US 12,405,252 B2
Method for detecting contents of whey protein and casein, and/or ratio thereof in milk powder
Lijun Chen, Beijing (CN); Tao Xu, Beijing (CN); Jingyao Chen, Beijing (CN); Weicang Qiao, Beijing (CN); and Junying Zhao, Beijing (CN)
Assigned to BEIJING SANYUAN FOODS CO., LTD., Beijing (CN)
Filed by Beijing Sanyuan Foods Co., Ltd., Beijing (CN)
Filed on Jul. 22, 2022, as Appl. No. 17/871,549.
Application 17/871,549 is a continuation of application No. PCT/CN2021/143234, filed on Dec. 30, 2021.
Claims priority of application No. 202110904028.8 (CN), filed on Aug. 6, 2021.
Prior Publication US 2023/0080697 A1, Mar. 16, 2023
Int. Cl. G01N 30/06 (2006.01); G01N 30/30 (2006.01); G01N 30/34 (2006.01); G01N 30/72 (2006.01); G01N 30/88 (2006.01); G01N 33/04 (2006.01)
CPC G01N 30/06 (2013.01) [G01N 30/30 (2013.01); G01N 30/34 (2013.01); G01N 30/72 (2013.01); G01N 30/88 (2013.01); G01N 33/04 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A method for detecting the contents of whey protein and casein, and/or the ratio thereof in milk powder by liquid chromatography-mass spectrometry, comprising:
1) Preparing a standard solution of whey protein with the characteristic peptide segments of α-lactalbumin and β-lactoglobulin, in accordance with the α-lactalbumin and β-lactoglobulin accounting for 20% and 50% of the whey protein, respectively;
2) Preparing a standard solution of casein with the characteristic peptide segments of α-casein and β-casein, in accordance with the α-casein and β-casein accounting for 50% and 40% of the casein, respectively;
3) Mixing the standard solution of whey protein from step 1) with the standard solution of casein from step 2) to prepare a series of mixed protein standard solutions with a series of whey protein:casein ratios;
4) Drawing standard curves with the ratio of whey protein to casein as abscissa and the peak area ratios of characteristic peptide segments of α-lactalbumin to β-casein and the peak area ratios of characteristic peptide segments of β-lactoglobulin to α-casein as ordinate;
5) Detecting the milk powder to be tested for the peak area ratios of the characteristic peptide segments of β-lactoglobulin to α-casein and the peak area ratios of the characteristic peptide segments of α-lactalbumin to β-casein;
6) Substituting the peak area ratio of the characteristic peptide segments of β-lactoglobulin to α-casein in the detected milk powder into the standard curve to determine the ratio M of whey protein to casein, and calculate the actual amounts of β-lactoglobulin and α-casein based on the ratio M thus determined;
and, substituting the peak area ratio of the characteristic peptide segments of α-lactalbumin to β-casein in the detected milk powder into the standard curve to determine the ratio N of whey protein to casein, and calculate the actual amounts of α-lactalbumin to β-casein based on the ratio N thus determined;
7) Acquiring the actual contents of whey protein and casein, and/or the actual ratio of whey protein/casein based on the actual amounts of α-lactalbumin, β-casein, β-lactoglobulin, and α-casein obtained from step 6).