Title: Determining Differences in Protein Hydrolysis in Fermented Food Products Analyzed using Mass Spectrometry

Yogurt is one of the most universally consumed and healthful dairy products in the world due to its physical and chemical characteristics. The objective of this study was to examine differences in protein fragmentation between yogurts made with various starter cultures. Yogurt samples were made using three commercially sold yogurt starter cultures (Activia, Fage, and Old Home) with a basic recipe. Casein was extracted at weekly intervals using standard methods and dissolved in a phosphate buffer until use; a control sample was extracted using the same method from milk. Fragmentation was first examined using gel electrophoresis. Protein concentrations were obtained and samples were desalted before they were investigated on a Matrix-Assisted Laser Desorption Ionizing Time-of-Flight (MALDI-TOF) Spectrometer. Results showed distinct cleavage sites of the protein with differences between starter cultures. All peptides originated from bovine casein Alpha S2 and were sliced from the middle of the protein sequence. While results were consistent with preliminary data, samples were not run in triplicate and thus not statistically significant. More experimentation should be conducted to determine significance and explore sensory attributes. The ultimate goal will be able to explain the effect of using different microorganisms on protein fragmentation and sensory characteristics.