Food Proficiency Testing Program Round 33 Skim Milk Powder

-- REPORT NO. 694 Food Proficiency Testing Program Round 33 Skim Milk Powder December 010 ACKNOWLEDGMENTS PTA wishes to gratefully acknowledge the technical assistance provided for this program by Dr M Buckley-Smith and Dr R Hutchinson, AsureQuality Limited (New Zealand). Thanks also to Mr M Withers and Mrs S Giannoulidis, AsureQuality Limited (Australia), who arranged for the supply of the samples and AsureQuality Limited (New Zealand) for the production of the samples. COPYRIGHT PROFICIENCY TESTING AUSTRALIA 010 PO Box 7507 Silverwater NSW 18 AUSTRALIA

-3- CONTENTS 1. FOREWORD 1. FEATURES OF THE PROGRAM 1 3. FORMAT OF THE APPENDICES 4. STATISTICAL DESIGN OF THE PROGRAM 5. EXTREME RESULTS Table A: Summary Statistics for All Tests 3 Table B: Summary of Statistical Outliers 3 6. PTA AND TECHNICAL ADVISERS' COMMENTS 4 Table C: Method of Measurement Uncertainty Estimation 14 7. REFERENCES 15 APPENDICES APPENDIX A Summary of Results Moisture A1.1 - A1. Total Nitrogen A.1 - A. Fat A3.1 Ash A4.1 - A4. APPENDIX B Homogeneity and Stability Testing B1.1 APPENDIX C Instructions to Participants C1.1 - C1. Results Sheet C.1

-1-1. FOREWORD This report summarises the results of a proficiency testing program involving the analysis of skim milk powder samples. It constitutes the thirty-third round of an ongoing series of programs involving chemical analysis of foodstuffs. Proficiency Testing Australia (PTA) conducted the testing program in November 010. The program coordinator was Dr M Bunt. The aim of the program was to assess laboratories' ability to competently perform the nominated tests. This report was authorised by Ms F Ward, PTA Quality Business Development Manager.. FEATURES OF THE PROGRAM (a) A total of 14 laboratories participated in the program, all of which returned results for inclusion in the final report. Laboratories from the following states and countries participated: 4 VIC NSW QLD 1 TAS 1 WA MALAYSIA 1 THAILAND 1 HONG KONG To ensure confidential treatment of results, each laboratory was allocated a unique code number. All reference to participants is by allocated code numbers. (b) The results reported by participants are presented in Appendix A. (c) (d) Laboratories were provided with two samples of approximately 175 g of skim milk powder, labelled PTA 1 and PTA. Participants were requested to determine the levels of: Moisture; Total Nitrogen; Fat; and Ash. Laboratories were required to perform all tests using the routine test methods which would normally be used to test customer supplied samples. (e) Laboratories were requested to perform the tests according to the Instructions to Participants provided and to record the results, along with an estimate of their measurement uncertainty (MU) for each result, on the accompanying Results Sheet, which was distributed with the samples. Copies of these documents appear in Appendix C.

-- (f) Prior to sample distribution, ten randomly selected samples were analysed for homogeneity by AsureQuality Limited (New Zealand). An additional three randomly selected samples were analysed for stability by AsureQuality Limited (New Zealand). Based on the results of this testing, the homogeneity and stability of the samples was established (see Appendix B). 3. FORMAT OF THE APPENDICES (a) Appendix A is divided into four sections (A1 A4). These sections contain the analysis of results reported by laboratories for Moisture, Total Nitrogen, Fat and Ash. Each section contains, where applicable: i) a table of results reported by laboratories for each test, with estimates of their measurement uncertainties, calculated z-scores and methods used; ii) a listing of the summary statistics; iii) ordered z-score charts; iv) a Youden diagram of laboratories results for the sample pair. (b) (c) Appendix B contains details of the homogeneity and stability testing. Appendix C contains copies of the Instructions to Participants and Results Sheet. 4. STATISTICAL DESIGN OF THE PROGRAM A uniform pair statistical design was chosen for this program. Samples PTA 1 and PTA were identical for Moisture, Total Nitrogen, Fat and Ash. 5. EXTREME RESULTS Robust z-scores have been used to assess each laboratory s testing performance. When calculated from single results, z-scores are used to detect excessively large or excessively small results in comparison to the consensus value (the median). Any result with an absolute z-score greater than or equal to three (i.e. -3 or 3) is classified as an outlier. For further details on the calculation and interpretation of robust z-scores, please see the Guide to Proficiency Testing Australia (008).

-3- Table A: Summary Statistics for All Tests The following table summarises the results submitted by participants for the program. Test Summary Statistics PTA 1 PTA Moisture (% m/m) Total Nitrogen (% m/m) Fat (% m/m) Ash (% m/m) No. of Results 13 13 Median 4.50 4.50 Normalised IQR 0.30 0.15 No. of Results 13 13 Median 5.060 5.060 Normalised IQR 0.074 0.08 No. of Results 1 1 Median Normalised IQR No. of Results 13 13 Median 7.870 7.880 Normalised IQR 0.096 0.111 Notes: 1. For each test, except Fat, the results for all test methods were pooled and the summary statistics, above, are for the pooled results.. Summary statistics for Fat were not calculated. Table B: Summary of Statistical Outliers The following table lists the laboratories (by code number) that obtained outliers for each test. Test Sample PTA 1 Sample PTA Moisture 14 4, 9, 1, 14 Total Nitrogen 3 3 Fat Ash 1 - Note: Z-scores for Fat were not calculated.

-4-6. PTA AND TECHNICAL ADVISERS COMMENTS The summary statistics and outliers identified for each of the tests are reported in Tables A and B on the previous page. Complete details of the statistical analyses appear in Appendix A. 6.1 Return rate All of the fourteen laboratories that participated in the program submitted results. Ten of these fourteen laboratories (71%) provided results for all four of the tests. The return rate for all tests is as follows: Moisture 13 out of 14 93% Total Nitrogen 13 out of 14 93% Fat 1 out of 14 86% Ash 13 out of 14 93% 6. Performance summary Samples PTA 1 and PTA were duplicate samples of the same batch of skim milk powder. One or more statistical outliers were reported by five of the fourteen laboratories (36%) that returned results in this round of the Food program. The last skim milk powder round of the Food program was Round 3 (see Report No 660). For comparison, 14% of the participants in Round 3 of the Food program reported statistical outliers. A total of 78 results were analysed in this round of the program. Of these results, eight (10%) were outlier results. In Round 3 of the Food program 3% of the total results reported were outlier results.

-5-6.3 Moisture Of the thirteen laboratories that tested the samples for Moisture, four laboratories tested using the Australian Standard method, AS 300.1.1. Two laboratories tested using AOAC 984.5. Two laboratories tested using AOAC 97.05. One laboratory tested using IDF 6A. Four laboratories tested using other methods. The temperatures used for moisture determination varied between 100 C and 130 C. The times used for moisture determination ranged between ten minutes and sixteen hours. The robust CVs of 6.6% and 3.3% for the two samples are lower than the values of 9.4% and 10.7% obtained in Round 3 of the Food program (see Report No 660). The exceptionally good CV for sample PTA was unexpected, considering both samples were duplicates from the same batch, so sample variability was unlikely to have been smaller for this sample. It is more likely that the small CV was due statistical chance from a small sample size (thirteen laboratories), and the improvement in laboratory testing variability lies somewhere between 3.3% - 6.6% CV. Laboratory 14 reported outliers for both samples, and laboratories 4, 9 and 1 obtained outliers for sample PTA, all requiring follow-up investigation. Laboratories and 9 may also wish to carry out an in-house investigation into their repeatability, as their test results for duplicate sample testing differed by more than twice the average difference between the samples. Moisture (% m/m) 1 10 Frequency 8 6 4 Mettlter Toledo LP16 Manual In-house (Sirim) IDF 6A AS300.1.1 AOAC 990.0 AOAC 984.5 AOAC 97.05 AACC 44-15A 0 0 0.5 1 1.5.5 3 3.5 4 4.5 5 5.5 6 Result (% m/m) Figure 1a. Effect of analysis method on Moisture test results (median = 4.5 %m/m). Confidence in the median for testing these duplicate samples was calculated using the standard error ((SD/Sqrt(n))*1.77) where the standard deviation (SD) is approximated using the normalised interquartile range. Median S1 = 4.50 %m/m ± 0.15 %m/m. Median S = 4.50 %m/m ± 0.07 %m/m.

-6- Recording of drying conditions was valuable for understanding results and the outermost results matched with the most extreme drying conditions of temperature (130 ºC) and time (16 hours). The most popular drying condition of 10 ºC, originally from the British Standard, was intended to measure free moisture only, but was more difficult to obtain agreement of results between laboratories than some other methods. Moisture (% m/m) Temperature 1 10 Frequency 8 6 4 130 105 103 10 100 0 0 0.5 1 1.5.5 3 3.5 4 4.5 5 5.5 6 Result (% m/m) Figure 1b. Effect of temperature on Moisture test results. Moisture (% m/m) Time 1 10 Frequency 8 6 4 16 hours 06 hours 05 hours 04 hours 0 hours 01 hours *10 mins 0 0 0.5 1 1.5.5 3 3.5 4 4.5 5 5.5 6 Result (% m/m) Figure 1c. Effect of time on Moisture test results.

-7- Variation between laboratories was considerably greater than within laboratory, with repeatability (r S1&S =0.3%) and Reproducibility (R S1 =0.83%, R S =0.415%) values similar to those published in IDF 6A, which is similar to most methods used here. One of the laboratories that reported results for Moisture did not provide an estimate of the MU for their results for either sample. Half of the laboratories (laboratories 1, 4, 10, 1, 13 and 14) who submitted MU information had at least one result further from the median than their stated MU. Also, the majority of stated MU values were less than the between laboratories variation (Reproducibility) mentioned previously. With the standard error of the median between 0.07-0.15 %m/m, the remainder of the difference between each laboratory s result and the median is due to laboratory variability. This indicates that the use of in-house repeatability standard deviations as an approximation of MU may not be appropriate (i.e. MU < 0. %m/m), and adding reproducibility MU from repeated proficiency rounds or reference material analysis may be helpful. Moisture (% m/m) ± MU 8 7 R MU Frequency 6 5 4 3 Mettlter Toledo LP16 Manual In-house (Sirim) IDF 6A AS300.1.1 AOAC 990.0 AOAC 984.5 AOAC 97.05 AACC 44-1 0 0 0.1 0. 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1. Measurement Uncertainty Figure 1d. Reported Measurement Uncertainty for Moisture Test.

-8-6.4 Total Nitrogen One of the thirteen laboratories that tested the samples for Total Nitrogen reported using the Australian Standard method, AS 300.1..1. One other laboratory reported using AS 300.1., but did not specify whether they used AS 300.1..1 or AS 300.1..1 Appendix A. One laboratory tested using AOAC 99.3. Two laboratories tested using AOAC 990.03. One laboratory tested using AOAC 930.9a. Seven laboratories used other methods for testing. The robust CVs of 1.5% and 1.6% for the two samples compare well with the values of 1.4% and 1.4% obtained in Round 3 of the Food program (see Report No 660). Laboratories 3 and 7 originally recorded Protein results instead of Total Nitrogen and had to re-submit their results. Laboratory 3 obtained outliers for both samples, requiring follow-up action. Laboratories 3, 4 and 11 may also wish to carry out an in-house investigation into their repeatability, as their test results for duplicate sample testing differed by more than twice the average difference between the samples. Total Nitrogen (% m/m) 14 Frequency 1 10 8 6 4 Nitrogen analyser Modified from AOAC 930.9 Kjeldahl method In-house (Tecator) AS300.1..1 AS 300.1. AOAC 99.3 AOAC 991.0 AOAC 990.03 AOAC 981.10 AOAC 930.9a AACC 46-1 0 4.5 4.6 4.7 4.8 4.9 5 5.1 5. 5.3 5.4 5.5 5.6 5.7 Result (% m/m) Figure a. Effect of analysis method on Total Nitrogen test results (median = 5.06 %m/m ± 0.04 %m/m). Due to the wide variety of methods used, submission of test conditions and standard methods claimed performance values (repeatability and Reproducibility) may give better insight in future rounds. However, results from this round indicate that combustion methods may be slightly higher. Variation between laboratories was moderately greater than within laboratory, with repeatability (r S1&S =0.13%) and Reproducibility (R S1 =0.1%, R S =0.3%) values being well within those inferred from IDF 9 (r CV = 0.5% and R CV =1%)

-9- and AOAC. This shows very good control of test conditions between methods and laboratories. Two of the laboratories that reported results for Total Nitrogen did not provide an estimate of the MU for their results for either sample. There were three out of eleven laboratories (laboratories 1, 3 and 4) which had at least one result further from the median than their stated MU. There were two distinctive groupings of stated MU, one group at the repeatability value and another at the reproducibility values stated above. With the standard error of the median between 0.036-0.040 %m/m, the remainder of the difference between each laboratory s result and the median is due to laboratory variability. This indicates that the use of in-house repeatability standard deviations as an approximation of MU may not be sufficient (ie MU < 0.1 %m/m), and adding reproducibility MU, e.g. from repeated proficiency and method R and r values may be helpful. Total Nitrogen (% m/m) ± MU Frequency 8 7 6 5 4 3 1 R MU Nitrogen analyser Modified from AOAC 930.9 Kjeldahl method In-house (Tecator) AS300.1..1 AS 300.1. AOAC 99.3 AOAC 991.0 AOAC 990.03 AOAC 981.10 AOAC 930.9a AACC 46-1 0 0 0.05 0.1 0.15 0. 0.5 0.3 0.35 0.4 0.45 0.5 0.55 0.6 Measurement Uncertainty Figure b. Reported Measurement Uncertainty for Total Nitrogen Test.

-10-6.5 Fat Twelve laboratories tested the samples for Fat. The Australian Standard method, AS 300.1.3, was used by five laboratories. One laboratory tested using AOAC 989.05. Three laboratories tested using AOAC 93.06. One laboratory tested using AOAC 003.06. Two laboratories used other methods for testing. There was a noticeable difference between the Fat results submitted for the different testing methods. Therefore, the results could not be pooled for analysis. Unfortunately, there was an insufficient number of results for any testing method to calculate summary statistics or z-scores for any of the methods used. Fat (% 14 1 Frequency 10 8 6 4 C1.07 AS300.1.3 AOAC 989.05 AOAC 93.06 AOAC 003.06 Acid hydrolysis 0 0 0.5 0.5 0.75 1 1.5 1.5 1.75.5.5.75 3 Result (% m/m) Figure 3a. Effect of analysis method on Fat test results (median = 1.0 %m/m). High values were obtained using the acid hydrolysis method, seen in figure 3a. The high carbohydrate content of the skim milk powder samples used in this round may be outside the scope of this method (refer IDF std 5b etc), and therefore not appropriate to use. High fat values for skim milk powder above 1% are uncommon because of the efficiency of dairy factory separators, therefore results in this round significantly above 1 %m/m should be viewed with caution and the laboratories in question should carry out an in-house assessment of appropriateness of methods used, depending on their circumstances and the fat content of their normal in-house test matrices. Variation between laboratories Reproducibility (R S1 =1.61%, R S =1.17%) was considerably greater than within laboratory repeatability (r S1&S =0.33%). The calculated Reproducibility was high compared with IDF 9C:1987 r = 0.1% and R = 0.%, which is similar to IDF 6A and most of the methods here. Two of the laboratories that reported results for Fat did not provide an estimate of the MU for their results for either sample. All ten laboratories who did submit MU information had at least one result further from the median than their stated MU. With the standard error of the median between 0.14-0.95 %m/m, the

-11- remainder of the difference between each laboratory s result and the median is due to laboratory variability (see Reproducibility above). The under-estimation of MU may be due to the very low fat levels seen in this skim milk powder, which may have meant that in-house repeatability standard deviations calculated from higher fat milk powders would not be appropriate to extrapolate to this situation. This is a similar situation to that found in the previous round (Round 3). The reproducibility value for laboratories with results of <1% fat was R <1% =0.1 %m/m, which was closer to the IDF reproducibility and may be a more useful estimate of MU. Fat (% m/m) ± MU 7 6 R IDF MU Frequency 5 4 3 C1.07 AS300.1.3 AOAC 989.05 AOAC 93.06 AOAC 003.06 Acid hydrolysis 1 0 0 0.0 0.04 0.06 0.08 0.1 0.1 0.14 0.16 0.18 0. 0. 0.4 Measurement Uncertainty Figure 3b. Reported Measurement Uncertainty for Fat Test.

-1-6.6 Ash Five of the thirteen laboratories that submitted results for Ash used the Australian Standard method, AS 300.1.5. One laboratory tested using AOAC 94.05. Five laboratories tested using AOAC 930.30. Two laboratories used other methods. Temperatures used for ashing ranged between 55 C and 600 C. Times of ashing varied between two hours and sixteen hours. The robust CVs of 1.% and 1.4% for the two samples compare well with the values of 0.9% and 1.0% obtained in Round 3 of the Food program (see Report No 660). Laboratory 1 reported an outlier for sample PTA 1, requiring follow-up action. Laboratories 3 and 1 may also wish to carry out an in-house investigation into their repeatability, as their test results for duplicate sample testing differed by more than twice the average difference between the samples. Ash (% m/m) 14 1 10 Frequency 8 6 4 In-house AS300.1.5 AOAC 94.05 AOAC 930.30 AACC 0801 0 7.1 7. 7.3 7.4 7.5 7.6 7.7 7.8 7.9 8 8.1 8. Result (% m/m) Figure 4a. Effect of analysis method on Ash test results (median = 7.875 %m/m ± 0.055 %m/m). Variation between laboratories was similar to within laboratory, with repeatability (r S1&S =0.0%) and Reproducibility (R S1 =0.7%, R S =0.31%) values similar to those published in IDF 90 for casein (r =0.15% and R = 0.5%), which is similar to most methods used here. This reflects very good control of test conditions both between test methods and laboratories. Two of the laboratories that reported results for Ash did not provide an estimate of the MU for their results for either sample. Six out of the eleven laboratories (laboratories 1, 3, 4, 7, 10 and 1) had at least one result further from the median than their stated MU. Also, the majority of stated MU values were much less than the between laboratories variation (Reproducibility) mentioned previously. With the standard error of the median between 0.047-0.055 %m/m, the remainder of the difference between each laboratory s result and the median is

-13- due to laboratory or method variability. Because of the similarity between repeatability and reproducibility in this round, it might have been expected that laboratory MU based on in-house repeatability standard deviations should have been a reasonable approximation of MU, however, a large number of laboratories underestimated their MU, and reproducibility values may prove more useful estimates. Ash (% m/m) ± MU 16 14 R MU 1 Frequency 10 8 6 In-house AS300.1.5 AOAC 94.05 AOAC 930.30 AACC 0801 4 0 0 0.1 0. 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1. Measurement Uncertainty Figure 4b. Reported Measurement Uncertainty for Ash Test.

-14-6.7 Measurement Uncertainty For this program, laboratories were requested to report an estimate of MU for each test result. The proportion of MU estimates returned for each individual test is as follows: Moisture 1 out of 13 9% Total Nitrogen 11 out of 13 85% Fat 10 out of 1 83% Ash 11 out of 13 85% From the results reported, there were a wide range of uncertainties reported, as shown in the tables in Appendix A. Participants were also asked to describe the method used for estimating their MU. Eight laboratories provided this information, which can be found in Table C below. Table C: Method of Measurement Uncertainty Estimation Lab Code Method Proficiency trial data, in-house precision data. 3 Best guess. 5 In-house precision data. 6 In-house precision data. 7 In-house precision data. 11 Running standard deviation from control charts and sample homogeneity variant from long term duplicate data. 13 In-house precision data, in-house accuracy data. 14 In-house precision data with proficiency trial data. Given that so many laboratories reported using some variation of the top down approach, involving in-house precision data, much more consistency in the MU values reported by the laboratories would be expected. It is recommended that laboratories ensure that greater attention be given to the manner in which they estimate MU and that they ensure a consistent and defensible approach to reporting MU. Calculation from ongoing proficiency performance and using method R and r values may assist with this.

-15-7. REFERENCES 1. Guide to Proficiency Testing Australia (008). (This document is located on the PTA website at www.pta.asn.au under Programs / Documents).. AS 300.1.1-008 Methods of chemical and physical testing for the dairying industry - General methods and principles - Determination of total solids and moisture. 3. AS 300.1..1-1991 Methods of chemical and physical testing for the dairying industry - General methods and principles - Determination of nitrogen - Reference Kjeldahl method. 4. AS 300.1.3-008 Methods of chemical and physical testing for the dairying industry - General methods and principles - Determination of fat - Gravimetric method. 5. AS 300.1.5-008 Methods of chemical and physical testing for the dairying industry - General methods and principles - Determination of ash. 6. IDF 9C (1987) Dried milk, dried whey, dried buttermilk and dried butter serum Determination of fat content (Röse-Gottlieb method). 7. IDF 0B (1993) Milk Determination of nitrogen content. 8. IDF 6A (1993) Dried milk and dried cream Determination of water content. 9. IDF 90 (1979) Rennet caseins and caseinates Determination of ash. 10. IDF 9 (1979) Caseins and caseinates Determination of protein content.

APPENDIX A Summary of Results

Section A1 Moisture

A1.1 Skim Milk Powder Moisture (% m/m) Samples PTA 1 & PTA Lab PTA 1 PTA Z-Scores Temp Code Average MU (±) Average MU (±) PTA 1 PTA ( o C) Time (hrs) Method Code 1 4.44 0.13 4.46 0.03-0.0-0.7 100 6 3 4.30 0.40 4.44 0.40-0.67-0.40 10 4 1 3 4.5 0.03 4.5 0.03 0.00 0.00 105 10 min 5 4 5.10 0.0 5.00 0.07.0 3.37 105 5 5 5 4.6 0.15 4.6 0.15 0.34 0.67 10 4 1 7 4.7 0.41 4.6 0.41 0.67 0.67 100 6 3 8 4.34-4.40 - -0.54-0.67 100 4 5 9 5.34 0.9 5.19 0.9.83 4.65 103 16 10 4.8 0.1 4.8 0.1 1.01.0 10 6 1 11 4.6 0.5 4.6 0.5 0.34 0.67 105 16 1 3.9 0.4 4.0 0.4 -.0-3.37 10 4 1 13 4. 0. 4.3 0. -1.01-1.35 10 4 14 3.3 0.11 3.3 0.11-4.05-8.09 130 1 5 Statistic PTA 1 PTA Method Codes Number No. of Results 13 13 1 = AS300.1.1 4 Median 4.50 4.50 = AOAC 984.5 Norm IQR 0.30 0.15 3 = AOAC 97.05 Robust CV 6.59% 3.9% 4 = IDF 6A 1 Minimum 3.3 3.3 5 = Other 4 Maximum 5.3 5. Range.0 1.9 Notes: 1. denotes an outlier (i.e. z-score 3).. The Youden diagram on the following page is provided for information only.

A1. Moisture (% m/m) - Sample PTA 1 3 9 4 Robust Z-Score 1 0-1 13 8 1 3 5 11 7 10-1 -3 14 Laboratory Code Moisture (% m/m) - Sample PTA 3 4 9 10 Robust Z-Score 1 0-1 8 1 3 5 7 11-13 -3 14 1 Laboratory Code Moisture (% m/m) 9 Sample PTA 3.5 4.0 4.5 5.0 1 4 14 3.5 4.0 4.5 5.0 Sample PTA 1

Section A Total Nitrogen

A.1 Skim Milk Powder Total Nitrogen (% m/m) Samples PTA 1 & PTA Lab PTA 1 PTA Z-Scores Method Code Average MU (±) Average MU (±) PTA 1 PTA Code 1 5.19 0.04 5.18 0.0 1.75 1.47 13 3 5.39 0.0 5.50 0.0 4.45 5.40 13 4 4.97 0.04 5.04 0.06-1.1-0.5 13 5 5.14 0.50 5.15 0.50 1.08 1.10 13 6 5.10 0.8 5.06 0.8 0.54 0.00 13 7 4.97 0.7 5.01 0.7-1.1-0.61 11 8 5.05-5.06 - -0.13 0.00 13 9 5.14-5.13-1.08 0.86 10 10 5.05 0.05 5.05 0.05-0.13-0.1 13 11 5.3 0.5 5.16 0.5.9 1.3 8 1 5.04 0.05 5.01 0.05-0.7-0.61 6 13 5.06 0.5 5.03 0.5 0.00-0.37 10 14 5.03 0.0 5.04 0.0-0.40-0.5 13 Statistic PTA 1 PTA Method Codes Number No. of Results 13 13 6 = AS300.1..1 1 Median 5.060 5.060 7 = AS300.1..1 Appendix A 0 Norm IQR 0.074 0.08 8 = AOAC 99.3 1 Robust CV 1.47% 1.61% 9 = AOAC 991.3 0 Minimum 4.97 5.01 10 = AOAC 990.03 Maximum 5.39 5.50 11 = AOAC 930.9a 1 Range 0.4 0.49 1 = IDF 0B 0 13 = Other 8 Notes: 1. denotes an outlier (i.e. z-score 3).. Laboratories 3 and 7 originally recorded Protein results instead of Total Nitrogen. 3. Laboratory 5 did not specify whether they used AS 300.1..1 or AS 300.1..1 Appendix A for Total Nitrogen. Their method has been recorded as "Other" (Method Code 13). 4. The Youden diagram on the following page is provided for information only.

A. Total Nitrogen (% m/m) - Sample PTA 1 3 3 1 11 Robust Z-Score 1 0-1 14 4 1 7 8 10 13 6 5 9 - -3 Laboratory Code Total Nitrogen (% m/m) - Sample PTA 3 3 11 Robust Z-Score 1 0-1 7 1 13 4 14 10 6 8 9 5 1 - -3 Laboratory Code Total Nitrogen (% m/m) Sample PTA 4.9 5.0 5.1 5. 5.3 5.4 5.5 11 3 4.9 5.0 5.1 5. 5.3 5.4 Sample PTA 1

Section A3 Fat

A3.1 Skim Milk Powder Fat (% m/m) Samples PTA 1 & PTA Lab Code PTA 1 PTA Average MU (±) Average MU (±) Method Code 1 1.6 0.14 1.7 0.07 15 0.83 0.135 0.91 0.135 14 4.81 0.1.75 0.0 19 5 0.86 0.15 0.79 0.15 14 6 1.10 0.01 1.14 0.01 16 7 1.60 0.5 1.30 0.5 19 8 0.75-0.77-16 9 0.80-0.77-17 10 0.90 0.0 0.89 0.0 14 11 1.40 0.14 1.40 0.14 14 1 0.75 0.10 0.85 0.10 14 14 1.65 0.10 1.40 0.10 16 Method Codes Number 14 = AS300.1.3 5 15 = AOAC 989.05 1 16 = AOAC 93.06 3 17 = AOAC 003.06 1 18 = IDF 9C 0 19 = Other Notes: 1. There was a noticeable difference between the Fat results submitted for the different testing methods. Therefore, the results could not be pooled for analysis.. There was an insufficient number of results for any testing method to calculate summary statistics or z-scores.

Section A4 Ash

A4.1 Skim Milk Powder Ash (% m/m) Samples PTA 1 & PTA Lab PTA 1 PTA Z-Scores Temp Code Average MU (±) Average MU (±) PTA 1 PTA ( o C) Time (hrs) Method Code 1 7.87 0.01 7.85 0.01 0.00-0.7 550 6 3 7.94-7.97-0.73 0.81 555 1 0 3 7.68 0.004 7.88 0.004-1.97 0.00 550.5 3 4 7.94 0.03 8.01 0.09 0.73 1.17 550 8 4 5 7.9 0.10 7.90 0.10 0.5 0.18 535 3 0 7 7.85 0.03 7.8 0.03-0.1-0.54 550 3 8 8.01-8.00-1.45 1.08 550 6 3 9 7.8 1.45 7.87 1.46-0.5-0.09 600 10 7.91 0.0 7.88 0.0 0.4 0.00 55 5 0 11 7.80 0.78 7.80 0.78-0.73-0.7 550 16 0 1 8.19 0.0 8.06 0.0 3.3 1.6 550 16 0 13 7.81 0.40 7.81 0.40-0.6-0.63 540 14 3 14 7.76 0.50 7.77 0.50-1.14-0.99 590 16 4 Statistic PTA 1 PTA Method Codes Number No. of Results 13 13 0 = AS300.1.5 5 Median 7.870 7.880 1 = AOAC 945.45 0 Norm IQR 0.096 0.111 = AOAC 94.05 1 Robust CV 1.% 1.41% 3 = AOAC 930.30 5 Minimum 7.68 7.77 4 = Other Maximum 8.19 8.06 Range 0.51 0.9 Notes: 1. denotes an outlier (i.e. z-score 3).. The Youden diagram on the following page is provided for information only.

A4. Ash (% m/m) - Sample PTA 1 3 1 13 8 Robust Z-Score 1 0-1 11 9 7 1 14 10 5 4-3 -3 Laboratory Code Ash (% m/m) - Sample PTA 3 1 Robust Z-Score 1 0-1 14 11 13 7 1 9 3 10 5 8 4 - -3 Laboratory Code Ash (% m/m) Sample PTA 7.6 7.7 7.8 7.9 8.0 8.1 3 1 7.6 7.7 7.8 7.9 8.0 8.1 8. Sample PTA 1

APPENDIX B Homogeneity and Stability Testing

B1.1 Homogeneity Testing Prior to distribution, ten samples of skim milk powder were selected at random and tested for homogeneity by AsureQuality Limited (New Zealand). Each sample was tested in duplicate for Total Nitrogen. The results of the homogeneity testing appear in the following table. Skim Milk Powder Total Nitrogen (% m/m) Sample No. Result A Result B A 5.111 5.096 B 5.133 5.147 D 5.138 5.161 E 5.148 5.139 F 5.16 5.143 H 5.147 5.155 I 5.156 5.135 J 5.141 5.145 L 5.14 5.147 M 5.164 5.146 Analysis of this data indicated that the samples were sufficiently homogeneous and, therefore, any participant results identified as extreme cannot be attributed to sample variability. Stability Testing Three samples were selected at random and tested for stability by AsureQuality Limited (New Zealand). The results, below, indicated that the samples were sufficiently stable for use in this program. Skim Milk Powder Total Nitrogen (% m/m) Sample No. Result A Result B C 5.130 5.150 G 5.143 5.150 K 5.140 5.137

APPENDIX C Instructions to Participants and Results Sheet

C1.1 PROFICIENCY TESTING AUSTRALIA Food Proficiency Testing Program Round 33, November 010 INSTRUCTIONS TO PARTICIPANTS To ensure that the results of this program can be analysed correctly, participants are asked to note carefully: 1) Two samples of skim milk powder (each approximately 175 g), labelled PTA 1 and PTA, have been provided for compositional analysis. These samples are provided in foil laminated sachets and should be stored below 30 C prior to testing. These samples may be tested for some, or all of the following tests, according to each laboratory s requirements. ) The tests to be performed in this program are: Moisture Total Nitrogen Fat Ash 3) The tests may commence as soon as samples are received. Analysts should be aware of analyte stability and perform tests in an appropriate order. 4) Tests are to be performed on each sample in duplicate and the average result reported on the Results Sheet. 5) Report results on the attached Results Sheet to the specified number of decimal places. Results should not be reported as greater than. or less than., as such data cannot be statistically analysed. 6) Please identify the methods used on the Results Sheet, using the Method Codes listed on Page of these instructions. Laboratories should use the routine test methods which would normally be used to test customer supplied samples. 7) Laboratories are also requested to calculate and report an estimate of measurement uncertainty (MU) for each reported measurement result. All estimates of measurement uncertainty must be given as a 95% confidence interval (coverage factor k ). 8) Return Results Sheets, either by mail, facsimile or email to: Mark Bunt Proficiency Testing Australia PO Box 7507 Telephone: +61 9736 8397 (1300 78 867) Silverwater NSW 18 Fax: +61 9743 6664 AUSTRALIA Email: mbunt@pta.asn.au 9) All results should arrive at the above address by no later than Wednesday 17 November 010. Results reported later than this date may not be analysed in the final report. Food, Round 33 November 010 Page 1 of 3

C1. PROFICIENCY TESTING AUSTRALIA Food Proficiency Testing Program Round 33, November 010 METHOD CODES Analysis Method Code Moisture (% m/m) Total Nitrogen (% m/m) Fat (% m/m) Ash (% m/m) AS300.1.1 AOAC 984.5 AOAC 97.05 IDF 6A Other (please specify) AS300.1..1 AS300.1..1 Appendix A AOAC 99.3 AOAC 991.3 AOAC 990.03 AOAC 930.9a IDF 0B Other (please specify) AS300.1.3 AOAC 989.05 AOAC 93.06 AOAC 003.06 IDF 9C Other (please specify) AS300.1.5 AOAC 945.45 AOAC 94.05 AOAC 930.30 Other (please specify) 1 3 4 5 6 7 8 9 10 11 1 13 14 15 16 17 18 19 0 1 3 4 Food, Round 33 November 010 Page of 3

C.1 PROFICIENCY TESTING AUSTRALIA Food Proficiency Testing Program Round 33, November 010 RESULTS SHEET Laboratory Code: Date Samples Received: Temperature on Arrival: Test Report results Sample PTA 1 Sample PTA to nearest Result MU (±) Result MU (±) Date Tested Method Code Moisture* 0.1% m/m Total Nitrogen 0.01% m/m Fat (see Note) 0.05% m/m Ash** 0.01% m/m * Please specify the temperature/time of moisture determination: o C/ hours. ** Please specify the temperature/time of ashing: o C/ hours. Please state below the method used to determine the measurement uncertainty (e.g. GUM (bottom up), proficiency trial data, in-house precision data, Horwitz equation, best guess, etc.) Note. Report results as % fat in sample, not as fat in dry matter. Print Name: Signature & Date: Food, Round 33 November 010 Page 3 of 3

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