Kjeldahl analysis of residue protein in wine

2019-07-23 14:06:33

As we all know, protein is the highest component of the composition of the organism, the most important component, the most important biological macromolecule, is an important nutrient indispensable for the human body, accounting for about 20% of body weight, and closely related to the origin and evolution of life. The residue of Moutai wine studied contains a large amount of protein, cellulose, etc. The protein that can be used as a raw material has a different meaning when measured by the Kjeldahl apparatus.

When nitrogen-containing organic matter is heated together with concentrated sulfuric acid, carbon, hydrogen, and nitrogen are converted into carbon dioxide, water, and ammonia, respectively, and ammonia reacts with sulfuric acid to produce ammonium sulfate. In order to speed up the Kjeldahl reaction, potassium sulfate or sodium sulfate is usually added to increase the boiling point of the reaction solution, and copper sulfate is added as a catalyst. Accurately measure 0.40 mL of concentrated hydrochloric acid in a 500 mL volumetric flask, dilute to volume with secondary distilled water, and transfer to a reagent bottle until calibration.

The concentrated alkali in the Kjeldahl analyzer reacts with ammonium sulfate in the digestion solution to release ammonia. The water vapor is used to distill the produced ammonia into a certain amount of boric acid solution with a certain concentration. The boric acid absorbs ammonia to make hydrogen in the solution. The ion concentration is reduced and then titrated with standard concentrations of hydrochloric acid until the original hydrogen ion concentration in the solution is restored. Finally, the amount of total nitrogen in the analyte is calculated based on the amount of hydrochloric acid used.

It is not only the determination of the protein content used in the above products, but also the correlation of the nitrogen content in the general substance can be determined by Kjeldahl determination, which of course has certain requirements for the composition of nitrogen. Kjeldahl determination of the use of wine residue can further improve its utilization, but also shows that the principle of waste in processing to do a qualitative and simple analysis.

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