AOAC SPIFAN WPC ERP-Final Action Review (Nov. 2017)

2016.15 (Nov. 2017) - WPC-31 Publications-Final Action Review

FOR ERP USE ONLY DO NOT DISTRIBUTE

Organic Formula

60

19

64.92

108

1.01

2.43

1.14

Formula with EDW @

60

19

60.56

101

1.47

2.61

1.21

Formula with raw milk

60

19

62.36

104

1.61

2.76

1.29

* Claims based on the formulation/label, #Based on the formulation and the calculation results from AOAC 2012.07. §Casein GlycoMacroPeptide, @Electrodialysis demineralized whey. The first five samples came from the SPIFAN test kit, and the next ten samples were sampled from the Chinese market .

A. Principle

In SDS-CGE, proteins in infant formula samples are denatured by the anionic surfactant SDS and reduced by β-mercaptoethanol. The SDS-bonded, electrically charged proteins migrate in an electrical field filled with a separation gel and are detected by UV at 220nm. Caseins and whey proteins are separated as two distinct, non-overlapping groups of peaks whose ratio can be established based on integrated areas without the need for a calibration curve. 1.4 was used as the mass-to-area correction factor for whey proteins vs caseins in the calculation of whey protein content. B. Apparatus a) ProteomeLab PA 800 plus, (Beckman Coulter, Inc., Fullerton, CA or equivalent), equipped with UV detector set at 220nm. Peak area can be integrated using any suitable software (Waters Empower, Beckman 32Karat, or equivalent). b) Bare, fused-silica capillaries of 50 μm ID × 30 cm with effective length of 20 cm (338451 from Beckman Coulter, Inc., Fullerton, CA or equivalent). c) Analytical balance: 4 decimal places. d) Temperature controlled water bath: 100±5 o C. e) Micro centrifuge for 1.5-mL vials. f) Vortex. C. Reagents a) SDS-MW gel buffer (A30341, Beckman Coulter, Inc. Fullerton, CA, recipe is readily supplied by the Vendor). b) SDS-MW analysis kit (390953 Beckman Coulter, Inc., Fullerton, CA) including: bare, fused- silica capillaries of 50 μm ID × 30 cm; SDS-MW gel buffer; SDS-MW sample buffer (100 mM Tris-HCl, pH 9.0, with 1% SDS); 10 kDa protein internal standard; acidic wash solution (high-purity 0.1 M HCl); basic wash solution (high-purity 0.1 M NaOH); and SDS-MW Size standard (10-225 kDa, 16 mg/mL). Contents of the kit can be replaced by equivalent sources. c) 10 kDa protein internal standard, (A26487, Beckman Coulter, Inc. Fullerton, CA). d) Water (LC grade). e) β-mercaptoethanol (M7154 or M6250 Sigma). g) Adjustable pipettes: 20, 100, 1000 μL (Eppendorf or equivalent). h) 2.0-mL safe-lock centrifuge tubes (e.g. Eppendorf 022363344). i) 10-mL round-bottom centrifuge tube (e.g. Eppendorf 022822179).