Food and Nutritional Sciences - Masters by Research Theses
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Item Studies on protein standardisation of skim milk powder-based systems using milk ultrafiltration permeate and lactose(University College Cork, 2024) Cusack, Maeve A.; O'Mahony, Seamus Anthony; Kelly, Alan; Kerry GroupThe protein content of skim milk powder (SMP) is often standardised to achieve more consistent composition and functionality, whilst also ensuring the protein content of the powder product is as close as possible to the target. This requirement for protein standardisation arises largely from the changes in chemical composition of raw milk, as influenced by stage of lactation, breed of cow, genetics and also factors including diet and weather. To achieve standardisation, two standardising media are permitted to reduce the protein content of milk, i.e., lactose and milk permeate. When lactose or skim milk permeate are added, either in liquid (reconstituted) or powder form, they reduce the protein content by effectively diluting the protein present in the milk. The objectives of the work reported in this thesis were to develop an optimised standardisation process, focused in particular on the approaches used for reconstitution of the standardisation media, lactose and skim milk permeate powder, including the influences of temperature, mixing time and holding time (Chapter 2). Both powders were reconstituted at 50% total solids and the resultant dispersions were analysed for a range of parameters, including pH, viscosity, colour, sediment, conductivity and lactose crystallisation. Reconstitution of the skim milk permeate and lactose powders at 80°C, followed by cooling to 60°C, was determined to be the optimal process for preparing the standardisation material, resulting in dispersions with low viscosity and low levels of sediment, when compared to those reconstituted at lower temperatures. This optimised standardisation process was then used in Chapter 3 to examine the influence of protein content modification and standardisation media on the functionality of low-protein skim-based systems, standardised with lactose or permeate to 3.3 and 3.5% protein, with unstandardised skim milk, with an average protein content of 3.92 ± 0.13% used as the control. These are considered low-protein skim-based systems as, when spray-dried, they produce powders with 16-22% protein, and do not meet the the Codex Alimentarius standard for SMP. The functionality of the low protein skim-based systems was investigated by measuring heat stability, particle size, viscosity and ethanol stability. The permeate-standardised skim milk systems had shorter heat coagulation times (<2 min) and increased particle size on heating from 45 to 85°C when compared to the lactose-standardised skim milk systems and unstandardised control. Mineral contents of the permeate-standardised systems were higher than those of the lactose-standardised skim milk systems. The results of this work clearly demonstrate that the additional minerals in the skim milk permeate systems strongly affected the functionality of the protein-standardised skim milk systems, particularly in applications involving high heat treatments. Rheological analysis showed minimal changes in viscosity on heating of all systems, indicating that the systems were stable at 90°C for 2 min and could be used in lower heat-treated end applications. The original research described in this thesis contributes new scientific knowledge to the process of protein standardisation, as applied to SMP, and to our understanding of the effects of protein standardisation on functionality and applications of skim milk-based systems.Item The influence of powder composition, physical properties, and design configurations on the suitability of process analytical technologies for the in-line analysis of moisture in dairy powders(University College Cork, 2024) Murphy, Áine L.; O'Mahony, Seamus Anthony; O'Callaghan, Tom F.; Behan, Ger; Kerry GroupMoisture content is one of the most important parameters to monitor and control in dairy powders. Increased moisture contents in the finished powder can allow a higher yield to be achieved, but could also lead to increased risks of quality issues such as microbial growth, stickiness, caking and impaired flowability. For these reasons, within the dairy industry, there is growing interest in the development, and in-line integration of, moisture analysers within drying and powder handling equipment. Near infrared (NIR) spectroscopy is a quick, non destructive, non-product contact option in such scenarios. The studies presented in this thesis involve investigation and identification of the most suitable location to install a non-product contact NIR in-line analyser in an industrial sized spray dryer used for drying a range of dairy powders, with different compositions and physical attributes. Two NIR analysers were studied (PAT 1 and PAT 2), across two spray dryers (Dryer A and Dryer B). The success criteria included (1) the analyser must be accurate to within 0.2% of the standard oven moisture test, (2) the analyser must last 6 months without re-validation, and (3) the analyser must enable operators to control spray dryer settings to achieve real-time optimisation of powder moisture content. This original research demonstrated that a vertical downpipe, located after the fluidised bed, before packaging, with an intermittent internal air purge system to clear any dust accumulation on the sapphire window was the optimal configuration. The main challenges with this configuration, as identified in Chapter 2, were powder (skim milk powder (SMP) and whey powder) accumulation on the sapphire window, and low powder flow rate, both contributing to insufficient powder passing in front of the NIR beam, leading to light reflection from other materials (e.g., stainless steel). To better understand and help mitigate these challenges, in Chapter 3, the physical and bulk handling properties (i.e., particle size and shape, bulk and tapped densities, surface free fat (SFF) and flowability) of SMP and full cream milk powder (FCMP) were investigated, using an in-house designed, laboratory-scale replication of the industrial analyser configuration. This work demonstrated that the analyser was accurate for measuring moisture content of both SMP and FCMP, provided that the flow of powder over the sapphire window was optimal (i.e., no gaps/patches in the flow of powder). This was confirmed by p-values greater than 0.05 for both powders, indicating that the differences between the oven and PAT tool moisture results were not significantly different. This work also clearly showed that particle size distribution (PSD) and particle shape were the main factors influencing the flowability of SMP (with larger, less spherical powder particles having the greatest flowability), which was supported by Pearsons correlation coefficient results, while PSD and SFF were the main factors influencing the flowability of FCMP (with larger particles having low SFF, demonstrating greatest flowability). From the new findings in this thesis, dairy researchers can have a greater scientific insight into the integration and optimisation of non-product contact, in-line moisture analysers such as PAT 2, into spray dryers, to control the moisture content in commodity dairy powders (SMP and FCMP). The conclusions drawn from Chapter 2 will simplify the process of locating a suitable installation point for such an analyser, and the knowledge created from Chapter 3 will enable dairy researchers to tailor processes (e.g., insert powder guiding systems to control the flow, install air purges) based on the properties of the respective powders (SMP or FCMP). The ultimate goal for the dairy research community when applying PAT tools in an industrial sized spray dryer in the future, would be that the spray dryer is automatically controlled (e.g., using an advanced process control system) based on the feedback of moisture results produced by the PAT tool, which will remove the risk of human error. This system will allow for increased powder yield (increased profit margin), the conservation of energy (sustainable processing), and a more consistent product with an increase in right-first-time material (satisfied consumers and a reduction in down-grade material).Item Investigating the influence of standardisation media on the physicochemical and functional changes of skim milk during evaporation(University College Cork, 2024) Long, Tom; O'Callaghan, Tom; O'Mahony, Seamus Anthony; Dairy Processing Technology CentreEvaporation and spray drying are two fundamental processes used across the dairy industry to produce high value ingredients. Seasonality induced changes in milk composition particularly prevalent in seasonal calving pasture based dairy systems like Ireland, can pose a series of challenges to processors with changing milk constituents that affect the functionality. In the production of skim milk powder, it is desirable for dairy processers to produce a powder that consistently adheres to the required protein concentration, as excessive levels of protein, which becomes a particular challenge in late lactation, will have a negative effect on process yield, efficiency, and overall profitability for the company. The aim of this research project was to simulate at lab scale, the effects of utilising lactose versus permeate for protein standardisation in skimmed milk, on the physiochemical and functional properties observed during evaporation. The first experimental chapter investigates the effects of permeate and lactose for standardisation of skim milk concentrate by varying total solids concentrations material on addition at 20% vs 50% and characterises the changes to physio-chemical properties during evaporation to ~50% solids. Results from this study indicate that standardisation of protein content can limit the increase of viscosity during the evaporation of skim milk concentrate, whereby the addition of lactose had a more potent effect in offsetting the increase in viscosity compared to permeate addition, and resulted in a lower viscosity overall. Heat stability and acid buffering capacity of the permeate standardised skim milk samples were higher when compared to the lactose standardised samples, offering insights into dynamics of pH changes during concentration. The second experimental chapter examines the effect of thermal treatment using a microthermics unit to simulate preheating of standardised materials prior to evaporation and if subsequent readjustment of pH back to native pH, after preheating and prior to evaporation has an effect on in process performance. After heat treatment, lactose standardised samples observed heat-induced changes such as a reduced pH, which was irreversible upon increasing the pH of the high heat skim milk prior to evaporation, highlighting the complexity of the casein micelle under varying processing conditions. The data from this study highlights the influence of thermal treatments on the pH of skim milk and its effects on concentrate viscosity, whereby the lactose standardised samples showed a greater increase in viscosity after the heat treatment was applied. The work from this research MSc. gives insight into the effects that standardisation media has on the physiochemical and functional properties of skim milk concentrate during production. These learnings may provide useful data to industry and manufacturers, whereby evaporating to a target viscosity rather than target milk solids would offer greater control and consistency during processing and therefore preventing product downtime with reduced C.I.P times and a reduced quantity of effluent being processed through treatment plants.Item Formulation, physicochemical and rehydration properties of whey protein powders containing nanoparticulated whey protein structures(University College Cork, 2024) Guralnick, Jacob R.; O'Mahony, James; Crowley, ShaneWhey proteins have important nutritional and functional properties, and are available commercially in multiple formats, ranging from protein concentrates to isolates. Diversification and enhancement of the functional properties of whey proteins is an ongoing area of research, which is driven by consumer demands, industrial requirements for innovation and regulatory considerations. This thesis examines novel whey protein structures (NWPS) and is comprised of four chapters, with the first chapter examining the future of food formulation and the role of whey proteins, specifically in the context of clean label and sustainable food systems. As a result, many food ingredients are being eliminated from formulations to meet these new demands, necessitating new ingredients to fill this void. NWPS represent an innovative way to utilise whey proteins by altering the secondary or tertiary structures of proteins with thermal treatment and shear to form new structures. Structures such as aggregates, microparticles and fibrils provide tailored emulsion, gelling and foaming properties compared to traditional and can find application in emerging food segments. Whey proteins processed with more recently-developed technologies, such as foam mat drying and 3D printing, could benefit from the inclusion of NWPS to enhance the functionalities of these rapidly evolving technologies by providing more a higher degree of tailoring. In the second chapter, nanoparticulation of whey proteins was achieved by subjecting reconstituted whey protein isolate (WPI¬C) solutions (10% protein, pH 7.0) to heat treatment at 90°C for 30 s with no added calcium (WPIH) or with 2.5 mM added calcium (WPIHCa). Spray-dried powders were prepared from unheated WPI (WPIUH) or nanoparticulated (WPIH and WPIHca) solutions, which were analysed and compared with a control sample (WPIC). WPIC, WPIUH, WPIH and WPIHCa solutions had whey protein denaturation levels of 0.0, 3.2, 64.4 and 74.4%, respectively. Computerised tomography scanning showed that 52.6, 84.0, 74.5 and 41.9% of WPIC, WPIUH, WPIH and WPIHCa powder particles had diameter ≤30 µm. WPIHCa and WPIH powders were cohesive, while WPIC and WPIUH powders were easy flowing, with marked differences in microstructure observed between WPIH and WPIHCa. There were no measured differences in wall friction, bulk density, or colour and, in addition, the rehydration performance was analysed and compared with original WPIC powder. The third chapter examined the rehydration properties of the powders produced in chapter two. Powder surface nanostructure and elemental composition were investigated using atomic force microscopy and X-ray photoelectron spectroscopy, followed by dynamic visualisation of wetting and dissolution characteristics using environmental scanning electron microscopy. The powder surface of WPIUH and WPIC generally displayed smooth surfaces, while WPIH and WPIHCa had micro-wrinkles with more significant deposition of nitrogen and calcium. WPIH¬ and WPIHCa exhibited lower wettability than WPIUH and WPIC during microscopic observation, while the solubility of these powders was broadly similar. This study demonstrated that heat- and mineral-induced aggregation of whey proteins before drying increased aggregate size, altered powder surface properties, and displayed poor wetting characteristics. The final chapter puts the results and conclusion of this thesis in context with the literature review. This thesis developed a fundamental understanding of WPI powder obtained from nanoparticulated whey proteins, which could be applied for developing functional whey-based ingredients in food formulation.Item A study of the milking performance of eight milking machines(University College Cork, 1968) Cowhig, Michael Joseph; Raftery, TomThere are twenty makes of milking machines available to the Irish farmer at present. Most of these are available in bucket and pipeline plants but two are available in pipeline plants only. However, 90% of the 30,000 milking machines in the Republic of Ireland are bucket type. All the machines available are the two-chamber type and normally work at a vacuum of 13" to 15" Hg. No two machines have exactly the same properties in pulsation characteristic or design of cluster assembly.