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Item Thermal taster status: Temperature modulation of cortical response to sweetness perception(Elsevier Inc, 2021-03-01) Eldeghaidy S; Yang Q; Abualait T; Williamson A-M; Hort J; Francis STTemperature is known to impact taste perception, but its reported effect on sweet taste perception in humans is inconsistent. Here, we assess whether thermal taste phenotype alters the temperature modulation of the brains' response to sweet samples and sweet taste perception. Participants (n = 24 balanced for thermal tasters (TT) and thermal non-tasters (TnT), 25 ± 7 years (mean ± SD), 10 males) underwent a thermal taste phenotyping session to study responses to cooling and warming of the tongue using a thermode. In a separate session, functional Magnetic Resonance Images (fMRI) were collected during sweet samples (87 mM sucrose) delivery at two temperatures ('cold' (5 ± 2 °C) and 'ambient' (20 ± 2 °C)) and the perceived sweetness intensity rated.In the phenotyping session, TTs had heightened perceptual temperature sensitivity to cooling and warming of the tongue using a thermode compared to TnTs. Although there was no significant effect during the fMRI session, the fMRI response to the 'cold sweet' sample across all participants was significantly increased in anterior insula/frontal operculum and mid-insula compared to the 'ambient sweet' sample, likely to reflect the perceptual difference to temperature rather than taste perception. TTs showed significantly increased fMRI activation patterns compared with TnTs and an interaction effect between thermal taster status and sample temperature, with TTs showing selectively greater cortical responses to 'cold sweet' samples compared to TnTs in somatosensory regions (SI and SII).The increase in cortical activation in somatosensory cortices to the 'cold sweet' stimulus correlated with perceptual ratings of temperature sensitivity to the thermode. The results highlight the importance of investigating the effects of thermal taster phenotype across a range of temperatures representing the reality of consumer consumption to beverages.Item The mathematical modelling of caking in bulk sucrose : this thesis is presented as partial fulfillment of the requirements for the degree of Master of Engineering in Bio process Engineering at Massey University(Massey University, 2002) Billings, Scott WEver since the need for bulk transportation of sugar, there have been problems with the product caking during storage and transportation. This project was carried out in order to try and understand the mechanisms behind caking, and by mathematically modelling the system, to find the conditions needed to avoid caking, and to compare these to the observations and experiences made by those working in the industry. A thermal analysis monitor was used to determine if significant quantities of amorphous sucrose existed on the dried sugar, to support the amorphous recrystallisation caking mechanism. The level of amorphous sucrose was found to be less than 0.1%, so it was reasoned that any moisture contribution from such a small fraction, even given its tremendously hygroscopic nature would be negligible in contrast to that from the humidity caking mechanism. The water activity at which capillary condensation begins to occur significantly was then investigated and found to be 0.8. At this critical water activity, significant capillary condensation between particles occurs, forming liquid bridges between the particles and causing the bed to lump. If the lumped bed is then subjected to an environment with a lower water activity, over time the liquid bridges will begin to crystallise, creating solid bridges between the particles. These solid bridges have several times the mechanical strength of the liquid bridges and it is at this point that the bed is considered to be caked. The data from this experiment was then further used to build a relationship between the water activity of a bed, the radius of the liquid bridges formed by capillary condensation (Kelvin radius), and the resulting lumped strength of the bed. A model based on the caking of lactose was then adapted for sucrose and validated by testing conditions of heat and moisture migration through a packed bed, and the resulting effect on the strength of caking. Various model parameters were then adjusted between experimentally known values in order to obtain the best-fit possible for the experimental data. The data from the experiment and the model agreed well, however the temperature data did exhibit some scatter, possibly caused by insufficient grounding of the measuring device, making it susceptible to noise. The model was then used to build up a graph of the effect of initial water activity, cold and hot temperatures on the maximum water activity that a bed would reach at the cold surface. Using the critical water activity, this graph can be used to represent the limits at which sucrose of a certain condition can be stored and transported without the sucrose caking. This also opens paths for future research, as this will allow conditions created by the changing of process conditions such as temperatures and residence times within the driers, to be measured in terms of whether the end product will have a tendency to cake.Item Tissue-specific responses to water deficit in the New Zealand xerophytic tussock species Festuca novae-zelandiae : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at Massey University, Palmerston North, New Zealand(Massey University, 2005) Clark, Gregory ThomasFestuca novae-zelandiae (Hack.) Cockayne is an endemic New Zealand perennial tussock forming grass of the family Poaceae. Morphologically F. novae-zelandiae exhibits a number of leaf adaptations associated with dehydration postponement as reflected in the climatic distribution of this species and its occurrence as a physiognomic dominant grass in semi arid short-tussock grasslands. Biochemical studies into the drought tolerance of this species have indicated the occurrence of tissue specific responses with respect to abscisic acid (ABA) and proline accumulation and protein turnover suggestive of a preferential protection of the tiller base and associated meristematic zones at the expense of lamina tissues. Further tissue specific biochemical responses to water-deficit stress in F. novae-zelandiae have been investigated. Changes in water-soluble carbohydrates (WSC) were monitoured over a 49-day dry-down period (decline in soil water content from 30% to 4%) in consecutive leaf segments comprising the leaf base (meristem region), elongation zone, the enclosed and exposed lamina, as well as basal sheath segments from the two next oldest leaves. In fully hydrated leaf tissues polymers of fructose (fructans) were the main WSC present and were mainly low molecular weight fructans of the inulin and neokestose series with the average degree of polymerization (DP) of fructan pools from 6 to 9. The highest fructan concentrations were present towards the leaf base. Fructan concentrations decreased over the course of the dry-down, although remained significantly higher in the meristem region of the tiller base with respect to any other tissue, until tissue water content fell below 45%. By day 49 of the dry-down period, the average DP of the fructan pool in tissues was from 3 to 5. Sucrose content increased in each tissue during the course of the dry-down, and was highest at the leaf base, where a concentration of 200 µmol g-1 dry weight was measured after 49 days of dry-down. The negative correlation between fructan and sucrose content, which indicates an inter-conversion dependent on tissue water content, suggests that, in this specises, fructans serve as a carbohydrate storage pool, while sucrose stabilises the meristem during extreme water deficit.