Quantitative LC-MS/MS Determination of Source-Specific Variations of Underivatized Free Amino Acids in Protein Powders

Abstract

This study reports a novel, validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to comprehensively profile underivatized free amino acids (FAAs) in diverse whey and plant-based protein powders from global sources, which are commonly consumed for their nutritional value. Though their overall protein composition is frequently promoted, the accurate profiles and patterns of unmodified FAAs, whose functions are significant in metabolism, taste and product quality, are less well described. The validated LC-MS/MS technique showed a broad linearity range, high precision, accuracy and recoveries of 75-121%, with low detection and quantification limits. The analysis and separation time of less than 9 min increases its efficiency. Substantial differences in the FAAs present and their levels, both in kind and quantity, were observed between whey and plant-based proteins from various geographical region. The amino acids like glutamine and L-tryptophan were consistently high-ranking in most species of whey and plant-based proteins investigated. Notably, amino acids linked to sweet taste such as glycine, alanine, serine, proline and threonine were significantly greater in the majority of whey proteins that directly causes acute disorders in healthy individuals as per the International Council on Amino Acid Science (ICAAS). Principal component analysis (PCA) was capable of separating the protein samples that were tested which accounted for 86.88% of the total variance, thus verifying different clustering by FAA profiles. These observations reinforce the significance of source diversity and geographical origin in characterizing the nutritional profile of protein powders beyond bulk protein content. The large-scale profiling of underivatized FAAs furnishes rich information useful for consumers, manufacturers and researchers interested in deciphering and optimizing the nutritional, functional properties of these ubiquitous dietary supplements.