproduced from an International Standard ISO 763:2003,
Fruit and vegetable products — Determination of ash insoluble in hydrochloric acid, and adopted as a Uganda
Standard . 
 
This standard was developed by the Food and agricu lture Standards Technical Committee, UNBS/TC 2. 
Wherever the words, "International Standard" a ppear, they should be replaced by "Uganda Standard."  
 
 
  
 Reference numbe r
ISO 763:2003(E)
© ISO 2003
  
 
 INTERNATIONAL 
STANDARD  ISO
763
Second edition
2003 -12-01
Fruit and vegetable products — 
Determination of ash insoluble in hydrochloric acid 
Produits dérivés des fruits et légumes — Détermination des cendres 
insolubles dans l'acide chlorhydrique 
 ISO 763:2003(E) 
PDF disclaimer 
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed b ut 
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editin g. In 
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Se cretariat 
accepts no liability in this area. 
Adobe is a trademark of Adobe Systems Incorporated. 
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-cr eation 
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bod ies. In 
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. 
 
©   ISO 2003 
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by an y means, 
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address be low or 
ISO's member body in the country of the requester. 
ISO copyright office 
Case postale 56 • CH-1211 Geneva 20 
Tel.  + 41 22 749 01 11 
Fax  + 41 22 749 09 47 
E-mail  copyright@iso.org Web  www.iso.org 
Published in Switzerland 
 
ii © ISO 2003 — All rights reserved
  ISO 763:2003(E) 
© ISO 2003 — All rights reserved  iii
 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 
established has the right to be represented on that committee. International organizations, governmental and 
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the 
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. 
International Standards are drafted in accordance with the rules given in the ISO/IEC 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 
vegetable products . 
This second edition cancels and replaces the first edition (ISO 763:1982), which has been technically revised. 
 INTERNATIONAL STANDARD ISO 763:2003(E)
 
© ISO 2003 — All rights reserved  1
 Fruit and vegetable products — Determination of ash insoluble 
in hydrochloric acid 
1 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 
ISO 7621). 
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. 
4 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 Boiling water bath . 
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 or platinum. 
                                                      
1) ISO 762,  Fruit and vegetable products — Determination of mineral impurities content . ISO 763:2003(E) 
2 © ISO 2003 — All rights reserved
 4.7 Filter paper , ashless. 
4.8 Analytical balance , capable of weighing to the nearest 0,000 2 g. 
5 Sampling 
It is important that the laboratory receive a sample which is truly representative and has not been damaged or 
changed during transport or storage. 
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). 
7 Procedure 
7.1 Preparation of first dish 
Heat an empty dish (4.6) in the furnace (4.2) set at the incineration temperature. Allow it to cool in the 
desiccator (4.5) then weigh to the nearest 0,000 2 g. Repeat until a constant mass is achieved. 
7.2 Test portion 
Weigh, to the nearest 0,01 g, in the previously prepared dish (7.1), 4 g to 25 g of the test sample (Clause 6) 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. 
Dry in the oven (4.4) set at 103 °C. This drying is not necessary for dry products. 
7.3.2 Incineration 
After drying (if appropriate), carbonize and then completely incinerate the product in the furnace (4.2) set at 
525 °C; the ash may still be grey after incineration. 
Pre-incineration at a distinctly lower temperature before placing in the furnace is sometimes necessary for 
products with a high sugar content in order to avoid foaming and subsequent loss of foam. For that purpose, slowly heat the dried sample on the hot plate until carbonization of the most of the organic matter. 
It is recommended to decrease the salt content of products containing more than 2 % of sodium chloride by 
the following method. Pre-incinerate the sample then wash the carbonaceous residue several times with small amounts of hot distilled water. 
7.3.3 Treatment with hydrochloric acid 
Allow the sample to cool in the desiccator (4.5). After cooling, add 10 ml to 25 ml of the hydrochloric acid 
solution (3.1). Cover with a watch-glass and heat in the boiling water bath (4.3) for 15 min ± 2 min. ISO 763:2003(E) 
© ISO 2003 — All rights reserved  3
 Transfer the residue to the ashless filter paper (4.7) placed in a funnel. Rinse the dish with hot water and 
transfer the contents of the dish to the filter paper. Wash the filter paper and its contents until there is no trace 
of chloride ions in the liquid flowing from the funnel [test with the silver nitrate solution (3.2) ]. 
7.3.4 Preparation of the second dish 
Prepare a new dish (4.6) as specified in 7.1 or clean the first dish. Heat it in the muffle furnace (4.2) to the 
incineration temperature. Allow it to cool in the desiccator then weigh to the nearest 0,000 2 g. Repeat until a constant mass is achieved. 
7.3.5 Drying and incineration 
Place the filter paper and residue in the dish. Dry in the oven (4.4) set at 103 °C, then incinerate in the muffle 
furnace (4.2), set at 525 °C, for 30 min ± 2 min. 
Cool in the desiccator (4.5), then weigh to the nearest 0,000 2 g. Repeat until a constant mass is achieved. 
8 Expression of results 
8.1 Method of calculation 
The ash insoluble in hydrochloric acid, w, expressed as a percentage by mass, is given by the formula 
23
01100 %mmwmm−=×− 
where 
m0 is the mass, in grams, of the dish and test portion (7.2); 
m1 is the mass, in grams, of the empty dish (7.1); 
m2 is the mass, in grams, of the dish and acid-insoluble ash (7.3.5); 
m3 is the mass, in grams, of the second empty dish (7.3.4). 
Report the results to two decimal places. 
8.2 Other method of expression 
For liquid products, it is possible to express the result in grams per 100 ml of product, by taking the test 
portion (7.2) by volume and by replacing the denominator ( m0 − m1) in the equation (see 8.1) by V, the volume 
of the test portion. 
9 Repeatability 
The absolute difference between two independent single test results, obtained using the same method on 
identical test material in the same laboratory by the same operator using the same equipment within a short 
interval of time, will in not more than 5 % of cases be greater than 0,01 g of ash insoluble in hydrochloric acid per 100 g of sample. ISO 763:2003(E) 
4 © ISO 2003 — All rights reserved
 10 Test report 
The test report shall specify: 
a) all information necessary for the complete identification of the sample; b) the sampling method used, if known; 
c) the test method used, with reference to this International Standard; 
d) all operating details not specified in this International Standard, or regarded as optional, together with 
details of any incidents which may have influenced the test result(s); 
e) the test result(s) obtained or, if the repeatability has been checked, the final quoted result obtained.  ISO 763:2003(E) 
ICS  67.080.01 
Price based on 4 pages 
© ISO 2003 — All rights reserved