Whey Protein Powder Analysis by Mid-Infrared Spectroscopy.

Rose Saxton,Owen M Mcdougal

doi:10.3390/foods10051033

Abstract

There is an ever-expanding number of high protein dietary supplements marketed as beneficial to athletes, body builders, infant formulas, elder care, and animal feed. Consumers will pay more for products with high protein per serving data on their nutritional labels, making the accurate reporting of protein content critical to customer confidence. The Kjeldahl method (KM) is the industry standard to quantitate dairy proteins, but the result is based on nitrogen content, which is an approximation of nitrogen attributable to protein in milk. Product tampering by third-party manufacturers is an issue, due to the lack of United States Food and Drug Administration regulation of nutraceutical products, permitting formulators to add low-cost nitrogen-containing components to artificially inflate the KM approximated protein content in products. Optical spectroscopy is commonly used for quality control measurements and has been identified as having the potential to complement the KM as a more nuanced testing measure of dairy protein. Mid-infrared (MIR) spectroscopy spectra of eight protein standards provided qualitative characterization of each protein by amide I and amide II peak absorbance wavenumber. Protein doping experiments revealed that as protein amounts were increased, the amide I/II peak shape changed from the broad protein powder peaks to the narrower peaks characteristic of the individual protein. Amino acid doping experiments with lysine, glutamic acid, and glycine, determined the limit of detection by MIR spectroscopy as 25%, suggesting that MIR spectroscopy can provide product quality assurance complementary to dairy protein measurement by the KM.

Highlights

Dietary protein is required to provide amino acid building blocks critical to growth and development, catalysts for biochemical reactions and mechanical support of tissues [1]
Each whey protein contains all of the essential amino acids, which makes them valuable ingredients in protein powder formulations, but not all protein sources are created equal, with milk, eggs, and legumes emerging as natural sources of premium protein for dietary supplements
Protein powder samples were loaded on the surface of the attenuated total reflectance (ATR) accessory and a force probe was tightened to ensure adequate contact with the crystal; a total of three spectra were collected for each protein powder, after every sample analysis, the crystal was cleaned with isopropanol and a new sample was analyzed

Summary

Introduction

Dietary protein is required to provide amino acid building blocks critical to growth and development, catalysts for biochemical reactions and mechanical support of tissues [1]. The two most abundant dairy proteins are casein and whey. Casein is the primary constituent of milk, used to make cheese, while whey is most often made into yogurt or spray-dried for use in nutritional supplements, among other products. Each whey protein contains all of the essential amino acids, which makes them valuable ingredients in protein powder formulations, but not all protein sources are created equal, with milk, eggs, and legumes emerging as natural sources of premium protein for dietary supplements. Dairy proteins, are a complete source of all amino acids in the right proportion to provide optimal nutritional benefit to the consumer

Methods

Results

Conclusion