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Item Fish sauce fermentation technology using New Zealand raw materials : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) at at Massey University, New Zealand(Massey University, 2025) Sharim, Nur SyazwanaDespite abundant raw material, industrial fish sauce production is absent in New Zealand, partly due to a paucity of prior research on how well cold-climate South Pacific fish ferment under temperate conditions with local solar salt. The present study investigates the effect of different fish sauce fermentation conditions using New Zealand raw materials (Hoki and snapper heads and frames as well as green-shell mussel), New Zealand solar salts (stoved and unstoved salts) and different temperatures on volatile fatty acid (VFA) production as well as bacterial composition and diversity. Four different fermentation set-ups were conducted to investigate different aims: 1. Laboratory scale fermentation to investigate the influence of different variables (including seafood material, type of salt and temperature) on fermentation. 2. Pilot scale fermentation to investigate the influence of sampling depth on fermentation. 3. Shell-on mussel fermentation to investigate the influence of mussel shell on mussel fermentation 4. Snapper fermentation with mussel shell added to investigate the influence of mussel shell on snapper fermentation. Four VFA were quantified in all fermentation in this study: acetic acid, propionic acid, butanoic acid and 3-methylbutanoic acid. Butanoic acid was detected only in fermentations with unstoved solar salt regardless of seafood material and fermentation temperature. The presence of butanoic acid exclusively in unstoved fermentations may be associated with the presence or abundance of bacterial groups associated with butanoic acid production in these fermentations. The current study found that VFA concentrations generally increased as the fermentation time increased. Salt type had more influence on VFA production than any other single variable including seafood material used, fermentation temperature and sampling depth. It was also revealed that seafood material had more influence on bacterial compositions than any other variable and seafood material appeared to be the primary determinant of the predominant bacterial family groups for the fermentations (Hoki paste – Micrococcaceae and Moraxellaceae; snapper paste – Carnobacteriaceae, Moraxellaceae and Pseudomonadaceae; and mussel paste – Flavobacteriaceae, Moraxellaceae, Paracoccaceae, Pseudomonadaceae and Roseobacteriaceae). Halobacteriales were found only in unstoved salt fermentations suggesting that salt type may be responsible for these results. However, this postulate could not be validated since insufficient intact nucleic acid could be recovered from the salts used to generate adequate bioinformatics information. Shell-on mussel and snapper plus shell fermentation revealed that the presence of mussel shell was associated with high pH in fish sauce fermentation, an observation not previously reported. However, no significant difference in pH was found in fermentations with different shell contents. In pilot scale snapper fermentation, sampling depth did not have a major influence on VFA production. However, sampling depth may influence the growth of some bacterial families to become the predominant groups by the end of the fermentation.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 Nonviable antibiotic-resistance-free bioactive postbiotics derived from viable probiotic lactobacillus spp. : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Manawatu, New Zealand. EMBARGOED until 14th January 2028(Massey University, 2024) Benhur, Steven ArielWith reports that viable cells of probiotic lactic acid bacteria (LAB) are unsafe when consumed by or administered to selected human beings, postbiotics comprising nonviable LAB cells and the products secreted by them are considered an option to avoid such risks, especially potential transmission of antibiotic resistance genes to other microbes. In this review, the functionality and safety of nonviable postbiotics relative to viable LAB Lactobacillus spp. were examined by collecting the relevant literature from databases and publications. The study indicated that, even after inactivation, postbiotics of Lactobacillus spp. remain active in the gastrointestinal tract with probiotic bioactivities such as antimicrobial action, barrier function, microbiota balance, immune-regulating and anti-inflammatory responses. As they lack cell viability devoid of resistance to antibiotics, postbiotics of Lactobacillus spp. are relatively risk-free but endowed with uncompromised activities and health benefits suitable for varied uses in food science and therapeutics, enlarging the scope for both progenitor probiotics and postbiotics derived from them. Safety-wise, compared to resistance-prone high-risk antibiotics, live probiotics are at low-risk shadowed by antibiotic resistance, while inanimate postbiotics are risk-free without the viability-linked antibiotic resistance.Item The influence of cations on biofilm formation of Listeria monocytogenes persistence strains : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology, Institute of Food Science and Technology, Massey University, Manawatū, New Zealand(Massey University, 2024) Chalke, SailiListeria monocytogenes is a Gram-positive pathogen, that possess a considerable risk to the human health with a high mortality rate. The persistence of pathogens through severe environmental conditions could be associated with their biofilm forming abilities. In this study, four different L.monocytogenes isolates from the seafood industry, were examined for their biofilm formation ability in the presence of three the cations: magnesium, calcium and sodium that are readily available in the seafood industry. Out of four the two isolates 15G01 and 33H04, were the persistent isolates from different seafood industry in New Zealand. Isolate 15A04 was a low biofilm former and the last isolate 16A01 was associated with a mussel contamination outbreak. The divalent cations, magnesium and calcium had a significantly greater effect on biofilm formation compared to the monovalent cation, sodium, especially at a concentration of 50mM. To further understand the effect, comparative transcriptomics was used on L.monocytogenes isolate 15G01 (a persistent and high biofilm forming isolate) and 15A04 (a low biofilm former). Both the isolates were exposed to 50mM concentrations of magnesium and sodium. In the presence of magnesium, various genes related to the phosphotransferase system, flagellar assembly, chemotaxis and various signal transduction receptors were upregulated. In case of sodium, the results indicated limited effect on gene expression for both the isolates. As biofilm is a community of bacteria enclosed in a self-induced matrix called EPS (extracellular polymeric substances), understanding the influence of cations on the composition of the EPS and the structural stability of biofilm is important. Magnesium enhanced the polysaccharide content, thus enhancing biofilm formation particularly in 15G01. eDNA concentration increased in the presence of cations however there were no significant differences among the cations. A unique hexagonal structure with voids were observed for the first time in the presence of magnesium and calcium for isolate 15A04. These findings contribute insights into the role of cations in biofilm formation, their involvement in regulating the complex network in biofilms and maintaining their structural integrity.Item Characterization and functional potential of tofu whey wastewater as a food ingredient : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand(Massey University, 2025) Jitpungtum, RoongchaiTofu whey, a liquid by-product of tofu production, is often discarded as wastewater, leading to environmental and economic concerns. However, its nutritional composition and bioactive properties suggest potential applications as a functional food ingredient. This study aims to characterize the physical and chemical properties of tofu whey liquid (TWL) and tofu whey powder (TWP), evaluate their functional properties, including foaming and emulsifying abilities, and investigate their bioactive properties. Additionally, their potential as an egg white substitute in meringue formulations was assessed. TWL is the liquid waste by-product generated during tofu-making and TWP is the powder obtained by removing most of the moisture from TWL. Chemical composition analysis revealed that TWL contained 97.34 ± 0.23% moisture, 0.38 ± 0.05% crude protein, 0.10 ± 0.06% fat, 0.43 ± 0.05% ash and 1.76 ± 0.23% carbohydrates, while TWP had 5.23 ± 1.04% moisture, 15.08 ± 0.35% crude protein, 1.54 ± 0.29% fat, 15.09 ± 1.74% ash and 62.88 ± 2.27% carbohydrates. The primary sugar identified was sucrose, and the proteins were mainly degraded subunits of glycinin and conglycinin. Mineral analysis showed significant levels of copper, chloride, iron, magnesium and potassium. Functionality testing demonstrated that TWL exhibited limited foaming properties, while TWP showed improved foam stability at a 10% concentration, maintaining over 50% stability after 30 minutes. When adjusted to pH 4 from pH 5.8, foam stability further improved, exceeding 60%. Emulsification studies indicated that TWL had poor stability at higher oil concentrations (20%) but performed better at lower oil concentrations (5%). In contrast, TWP exhibited enhanced emulsifying properties across various oil concentrations, particularly at pH 2 and pH 7–9, likely due to improved zeta potential. The addition of 500 mM NaCl further increased emulsion stability by promoting Na⁺-water interactions, enhancing electrostatic repulsion. Th bioactive properties of TWL and TWP were also analysed, including their antioxidant, antimicrobial, and anti-browning activities. The results indicated that both TWL and TWP contained decent levels of total phenolics, flavonoids, and saponins. These bioactive compounds suggest potential applications in extending food shelf life and enhancing overall product stability. As an egg white substitute in meringue, TWL and TWP produced mixed results. The best performance showing similar texture and rheological to egg white, was observed when TWL or TWP was incorporated with egg white, with minimal impact on meringue texture. Batter made with TWP alone showed no significant differences in density and φ (air incorporation) compared to egg whites, whereas TWL resulted in higher density and lower φ, correlating with increased batter viscosity. Overall, these findings highlight the potential of TWP as a sustainable functional ingredient with foaming, emulsifying, antioxidant, antimicrobial, and anti-browning properties. Future studies should explore further applications in food formulations and optimize processing conditions to enhance its bioactive and functional properties in various food systems.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 Revalorization, characterization and application of tofu industry by-product ‘okara’ as a food ingredient : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, New Zealand(Massey University, 2025) Limonchi Pina, MarianaThe potential of revalorising okara into a powder for use in various food products has been researched in the literature, but no universal consensus has been achieved. Some studies have focused on drying small quantities of okara under different conditions, while others have attempted to substitute wheat flour with okara powder, often with limited success or by combining it with other grains to form composite flours. This project aimed to characterize powders obtained under varying drying conditions to identify the optimal method in terms of nutritional value, functionality and efficiency. Okara powder was then used in bread, cookies and as bread crumbs to maximize the substitution of wheat flour. Two drying methods were tested: freeze-drying and convection oven drying. For convection oven drying, six different temperatures (50, 60, 70, 80, 90 and 100°C) were evaluated to determine their effects on the physicochemical characteristics of okara powder. A total of 580 g of fresh okara was dried per trial to simulate industrial conditions where much larger quantities are processed. Proximate analysis was conducted for each drying treatment. The results showed no significant differences in ash, protein, or fat content across drying conditions. The physical properties of the powders, such as colour, particle size distribution as a powder and as suspension, water activity, water-holding capacity, solubility, bulk density, tapped density, Carr Index and flowability, were also assessed, as these influence food formulation and development. The best drying conditions were determined based on drying time, water activity, water-holding capacity, particle size, and flowability. Convection oven drying at 90 °C and 70 °C was identified as optimal due to the quick drying time, and low water activity (e.g. improved stability against microbial growth and lipid oxidation). Although freeze-drying provided superior water-holding capacity, it required significantly more time and resulted in less stable powders in terms of moisture and water activity. Okara powder was then incorporated into its use in bread and cookies at varying concentrations. Okara powder and okara bread crumb were also tested as a coating agent for frying vegetables. For bread, preliminary trials with okara substitution levels (10, 25 and 50 %) of wheat flour showed that a maximum substitution level of 20% (okara-to wheat flour ratio of 20:80) was feasible. Hydration levels of 80%, 90% and 100% were tested, with 100% hydration yielding the best results in terms of height, colour, and textural properties due to complete protein hydration and minimal interference from fibre. For cookies, okara powder was used as the sole flour. The formulation of cookies avoided allergens apart from soy by excluding eggs and dairy, substituting with chia seed gel and coconut shortening. Three formulations were compared (V1, V2, V3) were developed, varying corn flour and fat content to address surface cracks caused by poor binding. The best formulation, V2, contained higher fat and less okara powder., resulting in improved binding and lower hardness, a desirable trait for biscuits. Although informal testing was conducted, formal sensory evaluation was not performed, which would have provided valuable insights into flavour, texture and overall acceptability. Future studies should include sensory evaluations to assess flavour, odour, soybean aftertaste, texture, and consumer acceptance. Additionally, determining the nutritional composition of the okara-containing bread and cookies compared to wheat flour-based products would provide further justification for okara revalorization. This project highlights the impact of drying treatments on okara powder functionality, new application levels in breads and cookies, and the critical role of water and fat in formulations using okara.Item Coconut oil body membrane materials and storage proteins as emulsifiers : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Manawatū, New Zealand. EMBARGOED until 7 July 2027.(Massey University, 2025) Şen, AylinAs consumer preferences shift towards natural and sustainable food ingredients, plant emulsifiers are emerging as feasible alternatives to synthetic and animal-based options. This PhD thesis aimed to investigate the emulsifying potential of two coconut-derived components: oil body membrane materials (OBMMs) and press cake proteins. The study began with the extraction and characterisation of coconut oil bodies (OBs) from fresh and frozen coconuts (Chapter 4). The objective was to establish an extraction protocol that maximises the OB yield. The interactions between OB membranes and non-OB proteins were also examined through various washing techniques. Findings indicated that OB yield from frozen coconuts exhibited less variability than that from fresh coconuts and revealed considerable amounts of exogenous proteins within the OBM protein fraction. Next, the research focused on optimising the extraction and functionality of OBMMs obtained through churning or freeze–thawing (Chapter 5). The main goal was to identify OBMM composition and improve its emulsification properties via extraction method optimisation. Results showed that freeze–thawing proved more effective than churning for OBMM extraction yield, with an additional freeze–thawing step further improving the functionality of the resulting OBMMs. This project then investigated the extraction and fractionation of coconut oil press cake proteins with the goal of obtaining a fraction with emulsification properties (Chapter 6). Three protein fractions were produced for this purpose: those soluble at pH 7, soluble at pH 4.5, and insoluble at pH 4.5. Findings highlighted that variable costs, particularly raw material expenses, greatly impacted the production cost of pH 4.5 insoluble proteins. Finally, the emulsification properties of coconut press cake protein fractions (obtained in Chapter 6) were evaluated in oil-in-water emulsions (Chapter 7). Results show that pH 4.5 insoluble fraction exhibited the highest emulsification ability and emulsion stability. Additionally, the emulsions with excess proteins (> 1.5% w/w) showed a time-dependent flocculation, which was attributed the slow bridging interactions between adsorbed and unadsorbed proteins. Overall, this study characterises coconut-derived materials (OBMMs and press cake proteins) and determines their emulsifying capabilities to indicate their suitability for emulsion-based food systems. It also highlights that minimally purified plant materials can maintain functional properties, offering natural and sustainable emulsifier alternatives.Item Effect of basil seed gum and its hydrolyzed oligosaccharides on yogurt culture growth and yogurt quality : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Auckland, New Zealand(Massey University, 2025) Liu, NinghuiBasil seeds are surrounded with a mucilage layer that has a remarkable swelling index in water and a high-water holding capacity. Basil seed gum (BSG) from this mucilage layer is a potential novel stabilizer for the food industry. The heterogeneous structure of BSG can affect digestibility in the body but it brings health benefits, such as balancing blood sugar levels, blood cholesterol and weight management, and is a good source of dietary fibre. The primary objective of this study was to examine the effects of basil seed gum (BSG) extracted from RO water in yogurt production. Secondly, it aimed to investigate the influence of enzyme-hydrolyzed BSG oligosaccharides on yogurt cultures and yogurt quality. Additionally, the study explored the use of erythritol as a sucrose replacement in yogurt production and its potential effects. Overall, this research examines the potential of BSG and its oligosaccharides as functional ingredients for enhancing yogurt production. The gum layer was successfully extracted in RO water instead of alkaline water, with a dry gum yield of 24.27 ± 0.64% at 50ºC, 1000 rpm for 2 h. BSG added at 0.06% to yogurt fermentation improved gel stability and water-holding capacity in yogurt samples but did not enhance the growth of YO-MIX® 726 yogurt cultures. BSG-oligosaccharides obtained through hydrolysis with xylanase in RO water under optimal conditions (E/S 2, 4 h, 65ºC) significantly improved the growth parameters of YO-MIX® 726 Lactobacillus acidophilus. The highest cell density (Max) of 1.02 OD₅₉₅ₙₘ was observed at 4% BSG-Oligosaccharides with maximum growth rate (µMax) at 0.10 h⁻¹ , compared to the control with 0.29 OD595nm and 0.06 h⁻¹, respectively. However, the highest prebiotic score (0.53) was observed at 3% of BSG-Oligosaccharides obtained from xylanase hydrolysis in RO water. BSG-Oligosaccharides enhanced the growth of YO-MIX® 726 probiotics at a concentration 1.5% and strongly protected cell survival after 21-Day shelf-life storage at 4ºC. Meanwhile, erythritol had no significant effect on yogurt quality or the yogurt cultures at ≤ 8%. A novel yogurt formulation containing 0.03% water-extracted BSG, 1.5% BSG Oligosaccharides from xylanase-hydrolyzed BSG in water, and 4% erythritol as a sugar substitute demonstrated reduced whey separation, improved bacterial growth, and enhanced probiotic survival. This product shows promise as a low-glycaemic, probiotic functional food with potential prebiotic benefits.Item Characterisation of proteases and lipases produced by Paenibacillus spp. and analysis of heat stability of these enzymes : a thesis presented in partial fulfilment of the requirements for the Master of Food Technology at Massey University, Manawatū, New Zealand(Massey University, 2025) Fang, JefferyThe aim of this study includes the isolation of Paenibacillus species from raw milk, investigation of Paenibacillus species that produces protease and lipase, investigation of the effect of temperature, growth medium and inoculum conditions (fresh and chilled) on the production of protease and lipase by Paenibacillus species and the heat stability of protease and lipase produced by Paenibacillus species. The isolation of Paenibacillus species from raw milk was carried out by using milk plate count agar and the isolated species were identified using Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry analysisThere were none Paenibacillus species isolated from raw milk therefore pre-isolated Paenibacillus species obtained from Massey University microbiology lab culture collection were used for further experiments. The production of protease and lipase were tested using milk agar and tributyrin agar plates respectively. Seven out of 26 isolates were strong positive for protease at 37 °C. Only 2 isolates were positive for proteolysis at 30 °C and 2 isolates were strongly positive for proteolysis at 30 °C. The effects of inoculum conditions (fresh and chilled) were tested by comparing the ability of isolated Paenibacillus species at day 1 (fresh) and day 31 (chilled) of storage and there were no obvious differences. The effect of medium was tested by growing Paenibacillus in TSB, 10% TSB and 1% skim milk. Paenibacillus produced more proteolysis in full strength Tryptic Soy Broth (TSB), 10% TSB and 1% skim milk. The enzyme activities were further investigated by using azocasein and p-nitrophenol palmitate assays. Seven isolates produced obvious amounts of proteolysis, and the highest amount of proteolysis produced was 72 U/mL. There was no proteolysis and lipolysis found after heat treatment at 100 °C for 10 minutes which indicated no production of heat-stable enzymes by the Paenibacillus isolates. In conclusion, the investigation of enzyme activities of species provides new insights for the dairy industry with no heat-stable enzymes produced by the Paenibacillus isolates tested. Further studies are required for medium effect on enzyme production and heat stability of enzyme produced by testing different medium of growth and different temperature conditions for the enzyme produced.
