Papers by Jason Hindmarsh
The Journal of Supercritical Fluids, 2016
The Journal of Supercritical Fluids, 2014
ABSTRACT Carbon-13 chemical-shift imaging (CSI) was used to study the distribution of CO2 in gree... more ABSTRACT Carbon-13 chemical-shift imaging (CSI) was used to study the distribution of CO2 in green pine sapwood that was partially dewatered by a process in which CO2 was cycled between the supercritical fluid and gas phases. Proton magnetic resonance imaging (MRI) was used to characterise the corresponding distribution of water. The CSI experiment showed strongest signals from cells with weakest proton MRI signals. This was consistent with a mechanism in which latewood bands provide pathways for supercritical CO2 to penetrate into the interior of a specimen. Supercritical CO2 also penetrated earlywood exposed on surfaces of the specimen.
LWT - Food Science and Technology, 2015
ABSTRACT Modelling the thermal processing of food matrices incorporating microorganisms requires ... more ABSTRACT Modelling the thermal processing of food matrices incorporating microorganisms requires heat stress death kinetics. It is demonstrated that proton nuclear magnetic resonance (1H NMR) is a rapid means of quantifying the heat stress death kinetics of a human probiotic bacterium (Bifidobacterium animalis subsp. lactis DR10™ or strain HN019). It was found that the ratio of the methylene (CH2) resonance at 1.2 ppm to the methyl (CH3) resonance at 0.9 ppm signal intensity as observed by 1H NMR was directly proportional to the percentage of death of a population of cells during heat stress. The derived death kinetic rate constants for a series of heating temperatures showed excellent correlation to the Arrhenius equation. The method has several advantages over existing methods for measuring bacterial death kinetics, as it can be carried out in situ with minimal preparation and without the addition of chemical agents.
The Journal of Physical Chemistry C, 2007
ABSTRACT We present the direct observation of surface-activated ice nucleation in undercooled suc... more ABSTRACT We present the direct observation of surface-activated ice nucleation in undercooled sucrose solution droplets. Video images of freezing sucrose solution droplets while suspended at the junction of a thermocouple show two distinctive nucleation mechanisms for a droplet. These are at the surface and in the volume of the droplet. Analysis of the temperature-dependent nucleation data support the conclusion that they are separate nucleation mechanisms. Increased sucrose concentration caused surface nucleation to become less favorable. The results are not entirely described by either the two-dimensional or the capillary theories of surface nucleation but do suggest that surface-activated nucleation is a pseudo-heterogeneous process.
Journal of Nutrition, 2014
Dietary actinidin influences the extent to which some dietary proteins are digested in the stomac... more Dietary actinidin influences the extent to which some dietary proteins are digested in the stomach, and it is hypothesized that the latter modulation will in turn affect their gastric emptying rate (GE). In this study, the effect of dietary actinidin on GE and gastric digestion of 6 dietary protein sources was determined in growing rats. Each dietary protein source [beef muscle, gelatin, gluten, soy protein isolate (SPI), whey protein isolate, and zein] was included in 2 semisynthetic diets as the sole nitrogen source. For each protein source, 1 of the 2 diets contained actinidin [76.5 U/g dry matter (DM)] in the form of ground freeze-dried green kiwifruit (Actinidia deliciosa cv. Hayward), whereas the other diet contained freeze-dried gold kiwifruit (Actinidia chinensis cv. Hort16A), which is devoid of actinidin (3.4 U/g DM). For both diets, dietary kiwifruit represented 20% of the diet on a DM basis. The real-time GE was determined in rats gavaged with a single dose of the diets using magnetic resonance spectroscopy over 150 min (n = 8 per diet). Gastric protein digestion was determined based on the free amino groups in the stomach chyme collected from rats fed the diets (n = 8 per diet) that were later killed. GE differed across the protein sources [e.g., the half gastric emptying time (T(½)) ranged from 157 min for gluten to 266 min for zein] (P < 0.05). Dietary actinidin increased the gastric digestion of beef muscle (0.6-fold), gluten (3.2-fold), and SPI (0.6-fold) and increased the GE of the diets containing beef muscle (43% T(½)) and zein (23% T(½); P < 0.05). There was an inverse correlation between gastric protein digestion and DM retained in the stomach (r = -0.67; P < 0.05). In conclusion, dietary actinidin increased gastric protein digestion and accelerated the GE for several dietary protein sources. GE may be influenced by gastric protein digestion, and dietary actinidin can be used to modulate GE and protein digestion in the stomach of some dietary protein sources but not others.
Journal of Nutrition, 2013
A rapid technique allowing the accurate determination of stomach emptying rate (SER) would be use... more A rapid technique allowing the accurate determination of stomach emptying rate (SER) would be useful for understanding the process of digestion. The development of a rapid magnetic resonance spectroscopy (MRS) technique based on the marker AlCl 3 -6H 2 O (Al-MRS) to determine the real-time SER of foods in a rat model is described. Experiments were conducted to establish several variables for the Al-MRS technique and validate the technique against the traditional serial slaughter method. Overnight feed-deprived rats (n = 8/treatment) were gavaged with a single dose of a semisynthetic meat or soy bean protein isolate-based diet containing the marker AlCl 3 -6H 2 O in acidified water (pH 2). Rats were either placed individually in the magnetic resonance spectrometer to estimate the SER from the real-time decrease in the aluminum (Al) signal or killed and their stomach chyme collected at prescribed times postprandially to determine the SER.
Langmuir, 2005
Presented is a novel application of pulsed field gradient (PFG)-NMR to the analysis of intercompa... more Presented is a novel application of pulsed field gradient (PFG)-NMR to the analysis of intercompartment exchange and the inner compartment droplet size distribution of a W/O/W multiple emulsion. The method involves monitoring the diffusional behavior of different components of the emulsion. Pfeuffer et al. [Pfeuffer, J.; Flogel, U.; Dreher, W.; Leibfritz, D. NMR Biomed. 1998, 11(1), 19-31.] 1 and Price et al. [Price, W. S.; Barzykin, A. V.; Hayamizu, K.; Tachiya, M. Biophys. J. 1998, 74(5), 2259-2271.] 2 proposed methods to extend Kä rger's PFG-NMR model of exchange between two compartments to accommodate spherical inner compartments. Each model enables the prediction of the oil membrane permeability, the inner compartment volume fraction, and a representation of the inner compartment droplet size distribution. The models were fitted to PFG-NMR experimental data of W/O/W emulsions. The Pfeuffer et al. model provided the best description of the observed experimental data. Predicted values of permeability and swelling were consistent with those reported in the literature for W/O/W emulsions. The addition of sorbitol to either the inner or outer water compartment resulted in an increase in the oil membrane permeability.
Journal of the Science of Food and Agriculture, 2012
Proton nuclear magnetic resonance (NMR)-based metabonomics has only recently been applied to nutr... more Proton nuclear magnetic resonance (NMR)-based metabonomics has only recently been applied to nutritional research. The limitation of any analytical technique is its sensitivity in detecting the smallest variation. Alterations in nutrition often produce only subtle metabolic modulations. The objective of this study was to determine if NMR-based metabonomics could detect variations in the metabolic profile of urine from pigs digesting either native casein (NC) or the same casein that had been enzymatically hydrolysed (EHC). NMR permits simultaneous detection of a large number of metabolites, thus allowing detection of unanticipated metabolic fluctuations that may otherwise have gone undetected with the use of only targeted analysis. Partial least squares discriminant analysis identified significantly (P < 0.05) higher urinary excretions of leucine, valine, taurine and glycine by pigs on the EHC-based diet. NMR-based metabonomics is a sensitive method that can uncover unanticipated metabolic changes brought about by physicochemical changes to the feedstock (i.e. hydrolysis). The data show a lower efficiency of retention by the kidney of some amino acids following ingestion of a hydrolysed protein.
Journal of Food Engineering, 2006
The freezing of single 2 mm diameter droplets of coffee solution in cold moving air down to À15°C... more The freezing of single 2 mm diameter droplets of coffee solution in cold moving air down to À15°C has been studied for 10-50 wt.% coffee solutions in a novel temperature monitoring apparatus and in a similar device installed within a nuclear magnetic resonance (NMR) spectrometer. Heat transfer measurements and modelling confirmed that droplet internal temperatures were almost uniform (low Biot number regime), which was consistent with the microstructures generated. Fundamental parameters which could be extracted from the data included nucleation temperature, degree of recalescence, freezing temperature, and extent of freezing and freeze concentration. The mode of nucleation (spontaneous or forced) was observed to depend on concentration, cooling rate and air temperature.
Journal of Food Engineering, 2007
The surface microstructure will determine a number of functional properties of a frozen powder su... more The surface microstructure will determine a number of functional properties of a frozen powder such as stickiness and flowability. In this study, cryo-SEM images were used to observe the influence of various solutes and freezing conditions had on the internal and surface microstructure of frozen droplets. A single droplet freezing method was used to simulate the physical changes taking place during a spray-freezing process. Sucrose solutions with added anhydrous milk fat (AMF) and whey protein concentrate (WPC) were investigated. The level of supercooling (nucleation temperature) significantly influenced the final microstructure of a frozen droplet. The greater the supercooling level, the larger the proportion of the droplet that has a fine cellular ice crystal structure. It was observed that a sucrose layer formed at the outer surface of sucrose solution droplets upon freezing. This could be the product of water evaporation or redistribution of sucrose during freezing. The concentrated sucrose layer showed a tendency to increase in thickness when nucleation was forced at the droplet surface. The presence of AMF and WPC at a high freezing rate, with a high droplet supercooling inhibited the formation of the surface sucrose layer, whereas at a low freezing rate with low droplet supercooling, a sucrose layer was formed with AMF fat globules and or WPC protein aggregates distributed within it. The inhibition of the formation of the sucrose surface layer could reduce the stickiness and increase the flowability of the frozen powder. Whereas, the redistribution of fat to the surface may also be a means of reducing the fat content of a frozen food powder without effecting its sensory impact. The results illustrate that both the composition and the freezing conditions will influence the functional properties of spray-frozen food powders.
Journal of Crystal Growth, 2005
A simple apparatus for observing the dendritic growth in transparent solutions at high undercooli... more A simple apparatus for observing the dendritic growth in transparent solutions at high undercoolings is described. This method involves the suspension of a droplet on the junction of a thermocouple. With this method it is possible to measure the ice dendrite growth velocity and tip radius to the limit of stable dendritic growth in sucrose solutions. Good agreement was observed with previous growth velocity data. Analysis with the Lipton, Kurtz and Trivedi (LKT) dendritic growth model showed that at high undercoolings the dendritic growth in sucrose solutions becomes predominately thermally and kinetically controlled, whereas the kinetic growth becomes increasingly diffusion and viscosity limited with increasing undercooling and melt solute concentration. The results supported previously proposed changes to the LKT model to accommodate high undercoolings and changing melt diffusivity and viscosity. r
Journal of Colloid and Interface Science, 2004
Various nuclear magnetic resonance (NMR) techniques were used to monitor the freezing behaviour o... more Various nuclear magnetic resonance (NMR) techniques were used to monitor the freezing behaviour of suspended 2-mm-diameter drops. The drops were composed of hydrocarbon oils emulsified in either water or water/sucrose mixtures. As such they were good model systems for the study of spray freezing, sharing structural similarities with potential products such as ice cream. In particular, simple 1H NMR spectroscopy was used to monitor and individually quantify the freezing or solidification behaviour of the various constituent species of the drops. In addition, the effect of freezing on the emulsion droplet size distribution (and hence emulsion stability) was also measured based on NMR self-diffusion measurements. The effect of freeze/thaw cycling was also similarly studied. The nucleation temperature of the emulsion droplets was found to depend on the emulsion droplet size distribution: the smaller the droplets, the lower the nucleation temperature. Emulsion droplet sizing indicated that oil-in-sucrose-solution emulsions were more stable, showing minimal coalescence, whereas oil-in-water emulsions showed significant coalescence during freezing and freeze/thaw cycling.
Journal of Agricultural and Food Chemistry, 2006
Liposomes were prepared from a milk fat globule membrane (MFGM) phospholipid fraction and from so... more Liposomes were prepared from a milk fat globule membrane (MFGM) phospholipid fraction and from soy phospholipid material using a high-pressure homogenizer (Microfluidizer). The liposomes were characterized in terms of general structure, phase transition temperature, lamellarity, bilayer thickness, and membrane permeability. The liposomes prepared from the MFGM fraction had a significantly higher phase transition temperature, thicker membrane, and lower membrane permeability. These differences were attributed to different phospholipid compositions of the MFGM and soy phospholipid fractions.
International Journal of Heat and Mass Transfer, 2005
ABSTRACT Nuclear magnetic resonance (NMR) was used to validate a simple model (based on the Stefa... more ABSTRACT Nuclear magnetic resonance (NMR) was used to validate a simple model (based on the Stefan number) for predicting the solid fraction formed during the recalescence of a supercooled liquid drop following nucleation. Experimental data were obtained using standard NMR techniques to measure the temporally resolved solid fraction of suspended drops following externally initiated nucleation. The results showed good agreement with the model predictions and also demonstrated the effectiveness of basic NMR techniques for obtaining such non-invasive data for the verification of solidification models.
Food Research International, 2009
High-protein snack bars (protein bars) contain high-quality protein, sugars and other low molecul... more High-protein snack bars (protein bars) contain high-quality protein, sugars and other low molecular weight polyhydroxy compounds (PHCs), high-energy confectionary fats, and a minimum of water (water activity ≤ 0.65). The consequence of the intimate mixing of these components in protein bars is that they can react together, creating sensory characteristics that are unacceptable to consumers.. This study examined the changes occurring in a model protein bar during storage for 50 days at 20 °C.
Food Research International, 2010
This study examined model protein bars made with whey protein isolate (WPI) or calcium caseinate ... more This study examined model protein bars made with whey protein isolate (WPI) or calcium caseinate and stored at 20 °C for 50 days. WPI bars remained very soft and, throughout storage, confocal micrographs showed a continuous matrix containing soluble protein and increasing quantities of glucose crystals. In contrast, calcium caseinate bars had a firm texture within 1−5 days of manufacture (fracture stress 199 ± 16 Pa) and hardened progressively during storage (final fracture stress 301 ± 18 Pa). Electrophoresis showed no evidence of covalent protein aggregation, but there were substantial changes in microstructure over the first day of storage, resulting in segregation of a protein phase from a water−glucose−glycerol phase. Proton nuclear magnetic resonance ( 1 H-NMR) relaxometry and nuclear Overhauser effect spectroscopy (NOESY) experiments showed that water migration away from protein towards glucose and glycerol occurred 10−18 h after manufacture, lowering the molecular mobility of protein. Phase separation was probably driven by the high osmotic pressure generated by the glucose and glycerol. These results confirm that the hardening of protein bars is driven by migration of water from protein to glucose and glycerol, and microstructural phase separation of aggregated protein.
Experiments in Fluids, 2005
ABSTRACT Magnetic resonance (MR) methods are used to provide both rapid real-time dispersion and ... more ABSTRACT Magnetic resonance (MR) methods are used to provide both rapid real-time dispersion and spatially resolved velocity measurements within suspended drops undergoing freezing. Two-mm-diameter drops composed of water, sucrose solution, oil-in-water emulsion or oil-in-sucrose-solution emulsion drops are thus studied. Dispersion measurements have been shown to give valuable insights into the transport processes and solidification behaviour of the freezing drops. It was possible to detect drop nucleation/recalescence, rupture and solution freeze concentration. Limited convection of unfrozen material, due to crystal growth, was detected. The spatial distribution of the velocity within freezing drops revealed the rotation of the water drops but not of drops composed of the other materials studied. Rapid increases in velocity were observed following nucleation, which were dampened down during subsequent heat-transfer-governed droplet freezing.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004
Measurement of the self-diffusion of constituent materials in highly super-cooled liquids mixture... more Measurement of the self-diffusion of constituent materials in highly super-cooled liquids mixtures was achieved using a simple droplet suspension technique combined with pulsed field gradient (PFG) nuclear magnetic resonance (NMR). The self-diffusion coefficients of both water and sucrose were determined over a range of concentrations from 10-50% (w/w) sucrose, and for temperatures down to −20 • C. The resultant self-diffusion data were in reasonably good agreement with the Vogel-Tamman-Fulcher (VTF) equation for both water and sucrose. The suspended droplets were subsequently frozen and the self-diffusion data for water used to estimate the concentration of the unfrozen fraction of the droplets.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2012
ABSTRACT Nuclear magnetic resonance (NMR) measurements were shown to be able to non-invasively qu... more ABSTRACT Nuclear magnetic resonance (NMR) measurements were shown to be able to non-invasively quantify the microstructure formed following freeze-concentration of (2 mm diameter) drops composed of a range of aqueous solutions (sucrose, fructose, coffee solution and NaCl). Specifically the surface-to-volume ratio and tortuosity of the resultant porous ice structures were uniquely quantified using pulsed field gradient (PFG) NMR measurements of restricted self-diffusion of the remaining unfrozen solution. These measurements were performed as a function of both solute concentration and freezing temperature. Validation was achieved via random walk self-diffusion simulations on SEM micrograph images of fracture planes through selected drops. Reasonably good agreement was produced between the NMR measurements and these simulations. A rapid version of the PFG measurement method was subsequently used to enable quantitative microstructure evolution measurements during the drop freezing process, as well as during subsequent ripening of the porous ice structure.
Chemical Engineering Science, 2004
Magnetic resonance imaging (MRI) is used to provide spatially resolved structural and chemical co... more Magnetic resonance imaging (MRI) is used to provide spatially resolved structural and chemical composition characterisation of droplets undergoing freezing. To this end, MRI is applied to a 2 mm diameter sucrose solution droplet, suspended in cold air. During the consequential solidiÿcation of the droplet, the spatial location of nucleation and the crystal growth of the droplet are followed using non-invasive two dimensional (2D) images; these are produced using the fast MRI technique, RARE. This is able to both quantify crystal growth rates, as well as the unfrozen liquid mass fraction for the optically opaque freezing droplets. Such information is of major interest in the veriÿcation of models describing the freezing of such droplets. The spatial re-distribution of the sucrose solute as a consequence of freezing is monitored using MR 1D chemical shift proÿling. The formation of a concentrated sucrose layer at the droplet surface was detected. ?
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Papers by Jason Hindmarsh