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Item Insights into wheat grain microstructure and composition for the development of novel flour with slow digestion properties and enhanced functional characteristics : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand(Massey University, 2025) AbhilashaWheat has been consumed as whole grains, broken grains, flattened format, and puffed format other than the flour format, which has a wide application in different types of food preparations. Wheat flour possesses a unique ability to form a cohesive dough that has viscoelastic properties. A range of products with wheat as their major ingredient are high glycaemic index (GI) foods as wheat flour contains highly digestible starch. However, the consumption of high GI foods is associated with chronic diseases such as diabetes, coronary heart disease, and obesity due to a rapid increase in blood glucose levels and secretion of insulin. The major objective of the research studies of this thesis included creating slowly digestible flour with improved functionality using slowly digested starch sources and non-starch components. Modifying wheat grain through different processing techniques alters the microstructure, and therefore, starch digestibility is impacted. Microstructure modification through various processing techniques, which can control the access of digestive enzymes to starch, could help develop products with controlled starch digestibility. To advance the understanding of the impact of wheat grain microstructure on starch hydrolysis, Chapter 3 explored a study on whole wheat grain in different commercially available forms (kibbled, cut grains, and flour) to understand the influence of microstructural changes on in vitro starch digestibility. The process of size reduction from raw intact grains to kibbled grains and flour caused an increase in overall starch hydrolysis (%) during simulated digestion in the order of flour>kibbled>cut>intact whole wheat grains. Cooking of these formats further increased their starch hydrolysis. However, both cooked cut and intact grains were low glycaemic with the expected glycaemic indices (eGI) of values of 54.08±0.03 and 41.98±0.04, respectively, revealing the role of intact microstructure in starch hydrolysis of wheat grains. Based on the role of intact microstructure, Chapter 4 investigated the possibility of reducing the starch hydrolysis in wheat grain formats (whole, flakes, and flour) by hydrothermal treatment and low-temperature storage of whole wheat grains. The extent of starch hydrolysis after oral-gastro-small intestinal digestion in vitro was significantly lower (p<0.05) in intact grains, flakes, and flours from the cold-stored grains than their non-cold-stored counterparts. In this study, scanning electron micrographs, pasting properties, water retention capacities, and relative crystallinity of the resulting flours revealed an enhanced degree of gelatinisation with the treatment temperature; however, cold-storage of treated grains resulted in a change in these properties due to the retrogradation of the starch. This study indicates that hydrothermal pre-treatment of grains followed by low-temperature storage for prolonged periods might help to reduce the starch digestibility of wheat grains and their resulting products and could be an effective strategy in developing reduced glycaemic impact grain products. However, in our preliminary trials, the flours from hydrothermally treated and low-temperature stored grains resulted in doughs of inferior viscoelastic properties. Furthermore, intending to create slowly digestible flour, Chapter 5 employed two approaches to modify a resistant starch: one involving soluble extracts from wheat flour and vital gluten (water solubles, salt-assisted water-solubles, and acid-solubles) and the other utilising hydrocolloids (guar gum, xanthan gum, locust bean gum, and carboxymethyl cellulose). Modifications from both approaches resulted in modified starch morphology with the formation of starch clusters mimicking the wheat flour. Moreover, the modification with hydrocolloids resulted in an improved pasting profile. Furthermore, in vitro digestion studies revealed that the starch hydrolysis rate was decreased for most of the cooked modified starches with wheat solubles and a slower starch hydrolysis profile until 60 min of simulated small intestinal digestion for most of the hydrocolloids used, carboxymethyl cellulose being the least effective in slowing the starch hydrolysis rate. Additionally, Chapter 6 evaluates the functionality and starch digestibility of a wheat flour system (dough and flatbread-chapatti) by utilising the modified starches created in Chapter 5 as low glycaemic ingredients. The interaction of the modified starches with vital gluten and wheat flour components resulted in improved viscosity of the functional flour. The microstructure of the functional flour dough indicated that the modified starches with wheat solubles (soluble extracts from wheat flour and vital gluten) and hydrocolloids improved the starch-protein matrix and gluten network. Furthermore, the in vitro digestion study revealed the overall starch hydrolysis of chapattis from all the functional flour formulations was significantly lower than the wheat flour chapatti. In conclusion, structural modifications of wheat grain could help reduce the overall starch hydrolysis of wheat grain products. Moreover, the wheat grain components have the potential to modify resistant starch sources to improve their functionality while retaining their slow digestion property. Also, utilising hydrocolloids to modify resistant starch sources could be an effective strategy to enhance the functionality of resistant starches in wheat-based systems. Modified resistant starches created using wheat solubles (soluble extracts from wheat flour and vital gluten) and hydrocolloids have potential applications with slow digestibility and improved functionality in wheat-based products.Item Fabrication, characterisation, and application of functional protein aggregates derived from faba bean protein isolates : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Auckland, New Zealand(Massey University, 2025-07-14) Hu, YinxuanThis thesis explores the preparation, characterisation, and applications of plant protein aggregates, derived from faba bean protein isolate (FPI). The formation of FPI aggregates was accomplished by various methods, including pH adjustments, salt addition, heat treatment, sonication, and thermosonication (TS). The physico-chemical properties and technofunctional characteristics of FPI aggregates formed by different treatments, such as ζ-potential, solubility, emulsification capability, and particle sizes, were also characterised in this study. Furthermore, the microstructure of the FPI aggregates in solutions was examined using various techniques, including light scattering, microscopies (TEM and SEM), and small angle neutron scattering. Additionally, this project further developed the TS method for formation of FPI fibrillar aggregates at pH 2 and amorphous aggregates at pH 7. The characteristics of FPI aggregates formed by TS and conventional heat treatment (CH) were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography linked to tandem mass spectrometry (LC-MS/MS). In addition, Thioflavin T (ThT) fluorescence, Fourier-transform infrared spectroscopy (FTIR) and circular dichroism (CD) were applied to investigate the differences in secondary structure between CH-treated FPI and TS-treated FPI, indicating that TS effectively converted FPI structures to be enriched in β-sheets. The gelation behaviours of different FPI aggregates at 10 wt% were studied by examining their rheological properties and observing the microstructure using scanning electron microscopy (SEM), indicating that TS-treatment of FPI at pH 7 facilitated the formation of stronger protein hydrogels. The functionality of FPI aggregates fabricated from various treatments at the oil-water and oil-air-water interfaces was also characterised. Emulsions (O/W) with various oil factions (ϕ) ranging from 0.2 (dilute emulsions) to 0.75 (high internal phase emulsions, HIPEs), were stabilised by suitable FPI aggregates selected based on their different physico-chemical properties. The findings indicate that higher FPI concentrations (~5 wt%) and pH values (~pH 9) result in better emulsification capabilities. Among all FPI aggregates studied in this project, fibrillar aggregates exhibited the best emulsification performance as they could stabilise emulsions with oil content up to 75% (v/v). However, emulsions stabilised by FPI aggregates induced from TS at pH 7 had the greatest application potential due to their long-term stability (up to 28 days) and compatibility with a neutral pH environment. Therefore, another study in this thesis was to investigate the application of FPI aggregates in stabilising vegetable oil-based whipped creams. TS-treated FPI at pH 7 exhibited superior functional properties compared to other treatments, such as CH and ultrasonication (US), in terms of visual appearance, overrun, and stability of whipped cream. Overall, this project provides fundamental insights into the physical-chemical and techno-functional properties of FPI aggregates, including their ability to stabilise and form emulsions, gels, and foams, with an emphasis on their potential applications in innovative food products such as 3D-printed emulsion gels and plant based whipped cream. The enhanced physicochemical and techno-functional properties of FPI aggregates fabricated in this study showed a great application potential as novel food ingredients for formulation of plant-based food products.Item Heat treatment and homogenization of bovine milk loosened gastric curd structure and increased gastric emptying in growing pigs(Elsevier Ltd, 2023-04) Ahlborn NG; Montoya CA; Hodgkinson SM; Dave A; Ye A; Samuelsson LM; Roy NC; McNabb WCDuring gastric digestion, bovine milk forms a curd, which consists largely of proteins and lipids. However, it is unknown how processing-induced changes to curd structure affects the gastric emptying of milk proteins and lipids. This study aimed to determine the impact of heat treatment and homogenization on gastric curd formation, and gastric emptying of dry matter (DM), proteins and lipids from bovine milk fed to pigs as a human model. Growing pigs (n = 180, mean ± standard error of the mean (SEM) bodyweight 22.4 ± 0.13 kg) consumed raw, or pasteurized non-homogenized (PNH), or pasteurized homogenized (PH), or ultra-high temperature treated homogenized (UHT) milk diets. A protein-lipid-free lactose (PLFL) solution was also fed as a test diet. At 0, 20, 60, 120, 180 and 300 min postprandially the entire gastrointestinal tract was dissected out. The gastric chyme (curd and liquid) fractions were collected after separation using a mesh screen. The DM, protein, and lipid contents of these fractions were quantified. Confocal, transmission electron microscopy, cryo-scanning electron microscopy and rheological analyses were conducted to determine the micro- and macrostructure of the curd. Overall, both heat treatment and homogenization influenced the in vivo gastric curd structure formed of bovine milk, although to different extents. The gastric emptying of DM, proteins, and lipids increased with the extent of processing. Gastric emptying rates of DM and proteins followed the pattern UHT > PH > PNH = raw, while emptying rates of lipid also differed between PNH and raw milk. Curd structure was the main gastric parameter affected in PNH milk.Item Alternative proteins vs animal proteins: The influence of structure and processing on their gastro-small intestinal digestion(Elsevier Ltd, 2022-04) Kaur L; Mao B; Beniwal AS; Abhilasha; Kaur R; Chian FM; Singh JBackground: Digestibility, an indicator of protein bioavailability, is essentially a measure of the susceptibility of a protein towards proteolysis. Proteins with higher digestibility have been linked with better health outcomes. Animal proteins are generally considered to be of better nutritional value than plant proteins not only because they are a good source of essential amino acids but also due to their higher digestibility in the human gastro-intestinal tract. With the recent emergence of alternative food protein sources, which are now processed in a completely new way to design new foods or new versions of the conventional foods, it has become extremely important to understand their digestion characteristics. Scope and approach: This review discusses the factors that affect protein digestibility, including protein source, structure, type of processing, and modification, with a particular focus on the effects of non-protein components present in food matrix. Key findings and conclusions: To obtain the desired functionality, particularly for alternate proteins, numerous physical, chemical, and enzymatic methods for modification have been reported. These modifications may alter structural characteristics of proteins by inducing structural modifications such as protein unfolding, crosslinking, and aggregation. Depending upon the protein reactivity during processing, the susceptibility of proteins towards hydrolysis by digestive enzymes might change, affecting not only the overall protein digestibility but also the rates of release of polypeptides and amino acids. The faster rates of protein digestion have been linked with muscle anabolism, suggesting the need and importance of classifying the new, emerging and alternative protein sources according to their rates of digestion into rapidly (RDP), slowly digestible (SDP) and resistant (RP) proteins. More research needs to be focussed on converting, through processing, the undigestible or RP into RDP or SDP to achieve better health outcomes.Item Characterisation of vanilla extracts based on sensory properties and chemical composition : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, New Zealand(Massey University, 2018) McCormick, DaynaAlthough vanilla is one of the most commonly used flavourings in the world, there is only limited information available about its flavour and chemical composition. The aims of this research were to use sensory analysis and chemical composition analysis to characterise vanilla extracts produced from beans from different regions and to investigate correlations between sensory data and chemical composition of the vanilla extracts. Other aims were to investigate the effect of solvent extraction, concentration of extracts and the combination of vanilla and fat or sugar on the sensory profile of vanilla extracts and formulated matrices. The vanilla extracts (ethanol or glycerol based), either commercial or laboratory extracted samples using vanilla beans sourced from India, Madagascar, Papua New Guinea, Tonga and Uganda, were characterised for aroma and flavour by a sensory panel trained. The panel found that the aroma and flavour of vanilla extracts varied depending on both the growing region and the solvent or solvent concentration used for flavour extraction.--Shortened abstractItem Resolving problems affecting the processing of dried marrowfat peas for fried foods : hard-seededness and cooking temperature and time : a thesis submitted in partial fulfilment of the requirements for the degree of Masters of Food Technology, Massey University, Palmerston North, New Zealand(Massey University, 2017) Ayaquil, Froilan T.The Midland Seed Ltd, a top agricultural seed producer in New Zealand, wishes to increase their level of technical knowledge regarding the processing of peas to assist with solving production problems. In this study, analyses were conducted to resolve if hard-seeded peas or the frying parameters caused the textural irregularities in fried marrowfat peas. Marrowfat peas (pisum sativum cv. Midichi and Midlea) from 16 different harvest locations and years (2014 to 2017) were subjected to tests such as hydration capacity, and sizing of peas were examined to ascertain how much hard-seeded peas were surfacing in a line batch and in different sizes (<6.7mm, 6.7-7.1 mm, 7.1 – 8.0 mm, and > 8.0mm) upon soaking (in different soaking times 12, 18 and 24 hours) and frying at 160°C for 12 minutes. Furthermore, frying conditions including, oil temperature, pea to oil ratio, were explored at a laboratory scale to obtain the most suitable frying parameters capable of producing fried marrowfat peas with consistent and highly acceptable organoleptic properties. It can be concluded from this study that the very low frequency of hard seeds found in marrowfat peas was not the cause of texture inconsistency generally. However, it was shown that cooling the oil to below 130°C, when peas were added to the oil, slowed temperature recovery of the oil and significantly increased pea hardness to unacceptable levels. Marrowfat peas fried at 160°C for 12 minutes, with a pea to oil ratio of between 1/20 and 1/40 resulted in peas consistently fried to a highly acceptable quality.Item Cellular changes during cold-pressed ‘Hass’ avocado oil extraction : a thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology, at Massey University, Auckland campus, New Zealand(Massey University, 2019) Yang, ShuoCellular changes during cold-pressed extraction of ‘Hass’ avocado (Persia americana Mill.) and ‘J5’ olive (Olea europaea L.) were investigated to understand how each step in the process affects oil release from the tissue and to ascertain if and how cold-pressed oil yields were influenced by cellular changes. Electrical impedance spectroscopy (EIS), electrical conductivity, light microscopy and rheological measurements were used to examine avocado and olive flesh and pulp structure at defined processing steps during both commercial and laboratory-based cold-pressed oil extraction. Light microscopy revealed most parenchyma cells in the fruit flesh were ruptured after the destoning and grinding steps. Concomitantly, a significant reduction in electrical resistance and a concurrent increase in conductivity of pulp tissue occurred when cells were ruptured during the destoning and grinding process. Malaxing assisted aggregation of oil into larger droplets, observed by microscopy. Increasing malaxing time resulted in a decrease in the solid-like behaviour (G’) of fruit pulp and an increase in cold-pressed oil yield, which correlated with the oil droplets in the fruit paste coalescing together and becoming larger. Idioblast cells in avocado flesh appeared to remain unruptured and intact during the extraction process. In comparison to the cold-pressed oil extraction of ‘Hass’ avocado, olive oil was easier to recover from ‘J5’ olive during cold-pressed extraction (at lower temperatures and for shorter times) as the olive paste was less viscous allowing the oil droplets to aggregate more easily. Processing of avocado fruit at three different stages of ripening (minimally-, fully- and over-ripe) produced higher oil yields and decreased oil quality (based on % free fatty acids and peroxide value) with riper fruit. Intact fruit and fruit pulp from the over-ripe fruit had higher conductivity and lower electrical resistance values, which indicated more cell rupture occurred when softer, riper avocado fruit are processed. For avocado fruit at six different stages of maturity (harvested between September and April during the 2016/17 season), light microscopy results showed there were more unbroken parenchyma cells in early season, less mature fruit. Polysaccharides in the cell walls were more strongly bound to cellulose in early-season avocado fruit. Late season fruit had more cell disruption during extraction corresponding to higher conductivity and lower electrical resistance values; hence higher extraction yields with increasing maturity. No significant compositional changes of the polysaccharides in the cell walls occurred during malaxing, which indicated that the malaxing step only promoted aggregation of the oil droplets. The malaxing temperature and ultrasound treatment at 20–25 kHz did not assist with cellular disruption during extraction. Higher malaxing temperature reduced the viscosity and increased the mobility of oil droplets and oil droplets were more likely to collide and aggregate to form larger droplets, reducing the G’ of the pulp tissue. The oil yield significantly increased from 1.05% to 13.43% with malaxing temperature increasing from 30 to 50 ⁰C, for early season fruit. Ultrasound treatment at 20–25 kHz decreased the G’ of the avocado pulp and helped the oil to aggregate. In conclusion, the avocado flesh cellular structure ruptured more easily in softer and late maturity fruit contributing to increased oil yields. Malaxing time, temperature and ultrasound treatment at 20–25 kHz influenced the degree of oil aggregation in fruit pulp and therefore improved the cold-pressed oil yield. Olive pulp was less viscous or less solid like during malaxing, resulted in faster oil agglomeration.Item Extraction, encapsulation and in-vitro stomach digestion of mamaku extract : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Palmerston North, New Zealand(Massey University, 2018) Tresidder, Rebecca EmilyProcess development aimed to scale up the extraction of Mamaku, with a resulting yield of 56%wt/wt (mass of liquid extract/100kg of fronds) and 2.8%wt/wt (mass of freeze-dried material/100kg of fronds); this being higher than the yield previously obtained at a small scale (~1% freeze-dried Mamaku). The concentration of the liquid extract followed by freezing, as opposed to freeze-drying it, improved the shear-thickening properties of the Mamaku solutions. The critical temperature for processing was identified to be 63oC, whereby mamaku can be treated for 60 minutes without degradation. Higher temperatures were detrimental for the rheological properties of this polysaccharide, exhibiting a complete loss of shear-thickening when heated to 110oC. The shear- thickening properties of Mamaku solutions were also reduced when exposed to body temperature (37oC) and at the acidic pH found in the human stomach (pH 2-4). Encapsulation experiments aimed to allow mamaku to be swallowed safely, targeting release in the stomach in a hydrated form, and without incorporating calories if used as an ingredient in functional foods aiming to target weight loss. Gelatin was chosen as the encapsulating agent and 7.5%wt/v concentration was selected, being this quantity able to successfully trap concentrated mamaku (4.5%wt/wt), but also exhibiting a melting point high enough (~31oC) to avoid melting in the mouth when consumed. A number of different encapsulation techniques were trialled. The most promising technique was the fluid gel system. The nozzle techniques proved not be suitable for the properties of mamaku. The emulsion templating system showed challenges around removing the oil. The micro-injector based system produced beads likely to be too large for practical use in a food product. Limitations in the encapsulation techniques included: (i) a low mamaku concentration was used (4.5%wt/v—obtained after concentration) and (ii) the gelatin gel appeared to be unstable when transferred to an aqueous environment. The in-vitro stomach digestion results highlighted that encapsulated mamaku by gelatin will be released in the stomach, allowing the shear-thickening properties to re-form. Above 2.2%wt/v Mamaku, some shear thickening was observed (at high shear rates) after digestion of the Mamaku + gelatin mixtures. At least a 4.0%wt/v Mamaku concentration was needed in these mixtures, to obtain similar shear-thickening viscosity values after digestion, as those found by placing the mixture just under the acidic stomach conditions. Overall, a minimum of 10%wt/v of rehydrated mamaku should be delivered to the stomach to gain optimal shear-thickening properties at biological shear rates (1-10s-1) similar to those found at native pH (~pH 5.3). Overall, more research is needed to conclude about the viability of encapsulating Mamaku using gelatin as well as optimizing the encapsulation process based on fluid gel formation.