AOAC 2019 First Action Methods

D. Samples

( a ) Commercial kombucha samples .--Ginger flavor, blueberry flavor, lemongrass and ginger flavor, and Sencha green tea. ( b ) Commercial fruit juice samples.-- Pressed apple juice and smooth orange juice. E. Certified Reference Materials (CRMs) ( a ) Ethanol-80; Lot No. FN02221601. ( b ) Ethanol-100; Lot No. FN08051301. ( c ) Ethanol-150; Lot No. FN06031503. ( d ) Ethanol-200; Lot No. FN03211401. ( e ) Ethanol-400; Lot No. FN04201501. F. Sample Preparation Procedure ( a ) Filter approximately 2 mL of sample solution using a 0.2 micron filter to remove live microorganisms that may be present in the sample. ( b ) Mix the solution using a vortex mixer for approximately 30 s to remove any residual gas. ( c ) Dilute the samples using distilled water to a concentration suitable for analysis. For all kombucha samples tested during this study, a dilution of 1:200 was suitable. 0.5 mL of sample [treated as described in F ( a ) and ( b )] was added to a 100 mL volumetric flask. Distilled water was added to bring to volume. ( d ) Analyze the samples as per the procedure outlined below. G. Assay Procedure See Table 2019.08B for summary of procedure. ( a ) Set the spectrophotometer to read absorbance at 340 nm. ( b ) Blank the spectrophotometer against air or water. ( c ) Prepare a blank cuvette by addition of the following reagents to a 3 mL UV cuvette: 2.1 mL distilled water, 0.2 mL bottle 1 (buffer), 0.2 mL bottle 2 (NAD dissolved as per section C ), and 0.05 mL bottle 3 (aldehyde DH). Cap the cuvette and mix by gentle inversion. ( d ) Prepare a sample cuvette by addition of the following reagents to a 3 mL UV cuvette: 2.0 mL distilled water, 0.2 mL bottle 1 (buffer), 0.2 mL bottle 2 (NAD dissolved as per section C ), 0.05 mL bottle 3 (aldehyde DH), and 0.1 mL of sample (prepared as per section F ). Cap the cuvette and mix by gentle inversion. Prepare in duplicate. For this validation, K-ETOH was tested with the following CRMs provided by Cerilliant:

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