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IS0
I NT ERN AT1 ON A L O RG A N IZATl O N FOR STANDARD IZATlO N
IS0 RECOMMENDATION
R 660
CRUDE VEGETABLE OILS AND FATS
DETERMINATION OF ACIDITY
1st EDITION
February 1968
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The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
IS0 Recommendation R 660, Crude vegetable oils and fats - Determination of acidiw,
The
was drawn up by Technical Committee ISO/TC 34, Agricultural food products, the Secretariat of
which is held by the Magyar Szabvanyügyi Hivatal (MSZH).
Work on this question by the Technical Committee began in 1961 and led, in 1963, to the
adoption of a Draft IS0 Recommendation.
In March 1966, this Draft IS0 Recommendation (No. 901) was circulated to ail the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature,
by the following Member Bodies :
Argentina Hungary Romania
Australia India South Africa,
Belgium Iran Rep. of
Bulgaria Ireland
Turkey
Chile Israel U.A.R.
Colombia Italy United Kingdom
Czechoslovakia Netherlands U.S.S.R
Finland New Zealand Yugoslavia
France Norway
Germany Poland
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council
which decided, in February 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 660-1968 IE
IS0 Recommendation R 660 February 1968
CRUDE VEGETABLE OILS AND FATS
DETERMINATION OF ACIDITY
1. SCOPE
This IS0 Recommendation describes a method for the determination of the free fatty acid content
of crude vegetable oils and fats. This can be expressed as an acid value or as conventional acidity.
2. DEFINITIONS
2.1 Acid value. Number of milligrammes of potassium hydroxide required to neutralize the free
fatty acids in 1 g of the oil or fat.
Conventional expression of the percentage of free fatty acids (see clauses 7.2 and
2.2 Acidity.
7.3).
3. PRINCIPLE
Solution of a known quantity of the oil or fat to be analysed in a mixture of ethanol and diethyl-
ether, followed by titration of the free fatty acids present with an ethanolic solution of potassium
hydroxide.
4. REAGENTS
Mixîure I + 1 v/v ethanol 95 y. v/v and diethyl ether. Neutralize exactly, just before use, by
4.1
means of the ethanolic potassium hydroxide solution (4.2), in the presence of 0.3 ml of indi-
cator (4.3) per 100 ml of this mixture (phenolphthalein or aikali blue 6 B, as the case may be
(see section 6).
4.2 Potassium hydroxide, approximately 0.1 N or, if necessary, approximately 0.5 N solution in
ethanol 95 y,, v/v. The exact concentration should be known, and checked immediately before
use. Use a solution prepared at least five days previously and decanted into a bottle of brown
glass, provided with a rubber stopper. The solution should be colourless or straw yellow.
NOTE. - It is recommended that the ethanol should be purified by adding 5 to 10 g of potassium hydroxide
to 1 litre of the ethanol, boiling for one hour under reflux and finally distilling over.
4.3 Indicator. Phenolphthaiein, 10 g per litre of ethanol 95 v/v or, if necessary, alkali blue 6 B,
20 g per litre of ethanol 95 v/v.
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ISO/R 660-1968 (E
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