Document Type

Thesis - Open Access

Award Date

2024

Degree Name

Master of Science (MS)

Department / School

Dairy and Food Science

First Advisor

Maneesha S. Mohan

Abstract

This thesis explored nanobubble (NB) technology in dairy processing and effluent treatment applications. A comprehensive review of the current understanding of NB technology in dairy processing, highlighted the fundamental properties of NBs, generation methods, and their interactions with individual milk constituents, as well as their mechanistic effects on functionality in different dairy products and applications. In the first part of this study (Chapter 3), air NBs were generated in water using hydrodynamic cavitation (HC), ultrasonic cavitation (US) and a combination of both at 4.5, 6.5 and 8.5 pH. The results showed that the higher the pH, the better is the stability NBs. HC produced lowest size of nanobubbles with significantly increased redox potential and conductivity levels, and dissolved oxygen across all pH levels. While US resulted in a reduction in dissolved oxygen post-treatment at all pH levels and was found to have significant impact on zeta potential with the highest values reported at pH 8.5. In the next study (Chapter 4) the interactions between air NBs and milk protein dispersions including whey protein isolate, whey protein hydrolysate, and micellar casein concentrate were studied at low concentrations to mimic the concentration of proteins in dairy wastewater streams. The study indicated that NBs increase the dissolved oxygen levels, enhance the zeta potential for micellar casein, and increases the surface hydrophobicity in milk protein dispersions. A decrease in fluorescence intensity was observed for whey protein with NBs, conversely, the fluorescence intensity increased for micellar casein with NBs. This study indicated that nanobubbles could interact with milk proteins via electrostatic and hydrophobic interactions and it was further confirmed by increased aggregation of milk proteins with NBs. Finally, we applied NB technology to dairy wastewater (DW) streams (Chapter 5), demonstrating its potential to enhance treatment efficiency and reduce environmental impact. The NBs increased the dissolved oxygen levels, significantly reduced the biochemical and chemical oxygen demands, in model and composite DW. Overall, this thesis advances our understanding of NB technology applications in DW treatment with HC being the best choice to generate air NBs owing to its ability to be scaled up at industrial level.

Publisher

South Dakota State University

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Available for download on Sunday, August 15, 2027

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Rights Statement

In Copyright