Document Type

Thesis - Open Access

Award Date

2020

Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Sergio Martinez-Monteagudo

Keywords

dairy manufacturing, hydrodynamic cavitation, ice cream, microbiology, rheology, skim milk concentrate

Abstract

The phenomenon of hydrodynamic cavitation involves the formation, growth, and subsequent collapse of bubbles when a given liquid experienced a reduction of pressure below its vapor pressure. The presence of cavitation limits the performance and the safe operation of many machinery and pumps. However, innovation in the design of the hydrodynamic cavitation devices has offered promising applications in the food and dairy industry. Upon collapse of the cavities, the fluid experiences significant mechanical effects (shear and turbulence) as well as instantaneously elevation of the fluid temperature. All these effects can be put to work for mixing, dispersion, particle size reduction, disinfection, and emulsification. In this thesis, the feasibility of using a rotational cavitator for different unit operations was systematic evaluated. The feasibility of hydrodynamic cavitation was evaluated in terms of analysis of cavitation parameters, characterization of the increase in the fluid temperature, microbial efficiency, and emulsification of ice cream mix. The analysis of the cavitator revealed that the velocities generated inside the rotational cavitator are sufficiently high to induce cavitation within the fluid. The development of the cavitation was influenced by the flow rate, speed of the rotor, temperature, and fluid properties. The pressure at which cavitation would first appear was calculated as a function of the operating parameters. The increase in the temperature of the fluid was modeled, showing satisfactory correlation with the experimental data. The increased in the temperature of the fluid due to cavitation was used to develop a process for assisting thermal pasteurization with the idea of reducing the log counts of thermoduric bacteria. The newly developed process can be operated within a wide range of processing conditions (50-300 L h-1, 600-3600 RPM, 70-85°C with residence time from 10-110 s). It was found a 3.5 log reduction of Bacillus coagulans by cavitation followed by thermal treatment, while thermal treatment along yielded a 2.77 log reduction. The hydrodynamic cavitation was applied during the manufacture of ice cream with the idea of reducing the concentration of stabilizers. Particle size of ice cream mix and rheology test was conducted to determine the influence of the stabilizer amounts in ice cream mix. Hydrodynamic cavitation itself reduced the particle size of cream and ice cream mix. Dynamic rheological measurements (strain and frequency sweeps) of ICM indicated increased product stability at a rotation speed of 3600 RPM and flow of 100 L -1. However, the mechanical spectra were considerable different. Imparted viscosities at medium shear rates were at least 2-fold greater compared to formulations homogenized conventionally.

Library of Congress Subject Headings

Cavitation.
Dairy processing.
Hydrodynamics.

Format

application/pdf

Number of Pages

92

Publisher

South Dakota State University

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Rights Statement

In Copyright