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    Recovery and characterisation of quinoa protein via neutral to alkaline extraction: protein profiles and heat-induced aggregation behaviour
    (Elsevier B V, 2025-10-03) Cui H; Roy D; Li S; Loo TS; Guo Q; Ye A; Marangoni AG
    This study investigated the impact of extraction pH (pH 7–11) on the yield, composition, protein profile and properties of quinoa protein isolate (QPI), including solubility, interfacial tension and heat-induced aggregation. Extraction pH considerably influenced protein yield, purity and solubility, with alkaline conditions promoting higher protein yield (from 27.4 % to 39.5 % as extraction pH increased from pH 7 to pH 11) but lower purity (from 89.7 % to 85.1 %) owing to the co-precipitation of carbohydrates. Sodium dodecyl sulphate–polyacrylamide gel electrophoresis analysis combined with liquid chromatography with tandem mass spectrometry revealed major protein profile in quinoa protein, confirming the abundance of 11S globulin. Moreover, extraction pH affected the solubility over a broad range of pH, interfacial properties and heat-induced aggregation behaviour of QPI. QPI extracted at pH 9 exhibited better solubility and better interfacial tension reduction capability but lower heat stability compared with QPI extracted at pH 11. Results from this study provided useful information and essential insights into the utilisation of quinoa proteins in various food applications.
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    Shelter aggregations, social behaviour, and seasonal plasma corticosterone levels in captive and wild Duvaucel's geckos, Hoplodactylus duvaucelii : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Albany, New Zealand
    (Massey University, 2010) Barry, Manuela
    The development of effective conservation management strategies is reliant on a thorough understanding of the basic biology and life history of the species of concern. New Zealand’s endemic herpetofauna species have undergone severe range contractions since human arrival due to habitat modifications and predation by introduced mammalian pests. Current conservation management practice involves the eradication of such pests as well as the restoration of habitat involving native species reintroductions. Albeit these conservation attempts, detailed information on physiology, ecology and behaviour of most New Zealand’s lizards is scarce, including the Duvaucel’s gecko (Hoplodactylus duvaucelii). In recent years, several H. duvaucelii have been translocated to islands within their historical range as part of restoration projects and in 2006/7 a captive breeding‐for‐release programme has been established. This provided an excellent opportunity to explore some fundamental aspects of H. duvaucelii’s basic physiology and behavioural ecology. I investigated seasonal plasma corticosterone concentrations of captive and wild geckos in relation to several physiological and ecological factors to enhance our understanding of natural fluctuations of seasonal hormone patterns. Such information can aid in evaluating stress related changes in hormone patterns of individuals and populations, which is particularly relevant for the captive management. I compared plasma steroid hormone patterns of captive geckos from a breeding colony with their wild source population over several seasons to assess whether captive lizards suffered from chronic stress, which could compromise their wellbeing and the fitness of future offspring. Further, I explored several aspects of H. duvaucelii’s social behaviour, including diurnal shelter aggregations, scent communication and social interactions using experimental and exploratory studies on captive and wild geckos. The hormone study provided evidence that H. duvaucelii are suitable for captive breeding as they seem to have adapted well to captivity and did not show a chronic elevation of stress hormone levels. Moreover, my research has shown that H. duvaucelii are essentially social lizards that form shelter aggregations year‐round. Adults showed a high tolerance of juveniles in their diurnal shelters and geckos were able to detect and discriminate scents from conspecifics in several social contexts. These social traits as well as the year‐round occurrence of male‐female pairs combined with H. duvaucelii’s life history traits suggest that this species may possess a social system of high complexity. In conclusion, this dissertation provides a foundation for future research and delivers the first insight into the social behaviour and basic endocrinology of this New Zealand endemic lizard.
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    The effect of heat on the structure and aggregation behaviour of bovine B-lactoglobulins A, B and C : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biochemistry at Massey University
    (Massey University, 1998) Manderson, Gavin Andrew
    The bovine milk protein β-lactoglobulin (BLG) possesses a thiol group which becomes solvent exposed at elevated temperatures, leading to the formation of disulphide-linked milk protein aggregates. This phenomenon is of interest to the dairy industry because milk is heat-treated in many modern processes. This study is concerned with how the structure of BLG is altered during and as a consequence of heat treatment and how aggregates are formed. Bovine BLG exhibits genetic polymorphism and the A, B and C variants, present in New Zealand milks, differ in their susceptibilities to heat-induced structural change and aggregate formation, and their response to heat treatment is examined in the present study. This study used the following techniques: near and far UV CD, intrinsic protein fluorescence, hydrophobic probe fluorescence, thiol group solvent-exposure and both native-PAGE and SDS-PAGE. Spectroscopic and thiol exposure results suggest that the tertiary structure of BLG is altered during and as a consequence of heat treatment and that the amount of β-sheet in this protein does not alter appreciably as a consequence of heat treatment. PAGE results indicate that BLG forms a mixture of non-covalently-linked and disulphide-linked aggregates during heating, and that disulphide-linked dimers in particular are associated into larger non-covalently-linked aggregates. These non-covalently-linked aggregates are intermediates and large disulphide-linked aggregates are the end product of the BLG aggregation pathway. β-Lactoglobulin A forms aggregates, particularly large disulphide-linked aggregates, more slowly than BLGs B and C. Spectroscopic and thiol availability results suggest that the "intrinsic thermostability" of BLG C is appreciably greater than that of BLG B, which is slightly greater than that of BLG A. Furthermore, the extent of "irreversible structural change" in molecules of BLG C which occurs as a consequence of heat treatment is less than that in molecules of BLG A, which is less than that in molecules of BLG B. In the case of BLGs A and B this reflects the slower rate at which aggregates of BLG A form compared to that of BLG B. The present study has advanced the understanding of the BLG aggregation mechanism and how the A, B and C variants differ in their response to heat treatment.