International Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION.MEXCIYHAPOAHAR OPl-AHl43ALWlfl fl0 CTAH,QAPTM3ALWlM.ORGANISATION INTERNATIONALE DE NORMALISATION
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Cereals and cereal products - Determination of moisture
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content (Basic reference method)
C&&ales et produits c&t?aliers - Dktermination de Ia teneur
Y en eau (Methode de r&f&ence fondamentalel
Second edition - 1985-12-15
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UDC 633.1 : 543.812 Ref. No. ISO 7114985 (E)
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Descriptors : agricultural products, cereal products, grains (food), water, determination of content, dehydration analysis.
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Foreword
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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. Esch 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, govern- .
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mental and non-governmental, in liaison with ISO, also take patt 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. They are approved in accordance with ISO procedures requiring at
least 75 % approval by the member bodies voting.
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International Standard ISO 711 was prepared by Technical Committee ISO/TC 34,
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Agricultural food products.
This second edition cancels and replaces the first edition (ISO 711-19781, of which it
constitutes a minor revision.
NOTE - This International Standard is based on’ Standa rd No. 109/1 of the International
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Association for Cereal Science and Technology ( ICC).
Users should note that all International Standards undergo revision from time to time
and that any reference made herein to any other International Standard implies its
latest edition, unless othewise stated.
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0 International Organkation for Standardkation, 1985
Printed in Switzerland
INTERNATIONAL STANDARD ISO 7114985 (EI
Bereals and cereal products - Determination of moisture
content (Basic reference method)
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0 Introduction 4 Principle
The basic reference method specified in this International Stan- lf necessary, grinding of a Sample, after conditioning, if re-
dard ensures complete removal of moisture from the product, quired. Drying of a test Portion under reduced pressure, at a
as has been demonstrated by tests of reversibility and addition temperature between 45 and 50 OC and in the presence of a
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of moisture, while avoiding any alteration in its Chemical com- desiccant, until constant mass is reached.
Position, particularly Oxidation and loss of volatile organic
substances.
5 Apparatus
1 Scope and field of application
Y 5.1 Analytical balance.
This International Standard specifies the basic reference
method for the determination of the moisture content of 5.2 Apparatus for reducing pressure to 1,3 to 2,6 kPa,2)
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cereals and cereal products. 1) for example a water pump.
The method is not applicable to maize, for which an identical 5.3 Grinding mill, having the following characteristics:
method, called the absolute method, is specified in the annex
to ISO 6540, Maize - Determination o f mois ture con ten t fon a) made of material which does not absorb moisture;
milied grains and on whole grainsl.
b) easy to clean and having as little dead space as
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This basic reference method, which necessitates the employ- possible;
ment of special equipment and experienced analysts, is
therefore only suitable for use in specialized laboratories, and is c) enabling grinding to be carried out rapidly and uni-
intended to serve as a Standard for checking and perfecting formly, without appreciable development of heat and, as far
routine methods for the determination of moisture content (sec as possible, without contact with the outside air;
particularly ISO 712). lt is not intended to be used for settling
d) adjustable so as to obtain particles of the dimensions
commercial disputes.
indicated in 7.1.1.
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2 References 5.4 Metal dish,3) non-corrodible under the test conditions,
with a sufficiently tight-fitting lid and having an effective sur-
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ISO 712, Cereals and cereal products - Determination of face area such as to allow the test Portion to be distributed in a
moisture content (Routine reference method). layer having a mass per unit area of not more than 0,3 g/cm?
ISO 950, Cereals - Sampling (as grain).
5.5 Cup, made from glass or porcelain.
3 Definition 5.6 Drying tube? of glass, in two Parts, one of which, in-
tended to,receive the dish (5.41, is closed at one end, while the
moisture content: The loss in mass, expressed as a per- other, intended to receive the cup (5.5), carries a semi-capilla’ry
centage, undergone by the product under the conditions tube, with a stopcock, for evacuation purposes. The two Parts
specified in this International Standard. are connected by a ground glass joint.
1) This method has been applied successfully to the following products: wheat, rice (Paddy, husked and milled rice), barley, millet, rye and oats, in
the form of grains, milled grains, semolina or flour.
2) i,3 to 2,6 kPa = 13 to 26 mbar = IO to 20 mmHg.
3) A suitable metal dish is shown, for information only, in figure 1.
4) A suitable drying tube is shown, for information only, in figure 2.
ISO 711-1985 (E)
The test Portion may be cooled in this apparatus after drying, a moisture content more than 17 % (mlm)t) or less than
desiccator (5.9) being then unnecessary for this Operation. 7 % (mlm)] shall be pre-conditioned so as to bring their
moisture content to between 7 and 17 % (mlm)t) [if possible
between 9 and 15 % (mlm) (sec 9.113, before grinding.
5.7 Constant-temperature oven, electrically heated,
enabling the part of the drying tube (5.6) containing the dish
If the moisture content is more than 17 % (m/mV) (the more
(5.4) to be maintained at a temperature between 45 and 50 OC.
frequent case), weigh, to the nearest 0,2 mg, about 3,5 g of the
laboratory Sample and pre-dry it in accordance with 7.3, except
5.8 Air-drying train : gas-washing bottle containing pure that the drying time shall be 1,5 to 2 h (sec 9.2) and it is
analytical gradesulfuric acid (g20 a 1,83 g/ml), connected to a unnecessary to renew the diphosphorus pentaoxide.
tube containing pure analytical grade diphosphorus pentaoxide
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spread on glass wool. If the moisture content is less than 7 % (mlm), place about
3,5 g of the laboratory Sample, weighed to the nearest 0,2 mg,
in a suitable atmosphere (usually that of the laboratory) and
5.9 Desiccator, containing an efficient desiccant.
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leave it to acquire a moisture content within the limits specified
above.
6 Sampling After conditioning, weigh the Sample to the nearest 0,2 mg,
grind it immediately in the grinding mill (5.31, adjusted to obtain
See ISO 950.
particles of the dimensions indicated in 7.1.1, and immediately
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proceed in accordance with 7.2.2.
7 Procedure
7.2 Test Portion
7.1 Preparation of the test Sample
7.2.1 For products not requiring to be ground, rapidly weigh,
Y to the nearest 0,2 mg, about 3 g of the test Sample (7.1 .l) into
7.1.1 Products not requiring to be ground the dish (5.41, previously dried and weighed, together with its
lid, to the nearest 0,2 mg.
Products having particles of sizes less than or equal to 1,7 mm,
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less than 10 % (mlm) being over 1 mm and more than
50 % (mlm) being less than 0,5 mm, do not need to be ground 7.2.2 In the case of products which have had to be ground,
before the determination. rapidly weigh all the grindings obtained (7.1.2.1 or 7.1.2.2) into
the dish (5.41, previously dried and weighed, together with its
Mix the laboratory Sample thoroughly before taking the test lid, to the nearest 0,2 mg.
Portion (7.2.1).
7.3 Drying
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7.1.2 Products requiring to be ground
Place the open dish (leaving its lid in the desiccator) containing
If the Sample does not have the particle size characteristics the test Portion (7.2) at the closed end of the drying tube (5.6);
mentioned in 7.1 .l, it shall be ground either without pre- introduce, near to it, the cup (5.5) containing a layer of
conditioning (7.1.2.1) or with pre-conditioning (7.1.2.2). diphosphorus pentaoxide about 1 cm thick. Fit the two Parts of
the drying tube together and reduce the pressure in the
assembled tube to a value of the Order of 1,3 to 2,6 kPa, using
7.1.2.1 Grinding without pre-conditioning
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the vacuum apparatus (5.2); this should be done gradually in
Order to avoid material being thrown out of the dish. Close the
For products which are not likely to undergo variations in connection to the vacuum apparatus, and place the part of the
moisture content in the course of grinding [in general, products tube containing the test Portion in the oven (5.71, controlled at
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with a moisture content between 7 and 17 % (mlm)t) 45 to 50 OC (sec 9.4).
(sec 9.111, carry out grinding without pre-conditioning.
When the diphosphorus pentaoxide agglomerates at the sur-
Adjust the grinding mill (5.3) to obtain particles of the dimen- face, renew it after restoring atmospheric pressure inside the
sions indicated in 7.1.1, grind a small quantity of the laboratory drying tube by causing air, which has passed through the dry-
Sample and discard it. ing train (5.81, to enter slowly through the semi-capillary tube.
Reduce the pressure in the drying tube again and continue the
Then quickly grind about 3,5 g of the laboratory Sample, and drying as before.
immediately proceed in accordance with 7.2.2.
After about 100 h, take the tube out of the oven, allow it to cool
7.1.2.2 Grinding with pre-conditioning to laboratory temperature and restore atmospheric pressure in-
side it as described above. Disconnect the two Parts of the
Products which are likely to undergo changes in moisture con- tube, quickly remove the dish, cover and weigh it to the nearest
tent in the course of grinding [in general, products with a 0,2 mg.
1) 15 % (mlm) in the case of oats and rice (Paddy, husked and milled rice).
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ISO 7114985 (EI
Repeat the operations specified above until the mass is prac- Take as the result the arithmetic mean of the two values
tically constant (i.e. until the differente between two successive obtained, if the requirement for repeatability (see 8.2) is
weighings at an interval of 48 h is less than 0,6 mg) (sec 9.3). satisfied. If it is not, the determinations shall be repeated.
Express the result to the second decimal place.
7.4 Number of determinations
Carry out two determinations on test portions taken from dif- 8.2 Repeatability
ferent test samples but from the same laboratory Sample.
The differente between the values obtained from two deter-
minations (sec 7.4) carried out simultaneously or in rapid suc-
cession by the same analyst shall not exceed 0,lO g of moisture
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per 100 g of Sample.
8 Expression of results
NOTE - With a little practice, differentes of less than 0,05 g of
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moisture per 100 g of Sample tan be obtained in the same laboratory.
8.1 Method of calculation and formulae
The moisture content, expressed as a percentage by mass of
the product as received, is given by the following formulae 9 Notes on procedure
a) without pre-conditioning : 9.1 The range of moisture contents given for conditioning
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100 products before grinding corresponds approximately to a
b-20 - m,) - laboratory atmosphere of temperature 20 OC and relative
mo ’ humidity 40 to 70 %. lt should be modified for other
where atmospheric conditions.
mo is the mass, in grams, of the test portion (7.2.1 or
7.2.2);
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Check that it enables the desired conditioning to be obtained
m1 is the mass, in grams, of the test Portion after with the apparatus and the products used.
drying (7.3).
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b) with pre-conditioning : 9.3 The drying period is of the Order of 150 h at least.
bz0- VI’)3 + m2 - -100 9.4 A coloration at the surface of the diphosphorus penta-
[ 1 m2
m3
m0 Oxide indicates the loss of traces of volatile organic substances
from the test Portion. With certain deteriorated products, if the
coloration becomes sufficiently pronounced, it is expedient to
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=loo (1 -y reduce the temperature of heating.
10 Test report
is the mass, in grams, of the test Portion (7.2.2);
The test report shall show the method used and the result
m1 is the mass, in grams, of the test Portion after
obtained. It shall also mention all operating details not specified
drying (7.3) ;
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in this International Standard, or regarded as optional, as well
m2 is the mass, in grams, of Sample taken before pre- as any incidents which may have influenced the result.
conditioning (7.1.2.2) ;
The report shall include all details required for the complete
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m3 is the mass, in grams, of the pre-conditioned identification of the Sample, and in particular the date on which
Sample (7.1.2.2). the analysis was carried out.
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ISO 711-1985 (E)
Dimensions in millimetres
114 int.
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128
Dish
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Lid
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NOTE - The dish shown in the diagram has a flat bottom of effective surface 16 cm* and an internal height of 14 mm. It may be used with the drying
tube shown in figure 2.
Figure 1 - Diagram of suitable metal dish and lid (for guidance only)
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ISO 711-1985 (El
Dimensions in millimetres
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0
m
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Stopcock with oblique
* Wall thickness = 2 mm 2 mm bore
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50
180 to 200
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NOTE - The drying tube shown in the diagram has a 40/50 ground-glass joint (40 mm in diameter at the large end, and having a length of the ground
Portion of 50 mm). It is suitable for use with the dish shown in figure 1. The Olive ending to the stopcock side arm may be replaced by a ground glass
joint.
Figure 2 - Diagram of suitable drying tube (for guidance only)
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