A proficiency test scheme for the quality control of black tea and development of quality control material for internal quality control |
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Authors: | Cemalettin Baltacı Huri İlyasoğlu Sevim Beyza Öztürk Sarıkaya Sevda Cavrar Nurettin Yaylı |
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Affiliation: | (1) Department of Food Engineering, Gumushane University, 29100 Gumushane, Turkey;(2) Trabzon Provincial Control Laboratory, 61100 Trabzon, Turkey;(3) Department of Chemistry, Karadeniz Technical University, 61080 Trabzon, Turkey |
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Abstract: | A proficiency test (PT) was organized for quality control analysis of black tea. Test materials for the analyses of total content of powder tea, moisture, total ash, acid-insoluble ash, water-soluble ash, alkalinity of water-soluble ash, water extract, crude fiber and caffeine were sent to the participant laboratories (n:43) in 2009. The assigned value, standard deviation of the parameters and z-scores of the participant laboratories were calculated using the data reported by the participants. The percentage of the reported results for analytes was found to be ranged from 67.5 to 100%. Acceptable z-scores were achieved by 80.5–97.5% of the participant laboratories. More than 15% of unacceptable results were obtained for acid-insoluble ash and caffeine analyses. The quality control material for quality control analysis of black tea was developed from the remaining material. |
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