T/YNRZ 011-2024 Determination of total amino acid content in coffee beans using spectrophotometry

Scope

Scope: This document specifies the terms and definitions, principles, instruments and apparatus, reagents and solutions, analytical procedures, result calculation, and detection report methods for the determination of total amino acids in raw coffee beans. This document is applicable to the determination of total amino acids in raw coffee beans; Main technical content: 1. Terms and definitions: The following terms and definitions are applicable to this document. 1.1 Coffee raw beans: Unroasted coffee beans, in accordance with the provisions of GB/T 18007 section 5.6. 1.2 Indophenol colorimetry: In accordance with the provisions of GB 5009.124. 2. Principles: Amino acids react with indophenol under pH 8.0 conditions to form a purple complex, which is measured by spectrophotometry at a wavelength of 570 nm. 3. Instruments and apparatus: 3.1 Analytical balance: With a sensitivity of 0.0001 g. 3.2 Visible spectrophotometer. 3.3 Ampoule bottles. 3.4 Ceramic evaporating dishes. 3.5 Colorimetric tubes: With ground joints, 50 mL. 3.6 Colorimetric cups: 1 cm. 3.7 Volumetric flasks: 25 mL, 50 mL, 100 mL, 1000 mL. 3.8 Alcohol burner. 3.9 Grinding machine or tissue crusher. 4. Reagents and solutions: Unless otherwise specified, all reagents used in this method are analytical grade (AR) and the water is distilled water. 4.1 Reagents 4.1.1 Leucine: Purity ≥ 98%. 4.1.2 Concentrated hydrochloric acid (HCl): Mass fraction ≥ 36%. 4.1.3 Sodium phosphate (Na2HPO4?12H2O). 4.1.4 Potassium phosphate (KH2PO4). 4.1.5 Indophenol: Purity ≥ 95%. 4.1.6 Tin dichloride (SnCl2?2H2O). 4.2 Solution preparation 4.2.1 6 mol/L hydrochloric acid solution: Take 500 mL of concentrated hydrochloric acid (6.1.2) and dilute with water to 1000 mL, mix well. 4.2.2 pH 8.0 phosphate buffer solution preparation 4.2.2.1 1/15 mol/L sodium phosphate: Weigh 11.9 g of dodecahydrate sodium phosphate (Na2HPO4?12H2O) and dissolve in water, then dilute to 1000 mL. 4.2.2.2 1/15 mol/L potassium phosphate: Weigh 0.908 g of p

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