ISO 5523-1981 scan

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International Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION.MEIK~YHAPO~HAR OPrAHM3ALWfl I-IO CTAH~APTM3ALWlWORGANISATION INTERNATIONALE DE NORMALISATION
Liquid fruit and vegetable products - Determination of
sulphur dioxide content (Routine method)
Produits liquides d&iv& des fruits et &gumes - Determination de Ia teneur en dioxyde de soufre (Methode pratique)
First edition - 1981-08-01
M
UDC 634/635 : 543.845 Ref. No. ISO 5523-1981 (EI
Descriptors : fruit and vegetable products, beverages, Chemical analysis, determination of content, sulphur dioxide.
Price based on 3 pages
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of
national Standards institutes (ISO member bodies). The work of developing Inter-
national Standards is carried out through ISO technical committees. Every member
body interested in a subject for which a technical committee has been set up 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.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the ISO Council.
International Standard ISO 5523 was developed by Technical Committee ISO/TC 34,
Agricultuml food products, and was circulated to the member bodies in July 1979.
lt has been approved by the member bodies of the following countries :
Australia
Austria
Brazil
Bulgaria
Canada
Chile
Cyprus
Czechoslovakia
Egypt, Arab Rep. of
Ethiopia
France
Germany, F. R.
Hungary
India
Indonesia
Israel
Italy
Kenya
Korea, Rep. of
Libyan Arab Jamahiriya
Malaysia
Mexico
Netherlands
Poland
Portugal
Romania
South Africa, Rep. of
Spain
Thailand
Turkey
Y ugoslavia
The member body of the following country expressed disapproval of the document on
technical grounds :
New Zealand
0
International Organization for Standardization, 1981
Printed in Switzerland
INTERNATIONALSTANDARD ISO 5523-1981 (E)
Liquid fruit and vegetable products - Determination of
sulphur dioxide content (Routine method)
0 Introduction
This method, which was developed for the determination of the
sulphur dioxide content of wines, has been found to be suitable
for liquid fruit and vegetable products, and tan be used as a
rapid method.
In the case of more precise analyses, or in cases of dispute, the
method specified in ISO 5522 shall be used.
1 Scope and field of application
This International Standard specifies a routine method for the
determination of the sulphur dioxide content of liquid fruit and
vegetable products.
2 References
ISO/R 385, Burettes.
ISO 648, Laboratory glassware - One-mark pipettes.
ISO 1773, Laboratory glassware - Boiling flasks fnarrow-
necked).
I SO 5522, Fruits, vegetables and derived products - Deter-
mination of total sulphur dioxide content.
3 Definitions
3.1 free sulphur dioxide : Sulphur dioxide as such or as
inorganic combinations of <H2S03, HS03 and SO;-.
3.2
bound sulphur dioxide content : The differente be-
tween the total sulphur dioxide content and the free sulphur
dioxide con tent .
4 Principle
4.1 Free sulphur dioxide
Direct iodometric titration of the product at a pH between 0,7
and 1, followed by a blank titration of the same product, freed
from sulphur dioxide by boiling under reflux or by binding its
free sulphur dioxide content with an excess of acetaldehyde
(ethanal) or propionaldehyde (propanal).
4.2 Bound sulphur dioxide
After titration of the free sulphur dioxide, rendering of the pro-
duct alkaline and titration of the sulphur dioxide liberated by
this hydrolysis with iodine in an acid medium.
A second iodometric titration after a second alkali hydrolysis
permits titration of the sulphur dioxide which may have recom-
bined, after the first hydrolysis, with any acetaldehyde present
in the product.
5 Reagents
All reagents shall be of recognized analytical quality and in par-
ticular shall not contain impurities which could be determined
as sulphur dioxide. The water used shall be distilled water or
water of at least equivalent purity, recently boiled.
5.1 Sodium hydroxide, approximately 4 mol/1 solution.1)
Dissolve 160 g of sodium hydroxide in water and dilute to
1 000 ml.
5.2
Sulphuric acid, 10 % (WV) Solution (180 g of H2S04
per litre) .
5.3 Starch, 5 g/l Solution containing 200 g of sodium
chloride (as preservative) per litre.
Maintain the Solution at boiling Point for 10 min during prepara-
tion.
1) Hitherto expressed as “approximately 4 N solution”.