Maltodextrin, also known as water-soluble dextrin or enzymatic dextrin with the English abbreviation MD, is a starch derivative free of free starch. It is prepared from starch or starchy raw materials through low-degree enzymatic hydrolysis, purification and spray drying. Under normal conditions, it is an amorphous white or slightly pale yellow powder without visible impurities to the naked eye, with a dextrose equivalent (DE) value usually ranging from 3 to 20. It features water solubility, high stability and low hygroscopy, and is often used as a filler, diluent or binder for pharmaceutical products.

Experimental Objective

  In the fields of chemistry and scientific research, determining the protein content of maltodextrin can evaluate the product's purity, monitor the introduction of impurities during the production process, and ensure product quality.

Experimental Basis

  The experiment is conducted in accordance with the First Method (Kjeldahl Nitrogen Determination Method) of the 0731 Protein Content Determination Method in the *Chinese Pharmacopoeia 2020*. The Shengtai Instrument ST-14BS Pharmaceutical Excipient Nitrogen Analyzer (4-hole) complies with this method and is thus selected for the experiment.

Experimental Equipment

① ST-18BS Pharmaceutical Excipient Nitrogen Analyzer

② Auxiliary components: sulfuric acid, boric acid aqueous solution, bromocresol green-methyl red mixed indicator, sodium hydroxide aqueous solution, standard acid titrant, mixed catalyst, analytical balance, etc.

Experimental Procedures

① Inspect the instrument, all utensils and solvents to ensure they are clean, dry and free of contamination.

② Dry the sample to constant weight at 105℃, weigh the sample (accurate to 0.1mg) and transfer it into a digestion tube, then add the mixed catalyst and concentrated sulfuric acid in a prescribed proportion.

③ Place the digestion tube on a digestion furnace, set the digestion parameters and start digestion. Digestion is deemed complete when the liquid turns blue-green and clear and transparent; if digestion is incomplete, continue the digestion process.

④ After the digestion solution is cooled to room temperature, transfer it into a volumetric flask. Rinse the flask with distilled water several times, combine all the washing liquid into the same volumetric flask, mix well and cool down, then make up the volume to the mark with distilled water. Take a quantitative portion of the digestion solution and place it in the reaction chamber of the distillation apparatus, add sodium hydroxide, and heat for distillation.

⑤ Add the mixed solution of boric acid and Tian's indicator into an Erlenmeyer flask, immerse the mouth of the condenser tube below the liquid level of the reagent, observe the color change process of the indicator. After complete absorption, titrate with standard sulfuric acid or hydrochloric acid solution, determine the titration end point and record the relevant data.

⑥ Calculate the experimental results and repeat the experiment for 1 to 3 times.

Experimental Results

  After calculation and analysis, the average protein content of the tested maltodextrin is 0.0148%, which meets the requirement of the Pharmacopoeia that the protein content of maltodextrin shall be less than 0.1%, thus complying with the relevant quality standards.