title: Kinetics of Conversion of Dihydroxyacetone to Methylglyoxal in Honey

authors: Grainger, Megan N.C.

subjects: Manuka

abstract: Mānuka honey contains a unique non-peroxide antibacterial activity which is highly sought after due to the perceived health benefits. Methylglyoxal (MGO) is the compound predominately responsible for this non-peroxide activity (NPA). Varying levels of dihydroxyacetone (DHA) are found in mānuka nectar which converts to MGO once honey is harvested; however, this is not a 1:1 conversion. The price of mānuka honey increases as the MGO concentration increases; hence some beekeepers store their honey for extended periods of time in an attempt to increase the concentration of MGO. The level of 5-hydroxymethylfurfural (HMF, a potentially toxic compound) must stay below 40 mg/kg if the honey is to be exported. Formation of HMF is predominately dependent on time and temperature. Therefore there is a trade off between storing honey to maximise the MGO concentration and retaining a low concentration of HMF. 

Currently there is not a lot of information on the conversion of DHA to MGO in a honey matrix and many beekeepers are unable to predict the maximum MGO concentration from an immature honey. The principal aim of this thesis was to learn more about the conversion of DHA to MGO in a honey matrix in order to create a tool that can predict the concentration of DHA and MGO over time when held at certain temperatures.

Four high performance liquid chromatography methods were compared to find a suitable method for the analysis of the three compounds of interest (DHA, MGO and HMF). The chosen method allowed all three compounds to be detected (using O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine, PFBHA, derivatisation) in a single 30 minute analysis.

A set of mānuka honeys were analysed for various chemical and physical properties (including moisture content, pH, acidity, amino acids, selected phenolics and trace elements) to identify potential factors that may contribute to the conversion of DHA to MGO. Amino acids and phenolic acids were identified as potential compounds that affected the conversion of DHA to MGO. 

Model systems (sugar and water) were used to control the reactions occurring during storage; DHA and individual perturbants were added to the artificial honey to isolate the effect of the perturbant on the conversion. Amino acids were the main focus of these systems; alanine enhanced the conversion of DHA to MGO, whereas DHA was lost to side reactions when proline was present. Real honey samples were also analysed; correlations between the rate constant for DHA disappearance and certain compounds were observed. Temperature influenced the rates of DHA conversion to MGO and also the efficiency of the reaction.
 
The information from the storage trials was used as a starting point to build a predictive model. This included equations for reactions involving DHA and perturbants (either enhancement of conversion to MGO or removal to a side product) and removal of MGO. The model used the initial concentrations of DHA, MGO, amino acids and some phenolic compounds to accurately predict the change in DHA and MGO over time when stored between 20 and 37 °C.

text: Kinetics of Conversion of Dihydroxyacetone to Methylglyoxal in Honey Mānuka honey contains a unique non-peroxide antibacterial activity which is highly sought after due to the perceived health benefits. Methylglyoxal (MGO) is the compound predominately responsible for this non-peroxide activity (NPA). Varying levels of dihydroxyacetone (DHA) are found in mānuka nectar which converts to MGO once honey is harvested; however, this is not a 1:1 conversion. The price of mānuka honey increases as the MGO concentration increases; hence some beekeepers store their honey for extended periods of time in an attempt to increase the concentration of MGO. The level of 5-hydroxymethylfurfural (HMF, a potentially toxic compound) must stay below 40 mg/kg if the honey is to be exported. Formation of HMF is predominately dependent on time and temperature. Therefore there is a trade off between storing honey to maximise the MGO concentration and retaining a low concentration of HMF. 

Currently there is not a lot of information on the conversion of DHA to MGO in a honey matrix and many beekeepers are unable to predict the maximum MGO concentration from an immature honey. The principal aim of this thesis was to learn more about the conversion of DHA to MGO in a honey matrix in order to create a tool that can predict the concentration of DHA and MGO over time when held at certain temperatures.

Four high performance liquid chromatography methods were compared to find a suitable method for the analysis of the three compounds of interest (DHA, MGO and HMF). The chosen method allowed all three compounds to be detected (using O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine, PFBHA, derivatisation) in a single 30 minute analysis.

A set of mānuka honeys were analysed for various chemical and physical properties (including moisture content, pH, acidity, amino acids, selected phenolics and trace elements) to identify potential factors that may contribute to the conversion of DHA to MGO. Amino acids and phenolic acids were identified as potential compounds that affected the conversion of DHA to MGO. 

Model systems (sugar and water) were used to control the reactions occurring during storage; DHA and individual perturbants were added to the artificial honey to isolate the effect of the perturbant on the conversion. Amino acids were the main focus of these systems; alanine enhanced the conversion of DHA to MGO, whereas DHA was lost to side reactions when proline was present. Real honey samples were also analysed; correlations between the rate constant for DHA disappearance and certain compounds were observed. Temperature influenced the rates of DHA conversion to MGO and also the efficiency of the reaction.
 
The information from the storage trials was used as a starting point to build a predictive model. This included equations for reactions involving DHA and perturbants (either enhancement of conversion to MGO or removal to a side product) and removal of MGO. The model used the initial concentrations of DHA, MGO, amino acids and some phenolic compounds to accurately predict the change in DHA and MGO over time when stored between 20 and 37 °C.

year: 2015

title: The silica issue in the limestone resource at McDonald's Oparure Lime Quarry

authors: Hansen, Orla

subjects: limestone

abstract: McDonald's Oparure Lime Quarry extracts limestone from the latest Oligocene to earliest Miocene aged Otorohanga Limestone formation of the Te Kuiti Group.  The quarry produces a range of limestone grades that are utilised by various industries, including the iron and steel, agricultural, and roading construction industries.  One of the most important aspects of production is quality control which is driven by quality restrictions on the chemical composition of the limestones imposed by the industrial end users.  In steel manufacture, silica is highly undesirable as it has detrimental effects on downstream processes such as the ability of calcium oxide to remove impurities from the steel and its abrasiveness inside pipes transporting lime into the steel making vessel.  A guideline of lt;1.7% silica content in the lime is required.  

McDonald's Lime Ltd and major shareholders Holcim New Zealand Ltd are aware that silica levels vary across the Oparure limestone resource, and so hold some concerns about their ability to maintain quality guidelines on their limestone products.  Consequently, it is relevant that knowledge be gained about the nature, distribution, and origin of silica-rich zones within the limestone resource so as to allow for greater certainty in quarry planning and operations.  

The main aims of this study were to determine the chemical stratigraphy of the limestone units in the quarry so as to assess primary sources of silica in the intact limestone (host limestone); to use field methods to measure the nature and distribution of a variety of discontinuity features which separate the intact rock blocks within the limestone rock mass; to identify sources of secondary silica-rich materials and their characteristics; and to determine the overall distribution of silica within the limestone resource.  Additionally, a ground penetrating radar (GPR) trial was undertaken to establish whether this geophysical technique is successful in detecting subsurface caves that may trap silica-rich materials.  

The host limestone or intact rock mass of the quarry units contains variable amounts of calcium carbonate, as follows: Caprock (av. 89.5%), Upper Steel (av. 98.2%), Aglime (av. 94.5%), High Grade (av. 97.2%), Lower Steel (av. 97.3%), and Sub-economic (av. 95%).  The remaining non-carbonate component largely resides in silica-bearing minerals such as clay minerals, quartz, feldspar, and glauconite, but also in authigenic minerals such as pyrite and gypsum.    

In McDonald's Oparure Lime Quarry six main discontinuity types are identified, all of which are associated with silica-rich materials.  The six discontinuity types are: (1) discrete seams; (2) diffuse seams; (3) subhorizontal stylolites; (4) subvertical stylolites; (5) joints; and (6) caves and other karst features.  Types (1), (2), and (3) have formed as a result of burial of the carbonate-rich sediments during which pressure dissolution has preferentially dissolved skeletal fragments, leaving behind and concentrating insoluble residue (siliceous material).  These are primary sources of silica.  Types (4) and (5) are produced as a result of tectonic activity, including deformation and uplift.  Subvertical stylolites formed by pressure dissolution associated with tectonic stresses during uplift of the limestones, and their contained silica also derives from a primary source inside the limestone strata.  Type (6) discontinuities are produced by dissolution by fresh water of the subaerially exposed limestone.  Joints, caves, and other karst features trap silica-rich materials sourced mainly from overlying overburden lithologies, including the Quaternary Kauroa Ash and the early Miocene Mahoenui Group mudstone; these are secondary sources of silica.  A distinctive leathery clay mineral called palygorskite occurs commonly as a chemical precipitate in both joints and caves as an infill.  A final source of silica identified that is not a discontinuity material, but is operation induced, involves the accumulation of blast and road dust coating rock surfaces, here referred to as surface accumulations.

The overburden units and discontinuity materials show a range of chemical compositions and some, such as cave infills, comprise greater than 60% SiO2.  The main siliceous minerals within overburden units and discontinuity materials are clays (smectite, palygorskite, gibbsite, vermiculite, halloysite, illite), quartz (and minor cristobalite), feldspar (oligoclase), and glauconite.  Carbonate minerals including mainly calcite and minor dolomite.  

GPR successfully detected cave structures to an effective penetration of about 10 m, but cave infills cannot be quantified using this method.

The knowledge gained in this study about the distribution, location, quantities, and nature of the silica materials in the limestone units, closely related to the different discontinuity types identified, has the potential to assist in determining appropriate processing techniques to minimise the silica issue at the Oparure Quarry.

text: The silica issue in the limestone resource at McDonald's Oparure Lime Quarry McDonald's Oparure Lime Quarry extracts limestone from the latest Oligocene to earliest Miocene aged Otorohanga Limestone formation of the Te Kuiti Group.  The quarry produces a range of limestone grades that are utilised by various industries, including the iron and steel, agricultural, and roading construction industries.  One of the most important aspects of production is quality control which is driven by quality restrictions on the chemical composition of the limestones imposed by the industrial end users.  In steel manufacture, silica is highly undesirable as it has detrimental effects on downstream processes such as the ability of calcium oxide to remove impurities from the steel and its abrasiveness inside pipes transporting lime into the steel making vessel.  A guideline of lt;1.7% silica content in the lime is required.  

McDonald's Lime Ltd and major shareholders Holcim New Zealand Ltd are aware that silica levels vary across the Oparure limestone resource, and so hold some concerns about their ability to maintain quality guidelines on their limestone products.  Consequently, it is relevant that knowledge be gained about the nature, distribution, and origin of silica-rich zones within the limestone resource so as to allow for greater certainty in quarry planning and operations.  

The main aims of this study were to determine the chemical stratigraphy of the limestone units in the quarry so as to assess primary sources of silica in the intact limestone (host limestone); to use field methods to measure the nature and distribution of a variety of discontinuity features which separate the intact rock blocks within the limestone rock mass; to identify sources of secondary silica-rich materials and their characteristics; and to determine the overall distribution of silica within the limestone resource.  Additionally, a ground penetrating radar (GPR) trial was undertaken to establish whether this geophysical technique is successful in detecting subsurface caves that may trap silica-rich materials.  

The host limestone or intact rock mass of the quarry units contains variable amounts of calcium carbonate, as follows: Caprock (av. 89.5%), Upper Steel (av. 98.2%), Aglime (av. 94.5%), High Grade (av. 97.2%), Lower Steel (av. 97.3%), and Sub-economic (av. 95%).  The remaining non-carbonate component largely resides in silica-bearing minerals such as clay minerals, quartz, feldspar, and glauconite, but also in authigenic minerals such as pyrite and gypsum.    

In McDonald's Oparure Lime Quarry six main discontinuity types are identified, all of which are associated with silica-rich materials.  The six discontinuity types are: (1) discrete seams; (2) diffuse seams; (3) subhorizontal stylolites; (4) subvertical stylolites; (5) joints; and (6) caves and other karst features.  Types (1), (2), and (3) have formed as a result of burial of the carbonate-rich sediments during which pressure dissolution has preferentially dissolved skeletal fragments, leaving behind and concentrating insoluble residue (siliceous material).  These are primary sources of silica.  Types (4) and (5) are produced as a result of tectonic activity, including deformation and uplift.  Subvertical stylolites formed by pressure dissolution associated with tectonic stresses during uplift of the limestones, and their contained silica also derives from a primary source inside the limestone strata.  Type (6) discontinuities are produced by dissolution by fresh water of the subaerially exposed limestone.  Joints, caves, and other karst features trap silica-rich materials sourced mainly from overlying overburden lithologies, including the Quaternary Kauroa Ash and the early Miocene Mahoenui Group mudstone; these are secondary sources of silica.  A distinctive leathery clay mineral called palygorskite occurs commonly as a chemical precipitate in both joints and caves as an infill.  A final source of silica identified that is not a discontinuity material, but is operation induced, involves the accumulation of blast and road dust coating rock surfaces, here referred to as surface accumulations.

The overburden units and discontinuity materials show a range of chemical compositions and some, such as cave infills, comprise greater than 60% SiO2.  The main siliceous minerals within overburden units and discontinuity materials are clays (smectite, palygorskite, gibbsite, vermiculite, halloysite, illite), quartz (and minor cristobalite), feldspar (oligoclase), and glauconite.  Carbonate minerals including mainly calcite and minor dolomite.  

GPR successfully detected cave structures to an effective penetration of about 10 m, but cave infills cannot be quantified using this method.

The knowledge gained in this study about the distribution, location, quantities, and nature of the silica materials in the limestone units, closely related to the different discontinuity types identified, has the potential to assist in determining appropriate processing techniques to minimise the silica issue at the Oparure Quarry.

year: 2008

title: Māori diaspora: Being Māori on the Gold Coast

authors: Henderson, Eve Ngāwaiata

subjects: Māori

abstract: An estimated one in five Māori now live in Australia with the largest concentration on the Gold Coast. My research gives voice to the lived realities of the Māori diaspora and is informed by my own reflections as a first-generation Australian-born Māori and those of my whānau. Through discussion with whānau who either emigrated over to Australia as adults or were born and raised in Australia because of their parents’ emigration, in my thesis I shed light on constructions of identity and notions of belonging for Māori on the Gold Coast living on the traditional land of the Aboriginal and Torres Strait Islander Peoples. 

With an understanding of the entangled complexities on undertaking research on Māori living on the land of another Indigenous Peoples, I utilise both Kaupapa Māori and Indigenous Research paradigms as the foundation for this thesis. Using pūrākau  as method, with a storytelling approach, I had expected to be sitting with my whānau kanohi ki te kanohi, sharing food and laughs in the home. However, Covid-19 put a halt to my desired research approach. Despite this hurdle, I was able to collate and combine our shared stories to express what it is to be Māori on the Gold Coast through the utilisation of online spaces. Through my findings, I demonstrate that Māori on the Gold Coast articulate a range of ways to be Māori with diverse and hopeful views for the future. This challenges dominant Māori scholarship which often excludes and invisibilizes Māori experiences outside of Aotearoa, as if people cease to be Māori once they have left. 

This thesis adds to Indigenous diasporic discussions in communicating the fluidity of Māori identity. I argue that Māori have a connection to Aotearoa that is not necessarily tied physically to the whenua, nor bound to preconceptions and measures of history. Understanding our diaspora is essential for considering future implications for Indigenous solidarity, and for cultural growth and retention.

text: Māori diaspora: Being Māori on the Gold Coast An estimated one in five Māori now live in Australia with the largest concentration on the Gold Coast. My research gives voice to the lived realities of the Māori diaspora and is informed by my own reflections as a first-generation Australian-born Māori and those of my whānau. Through discussion with whānau who either emigrated over to Australia as adults or were born and raised in Australia because of their parents’ emigration, in my thesis I shed light on constructions of identity and notions of belonging for Māori on the Gold Coast living on the traditional land of the Aboriginal and Torres Strait Islander Peoples. 

With an understanding of the entangled complexities on undertaking research on Māori living on the land of another Indigenous Peoples, I utilise both Kaupapa Māori and Indigenous Research paradigms as the foundation for this thesis. Using pūrākau  as method, with a storytelling approach, I had expected to be sitting with my whānau kanohi ki te kanohi, sharing food and laughs in the home. However, Covid-19 put a halt to my desired research approach. Despite this hurdle, I was able to collate and combine our shared stories to express what it is to be Māori on the Gold Coast through the utilisation of online spaces. Through my findings, I demonstrate that Māori on the Gold Coast articulate a range of ways to be Māori with diverse and hopeful views for the future. This challenges dominant Māori scholarship which often excludes and invisibilizes Māori experiences outside of Aotearoa, as if people cease to be Māori once they have left. 

This thesis adds to Indigenous diasporic discussions in communicating the fluidity of Māori identity. I argue that Māori have a connection to Aotearoa that is not necessarily tied physically to the whenua, nor bound to preconceptions and measures of history. Understanding our diaspora is essential for considering future implications for Indigenous solidarity, and for cultural growth and retention.

year: 2021