Main Article Content
The quality control system for sugar testing by analytical laboratories provides reliable test results according to the standard method and indicates good quality of results. The Office of Cane and Sugar Board mandated the act of government administration regulations, focusing on fairness and maintaining benefits for the cane industry, sugar industry, and consumer. Analytical testing of polarization and color of sugar is needed to identify the quality of refined sugar for both national and international customers. Testing of polarization and color of sugar between laboratories plays a significant role in the comparison of reliability of test results. This study, therefore, aims to evaluate laboratory performance on testing of polarization and color of sugar. For laboratory performance, refined sugar that had passed homogeneity and stability tests was used as the test material. Participating 69 laboratories were requested to analyze polarization and color of refined sugar. Laboratory analytical performance was statistically evaluated using the robust z score. Laboratory performance (|z score| ≤ 2) was found satisfactory for analyses of both polarization and color (64 out of 65 laboratories, 98.5 %). The findings demonstrate good performance of laboratories that conduct polarization and color tests of refined sugar from both government and private companies, providing reliable quality of sugar. Output from this study could indicate a reliable quality testing of refined sugar and provide a confidence for cane industry, sugar industry, and consumer.
 Royal Thai Government Gazette, Notification of The Office of Cane and Sugar Board, Vol. 113, Part 70d, Page 118, August 29, 1996, Available Source: http://www.sugarzone.in.th/law/sugar_law/kon_quality_sugar_correct_2539.pdf, July 19, 2019. (in Thai)
 Final Report, 2018, Proficiency Testing of Polarization and Color of Sugar, Round No. 2 of 2018. (in Thai)
 Final Report, 2018, Proficiency Testing of Polarization and Color of Sugar, Round No. 1/2 of 2018. (in Thai)
 Final Report, 2010, Proficiency Testing of Polarization and Color of Sugar, Round No. 15, 2010. (in Thai)
 Final Report, 2013, Proficiency Testing of Polarization and Color of Sugar, Round No. 22, 2013. (in Thai)
 Shalabh, T.K.II, Chapter 4: Stratified Sampling, pp. 1-27, Sampling Theory, Department of Mathematics and Statistics, Indian Institute of Technology, Kanpur.
 Accreditation ISO 17025: 2005 for Testing No. 17T025/0516, 2016, Testing Laboratory Cane and Sugar Industry Promotion Center Region 2, Kamphaengphet, Accreditation No. TESTING 0241, Certificate no, 16T041/ 0373.
 ICUMSA Method GS2/3-1, 2011, The Braunschweig Method for the Polarisation of White Sugar by Polarimetry-Official (Reference) Method.
 ICUMSA Method GS2/3-10, 2011, The Determination of White Sugar Solution Colour-Official.
 ISO 13528:2015(E), 2015, Statistical Methods for Use in Proficiency Testing by Interlaboratory Comparisons, Geneva.
 ISO/IEC 17043: 2010, 2010, International Standard Conformity Assessment-General Requirements for Proficiency Testing, Geneva.