scholarly journals Kinetics of Whey Protein Glycation Using Dextran and the Dry-Heating Method

Foods ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 528 ◽  
Author(s):  
Na Li ◽  
Abhiram Arunkumar ◽  
Mark R. Etzel

Glycation of proteins by polysaccharides via the Maillard reaction improves the functional properties of proteins in foods, such as solubility, heat stability, emulsification, foaming, and gelation. Glycation is achieved by either the dry heating or the wet heating method, and considerable research has been reported on the functionality of the reaction mixture as tested in foods. While the characteristics of the glycates in foods have been well studied, the kinetics and equilibrium yield of the protein-polysaccharide glycation reaction has received little attention. Industrial manufacture of the glycates will require understanding the kinetics and yield of the glycation reaction. This work examined the glycation of whey protein isolate (WPI) and glycomacropeptide (GMP) by using dextran and the dry-heating method at 70 °C and 80% relative humidity. The disappearance of un-glycated protein and the creation of glycated protein were observed using chromatographic analysis and fluorescence laser densitometry of sodium dodecyl sulfate-polyacrylamide gels. Data were fit using a first-order reversible kinetic model. The rate constants measured for the disappearance of un-glycated protein by sodium dodecyl sulfate-polyacrylamide (SDS-PAGE) (k = 0.33 h−1) and by chromatographic analysis (k = 0.38 h−1) were not statistically different from each other for WPI-dextran glycation. Dextran glycation of GMP was slower than for WPI (k = 0.13 h−1). The slower rate of glycation of GMP was attributed to the 50% lower Lys content of GMP compared to WPI. Yield for the dry-heating dextran glycation method was 89% for WPI and 87% for GMP. The present work is useful to the food industry to expand the use of glycated proteins in creating new food products.

2017 ◽  
Vol 100 (2) ◽  
pp. 510-521 ◽  
Author(s):  
Ping Feng ◽  
Christophe Fuerer ◽  
Adrienne McMahon

Abstract Protein separation by sodium dodecyl sulfate-capillary gel electrophoresis, followed by UV absorption at 220 nm, allows for the quantification of major proteins in raw milk. In processed dairy samples such as skim milk powder (SMP) and infant formulas, signals from individual proteins are less resolved, but caseins still migrate as one family between two groups of whey proteins. In the first group, α-lactalbumin and β-lactoglobulin migrate as two distinct peaks. Lactosylated adducts show delayed migration times and interfere with peak separation, but both native and modified forms as well as other low-MW whey proteins still elute before the caseins. The second group contains high-MW whey proteins (including bovine serum albumin, lactoferrin, and immunoglobulins) and elutes after the caseins. Caseins and whey proteins can thus be considered two distinct nonoverlapping families whose ratio can be established based on integrated areas without the need for a calibration curve. Because mass-to-area response factors for whey proteins and caseins are different, an area correction factor was determined from experimental measurement using SMP. Method performance assessed on five infant formulas showed RSDs of 0.2–1.2% (within day) and 0.5–1.1% (multiple days), with average recoveries between 97.4 and 106.4% of added whey protein. Forty-three different infant formulas and milk powders were analyzed. Of the 41 samples with manufacturer claims, the measured whey protein content was in close agreement with declared values, falling within 5% of the declared value in 76% of samples and within 10% in 95% of samples.


2018 ◽  
Vol 55 (5A) ◽  
pp. 26
Author(s):  
Tran Le Thu

In combination with the Lumifuge centrifugation and Zeta potential apparatuses, the influence of a varying molar ratio of Sodium Dodecyl Sulfate (SDS) to Whey Protein Isolate (WPI) on the stability of the whey protein emulsions at pH 4 and pH 5.5 is observed. Two whey protein stabilized emulsions were prepared by homogenizing 20 wt. % soybean oil and 80 wt. % whey protein solutions (0.5 wt.% whey protein in buffer, pH 4 and pH 5.5) at room temperature.By observation, the droplets are weakly flocculated at a ratio of SDS to whey protein of 256. This shows that there is a strong electrostatic repulsion between the emulsion droplets if much surfactant is adsorbed to the protein molecules, which prevents them from aggregating. The magnitude of the measured zeta potentials explained the stability of the emulsion at pH 4 as well as the emulsion at pH 5.5 is ensured at SDS to whey protein ratio equal to 256. The results of the transmission profile by Lumifuge separation analyzer at different time and at 3000 rpm (1200 g) elucidated that the stability of the whey protein emulsion at pH 4 and 5.5 is obtained upon dilution with SDS-WPI ratio of 256. 


The Analyst ◽  
2001 ◽  
Vol 126 (4) ◽  
pp. 457-464 ◽  
Author(s):  
Mayte Gil-Agustí ◽  
M. Elisa Capella-Peiró ◽  
Llorenç Monferrer-Pons ◽  
Josep Esteve-Romero ◽  
María Celia García-Alvarez-Coque

2018 ◽  
Vol 101 (5) ◽  
pp. 1566-1577 ◽  
Author(s):  
Ping Feng ◽  
Christophe Fuerer ◽  
Adrienne McMahon ◽  
K Arendse ◽  
A Chanady ◽  
...  

Abstract A multilaboratory testing study was conducted on AOAC First Action Official Method SM 2016.15: Quantification of Whey Protein Content in Infant Formula Powders by Sodium Dodecyl Sulfate–Capillary Gel Electrophoresis (SDS-CGE). Nineteen laboratories participated in the analysis of duplicate blind-coded samples of 15 formula powder products for infants and young children. Electrophoregrams were recorded at UV220 nm and integrated. The normalized peak areas of whey and casein proteins were summed separately to calculate total whey protein content. Apart from one sample [NIST Standard Reference Material (SRM) 1849a], relative standard deviation of repeatability (RSDr) and reproducibility (RSDR) ranged from 0.83 to 2.11% and from 2.18 to 4.22%, respectively, and Horwitz ratios ranged from 1.02 to 1.85, meeting the precision limits specified in the whey protein Standard Method Performance Requirements and in the guidelines recommended for the Horwitz ratio. In these samples, the measured whey protein content was between 98 and 108% of the declared value. NIST SRM 1849a showed atypical results, with elevated RSDr (3.51%), RSDR (5.94%), Horwitz ratio (2.62), and recovery (134%). There is no clear reason for this. The percent whey protein value for NIST is calculated from the formulation and is not a reference or certified value. Multiple instrument models and makes, as well as capillary sources, were used in this collaborative study, demonstrating the robustness of the method. The method is fit-for-purpose for the quantification of whey protein content in milk-based formula powder products for infants and young children. It is not applicable to the analysis of hydrolyzed or plant protein–based infant formulas.


Sign in / Sign up

Export Citation Format

Share Document