The most important nutrient in milk powder is protein, and the melamine incident that occurred in previous years was also because of the addition of harmful substances to the human body for protein content. Therefore, it is very important to determine the protein content. In addition, there are many methods to determine the protein content, protein analyzer is one of them, using the instrument to determine, in addition, Kjeldahl method, trace Kjeldahl method and so on. This article mainly discusses how to improve the determination of protein content in milk powder. Sodium Ascorbyl Phosphate,Sodium Calcium Ascorbyl Phosphate,Phosphate Ester Sodium,Sodium Ascorbyl Phosphate Eucerin JINGJIANG HENGTONG BIO-ENGINEERING CO.,LTD , https://www.htphosphate.com
When determining the protein in milk powder, the sample amount of milk powder should be 0.600~0.700g, because the content of protein in milk powder is not less than 12.0%, if it is in accordance with national standards "Determination of protein in food" (GB/T5009.5) -2003) sampling range (0.200 ~ 2.000g) of milk powder sampling, sampling volume of 0.200g, the volume of 0.050mol/L hydrochloric acid standard titrant consumed during titration is about 0.60m, l titration error Large; If the sampling amount is 2.000g according to the “Determination of infant formula and powdered protein†(GB/T5413.1-1997), due to the large sample size, carbonized particles may easily adhere to the Kjeldahl flask when splashed during digestion. On the wall of the bottle, after cooling, shake the flask gently or flush with 30% hydrogen peroxide solution to continue digestion. This is cumbersome.
When milk powder is digested, copper sulfate acts as a catalyst to accelerate the oxidation. The role of potassium sulfate is to increase the boiling point of sulfuric acid and increase the reaction rate. 10 g of potassium sulfate can increase the boiling point of sulfuric acid to 400 °C, but too much potassium sulfate will Caused the boiling point is too high, the generated NH4HSO4 will decompose at 513 °C, leading to low results. The comparison experiment shows that when the sample quality is the same and the power of the adjustable electric furnace is constant, the greater the amount of copper sulfate and potassium sulfate, the shorter the time required for digestion to clear and transparent; the amount of copper sulfate is 0.20 to 1.00 g and sulfuric acid When the amount of potassium is between 3 and 10 g, there is no difference in the protein determination results of the same milk powder sample. However, as the amount of potassium sulfate increases, the snow-like ammonium sulfate crystals and potassium sulfate formed after the cooling of the digestate precipitate more, and the capacity is increased. It is not easy to transfer the bottle when it is transferred to volume. Therefore, the amount of copper sulfate is preferably 0.20~0.30g, and the amount of potassium sulfate is 3~6g.