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    Characterising honeys in situ by spectral methods : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Manawatu, New Zealand. EMBARGOED to 20 September 2024.
    (Massey University, 2023) Truong, Hien Thi Dieu
    New Zealand mānuka honey is derived mainly from Leptospermum scoparium nectar and is valuable through accumulation of antibacterial methyl glyoxal (MGO). Mānuka honey also has a strong polyphenolic profile. Some phenolics act as chemical markers aiding verification of botanical origin as Leptospermum scoparium. A total of eight key chemical markers (DHA, MGO, 3-PLA, 4-HPLA, 2’-MAP, 2-MBA, Leptosperin and LepteridineTM) are found at higher levels in mono-mānuka honey than in multi-mānuka honey, with little or none in other floral honeys. These key markers signify mānuka honey quality and purity (i.e., monoflorality of L. scoparium). The quality and purity of mānuka honeys depend on multiple factors, largely determined by botanical source, which define the value of the final honey product. Available nectar is, in turn, influenced by geographic district and season. Wild harvest honey is naturally a mixture from different nectars. Honey quality varies among apiaries, between beehives and even in a honey frame. Current industry practice lumps all frames of the same apiary together for extraction. Potentially, “good” quality frames of mānuka honey could be mixed with “bad” quality frames. This bulked process can limit the monetary value of mānuka honey. Quality assessment of honey while still in the frame before bulk extraction is of great of interest to the honey industry to preserve the value of mānuka honey at source and to ensure authenticity. The current study used rapid and non-destructive methods such as NIR and fluorescence combined with chemometrics, machine learning and deep learning to evaluate mānuka honey in the frame. The study focuses on assessment of mānuka honey quality in two ways: 1) direct measurement of levels of eight key chemical makers; 2) indirect measurement of potency (based on UMFTM score) and purity (verification of botanical origin as L. scoparium) that are built from key chemical markers. Honey samples (n ~ 1656) representing 200 L drums, each extracted from multiple frames, spanning eight geographic districts across New Zealand, were scanned with NIR non-imaging (350 - 2500 nm) and imaging (547 – 1701 nm) sensors. A sub-dataset of 100 honey samples was scanned in excitation-emission matrix mode (250 - 400/300 - 600 nm) under in-line geometry by a fluorescence sensor. Once techniques were verified, freshly uncapped seven honey frames were scanned and modelled to evaluate the current optical methods used. Overall, the research showed the capability of NIR methods for measurement of honey potency and purity in the frame, achieving 70 - 80 % accuracy. However, NIR methods showed limited ability to measure levels of individual key chemical markers, giving 60 - 70 % accuracy, due to the complexity of the honey matrix. This study has calculated the economic benefit of using NIR methods for sorting honey frames into different quality buckets (UMFTM buckets and MPI honey buckets) before lumped extraction. The greatest revenue increase is found for apiaries with large variation between frames and in seasons with high curvature in the price-quality curve. Later, this study employed fluorescence-based methods that further improved prediction of almost all key chemical markers, in particular two polyphenolic fluorescence markers, Leptosperin and LepteridineTM, to above 80 % accuracy. Moreover, the fusion of NIR and fluorescence data further enhanced predictability of chemical markers, potency and purity of mānuka honey to 90 - 100 % accuracy. In conclusion, this study confirms the fusion of NIR and fluorescence methods has great potential for at-line/on-line assessment of New Zealand mānuka honey while still in the frame. This research provides basic scientific guidance for future application of NIR and fluorescence methods for quality assessment of honey in general and has implications for other wild harvest foods.
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    Infrared induced dynamics of loosely bound molecules : the dynamical process of vibrational state to continuum coupling for trans-1, 2-dichloroethylene (DCE) using infrared spectroscopy : Master of Science in Physics at Massey University, Albany, New Zealand
    (Massey University, 2019) Alrsheedi, Fatimah N.
    The infrared absorption spectrum of crystalline trans-1, 2-dichloroethylene has been measured down to 50 K using a specially designed and constructed infrared (IR) cell, using a Nicolet iS50R FT-IR. The IR scans show the absorbance of trans-1, 2-dichloroethylene molecules at bu CH stretch (9), bu CH bend (10), au CH bend (6) and bu CCl stretch (11) are changed at different temperature conditions. In the solid phase, the absorption spectra of crystalline trans -1, 2-dichloroethylene at different temperatures demonstrates a dramatic change in some of the peak shapes for bu CH stretch (9), bu CH bend (10), au CH bend (6) and bu CCl stretch (11). Instead of a symmetric lineshape that would generally be expected for the excitations of these modes, the spectra clearly showed asymmetric lineshape in some of the peaks as result of the presence of Fano resonance which is not commonly seen in infrared spectroscopy. Although asymmetric peaks are often attributed to interference from reflected rays due to refractive index changes at boundary surfaces the observation, in some cases, of complete peak inversion allows for an unambiguous identification of Fano interference as the source of the asymmetry. The origin of this effect refers to quantum interference on the optical absorption through the coupling between the discrete and continuum states in which the excited eigenstates are mixtures of the discrete and continuum states, as the excitation of trans -1, 2-dichloroethylene occurring simultaneously with the continuum background transitions. In this thesis, we report IR spectroscopic observations that show interference between the vibrational states of the molecules of trans -1, 2- dichloroethylene with the continuum background states. The background continuum arises from the overlapping of many other resonances due to the overtone/ combination bands and coupling of other vibrational states, including the bulk optical phonons, providing essentially a broad continuum. Individual resonances are conspicuous at low temperature and continuously reduce with increasing temperature. Additionally, the IR bands for the fundamental modes have been observed and discussed in this work. Further, the overtone and combination bands are also assigned on the basis of (gas phase) anharmonic calculations as the analysis of anharmonic and harmonic frequencies shows that the anharmonic frequencies are close and correspond better with the experiment than those acquired using a harmonic approximation.
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    Investigation into the interactions of supercritical argon as a solvent with trans-1,2-dichloroethylene using ultraviolet-visible and infrared spectroscopy : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Chemistry at Massey University, Auckland, New Zealand
    (Massey University, 2018) Moffet, Erin Sarah
    This thesis looks at the uses and interactions of argon as a solvent at or above its supercritical temperature and pressure. A supercritical fluid allows for a range of properties depending on where the conditions of pressure and temperature are in relation to the critical point of the chosen substance. These supercritical fluids have been shown to be useful across many areas of industry and research and are the ideal fluid to use in a molecular beam pulsed valve. Solubility interactions of argon and trans-1,2-dichloroethylene (DCE) across multiple conditions were monitored using ultraviolet-visible (UV-Vis) and infrared (IR) spectroscopy. Two high pressure cells were designed, constructed and tested to withstand the 50 atmospheres and 140 K conditions required. The initial cell focused on UV-Vis spectroscopy with the DCE vapour showing an exponential decrease in absorbance as the temperature in the cell was reduced. Changing conditions to reach the supercritical region of argon resulted in a significant increase in the absorbance and therefore the solubility of DCE. The second cell constructed focuses on analysis using infrared spectroscopy and showed clear peak shifts and shape changes at the bu CH stretch (ν9) and bu CH bend (ν10) for trans-1,2-dichloroethylene (DCE) The intensity at au CH bend (ν6) and bu CCl stretch (ν11) proved to be less informative. DCE vapour acted predictably as the temperature was reduced, resulting in a significant drop off in absorbance similar to that observed in the UV-Vis. In changing to the supercritical and liquid argon conditions resulted in the appearance of an asymmetric lineshape characteristic of Fano resonance, which is not common in infrared spectroscopy. This suggest that there is an interaction occurring between a discrete state of DCE that couples to a background continuum process. This Fano resonance does not appear to be present in an argon matrix isolation.