SIST ISO 750:1998

SLOVENSKI STANDARD
01-november-1998
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Fruit and vegetable products -- Determination of titratable acidity
Produits dérivés des fruits et légumes -- Détermination de l'acidité titrable
Ta slovenski standard je istoveten z: ISO 750:1998
ICS:
67.080.01 Sadje, zelenjava in njuni Fruits, vegetables and
proizvodi na splošno derived products in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 750
Second edition
1998-08-01
Fruit and vegetable products —
Determination of titratable acidity
Produits dérivés des fruits et légumes — Détermination de l’acidité titrable
A
Reference number
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.
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.
International Standard ISO 750 was prepared by Technical Commitee ISO/TC 34, Agricultural food products,
Subcommittee SC 3, Fruit and vegetable products.
This second edition cancels and replaces the first edition (ISO 750:1981), which has been technically revised.
©  ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
INTERNATIONAL STANDARD  © ISO ISO 750:1998(E)
Fruit and vegetable products — Determination of titratable acidity
1 Scope
This International Standard specifies two methods for the determination of the titratable acidity of fruit and vegetable
products:
 a potentiometric reference method;
 a routine method using a coloured indicator.
By convention, the latter method does not apply to wines.
In the case of some coloured products, it may be difficult to determine the endpoint of the titration in the latter
method and the former method should preferably be used.
NOTE — The determination of titratable acidity is of no value in the case of products to which sulfur dioxide has been added.
2 Principle
2.1 Potentiometric method
Potentiometric titration with a standard volumetric solution of sodium hydroxide.
2.2 Routine method
Titration with a standard volumetric solution of sodium hydroxide in the presence of phenolphthalein as indicator.
3 Reagents
Use only reagents of recognized analytical grade, and distilled or demineralized water or water of equivalent purity.
1)
3.1  Sodium hydroxide, standard volumetric solution, c(NaOH) = 0,1 mol/l.
3.2  Buffer solutions, of known pH.
3.3  Phenolphthalein, 10 g/l solution in 95 % (V/V) ethanol.
4 Apparatus
Usual laboratory apparatus and, in particular, the following.
4.1  Homogenizer or mortar and pestle.
4.2  Pipettes, to deliver 25 ml, 50 ml or 100 ml.

1) Previously expressed as "0,1 N standard volumetric solution."
© ISO
4.3  Conical flask, capable of being fitted with the reflux condenser (4.7).
4.4  Volumetric flask, of capacity 250 ml.
4.5  Beaker, of capacity 250 ml, together with a magnetic or mechanical stirrer.
4.6  Burette, of capacity 50 ml.
4.7  Reflux condenser.
4.8  Analytical balance, capable of weighing to the nearest 0,01 g.
4.9  pH-meter, accurate to at least 0,05 pH units.
4.10  Water bath.
5 Sampling
It is important the laboratory receive a sample which is truly representative and has not been damaged or changed
during transport or storage.
Sampling is not part of the method specified in this International Standard. As there is no specific International
Standard dealing with fruit and vegetable products, it is recommended that the parties concerned come to an
agreement on the subject.
6 Preparation of test sample
6.1 Liquid products
Liquid products include products from which the liquid is easily separable (e.g. juices, canned fruit syrups, pickling
liquids, brines, liquids from fermented products).
Take part of the previously mix
...