GB/T 5530-2005 PDF English
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| GB/T 5530-2005 | English | 290 |
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Animal and vegetable fats and oils -- Determination of acid value and acidity
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| GB/T 5530-1998 | English | 279 |
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Animal and vegetable fats and oils--Determination of acid value and of acidity
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| GB/T 5530-1985 | English | RFQ |
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Inspection of vegetable oils--Methods for determination of acid value
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GB/T 5530-2005: Animal and vegetable fats and oils -- Determination of acid value and acidity---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT5530-2005
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 67.200.10
X 14
GB/T 5530-2005 / ISO 660:1996
Replacing GB/T 5530-1998
Animal and vegetable fats and oils - Determination of acid
value and acidity
(ISO 660:1996, IDT)
ISSUED ON: NOVEMBER 11, 2005
IMPLEMENTED ON: DECEMBER 01, 2006
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
National Standardization Administration.
Replaced
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Hot ethanol determination method ... 5
4.1 General... 5
4.2 Principle ... 5
4.3 Reagents ... 5
4.4 Instruments ... 6
4.5 Sampling ... 6
4.6 Specimen preparation ... 6
4.7 Procedure ... 6
5 Cold solvent method ... 7
5.1 General... 7
5.2 Principle ... 7
5.3 Reagents ... 7
5.4 Instruments ... 9
5.5 Sampling ... 9
5.6 Specimen preparation ... 9
5.7 Procedure ... 9
6 Potentiometer method ... 10
6.1 Principle ... 10
6.2 Reagents ... 10
6.3 Instruments ... 10
6.4 Sampling ... 11
6.5 Specimen preparation ... 11
6.6 Steps ... 11
7 Result expression ... 12
7.1 Acid Value ... 12
7.2 Acidity ... 13
8 Precision ... 13
8.1 Repeatability ... 13
8.2 Reproducibility ... 14
9 Experimental report ... 14
Appendix A (Informative) Joint laboratory test results ... 15
References ... 17
Animal and vegetable fats and oils - Determination of acid
value and acidity
1 Scope
This standard specifies the methods for determining the acidity in animal and vegetable
oils and fats (two titration methods and one potentiometer method); the acidity is
usually expressed as acid value. The hot ethanol determination method in this standard
is the reference method. The cold solvent method is applicable to light-colored oils and
fats.
This standard does not apply to waxes.
2 Normative references
The provisions in following documents become the provisions of this Standard through
reference in this Standard. For the dated references, the subsequent amendments
(excluding corrections) or revisions do not apply to this Standard; however, parties who
reach an agreement based on this Standard are encouraged to study if the latest versions
of these documents are applicable. For undated references, the latest edition of the
referenced document applies.
GB/T 6682-1992 Water for analytical laboratory use - Specification and test
methods (neq ISO 3696:1987)
GB/T 15687 Oils and fats - Preparation of test sample (GB/T 15687-1995, eqv ISO
661:1989)
3 Terms and definitions
The following terms and definitions apply to this standard.
3.1
Acid value
The number of milligrams of potassium hydroxide required to neutralize the free
fatty acids in 1 gram of oil and fat, as determined by the method specified in this
standard, expressed in milligrams per gram.
3.2
Acidity
The free fatty acid content determined by the method specified in this standard,
expressed in mass fraction.
Note 1: When the result is written as "acidity" without detailed description, this "acidity" is
usually expressed in terms of oleic acid.
Note 2: When the sample contains mineral acids, fatty acids are usually determined.
4 Hot ethanol determination method
4.1 General
This method is a reference method for the determination of the acid value of fats (see
Chapter 1).
Note 3: Under the conditions specified in this method, short-chain fatty acids are volatile.
4.2 Principle
The specimen is dissolved in hot ethanol and titrated with sodium hydroxide or
potassium hydroxide aqueous solution.
4.3 Reagents
Unless otherwise specified, only reagents confirmed as analytically pure are used. The
water used shall meet the requirements of grade-3 water in GB/T 6682-1992.
4.3.1 Ethanol: The minimum concentration is 95%.
4.3.2 Sodium hydroxide or potassium hydroxide: The concentration of the standard
solution is c(NaOH or KOH) = 0.1 mol/L.
4.3.3 Sodium hydroxide or potassium hydroxide: The concentration of the standard
solution is c(NaOH or KOH) = 0.5 mol/L.
4.3.4 Phenolphthalein indicator: 10 g/L; 10 g of phenolphthalein is dissolved in 1 L of
95% ethanol solution.
Note 4: When measuring darker samples, add 1 mL of 0.1% methylene blue solution to every
100 mL of phenolphthalein indicator solution, to observe the titration endpoint.
4.3.5 Basic blue 6B or thymolphthalein (for dark oils and fats): 20 g/L; 20 g of basic
(4.3.2), until the solution changes color. Keep the solution unchanged for 15 s, which
is the end point.
Note 6: When the color of the oil is dark, more ethanol and indicator need to be added.
Transfer the neutralized ethanol to the conical flask containing the test sample; mix
thoroughly; boil. Titrate with sodium hydroxide or potassium hydroxide standard
solution (4.3.2 or 4.3.3 depends on the estimated acid value of the sample); shake
thoroughly during the titration process. When the solution changes color and remains
unfaded for 15 seconds, the titration end point is reached.
5 Cold solvent method
5.1 General
This method is applicable to light-colored oils and fats.
5.2 Principle
The sample is dissolved in a mixed solvent and titrated with potassium hydroxide
ethanol solution.
5.3 Reagents
Unless otherwise specified, only reagents confirmed to be analytically pure are used.
The water used shall meet the requirements of grade-3 water in GB/T 6682-1992.
5.3.1 Ether and 95% ethanol: 1 + 1 volume mixture.
Warning: Ether is highly flammable and can generate explosive peroxides. It must
be used with extreme caution.
Before use, add 0.3 mL of phenolphthalein solution (5.3.3) to every 100 mL of mixed
solvent; accurately neutralize with potassium hydroxide ethanol solution (5.3.2) (see
note in 4.7.2).
If it is not possible to use ether, the following mixed solvents can be used:
- Toluene and 95% ethanol, 1+1 volume mixture;
- Toluene and 99% isopropanol, 1+1 volume mixture;
- When determining crude oil and refined vegetable fats, 99% isopropanol can be
used instead of the mixed solvent.
ethanol, 8 g of potassium hydroxide, 0.5 g of aluminum flakes; boil and reflux for 1 h;
then immediately distill; dissolve the required amount of potassium hydroxide in the
distillate; let it stand for a few days; slowly pour out the supernatant; discard the
potassium carbonate precipitate.
5.3.2.3 The solution can also be prepared by non-distillation method: Add 4 mL of
aluminum butyrate to 1000 mL ethanol; let it stand for a few days; slowly pour out the
supernatant; dissolve the required potassium hydroxide. The prepared solution needs to
be calibrated.
Note: The preparation and calibration of potassium hydroxide or sodium hydroxide standard
solution can also be carried out, in accordance with the national standard GB/T 601-2002.
5.3.3 Phenolphthalein indicator, see 4.3.4.
5.3.4 Basic blue 6B or thymolphthalein, see 4.3.5.
5.4 Instruments
Conventional laboratory instruments, as well as the microburette described in 4.4.1.
5.5 Sampling
See 4.5.
5.6 Specimen preparation
See 4.6.
5.7 Procedure
5.7.1 Weighing the sample
According to the estimated acid value, use a sufficient amount of sample (5.6) as shown
in Table 1. Weigh the sample into a 250 mL conical flask.
5.7.2 Determination
5.7.2.1 Dissolve the sample (5.7.1) in 50 mL ~ 150 mL of the pre-neutralized mixed
solvent (5.3.1).
Titrate with potassium hydroxide solution (5.3.2) (see 5.7.2.3) while shaking, until the
indicator shows the endpoint described in 4.7.2.
5.7.2.2 When the acid value is < 1, a nitrogen flow needs to be slowly introduced into
the solution.
5.7.2.3 When the volume of 0.1 mol/L potassium hydroxide solution (solution A)
required for titration exceeds 10 mL, use 0.5 mol/L potassium hydroxide solution
(solution B) instead.
5.7.2.4 If the solution becomes turbid during titration, add an appropriate amount of
mixed solvent (5.3.1) until it becomes clear.
6 Potentiometer method
6.1 Principle
In anhydrous medium, potassium hydroxide isopropanol solution is used to titrate the
free fatty acids in the specimen by potentiometric titration.
6.2 Reagents
All reagents used are analytically pure; the water used shall meet the requirements of
grade-3 water in GB/T 6682-1992.
6.2.1 4-Methyl-2-pentanone (methyl isobutyl ketone): Neutralize with potassium
hydroxide solution (6.2.2) before use and measure with a pH meter (6.3.1).
6.2.2 Potassium hydroxide standard solution C: 0.1 mol/L potassium hydroxide
isopropanol solution; the preparation method is as shown in the method for preparing
solution A (5.3.2).
6.2.3 Potassium hydroxide standard solution D: 0.5 mol/L potassium hydroxide
isopropanol solution; the preparation method is as shown in the method for preparing
solution B (5.3.2).
6.3 Instruments
Routine laboratory instruments, as well as the following instruments:
6.3.1 pH meter: Equipped with glass electrode and calomel electrode.
The saturated potassium chloride solution and the experimental solution are kept in
contact with a sintered glass or porcelain disk, which has a thickness of at least 3 mm.
Note 9: Soak the glass electrode in methyl isobutyl ketone for 12 hours before titration. Gently
wipe it dry with filter paper before use. Rinse it with methyl isobutyl ketone, isopropanol,
distilled water immediately after the measurement.
Note 10: If the electrode effect is poor, soak it in 1 mol/L hydrochloric acid isopropanol solution
for 14 hours to revive the electrode. The soaked electrode shall be rinsed with distilled water,
isopropanol, methyl isobutyl ketone in turn.
Note 11: A coarse sintered glass or porcelain disk is used to maintain contact between the
saturated potassium chloride solution and the experimental solution, to prevent the generation
of diffusion current and additional voltage.
6.3.2 Magnetic stirrer.
6.3.3 Analytical balance, same as 4.4.2.
6.4 Sampling
See 4.5.
6.5 Specimen preparation
See 4.6.
6.6 Steps
6.6.1 Weighing
Weigh 5 g ~ 10 g of sample (6.5) to the nearest 0.01 g. Place in a 150 mL beaker.
6.6.2 Determination
6.6.2.1 Dissolve the sample (6.6.1) in 50 mL of 4-methyl-2-pentanone (6.2.1).
Insert the electrode of the pH meter (6.3.1); start the magnetic stirrer (6.3.2); titrate to
the equivalence point with potassium hydroxide solution (select 6.2.2 or 6.2.3 according
to the estimated acidity).
Note 12: The equivalence point usually corresponds approximately to a certain pH value and
can be determined by observing the turning point of the neutralization curve by graphical
method; the equivalence point can also be calculated by the pH change value (the first
differential of the functional relationship of the added potassium hydroxide isopropanol
solution is the maximum value, or the second differential is equal to zero).
6.6.2.2 The turning point of cottonseed oil with high gossypol content cannot be
measured. In this case, the pH value corresponding to the equivalence point when oleic
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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