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Item Magnesium enrichment of skim milk : 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, 2019) Begum, NoorzahanEffective magnesium enrichment of dairy products depends on the amount of magnesium salt added and the nature of its distribution between the serum and micellar phases. Thus, this study firstly aimed to profile the magnesium distribution in skim milk as a function of pH (pH 5.50 to 7.20), preheating temperatures (20 to 80 ± 1 °C) and concentration of added magnesium chloride (0 to 40 mmol L-1). The second aim was to investigate the rheological properties of magnesium-induced skim milk gels as a function of different concentrations of magnesium chloride (0 to 20 mmol L-1) added to heated skim milk. The total concentration of magnesium in skim milk and serum was determined using a complexometric titration (EDTA titration) and the EDTA results were validated by atomic absorption spectroscopy (AAS). The measurement of ionic magnesium (Mg2+) in milk is of importance for understanding the bioavailability of magnesium-enriched dairy products. Hence, the concentration of ionic magnesium (Mg2+) in the serum phase was measured using a novel magnesium fluorescence dye (Magnesium 510 probe). In all the samples, a reduction in the pH increased the total soluble magnesium and ionic magnesium (Mg2+) concentrations in the serum phase, regardless of whether magnesium chloride (15 mmol L-1) was added or not to skim milk at 20 ± 1 °C. At pH 5.50, more than 92% magnesium was found in the serum phase for both added (15 mmol L-1) and no added magnesium chloride samples. The concentration of magnesium in the serum phase remained unchanged as the preheating temperature was increased from 20 to 80 ± 1 °C. The addition of magnesium chloride to skim milk reduced the milk pH and increased the ionic magnesium (Mg2+) and total soluble magnesium concentration in the serum phase at 20 ± 1 °C. The pH values are important for new magnesium-enriched dairy products as the distribution of added magnesium chloride in the serum phase was different dependent on pH adjustment between the pH 6.50 and natural pH 6.70. Rheological measurements using cone and plate geometry at constant strain showed that the addition of 5 mmol L-1 magnesium chloride induced the gelation of skim milk after 22 min of heating at 80 °C in the rheometer. The time and temperature for reaching the gelation in skim milk depended on preheating and concentration of added magnesium chloride. A higher concentration of added magnesium chloride achieved gelation at a lower temperature in the rheometer. With the magnesium-induced gels, G’ values obtained were found to increase with increasing concentrations of added magnesium chloride (0 to 20 mmol L-1), increasing holding times (10 to 60 min) and increasing heating temperatures (70 to 80 °C). Compared with samples with 5 mmol L-1 magnesium chloride, those with 15 mmol L-1 magnesium chloride showed a more rapid increase in G’. The G’ value obtained with 15 mmol L-1 magnesium chloride was 15.01 Pa at 80 °C during 10 min of holding and cooling to 20 °C rapidly increased the final G’ value to 81.44 Pa. In contrast, the addition of 5 mmol L-1 magnesium chloride resulted in the formation of a weak gel with a final G’ value of 6.87 Pa after cooling to 20 °C. The oscillation stress of milk gels also increased with increasing magnesium chloride concentration, heating temperatures and holding times in the rheometer. Preheating significantly (P < 0.05) affected the strength of magnesium-induced skim milk gels. The addition of 20 mmol L-1 magnesium chloride to preheated skim milk followed by heating at 85 °C then cooling to 20 °C formed strong skim milk gels. In parallel, samples with no added magnesium chloride did not undergo gelation. In conclusion, the distribution of magnesium was influenced by pH and magnesium concentration added and the strength of magnesium-induced gels was influenced by magnesium concentration added, preheating and the heating time and temperature in the rheometer. The technology of making magnesium-induced skim milk gels can be exploited commercially for the formation of non-fermented dairy products supplemented with magnesium.Item Fate of hydroxyapatite nano particles during in vitro gastrointestinal digestion : a thesis presented in partial fulfilment of the requirements for the degree of Master in Food Technology at Massey University, Riddet Institute and Massey Institute of Food Science and Technology, Palmerston North, New Zealan(Massey University, 2018) Choki, KinleyThere is an increasing change in population demographics towards an aging population in the world, which had led to the availability of various commercial nutritionally supplemented products. Hydroxyapatite (HA), with chemical formula Ca10(PO4)6(OH)2, is an insoluble calcium salt used for calcium supplementation because of its similarity to the minerals found in human bone and teeth. The insoluble calcium salts are preferred over the soluble ones because of their high heat stability during milk processing under high heat treatment. However, the drawback of insoluble calcium salts is the tendency to sediment during storage resulting in unfavourable gritty texture. Thus, reduction in particle sizes into micron to nano-size improves the dispersion of these insoluble salts. However, the application of nano-sized particles in food products have raised concerns from both the regulatory organizations and consumers on the implications related to both the environmental and health safety aspects. Thus, the objective of the study is to determine the digestion behaviour of nano-sized needle/rod shaped HA (nHA) when added into skim milk during in vitro gastrointestinal digestion. Determination of calcium such as soluble and ionic calcium was conducted to determine the dissolution of nHA. The structural changes and the crystallographic changes of nHA were determined using electron microscopy and x-ray diffraction techniques. The results of in vitro gastric digestion showed presence of undissolved nHA particles even after 240 min of gastric and 120 min of intestinal digestion when examined under TEM, while the XRD analysis detected the presence of crystalline nHA in the first 120 min of gastric digestion. Thus, the possible mechanisms leading to the incomplete dissolution of nHA under acidic conditions of the stomach are discussed subsequently.Item Further applications for the heat shock puffing of food gels : a thesis presented in partial fulfilment of the requirement for the degree of Master of Food Technology in Food Processing at Massey University, Palmerston North, New Zealand(Massey University, 1967) Ooraikul, BunchaFactors governing the puffability of food gels were studied in detail. Some experiments were conducted and results discussed on the effects of soluble solids, changes of pH and pretreatment of food gels on their water holding capacity. The effects of the soluble solids, fat and fibrous texture on the thermoplasticity of food gels were also examined. The application of a puffing technique was directed toward two main types of food, i.e. non-protein foods which include carrots and bananas and protein foods which include three types of cheese, fish and meat. Different techniques were necessary to manipulate each product to puff. Carrot slices may be puffed raw but the product characteristics may differ widely from those of blanched and leached slices. Some foods such as bananas with high sugar content and cheese with high fat content may not without the addition of sufficient amount of a puffing agent. Fish and meat as fibrous protein foods need similar physical and chemical modifications, before their products can puff, such as the destruction of their fibrous structure and the adjustment of the pH to alter their water holding capacity to a suitable level. The food gels may be puffed by other heat-shock techniques other than deep-fat frying. Radiant heat was applied successfully to puff food gels such as sodium caseinate gel, starch gel, and fish product. The products could be puffed to the comparable volumes achieved by deep-fat frying techniques, yet they were superior in some respects. They were free of fat pick-up problems. They could be rehydrated very quickly and the rehydration rate of the radiant heat puffed fish product, for example, was comparable to that of the dehydrated products of the highly sophisticated processes such as freeze-drying, and vacuum contact plate drying. [FROM SUMMARY]Item Development of food-grade microparticles from lignin : 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, 2015) Stewart, Hayley ElizabethAn opportunity presented itself to develop a new food ingredient from the wood biopolymer lignin. Lignin is set to become a high-yielding and inexpensive by-product of lignocellulosic biorefining processes. The aromatic heteropolymer is water insoluble, relatively hydrophobic, non-digestible in its native form, and also considered to be non-toxic. Retention of these properties in isolated lignin may enable a microparticulate food ingredient, with particular use as a fat mimetic, to be developed. Lignin was extracted from shrub willow using an organosolv pulping procedure. A reactor vessel suitable for pulping under organosolv conditions was obtained, modified and commissioned. Using central composite design, an ethanol concentration of 60% (v/v), extraction time of 132 minutes and extraction temperature of 195°C were found to extract lignin of the highest yield and purity. The total lignin content of lignin extracted from chipped, untreated willow under these conditions was 96.53 ± 0.10% (w/w). An anti-solvent precipitation technique was explored for the ability to produce lignin microparticles. An aqueous-organic solution of lignin was dispersed into a much larger volume of water, whereby leaching of organic solvent from the dispersed phase into the water resulted in progressive precipitation of the lignin solute, ultimately producing a suspension of solid microparticles. Temperature and addition of surfactant were investigated as a means of controlling particle properties. Increasing initial water temperature between 4 and 80°C produced increasingly large agglomerates of uniform sub-micron primary particles, increasingly fused into monolithic masses. Faster removal of ethanol, hydrophobic interactions or an increase in rate of diffusion limited coalescence may be responsible for the increased fusion at higher temperatures. Incorporating the ionic surfactant sodium dodecyl sulfate (SDS) or cetyltrimethylammonium bromide (CTAB) in the water at temperatures of 20-60°C during anti-solvent precipitation produced spherical, monodisperse lignin particles in the range 0.1-0.2 μm. However, concentrations of these surfactants greater than 1% (w/v) caused aggregation of primary particles, probably due to bridging between bilayers of surfactant at high concentration. The non-ionic surfactants Tween 20 and sucrose ester were unable to prevent particle fusion at the 60°C preparation temperature, indicating that the electrostatic repulsion between particles coated with SDS and CTAB is important to stability. The ability to manipulate the size of SDS-stabilised particles using added salt and adjustment of pH was determined. The electrostatic mechanism of stabilisation by SDS was confirmed by the ability of added potassium chloride and calcium chloride to destabilise lignin particles. Measured particle size increased with the concentration of added salt, due to either greater fusion of lignin during particle formation or to aggregation of primary particles, depending on whether the salt was added before or after particle formation. Decreasing the pH of the suspension of particles to 1.5, which is lower than the pKa of SDS, caused primary particles to aggregate. For destabilisation with salt and pH, generally only the relative volumes of particles in two modal distributions (~0.1-2 μm and ~1-100 μm) appeared to change. This indicates that the ability to control particle size may be limited by aggregation kinetics. Adjustment and control of pH throughout particle formation may enable the preparation of particles in the intermediate size range, such as narrowly distributed 1-10 μm particles. The ability to prepare particles of various and controlled size is important for maximising industry applications. To highlight a possible application of food-grade lignin microparticles, the performance of particles as Pickering stabilisers of oil-in-water emulsions was evaluated. A literature method of emulsion formation involving the redispersion of dried lignin particles and various pH-modification steps, and a method using lignin in the form of freshly prepared microparticle suspensions were explored. Both methods produced emulsions stable to coalescence for five months of chilled storage, although the pH-modification method produced slightly smaller (D[3,2] of 2.7-11.9 μm) oil droplets than the fresh suspension method (D[3,2] of 11.6-31.2 μm). It may be possible in the future to produce smaller emulsion droplets by using a higher energy emulsification technique and by utilising sub-micron lignin particles, rather than ~10 μm particles. Three main areas in which work could be carried out to move this project forward have been identified. These areas are: 1. Lignin characterisation – including molecular weight, chromatography to determine lignin fragment types and contact angle. 2. Control of particle size – including the investigation of more food-grade surfactants, ultrasonic mixing and controlled pH changes during anti-solvent precipitation. 3. Food applications – including further investigation into Pickering emulsions, foam stabilisation and fat mimetic applications.Item Polysaccharide and exopolysaccharide utilisation in processed and natural cheese systems : 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, 2011) Saija, NileshSeveral polysaccharides are of interest in dairy products because of their ability to bind water and other components of the food systems, often leading to major changes in their functional properties. This work aimed to measure and understand the effects of specific polysaccharides in cheeses on the rheological properties related to functionality. The following polysaccharide−cheese systems were used: the microbial polysaccharides xanthan gum (xanthan), high acyl gellan gum (Gellan-H) and low acyl gellan gum (Gellan-L) in processed cheese and an exopolysaccharide (EPS) from a lactic acid bacteria (LAB) in very low fat Mozzarella cheese. Locust bean gum (LBG) was also used with xanthan. Model processed cheese using rennet casein and soya oil was developed on a small scale (30 g) using a controlled temperature, stirrer speed and time of mixing. Initially, lactose content, moisture losses and sample preparation were standardised to lower the variability in rheological measurements. The effects of xanthan, xanthan+LBG, Gellan-H and Gellan-L on the rheology of the processed cheese were studied. As the polysaccharide concentration increased from 0.0 to 2.0% (wt/wt), the fracture stress (firmness) increased whereas the fracture strain (longness) decreased for gellan gum and the effect depended on the polysaccharide. The crossover temperature (where G' = G''), an indicator of viscoelasticity, was increased dramatically by these polysaccharides. Confocal laser scanning microscopy showed polysaccharide clusters in the protein matrix for Gellan-H, xanthan and xanthan+LBG but not very distinct clusters for Gellan- L. The effect of Gellan-H and Gellan-L on the water mobility and spreading properties of model processed cheese was investigated. Spreading properties were measured by elongational viscosity, and water mobility was measured by nuclear magnetic resonance (NMR) relaxometry. The NMR data revealed that both polysaccharides significantly reduced the water mobility in the cheese but that the reduction was greater for Gellan-H. The rheology data showed that the addition of polysaccharide increased the elongational viscosity for processed cheese containing both Gellan-H and Gellan-L. In situ exopolysaccharide (EPS)-producing cultures are widely used to improve moisture retention and texture in low fat cheese manufacture but are limited by a low level of EPS production. The aim of this study was to develop an “all-dairy” ingredient with an increased content of EPS and greater functionality of the EPS for dairy applications such as Mozzarella cheese. An EPS-producing Streptococcus thermophilus was chosen and its growth was optimised for the development of the bioingredient. The fermented biomass was harvested at the end of the exponential phase and freeze dried. The reduced viable cell count and the retention of ropiness of the powder from the drying process enabled a higher level of EPS inoculation in a preliminary Mozzarella cheese manufacturing trial. Pilot-scale very low fat model Mozzarella cheese was manufactured with and without added EPS powder and in situ EPS culture (EPS-C). Large strain rheology, elongational viscosity, melt and NMR relaxometry were used to determine the effects of the in situ and added EPS on the functionality of the cheeses. Cheeses made with the EPS ingredient (EPS-P) retained the highest moisture content (66.0%) without any visible serum exudation. The cheeses made with non-EPS-producing cultures (CTR) and EPS-C had lower moisture contents of 57.5 and 60.2% respectively. Such higher moisture retention of the cheeses made with EPS-P was reflected in the rheological properties of the final cheeses. The cheeses made with EPS-P exhibited greater meltability, lower elongational viscosity and lower modulus of deformability (stiffness) and fracture stress than those made with EPS-C and CTR. Future work to develop this area of the functional effects of the addition of polysaccharides to cheese would include protein−polysaccharide interactions and better definition of the water affinity of polysaccharide compared with that of protein.Item Glucono-[delta]-lactone-induced gelation of some meat components at chilled temperatures : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology and Bioprocess Engineering at Massey University, Palmerston North, New Zealand(Massey University, 1994) Ngapo, Tania ManuIn this study, 1,5-glucono-δ-lactone, was used to achieve acid-induced gelation of meat, myofibrillar protein and myosin at 4°C. The mechanisms of gelation of myofibrillar protein and myosin were investigated. The effects of addition of sodium chloride and tetrasodium pyrophosphate to myosin and myofibrillar protein, with and without 1,5-glucono-δ-lactone, were also studied. In addition, the presence of other phosphates, orthophosphatc, tripolyphosphate and hexametaphosphate, in a myosin system were studied to aid in an understanding of the the observed effects of tetrasodium pyrophosphate on myosin. At about pH 4.5, it was observed that extraction of the A-band of myofibrillar protein occurred. It was suggested that an impregnated composite system of myosin reinforcing the myofibrillar structure had formed. At about pH 4.0, complete extraction of the A-band occurred. Dissolution of the myofibrillar structure was suggested to result in myosin network formation of weaker Young's Modulus than the impregnated composite system. Addition of 1,5-glucono-δ-lactone to myosin resulted in the exposure of hydrophobic sites as the pH decreased and it was suggested that acid-induced denaturation had occurred. Gel formation occurred parallel to denaturation. At pH 4.0, the gel became liquid-like and was suggested to be a result of excess repulsive electrostatic interactions. Hydrogen bonding and hydrophobic interactions were shown to be involved in gel formation, whereas sulfhydryl bonding appeared not to be involved in gelation. Sodium chloride was postulated to enhance gel rigidity through its effects on the isoelectric point of myosin. The inclusion of tetrasodium pyrophosphate resulted in network formation prior to acid-induced denaturation and was suggested to enhance hydrogen bonding. The acid-induced gels appeared to revert to myosin or myofibrillar protein when immersed in quiescent water, a condition where unimpeded diffusion of ions was obtained. However, a slow rate of ion diffusion resulted in the formation of a 'strong', translucent gel which was dense to the point of being effectively impermeable to ion migration. These gels were hypothesized to have formed through the displacement of sodium and potassium ions with protons, enhancing hydrogen bonding. Myosin was observed to have a stronger affinity for sodium than for potassium.Item Studies into factors responsible for the acceptability of pork on the Singaporean market : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2011) Leong, Jasmine Woon Ying; Leong, Jasmine Woon YingThe thesis reports the results of a series of studies looking into the acceptability of pork on the Singapore market. Anecdotal comments have indicated that pork from some countries had a less acceptable flavour than that produced locally, so a survey was conducted to clarify the situation. This indicated that imported pork, including that from New Zealand, had an undesirable mutton-like flavour. Using pork from female pigs fed either a plant only diet (NZP) or one that included some animal products (NZA) it was shown that Singapore consumers favoured the former due to a lower mutton note. The use of garlic essential oil (GEO) to improve the acceptability of NZ pork either by adding it directly to pork or feeding it to pigs was demonstrated. With increasing GEO, garlic flavour strength increased and mutton flavour strength decreased even when diets of the pigs included animal products. Concentrations of indolic compounds (indole and skatole) in backfat increased with increasing dietary garlic concentration (P<0.001), and were higher in backfat from the NZA group (P<0.05), but were unaffected by different dietary lipid sources (fish oil, tallow, and a mix of linseed oil and soya oil). A highly acceptable low-fat (<10%) and low-salt (<450 mg/100 g) pork ball with an n-6/n-3 ratio of <4 was developed as a premium product, and effects on its acceptability were assessed using pork from pigs on different diets. A supplement containing selenium, vitamin E, vitamin C and CLA fed to pigs led to pork and pork balls with increased levels of these items. Inclusion of fish oil in the diet (4.4%) increased the levels of the long chain n-3 fatty acids (LCN3FA) in the pork and pork balls, but also increased measures of oxidation (TBARs), especially after a period of storage, and decreased the acceptability of the product due to increased off-flavours (rancid and aftertaste). This occurred when fish oil was removed from the diet either 28 days or 49 days (early and late feeding stage) before slaughter. Further research into ways of improving the flavour aspects of these products is required.Item Emulsifying properties of a novel polysaccharide extracted from the seeds of basil (Ocimum basilicum L.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Palmerston North, New Zealand(Massey University, 2010) Osano, JoenalynThe present study investigated the emulsifying properties of a novel polysaccharide extracted from the seeds of Basil (Ocimum bacilicum, L.). Emulsifying properties of basil seed gum (BSG) were evaluated in terms of emulsion droplet size distribution (d32 and d43), rheological properties (apparent viscosity and viscoelasticity), droplet charge (zeta potential), visual phase separation (at 20oC for 1 month period), and adsorption properties (surface/interfacial tensions). Soya oil-in-water emulsions (30% wt/wt) were formulated and stabilised by BSG containing <1.2% (wt/wt) protein and a major glucomannan fraction. Different BSG concentrations (0.1-1% wt/wt) were tested, as well as the effect of pH (1-12), salt (5-70 mM NaCl), heating (80oC, 30 mins) and purification (removal of proteins from gum) on 0.3% (wt/wt) BSG-stabilised oil-in-water emulsions. Emulsions with monomodal droplet distributions and with oil droplet size below 1.0 μm (d32) were formed with as little as 0.3% (wt/wt) BSG. The emulsifying properties of BSG were sensitive to changes in pH and salt. Generally, small emulsion droplets were formed at pH above 6.0 and low ionic strength. However, larger droplets were formed and zeta potential values decreased at low pH and high ionic strength. Microstructures confirmed the occurrence of coalescence over time. BSG appeared to exhibit strong hydrophobic character as fluorescing dye (usually for proteins) was detected at the interface, as well as polysaccharide inclusions were trapped within coalescing droplets after homogenisation, suggesting its strong adsorption. Heating and purification reduced the emulsifying properties of BSG. Nevertheless, the emulsions remained stable against phase separation. The rheological properties of BSG emulsions appeared to be dependent on gum concentration and purification, but independent on pH, salt, and heating, which suggests the resistance of BSG to processing conditions, and thereby it could provide strong emulsion stability. Surface/interfacial tension measurements confirmed the adsorption of BSG at the oil-water interfaces. All gum preparations (crude, purified and protein-free) exhibited an ability to lower the tensions at the interface. However, purification of the gum reduced its adsorption activity, indicating that (i) protein plays an important role in gum adsorption, but it is not an absolute driving force for adsorption and (ii) gum itself becomes altered by the purification process. BSG (0.17 % wt/wt carbohydrate purity) demonstrated excellent emulsifying and stabilising properties when compared to some other polysaccharides. Protein-free BSG produced larger droplets than crude BSG, but still it produced stable emulsions, comparable to other gums, such as sugar beet pectin. This suggests that the emulsifying and stabilising mechanism of the gum is not only ascribed to the surface-active protein moiety, but could also be attributed to the hydrophobic character of the polysaccharide itself. Overall, BSG is a promising gum, which can be considered as a novel hydrocolloid emulsifier.