Document Type

Thesis - Open Access

Award Date

2026

Degree Name

Master of Science (MS)

Department / School

Dairy and Food Science

First Advisor

Prafulla Slunke

Abstract

This thesis explores the effects of processing history on the enzymatic susceptibility and functional properties of high-protein dairy ingredients, with a specific focus on ultrafiltered (UF) and microfiltered (MF) retentates and spray-dried powders. While retentates and powders are often used interchangeably in industrial applications, processing steps, such as drying, can induce structural and physicochemical changes that affect protein functionality and enzyme accessibility. Milk protein concentrates (MPC) and micellar casein concentrates (MCC) were standardized to 10% protein and subjected to enzymatic treatments, including proteolysis (Alcalase and rennet) and crosslinking (transglutaminase and laccase). Structural modifications were evaluated using capillary gel electrophoresis, non-protein nitrogen (NPN), non-casein nitrogen (NCN), particle size distribution, and zeta potential. Functional properties, including solubility, color, foaming, emulsification, and rheological behavior, were evaluated. Two-way ANOVA was used to evaluate the effect of each factor and their interactions. Tukey’s HSD test was used for means comparison. Results demonstrated that product form (retentate or powder) significantly influenced enzymatic susceptibility and functional performance. For MPC systems, retentates differed significantly from reconstituted powders in mineral composition, whereas no such form-dependent difference was observed for MCC. Reconstituted powders exhibited superior foaming properties, higher viscosity, and shear-thinning behavior, while retentates showed better emulsifying properties and shear-thickening behavior. Alcalase treatment generated a greater proportion of low-molecular-weight peptides, whereas rennet caused no significant shift in molecular weight–based peptide distribution. Both proteolytic treatments improved foaming and emulsification properties. Transglutaminase crosslinking promoted the formation of high-molecular-weight peptides and increased viscosity, while laccase treatment produced some improvements in foaming performance. The extent of these modifications differed between retentates and powders, highlighting the roles of protein structure, mineral balance, processing history, and the availability of enzyme sites. Overall, this study establishes that retentates and powders are not functionally equivalent despite similar compositions. The findings emphasize the importance of considering processing-induced structural changes when selecting protein ingredients for targeted applications. This work provides valuable insights for the dairy and food industries to optimize ingredient functionality through informed selection and enzymatic modification strategies.

Publisher

South Dakota State University

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Rights Statement

In Copyright