SIST ISO 2448:1998

INTERNATIONAL ISO
STANDARD 2448
Second edition
1998-08-01
Fruit and vegetable products —
Determination of ethanol content
Produits dérivés des fruits et légumes — Détermination de la teneur
en éthanol
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 2448 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 2448:1973), which has been technically revised.
Annex A forms an integral part of this International Standard.
©  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 2448:1998(E)
Fruit and vegetable products — Determination of ethanol content
1 Scope
This International Standard specifies a method for the chemical determination of ethanol in fruit and vegetable
products.
The method is not applicable to products containing more than 5 % (m/m) of ethanol.
In the case of products containing essential oils, it is necessary to remove the latter (see annex A).
2 Definition
For the purposes of this International Standard, the following definition applies.
2.1
ethanol content
mass of the substances determined by the method specified in this International Standard, expressed as a
percentage by mass for solid products or as grams per 100 ml for liquid products
3 Principle
Separation of the ethanol by distillation, followed by oxidation by potassium dichromate in a sulfuric acid medium.
Determination of the excess dichromate by ammonium iron(II) sulfate in the presence of iron(II)-1,10-
phenanthroline as indicator.
4 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or
water of equivalent purity.
4.1  Sulfuric acid (H SO ), r = 1,84 g/ml.
2 4
4.2  Dilute sulfuric acid, r = 1,49 g/ml, containing 500 ml of sulfuric acid (4.1) per litre.
4.3  Calcium hydroxide [Ca(OH) ], suspension obtained by shaking 110 g to 112 g of calcium oxide in 1 litre of
water.
4.4  Potassium dichromate solution, containing 42,572 g of K Cr O per litre. 1 ml of this solution is equivalent to
2 2 7
0,01 g of ethanol.
containing 1,372 g of KMnO per litre. 10 ml of this solution is equivalent
4.5 Potassium permanganate solution,
to 1 ml of ammonium iron(II) sulfate solution (4.6).
4.6  Ammonium iron(II) sulfate solution [(NH ) Fe(SO )].
4 2 4
© ISO
Dissolve 170,2 g of ammonium iron(II) sulfate hexahydrate in water. Add 20 ml of sulfuric acid (4.1) and dilute to
1 litre with water.
Stabilize by the addition of aluminium chips. 2 ml of this solution is equivalent to 1 ml of potassium dichromate
solution (4.4).
4.7  Iron(II)-1,10-phenanthroline solution.
.
Dissolve 0,695 g of iron(II) sulfate heptahydrate (FeSO 7H O) in 100 ml of water. Add 1,485 g of
4 2
.
1,10-phenanthroline monohydrate (C H N H O) and heat to aid solution.
12 8 2 2
The solution keeps well.
5 Apparatus
Usual laboratory apparatus and, in particular, the following.
5.1  Distillation apparatus, comprising a 500 ml flask surmounted by a fractionation column and a condenser
ending in a slightly tapered extension piece long enough to reach to the bottom of a 100 ml volumetric flask.
Any other steam distillation apparatus may be used, provided that it satisfies the following criterion.
No loss of ethanol greater than 0,02 % shall occur in the course of a distillation; i.e. 200 ml of a 10 % (V/V)
ethanol/water mixture distilled five times in succession shall contain at least 9,9 % of ethanol after the last
distillation.
5.2  Heating apparatus, which does not cause even slight decomposition of the extractable materials contained in
the flask.
of capacity 100 ml.
5.3 Volumetric flasks,
5.4  Pipettes, of capacities 5 ml, 10 ml and 20 ml.
5.5  Burettes, of capacity 50 ml, fitted with a stopcock.
5.6  Wide-necked flasks, of capacity 250 ml, fitted with ground glass stoppers, clean, dry, free from grease and
airtight (absolute tightness can be ensured with the aid of a polytetrafluorethylene sleeve).
5.7  Blender.
5.8  Balance, capable of weighing to the nearest 0,01 g.
6 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.
7 Preparation of test sample
7.1  Solid or thick products (purée, marmalade or jam, fruits, vegetables)
Blend mechanically the whole of the sample supplied. Take care that the temperature of the product does not rise.
Take a sufficient quantity of the product to enable two parallel determinations to be carried out.
© ISO
7.2  Liquid products (juices, pulps and syrups)
Thoroughly mix the sample. Take a sufficient quantity of the product to enable two parallel determinations to be
carried out.
8 Procedure
NOTE If it is required to check whether the repeatability requirement (clause 10) is met, carry out two determinations in
accordance with 8.2.1 to 8.2.3.
8.1 Test portion
Weigh, to the nearest 0,01 g, a mass of the prepared sample, or take a volume of it such that the quantity of ethanol
collected in 100 ml of distillate is less than 1 g.
8.2 Determination
8.2.1 Distillation
Dilute the test portion with about 50 ml of water and transfer it quantitatively to the flask of the distillation apparatus
(5.1). Rinse
...