CA 3d-02 Sediments

SAMPLING AND ANALYSIS OF COMMERCIAL FATS AND OILS

AAOCS Official Method Ca 3d-02 Reapproved 2009

Determination of Sediment in Crude Fats and Oils—Centrifuge Method DEFINITION

 A homogenized test sample is subjected to centrifuging as specified. The amount of separated material, called sediment (part of the insoluble matter in a crude fat or oil which can be centrifugally separated and is the total amount of the unclear layer of components collected at the bottom of the measuring tube after centrifuging) is volumetrically measured in a calibrated centrifuge tube. SCOPE

This method determines sediment that can be separated from crude fats and oils by centrifugal force. The method is applicable to crude oils and to oils with a sediment content of 0.03 mL per 100 g to 15 mL per 100 g, obtained by means of extraction and/or crushing. The method is not applicable to fats which are not liquid at a temperature of 20°C. This method is identical to International Organization of Standardization (ISO) 15301. APPARATUS

Usual laboratory apparatus and, in particular particular,, the following: 1. Centrifuge tubes, 100 mL capacity, capacity, pear- or cone-shaped, made from thoroughly annealed glass and fitted with a stopper (see Figures 1 and 2) (see Notes, 2). 2. Buckets, for centrifuge tubes tubes (Apparatus,1), (Apparatus,1), resistant resistant to fats and oils. 3. Centrifuge, suitable for the centrifuge tubes (Apparatus, (Apparatus, 1) placed placed in the buckets (Apparatus, (Apparatus, 2), 2), capable of controlling controlling the rotational frequency so as to give a radial acceleration at the narrow part of the tubes of 700 to 800 times. See Notes, 3 for the calculation of the rotational frequency of the centrifuge. In rooms which are not air-conditioned, use a centrifuge capable of maintaining its temperature between 20°C and 25°C. 4. Balance, capable of weighing to the nearest 0.01 g. SAMPLING

1. It is important that the laboratory receive a sample which is truly representative representative and has not been damaged damaged or changed during transport or storage. 2. A recommended SAMPLINGmethod SAMPLINGmethod is given in AOCS AOCS Official Method Method C 1-47 or ISO 5555 (1). 3. Store laboratory samples in glass or polyethylene terephthalate (PET) (PET) bottles. TEST SAMPLE PREPARA PREPARATION TION

1. Prepare the test sample in accordance accordance with ISO 661. 2. Bring the test sample, if necessary, to a temperature of between 20°C and 25°C. 3. Redisperse any sediment in the oil from from the bottom of the sample bottle to ensure a sufficiently homogeneous and represenrepresentative sample. Immediately proceed in accordance with Procedur Procedure. e. PROCEDURE

1. Weigh two centrifuge centrifuge tubes (Apparatus, (Apparatus, 1) 1) to the nearest 0.1 g. 2. Transfer the prepared test sample sample (see Test Test sample preparation, 1-3) to each each of the centrifuge tubes. 3. Weigh the tubes and place them in the buckets (Apparatus, 2) of the centrifuge (Apparatus, 3). Adjust speed to give a radial acceleration at the narrow part of tubes of 700-800 × g. 4. Centrifuge for 1 h ± 5 s. 5. Read sediment volumes up to and including 1.5 mL to the nearest 0.03 0.03 mL. Read sediment volumes greater greater than 1.5 mL to the nearest 0.5 mL. 6. When using a cone-shaped tube, it may be more difficult to read the volume of the unclear unclear layer; read the sediment sediment volumes as accurately as possible. 7. If in a pear-shaped tube the separation is not complete (clear layer in the neck of the narrow narrow tube section of the tube), the sediment reading should be corrected for this volume. 8. Record Record the × g force (rpm) used or the swing diameter and the rpm of the centrifuge (Notes, 3). 9. Record the temperature before before and after centrifuging. centrifuging.

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SAMPLING AND ANALYSIS OF COMMERCIAL FA FATS TS AND OILS

Ca 3d-02 •

Determination of Sediment in Crude Fats and Oils—Centrifuge Method

EXPRESSION OF RESULTS

Calculate the sediment content of the test sample using the equation: w 

V   =

(m1

100

× −

m2 )

 

Where— w  =  = the numerical value of the sediment content of the test sample, in milliliters per 100g  V = V  = the numerical value of the sediment volume, in milliliters m1 = the numerical value of the mass of the centrifuge tube with the test portion, in grams m2 = the numerical value of the mass of the centrifuge tube, in grams Calculate the mean of the results for the two tubes and report the results to the nearest 1 mL per 100 g. PRECISION

1. Details of interlaboratory tests on the precision of the method are are given in Tables Tables 1 and 2. The values values derived from these tests may not be applicable to concentration ranges and matrices other than those given. The precision of the method was established by two interlaboratory tests organized by the Netherlands Oils, Fats and Oilseeds Trade Trade Association (NOFOTA) (NOFOTA) in cooperation with the Federation of Oils, Seeds and Fats Associations (FOSFA International) in 1996 and 1997/1998 and carried out in accordance with International Organization of Standardization 5725-2 (3). In the first test 12 laboratories participated. Six (spiked) samples of crude sunflower seed oil were investigated. In the second test 9 laboratories participated. Four (spiked) samples of crude sunflower seed oil were investigated. See Tables Tables 1 and 2 for a summary of the statistical results of the tests. Comparison with the 96 h method  In the two interlaboratory tests, the centrifuge method was compared with the method which leaves the test sample to stand at a controlled temperature for 96 h. Applying regression analysis to the results of both interlaboratory tests for the relation between the two methods, the following equation was established (with a correlation coefficient of 0.96): w 2 = 2.5  2.5w  w 1 − 0.5 w 1 = the numerical value of the sediment content obtained with the 96 h method, in milliliters per 100 mL w 2 = the numerical value of the sediment content obtained with the centrifuge method, in milliliters per 100 mL This indicates that the centrifuge method may be considered as a good alternative to the 96 h method, where a rapid control method is required for levels of sediment exceeding 0.5 mL per 100 mL. 2. Repeatability  The absolute difference between two independent single test results, obtained using the same method on identical test material in the same laboratory by the same operator using the same equipment within a short interval of time, will in not more than 5% of cases exceed the repeatability limit given in or derived from Table Table 3. 3. Reproducibility  The absolute difference between two single test results, obtained using the same method on identical test material in different laboratories by different operators using different equipment, will in not more than 5% of cases exceed the R reproducibility limit given in or derived from Table Table 3. NOTES

1. The sediment contains, for example, example, phospholipids, impurities, impurities, dirt, etc. dispersed dispersed in a water-containing water-containing phase, and can be quantified according to this method. Any white crystalline components deposited on top of and within the dark layer of insoluble materials are regarded as part of the sediment. 2. Reading the volume of the unclear layer may be more more difficult in a cone-shaped cone-shaped tube than in a pear-shaped pear-shaped tube. 3. The relationship between centrifugation centrifugation parameters is given by the equation: n

 

=

1,337

a r  d 

Where—  n =  n  = the numerical value of the rotational frequency, frequency, in min –1; a r  = the relative radial acceleration (for example a r  = 700 or a r  = 800);  d  =   = the numerical value of the diameter of swing, measured between the tips of opposite tubes when tubes are in a rotating position, in millimeters.

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SAMPLING AND ANALYSIS OF COMMERCIAL FA FATS TS AND OILS

Ca 3d-02 •

Determination of Sediment in Crude Fats and Oils—Centrifuge Method

REFERENCES

1. ISO 5555:1991, Animal and vegetable fats and oils—Sampling. 2. ISO 5725-1:1994, Accuracy Accuracy (trueness and precision) precision) of measurement methods and results—Part results—Part 1: General General principles and definitions. 3. ISO 5725-2:1994, Accuracy (trueness and precision) precision) of measurement methods and results—Part results—Part 2: Basic Basic method for the determination of repeatability and reproducibility of a standard measurement method.

Table 1 Statistical results of the interlaboratory test organized in 1996.

Parameter

Sample

Number of laboratories retained after eliminating outliers Mean sediment content, mL per 100 g Repeatabilityy standard deviation (s  Repeatabilit ( s r ), mL per 100 g Repeatability Repeatabili ty coeffici coefficient ent of variatio variation, n, % Repeatabilityy limit ( r ) [r  Repeatabilit [r  =  = 2.8 × s r ], mL per 100 g Reproducibilityy standard deviation (s  Reproducibilit ( s R ), mL per 100 g Reproducibility Reproducibi lity coeffici coefficient ent of variation variation,, % Reproducibilityy limit ( R ) [R  Reproducibilit [R  =  = 2.8 × s R ], mL per 100 g

12 0.75 0.04 4.76 0.10 0.26 34.6 0.72

12 1.36 0.06 4.29 0.16 0.22 16.0 0.61

12 0.54 0.04 6.85 0.10 0.26 47.9 0.72

11 1.62 0.06 3.60 0.16 0.28 17.2 0.78

10 2.07 0.03 1.59 0.09 0.26 12.6 0.73

11 2.61 0.07 2.78 0.20 0.35 13.5 0.99

Table 2 Statistical results of the interlaboratory test organized in 1997/1998.

Parameter

Sample

Number of laboratories retained after eliminating outliers Mean sediment content, mL per 100 g Repeatabilityy standard deviation (s  Repeatabilit ( s r ), mL per 100 g Repeatabilityy coefficient of variation, % Repeatabilit Repeatabilityy limit ( r ) [r  Repeatabilit [r  =  = 2.8 × s r ], mL per 100 g Reproducibilityy standard deviation (s  Reproducibilit ( s R ), mL per 100 g Reproducibilityy coefficient of variation, % Reproducibilit Reproducibilityy limit ( R ) [R  Reproducibilit [R  =  = 2.8 × s R ], mL per 100 g

7 0.07 0.00 0.00 0.00 0.07 97.8 0.20

8 1.28 0.04 2.77 0.10 0.12 9.1 0.33

8 1.20 0.04 2.95 0.10 0.08 7.0 0.24

7 2.39 0.00 0.00 0.00 0.35 14.8 0.99

Table 3 Repeatability limit (r ) and reproducibility limit (R).

Sediment content mL per 100 g