The invention discloses a determination method for detecting true
protein content through a
salting-out method. The method comprises the following steps of 1) weighing a sample, placing the sample in a container, adding a proper amount of water, heating to boiling, and then transferring into a water bath at 80 DEG C for 30 minutes; 2) taking out from the water bath, immediately and slowly adding
sodium hydroxide, then adding
copper sulfate, standing and aging to obtain a
test solution; 3) filtering the
test solution after standing, and washing the precipitate for several times; 4) fully
drying the precipitate and the
filter paper, putting the precipitate and the
filter paper into a
nitrogen determination and
elimination tube, firstly adding 15mL of
sulfuric acid, standing, slowly heating and pre-digesting, then taking down and cooling, then adding
sulfuric acid,
anhydrous sodium sulfate and
copper sulfate again, heating to 420 DEG C, digesting to be clear, and obtaining a to-be-tested sample; and 5) determining
nitrogen of the to-be-detected sample by using a
Kjeldahl method to obtain the content of true
protein in the sample. According to the method, the result of detecting the true
protein content in the feed or a dairy product by using the
salting-out method is more accurate, and the
repeatability and the stability of the detection result are improved.