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<p dir="ltr">Pasteurizing honey is essential for delaying crystallization, improving safety, and extending shelf life, but traditional methods raise concerns over energy efficiency and quality changes. Microwave (MW) heating at 915 MHz offers efficient, volumetric heating, preserving flavor and nutrients while reducing energy usage. Its precise control ensures safety in shorter timeframes, making it a promising alternative for honey pasteurization. This study evaluated the effectiveness of 915 MHz MW heating for honey pasteurization, focusing on hydroxymethylfurfural (HMF), crystallization, physicochemical properties, microbial safety, and consumer perception and acceptance. Honey samples were processed at power levels of 15, 16, and 18 kW with a flow rate of 1.62 gal/min, resulting in specific energy fluxes of 4.35, 4.87, and 5.97 J/kg·s⁻¹. Increased specific energy fluxes had no statistically significant effect on the HMF and microbial loads. The MW treatment effectively controlled HMF content within acceptable limits. As specific energy fluxes increased to 5.97 J/kg. s^-1HMF Content increased from 18.88 ± 0.05 mg/kg to 20.31± 1.46 mg/kg, a fructose/glucose ratio of 1.17 at 4.87 J/kg·s⁻¹ indicating potential delay in crystallization. There was a significant increase in total phenolic content from 214 ± 5.01 mg of gallic acid/kg to 569 ± 35.91 mg of gallic acid/kg. The study also showed significant changes in moisture content, water activity, color, pH, viscosity, and total sugar content. A sensory evaluation with 69 participants showed no significant differences in aroma, flavor, and overall liking compared to commercial honey. These findings emphasize the potential of MW heating as a viable alternative for honey pasteurization.</p>

M.Tech. (Mechanical Engineering Technology) / Please refer to full text to view abstract

Submitted in fulfilment of the requirements for the Degree of Master of Technology: Organic Chemistry, Durban University of Technology, 2011. / ortho-Deoxygrisan (38), a spirodienone was synthesised from bisphenol (42) using both conventional and microwave assisted methods. The bisphenol (42) was synthesised from phenol (52) by conventional and microwave assisted methods. Benzophenone (43) was synthesised from compound (49) which in turn was synthesised from compound (53) by chromic acid oxidation in acetic anhydride or acetic acid. Compound (53) was synthesised from bisphenol (42) by mono-acetylation method.Acid-catalysed rearrangement of ortho-deoxygrisan (38) in the absence of light was investigated. Chromatography of the reaction mixture afforded compound (D) as a major component. Attempts to synthesise ortho-grisan (50) from benzophenone (43) were unsuccessful. Microwave assisted selenium dioxide oxidation of compound (53) gave a yellow compound C. The spectra of this compound were very similar to the spectra of ortho-deoxygrisan (38). However, selenium dioxide was reacted with compound (53) in the absence of microwave to give a yellow solid B. The 1H NMR spectral data of this compound led to the proposed structure B for it. / National Research Foundation.

We present Bessel function and Gaussian beam models for a study of microwave power deposition in bounded and inhomogeneous lossy media. The aim is to develop methods that can accurately simulate practical results commonly found in electromagnetic hyperthermic treatment, which is a noninvasive method. The Bessel function method has a closed form solution and can be used to compute accurate results of electromagnetic fields emanating from applicators with cosinusoidal aperture fields. On the other hand, the Gaussian beam method is approximate but has the capability to simplify boundary value problems and to compute fields in three-dimensions with extremely low CPU time (less than 30 sec). Although the Gaussian beam method is derived from geometrical optics theory, it performs very well in domains outside the realm of geometrical optics which stipulates that aperture dimension/λ ≥ 5 in the design of microwave systems. This condition has no relevance to the Gaussian beam method since the method shows that a limit of aperture dimension/ λ ≥ 0.9 is possible, which is a very important achievement in the design and application of microwave systems. Experimental verifications of the two theoretical models are integral parts of the presentation and show the viability of the methods.

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Thesis (Ph. D.)--Washington State University. / Includes bibliographical references.

M. Tech. Chemical Engineering. / Aims of this study is to determine the relationship between the temperature of the coal coke (and other mixtures) and the measured microwave impedance in the waveguide feeding the applicator.

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