Publication Date

5-2021

Date of Final Oral Examination (Defense)

3-5-2021

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biomolecular Sciences

Department

Biology

Major Advisor

Owen McDougal, Ph.D.

Advisor

Henry Charlier, Ph.D.

Advisor

Juliette Tinker, Ph.D.

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. 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. Infrared (IR) spectroscopy offers advantages over the KM in that IR provides an accurate representation of protein content in dairy products, and the results can be achieved very quickly. Protein analysis by IR has been used to study protein degradation in aged cheeses, and milk whey powder adulteration in whey protein concentrate supplements. The hypothesis of this thesis is that if mid-infrared (MIR) spectroscopy can be used to characterize individual whey proteins, then MIR should be applicable to qualitative analysis of protein powders and quality control monitoring of protein powder products for adulteration by inexpensive protein or amino acids. Protein powder analysis by KM revealed that the calculated total percent protein of the five protein powders tested was lower than the value stated on the product label, the percent variation between label protein content and that of the KM ranged from 2.9% to 9.5%. MIR spectroscopy spectra of four whey protein standards and four other protein standards provided qualitative characterization of each protein by amide I and amide II peak absorbance wavenumber. 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 of the products. Protein powders have been found to be doped with the amino acids glycine, leucine, and glutamic acid and inexpensive proteins, like bovine serum albumin. Controlled doping experiments were conducted with each of the above listed adulterants to assess the effectiveness of MIR spectroscopy to rapidly detect product tampering. Protein doping experiments revealed that as BSA amounts were increased, the amide I/II peak shape changed from the broad protein powder peaks to the narrower BSA peaks. Amino acid doping experiments revealed that the limit of detection for MIR spectroscopy, for the three amino acids used in this study, is 25%. MIR spectroscopy results may offer product quality assurance that is complementary to dairy protein measurement by the KM.

DOI

10.18122/td.1799.boisestate

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