Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

Settings

Subject: search.filters.subject.Absorption and adsorption

Search Results

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    The effect of milk processing on protein digestion and amino acid absorption in the gastrointestinal tract of pigs as a model human : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Sciences at Massey University, Manawatū, New Zealand
    (Massey University, 2024-06-19) Ahlborn, Natalie Gisela Marlis
    Globally, milk is processed using heat and homogenisation to improve food safety and extend shelf life. These common processing techniques can alter the native structures present in milk, including protein structures. However, the impact of these processing-induced changes on the digestion of milk protein and subsequent absorption of amino acids in the human body is not yet fully understood. The overall objective of this research was to understand how heat treatment and homogenisation affect milk protein coagulation and digestion in the stomach, and to investigate how changes to gastric coagulation (curd formation) influence amino acid (AA) absorption in the small intestine and AA concentrations in blood circulation. Due to the limited accessibility of the human gastrointestinal tract, pigs were used as a model of the human. An initial study using raw bovine (cow), caprine (goat), and ovine (sheep) milk established the role of gastric curd formation in small intestinal AA absorption in piglets at a single postprandial time point. Specifically, differences in the retention of AA in the gastric curd were responsible for differences in the small intestinal AA absorption across milk of different species. A separate study using bovine milk as a milk model was then conducted to determine the effect of heat treatment and homogenisation on the kinetics of milk protein digestion and small intestinal AA absorption. The selected processing treatments were pasteurisation, ultra-high temperature treatment (UHT), and homogenisation. Raw milk was included as a comparator. In the stomach, heat treatment and homogenisation altered the strength and structure of the curd formed during gastric digestion, which in turn affected both milk protein hydrolysis and the rate of AA entering the small intestine. Differences in the release of digested protein and AA into the small intestine were reflected in the kinetics of AA absorption of the processed milk types. For example, UHT milk had both a faster rate of AA entering the small intestine and a faster rate of AA absorption. Processing also altered the appearance of some AA in blood circulation; however, these differences were not directly reflective of the differences observed in their small intestinal absorption kinetics. In conclusion, this PhD research demonstrated that the rate of small intestinal AA absorption was modulated by gastric curd formation, indicating that milk processing could be used as a strategy to modulate protein digestion and AA absorption in the gastrointestinal tract.
  • Thumbnail Image
    Item
    Metal-organic frameworks for selective gas separation : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatū, New Zealand
    (Massey University, 2019) Taheri Qazvini, Omid
    With an ever increasing need for a more energy-efficient and environmentally benign procedure for gas separation, adsorbents with tailored structures and tunable surface properties are in high demand. Metal–organic frameworks (MOFs), constructed from metalcontaining nodes connected by organic bridges, are such a new type of porous materials. They are promising candidates as adsorbents for gas separations due to their large surface areas, adjustable pore sizes and controllable properties, as well as acceptable thermal stability. However, the bottleneck in this context is that MOFs are expensive to be fabricated and majority of them are not stable in harsh environments, which are often required by industrial processes. In this thesis, we introduce three families of metal-organic frameworks with exceptional gas separation performance for a variety of different gas mixtures separation. Their unique separation performances are well supported by isotherm measurement, X-ray crystallography, DFT calculations, and breakthrough test. These MOFs are all readily synthesizable by inexpensive precursor and highly stable at extreme conditions.
  • Thumbnail Image
    Item
    A study of the digestion of protein in humans using ileal and faecal assays : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in biochemistry at Massey University
    (Massey University, 1989) Rowan, Angela Marie
    A study was conducted with 12 adult human subjects including six ileostomates, to determine the digestibility of protein in a single mixed diet. Significant (P<0.05) differences were found between ileal and faecal amino acid digestibility values for most amino acids (histidine, arginine, aspartate, threonine, serine, glycine, proline, valine, leucine, phenylalanine, methionine, cysteine and tryptophan). The ileal digestibility coefficients ranged from 71.5 to 93.6% for glycine and lysine, respectively, whereas the faecal values ranged from 77.9 to 94.7% for glycine and leucine, respectively. The absolute differences between the methods ranged from 0.2 to 15.0% units for alanine/isoleucine and glycine respectively, and the average of the differences was 3.7% units. The ileostomised growing pig (25kg) was investigated as a model animal to allow more routine determination of the ileal digestibility of protein in human foods, and good agreement was found between the species for apparent ileal amino acid digestibility. There were no significant differences between the two species for the apparent ileal amino acid digestibilities of amino acids, except for lysine, glutamate, proline and alanine. The endogenous flows of amino acids at the terminal ileum were determined in both species, following consumption of a single protein-free meal. The amino acid compositions of the protein flows were similar for pigs and humans, with significant differences only being found for histidine, threonine, alanine, valine and methionine. The endogenous flows were used to correct apparent coefficients to give true estimates of digestibility. The latter values indicated near complete absorption of the dietary amino acids for the human subjects and growing pigs. When the interspecies comparison was based on the true digestibility values, there were only significant differences for the amino acids glutamate, phenylalanine, cysteine and methionine. The absolute differences between the mean amino acid digestibility values for each species were smaller for true coefficients than for the apparent values. The daily excretions of deoxyribonucleic acid (DNA) and diaminopimelic acid (DAP) were determined to indicate the levels of bacteria present at the terminal ileum and in the faeces of pigs and humans. There were higher levels of both of these marker compounds in human faeces samples than in ileal digesta. The opposite was observed for DNA in the pig, while the levels of DAP were similar at the two sites. The digestibility of fibre was also determined to indicate the extent of bacterial activity at these sites, and the values were greater in the faeces than in the ileostomy output of both species.
  • Thumbnail Image
    Item
    Adsorption-desorption characteristics of phenoxyacetic acids and chlorophenols in a volcanic soil : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Process and Environmental Technology Department at Massey University, Palmerston North, New Zealand
    (Massey University, 1994) Susarla, Sridhar
    A study on the adsorption and desorption behaviour of 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 2,4-dichlorophenol (2,4-DCP), 2,4,5-trichlorophenol (2,4,5-TCP) and para-chloro-ortho-cresol (PGOC), found in high concentrations in a New Zealand landfill. Volcanic soil with an organic matter content of 8.7% was used as adsorbent. Results of studies to determine the equilibrium sorption behaviour for each chemical showed the adsorption data for both phenoxyacetic acids and chlorophenols could be described by a Freundlich-type isotherm equation, the adsorption capacity followed the order: 2,4,5-T > MCPA > 2,4-D > 2,4,5-TCP > PCOC > 2,4-DCP at all pH and temperature values. Sorption capacity decreased with increasing pH and temperature; the heat of adsorption values indicating chemicals were adsorbed either by physical or hydrogen bonding to the soil surface. Results show only 2-4% of the total surface was occupied indicating chemical adsorption to specific sites present in the soil organic matter. The desorption results indicate isotherm parameters were dependent on the amount of each chemical adsorbed onto the soil. A linear relationship was developed to obtain the desorption parameters from the adsorption isotherm parameters. Desorption experimental results reveal that all the solutes adsorbed could not be desorbed, indicating a fraction of the chemical was resistant to desorption. A modified Freundlich-type equation described the competitive equilibrium adsorption and desorption of 2,4-D-MCPA, 2,4-D-PCOC and MCPA-PCOC mixtures. The model incorporated competition coefficients and was found to fit measured data, satisfactorily. The competition coefficients were linearly related to the initial concentration of the solutes in case of adsorption, and on the amount of chemical adsorbed for desorption. The results showed that the adsorption capacity of each solute decreased by about 8-12% in presence of the other competing solutes. However, in case of MCPA, the capacity decreased by 31% in the presence of 2,4-D. The desorption results reveal that 2,4-D and MCPA desorbed to a lesser extent in the bicomponent system compared to the corresponding single solute system. Similarly, the desorption of PCOC was less in the presence of 2,4-D than of MCPA compared to single solute system. A spinning basket reactor determined the kinetics of sorption for phenoxyacetic acids and chlorophenols. The film-mass transfer coefficients determined from the initial uptake rate data for the first 45 seconds, while the surface diffusion coefficients were obtained by fitting the experimental results with a homogeneous surface diffusion model solution. The desorption diffusion coefficients were found to be of the same order of magnitude as those of adsorption diffusion coefficients. The bicomponent surface diffusion coefficients were found to be slightly smaller (less than 10%) than single solute surface diffusion coefficients and this was due to competition between the solutes. A surface diffusion model based on equilibrium sorption, film-mass transfer and surface diffusion coefficient along with dispersion was used to predict the soil column data. All the parameters in the model were determined from independent experiments or calculated from literature correlations. The results from the column studies indicate that an increase in the concentration and flow rate resulted in the solutes moving faster in the column. A significant tailing of the chemical was observed at low concentrations for all the solutes. The results indicate that sorption played a dominant role in the transport of chemicals in columns. The breakthrough and elution for phenoxyacetic acids was in the order 2,4-D > MCPA > 2,4,5-T. For chlorophenols the order was: 2,4-DCP > PCOC > 2,4,5-TCP. The HSDM also used to predict the adsorption and desorption of bicomponent mixtures and the results indicated that the breakthrough and elution occurred earlier than in single solute systems. The order of breakthrough and elution was PCOC > 2,4-D > MCPA. To conclude, this thesis presents a detailed investigation of the adsorption and desorption characteristics of phenoxyacetic acids and chlorophenols for single and dual component systems in a volcanic soil. This study has identified the mechanisms and processes responsible for the leaching of the chemicals and can be used in remediation of a contaminated soil.
  • Thumbnail Image
    Item
    Biosorption and leaching of heavy metals from activated sludge applied to soil : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2002) Mahenthiran, Pushpalatha
    Accumulation of heavy metals in sewage sludge and soil and their subsequent movement to ground water and surface water are major environmental issues. Cadmium (Cd), copper (Cu), zinc (Zn), nickel (Ni) and chromium (Cr) are the most commonly occurring sludge-borne heavy metals in New Zealand. The potential toxicity of these heavy metals depends more on their availability and mobility than on their total content. This study examined the adsorption-desorption and potential leachability of these heavy metals in sewage sludge and a volcanic soil. Results of adsorption - desorption experiments using Cd, Cu, Zn and Ni showed that activated sewage sludge sorbed Cd, Cu and Zn more effectively than Ni. Adsorption capacities of Cd, Cu and Zn were 35.7-44.8, 14.1-26.4 and 57.5-59.5 mg/g biomass, respectively. The affinity of activated sewage sludge with Ni was very low thereby no further isotherm study was carried in Ni. Biosorption increased with increases in pH. Adsorption capacity also increased with increases in initial metal ion concentration but the adsorption yield decreased. Chloride ion concentration (0.145 N) had a more significant effect on the reduction of adsorption of Cd than on the reduction of the adsorption of either Cu or Zn. A desorption study was carried out using deionized water, 0.1 N Na2SO4,0.1 N K2SO4,0.1 M Na citrate, and 0.1 M Na2CO3 solutions and the results showed that Zn desorbed more in every desorbing agent. Results of the study of the adsorption behaviour of Zn in volcanic Egmont soil in the presence of phosphate showed an increase in adsorption of Zn and the presence of nitrate did not show any significant difference in adsorption. Both 500 and 1000 mg/kg phosphate levels reduced the water-soluble Zn in volcanic Egmont soil remarkably. The desorption study showed that more Zn was desorbed with 0.1 M KNO3 than with deionized water and 0.1 M KH2PO4. An in situ leaching study was carried out in volcanic Egmont soil using Zn amended sewage sludge and inorganic Zn as Zn sources and soil columns were pretreated with nitrate and phosphate anions. More Zn leached from inorganic Zn applied soil columns than from Zn amended sewage sludge applied soil columns. There was no substantial difference in the amount of Zn leached between nitrate and phosphate treated columns. Determination of total acid digestible Zn in sewage sludge and inorganic Zn applied soils showed a greater accumulation of Zn in 0-10 cm depth. More Zn moved to the lowest (25-32 cm) depth in the nitrate treated inorganic Zn applied soil column and less Zn moved to the lowest (25-32 cm) soil depth in the phosphate treated sewage sludge applied column. Fractionation of Zn in Zn amended sewage sludge showed that most of the fractions of Zn were in water-soluble and exchangeable, followed by carbonate and organically complexed forms. However, fractionation of Zn in control volcanic Egmont soil showed that most of the Zn was in oxide and residual forms. After the application of both Zn amended sewage sludge and inorganic Zn, the overall percentages of water-soluble and the exchangeable, carbonate and organically complexed forms of total Zn increased. All the fractions of Zn in both sludge and inorganic Zn applied columns decreased with the increase in soil depthFractionation of Zn in inorganic Zn applied soil showed that the increase in the exchangeable and oxide forms of Zn was higher in the phosphate than in the nitrate treatment. The overall percentage of the water-soluble and the exchangeable and the carbonate forms of total Zn increased except the organic, the oxide and the residual form in inorganic Zn applied soil columns. The results of this study suggest that activated sewage sludge has a high affinity for Cd, Zn and Cu. Zn desorbed from sewage sludge more easily than Cu indicating that the Zn from the sewage sludge may be more reactive than Cu in soil. Ex situ and in situ studies showed that phosphate remarkably limited the Zn movement in both sewage sludge and inorganic Zn applied soils but nitrate did not have any significant impact on the movement of Zn.