Process and Chemical Engineering - Doctoral Theses
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Item The post-dehydration processing and the effects on the structural modifications and functionalities of milk protein powders(University College Cork, 2017) Ji, Junfu; Miao, Song; Cronin, Kevin; Fitzpatrick, John J.; Department of Agriculture, Food and the MarineThe variability of the raw materials, the diversity of the chemical compositions and the heterogeneity of structures are believed to contribute to the complexity in the physicochemical behaviours of dairy powders. Post-dehydration technology is widely used as an effective method to modify the structural properties and potentially improve the functionalities of dairy powder. In the present study, the dairy powders were firstly agglomerated by fluidised bed (FB) to investigate the effects on their rehydration processes. Then milk protein isolate powder (MPI) was used as the model system, which was agglomerated by fluidised bed and high shear mix (HS) granulators, using different liquid binders and comparing different granule sizes. The impact of both agglomeration methods on powder structures, as well as the consequent effects on the rehydration abilities, flowability and water adsorption are investigated. MPI agglomerated by FB had the more irregular shapes and porous structures. However, densely packed structures of HS granules caused the higher bulk density and lower porosity. Their shapes were more like spheres with smoother surfaces. FB agglomeration significantly improved the dynamic wetting of MPI and micellar casein powders, by requiring shorter wetting time, being more quickly penetrated by water droplets and absorbing more water by capillary force. But the influences on whey protein were limited, only if using lecithin as a liquid binder. Agglomeration exhibited no advantageous effects on the solubilisation of milk protein powders. The HS granules even delayed the release of materials. The denselypacked structures made MPI adsorbed least moisture and showed the slowest adsorption kinetics. Meanwhile, these MPI granules have significantly better powder flow behaviours. The study provided information about the post-dehydration process as a useful technique to modify the structures of dairy powders, which could be helpful to enhance the wetting process, control the water adsorption and improve the powder flowability.Item Dry mixing of spice powders - investigation of effect of powder properties on mixture quality of binary powder mixtures(University College Cork, 2014) Shenoy, Pooja; Fitzpatrick, John J.; Ahrné, Lilia; European CommissionDry mixing of binary food powders was conducted in a 2L lab-scale paddle mixer. Different types of food powders such as paprika, oregano, black pepper, onion powder and salt were used for the studies. A novel method based on a digital colour imaging system (DCI) was developed to measure the mixture quality (MQ) of binary food powder mixtures. The salt conductivity method was also used as an alternative method to measure the MQ. In the first part of the study the DCI method was developed and it showed potential for assessing MQ of binary powder mixes provided there was huge colour difference between the powders. In the second and third part of the study the effect of composition, water content, particle size and bulk density on MQ was studied. Flowability of powders at various moisture contents was also investigated. The mixing behaviour was assessed using coefficient of variation. Results showed that water content and composition influence the mixing behavior of powders. Good mixing was observed up to size ratios of 4.45 and at higher ratios MQ disimproved. The bulk density had a larger influence on the MQ. In the final study the MQ evaluation of binary and ternary powder mixtures was compared by using two methods – salt conductivity method and DCI method. Two binary food and two quaternary food powder mixtures with different coloured ingredients were studied. Overall results showed that DCI method has a potential for use by industries and it can analyse powder mixtures with components that have differences in colour and that are not segregating in nature.Item Mathematical modelling and optimisation of the formulation and manufacture of aggregate food products(University College Cork, 2010-07) Baş, Nurşin; Byrne, Edmond P.; Fitzpatrick, John J.; Department of Agriculture, Fisheries and Food, IrelandIn this PhD study, mathematical modelling and optimisation of granola production has been carried out. Granola is an aggregated food product used in breakfast cereals and cereal bars. It is a baked crispy food product typically incorporating oats, other cereals and nuts bound together with a binder, such as honey, water and oil, to form a structured unit aggregate. In this work, the design and operation of two parallel processes to produce aggregate granola products were incorporated: i) a high shear mixing granulation stage (in a designated granulator) followed by drying/toasting in an oven. ii) a continuous fluidised bed followed by drying/toasting in an oven. In addition, the particle breakage of granola during pneumatic conveying produced by both a high shear granulator (HSG) and fluidised bed granulator (FBG) process were examined. Products were pneumatically conveyed in a purpose built conveying rig designed to mimic product conveying and packaging. Three different conveying rig configurations were employed; a straight pipe, a rig consisting two 45° bends and one with 90° bend. It was observed that the least amount of breakage occurred in the straight pipe while the most breakage occurred at 90° bend pipe. Moreover, lower levels of breakage were observed in two 45° bend pipe than the 90° bend vi pipe configuration. In general, increasing the impact angle increases the degree of breakage. Additionally for the granules produced in the HSG, those produced at 300 rpm have the lowest breakage rates while the granules produced at 150 rpm have the highest breakage rates. This effect clearly the importance of shear history (during granule production) on breakage rates during subsequent processing. In terms of the FBG there was no single operating parameter that was deemed to have a significant effect on breakage during subsequent conveying. A population balance model was developed to analyse the particle breakage occurring during pneumatic conveying. The population balance equations that govern this breakage process are solved using discretization. The Markov chain method was used for the solution of PBEs for this process. This study found that increasing the air velocity (by increasing the air pressure to the rig), results in increased breakage among granola aggregates. Furthermore, the analysis carried out in this work provides that a greater degree of breakage of granola aggregates occur in line with an increase in bend angle.