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Ref. No. : ISO/R 729-1968 (E)
IS0
I N T E R N AT I O N A L ORGANIZATION FOR STAN DA RD I ZAT I O N
IS0 RECOMMEN DATION
R 729
01 c
DETERMINATION OF ACIDITY OF OILS
1 st ED IT I ON
May 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
The IS0 Recommendation R 729, Oleaginous seeds - Determination of acidiîy of oils,
was drawn up by Technical Committee ISO/TC34, Agricultural food products, the Secre-
tariat of which is held by the Magyar Szabvànyttgyi 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. 902) was circulated to all
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
Ireland
Bulgaria Turkey
Chile Israel U.A.R.
Colombia Italy United Kingdom
Czechoslovakia Net herlands 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 May 1968, toaccept it asan ISORECOMMENDATION.
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ISO/R 729-1968 (E)
IS0 Recommendation R 729 May 1968
OLEAGINOUS SEEDS
DETERMINATION OF ACIDITY OF OILS
1. SCOPE
1.1
This IS0 Recommendation describes a method for the determination of the
acidity of oil present in oleaginous seeds. The acidity can be expressed as an
acid valw or as conventional acidity.
Field of application ~
1.2
The present IS0 Recommendation does not apply to cotton seed with adherent
linters.
2. DEFINITIONS
2.1 Acid value. Number of milligrammes of potassium hyuroxide requlred to neutral-
ize the free fatty acid in 1 g of the oil.
2.2
Acidity. Conventional expression of the percentage of free fatty acids (see claus-
es 7.2 and 7.3).
3. PRINCIPLE
3.1 Solution, in a mixture of ethanol and diethyl ether, of the oil extracted in the
determination of the oil content of the seeds, followed by titration of the free
fatty acids present with an ethanolic solution of potassium hydroxide.
The oil for the determination of acidity shouldbe extractedas soonas the seeds
3.2
concerned are ground, and analysed as soon as the last weighing of the extrac-
tion flasks has been made.
3.3 The acidity may be determined on the oil from the product as received (pure
seed + impurities) or, if required, on the pure seed.
4. REAGENTS
Mixture, 1 + 1 v/v of ethanol 95 % v/v and diethyl ether. Neutralize exactly.
4.1
just before use, by means of the ethanolic potassium hydroxide solution (4.2),
in the pr'esence of O. 3 ml of indicator (4.3) per 100 ml of this mixture (phenol-
phthalein or alkali blue 6 B, as the case may be, see clause 8.2).
4.2 Potassium hydroxide, approximately O. 1 N, or if necessary, approximately O. 5 N
solution in ethanol 95 % 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 1 hour under reflux and fmaiiy distilling over.
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ISO/R 729-1968 (I
Indicator, .phenolphthalein, 10 g per litre solution in ethanol 95 % v/v or, if
4.3
necessary, alkali blue 6 B, 20 g per litre solution in ethanol 95 % v/v.
5. APPARATUS
Burette, graduated in O. 1 ml, complying with the specification for class of accuracy
A of IS0 Recommendation R 385, Burettes.
6. PROCEDURE
6.1 Test portion
Carry out the determination,
immediately after the extracti
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