When corn gluten powder is wet corn starch or corn syrup, raw corn to remove starch, germ and corn after the rest of the product, its appearance is golden, with roasted corn flavor, and has a special smell of corn fermentation, corn protein powder contains rich amino acids and natural pigments-lutein, is an important feed raw materials,
Especially in chicken feed is widely used, because of this, in recent years the market of various fake corn protein powder flooding.
Fake corn gluten powder mixed with a large number of small rice noodles, corn flour and protein, so the composition of amino acids, content and the content of flavonoids changes very large, conditional laboratory test samples of amino acids, ammonia, leaf yellow content is easy to identify authenticity, ordinary laboratories can use the following methods to identify the authenticity:
1. Dissolution of samples in water
Pure corn protein powder in the water insoluble, rapid precipitation, the water solution is colorless clarified transparent (lutein insoluble in water), fake corn protein powder suspended in the water, precipitation is very slow, its aqueous solution is cloudy, and even yellow (mixed with water-soluble pigments).
2. Microscope examination Place the sample under a microscope magnified 10-20 times, if found to have yellow fragile particles, carefully clip a few grains in a 50ml beaker, add about 0.5ml chromotropic acid (1g/l concentrated sulfuric acid solution), the electric stove micro-heat to just produce micro-smoke, remove slowly add 10-15ml water, if the solution into purple,
The sample contains protein essence, which belongs to inferior products.
3. Determination of urea content in protein powder (method one) take 50g protein powder, add 200ml distilled water vibration 2min, static set 30s, three layer filter paper filtered, take 20ml in the 50ml triangle bottle, add 1mol/l sodium hydroxide 10ml, add soybean (3890,-19.00,-0.49%) liquid number drops, Static placed 2-3min, Ganailles reagent 3 drops.
The presence of urea is indicated by the formation of yellow-brown precipitation in the specimen.
Take the method one filtrate 20ml, add the soybean powder a little, add cresol red Solution 3 drops, in 70 ℃ water bath heat 2-3min, if appear the darker pink indicates that urea exists.
4. Determination of ammonium salt in protein powder The same test with the urea method is basically the same, just do not add soybean liquid, if the yellow-brown precipitation is containing ammonium salt. The ammonium nitrate and barium chloride solution were used to titration the solution containing the ammonia protein powder, and the ammonium chloride and ammonium sulfate were preliminarily determined in the case of white precipitation.