Process and Chemical Engineering - Doctoral Theses

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Sustainable food process engineering
(University College Cork, 2023) Bremenkamp, Ina; Sousa Gallagher, Maria J; Oliveira, Jorge C.; European Regional Development Fund; European Commission
Food is a basic need and food packaging plays an important role in providing safe food to the world. Food packaging innovations in the past were important milestones for the development of the food sector, by ensuring safety, prolonging quality, and enabling the current supply chain. Nevertheless, the focus has drifted and innovations in the food sector are starting to be driven by ecological needs. The current food packaging options present challenges due to the dependency on fossil raw materials and the accumulation of durable single used packaging waste. Therefore, food packaging innovations need to be adjusted to the new demands, by not being an environmental burden, but still providing product protection, safety, and supporting various supply chains. Design strategies as eco-packaging design, circular economy design and design for recycling are important drivers. Furthermore, the development, improvement, and standardisation of biopolymers for replacing fossil sourced packaging materials are being widely studied. This opens up opportunities for relieving the current environmental burden of food packaging. This thesis focuses on alternative food packaging for ready to eat (RtE) seafood products, a food category that ultimately provides healthy and convenient food to consumers. RtE is a food product group with increasing turnovers, supporting different life styles, e.g., eating on the go, fast and simplified product preparation as well as healthy eating. Seafood products provide essential nutrients and are a valuable food source, rich in nutrients that are particularly important for elderly people, a growing consumer group all over the world. The objective of this thesis was the investigation of biobased edible coatings as sustainable packaging development for RtE seafood products by using a quantitative methodology. A quantitative packaging development approach, in contrast to the often-used qualitative approach in industry, supports an optimal packaging material selection based on the product characteristics and its potential supply chain. Currently a challenging task in the development of eco-food packaging systems is the assessment of the environmental burden. Every action or product has an environmental impact, but the environmental impact can be significantly influenced by the selected options. A systematic review of existing life cycle assessments (LCA) for investigating environmental challenges of novel food packaging systems in the field of RtE fish and meat products was undertaken and revealed a significant impact of the selected LCA approach on the evaluated environmental impact, highlighting the importance of transparent LCA studies, using fair comparisons and a holistic scope. A step by step approach by shifting the LCA focus to different objectives, such as the whole food-packaging system, comparing different packaging materials and systems, is recommended to allow a comprehensive understanding of the environmental impact of food-packaging system. This enables industry stakeholders to make informed decisions, taking an active role that balance necessity, wastefulness, and creating efficient and sustainable packaging solutions. A critical review of edible coatings for chilled RtE food products was also performed to understand the state of the art and identify knowledge gaps for further developments. Edible coatings have been studied for RtE food products mainly to improve the microbiological stability; with other quality parameters receiving much less attention. Only few products within the RtE seafood category were tested in combination with edible coatings. Edible coatings can be sourced from natural resources, including land or marine based biomass. The direct use of food resources as packaging can create a burden on the food supply chain. The conversion of food industry waste products to edible coatings allows an optimal use of the full harvested biomass, but has some challenges, e.g., volume availability, collection, and possible high energy demand during transformation. Also, during the selection of an edible coating material, the supply chain impact should be reviewed, and additionally industrial scale up feasibility should be assessed for a successful industrial application. Biobased materials often have a limited potential, but by combining multiple biobased materials, the coating properties can be optimised. Aspects considered included the methodology for coating application, assessment of coating performance, and edible coating challenges as part of the food system were also discussed. Edible coatings are a complex topic but provide an interesting approach for developing eco-food packaging systems. Developing a tailored packaging system for a RtE seafood product requires the identification of critical quality parameters and understanding of the influence of environmental conditions on the product quality. Therefore, the degradation process of two RtE seafood products, a RtE baked fish product and a RtE minced fish patty, were investigated by studying the microbiological, chemical, and physical properties. The studied sorption isotherm behaviour showed a sigmodal shape, and the best model fitting was reached with the Peleg model, followed by the Guggenheim-Anderson-de Boer (GAB) model. The storage experiments revealed that water loss and microbial growth are important product quality parameters for both tested RtE seafood products, while fat oxidation was only a critical quality parameter for RtE seafood products with a higher fat content. By understanding the underlying reaction of degradation processes and the effect of environmental factors such as oxygen, light, and relative humidity, the required packaging properties were identified. The application of chitosan and alginate coatings for RtE baked fish products were studied. A full factorial experimental design was used to investigate the effect of coating material composition on microbial growth, water loss and lipid oxidation under optimal (4°C) and abuse (14°C) storage conditions. A 3^2 full factorial design was used to study the effect of chitosan concentration (1, 2 and 3%), and glycerol concentration (0, 15 and 30% w/w chitosan). The effect of the composition of an alginate coating was studying with a 2^3 full factorial design. The studied factors were alginate concentration (1 or 2% (w/v)), glycerol concentration (0 or 1.5% (w/w) alginate) and crosslinking the alginate coating with CaCl2 to form calcium alginate (yes/no). The results showed that a chitosan coating with 1% (w/v) chitosan in 1% (v/v) acetic acid, and 15% (w/w chitosan) glycerol, or 1% (w/v) alginate coating with no glycerol, and no crosslinking showed the best performance in controlling the tested safety and quality parameters. Additionally, a full experimental factorial design was performed to study the combined effect of an alginate and chitosan coating applied as a double coating, and single coating. The double coating tested did not provide a combined product protection. A desirability method was used to identify the shelf life of chitosan, alginate and double coated RtE products based on multi quality parameters. It was concluded that chitosan coated samples showed the best performance with a three- fold shelf life extension compared to uncoated products. Improving product safety and quality by combining different protection methods, known as hurdle technology, is a common approach. The applied hurdles can differ. Well applied examples are sanitizing, packing and cold storage for fruits and vegetables. A novel sanitizing system consists of the use of cold plasma treatment, avoiding the use of chemicals to reduce microbiological contamination and increase safety. The combination of cold plasma treatment and an equilibrium modified atmosphere packaging (EMAP) for cherry tomatoes was investigated under controlled temperature (10 and 20°C) throughout storage. Statistical analysis of the results showed that plasma treatment did not negatively affect the quality of the product. A higher microbiological growth was detected within the packed cherry tomatoes, while a plasma treatment before packing reduced growth of microorganism during the early days of storage. Package was important to prevent weight loss and changes in total soluble solid content over 14 days of storage. The combination of cold plasma, temperature and EMAP design ensured the quality retention of cherry tomatoes, which suggests that they have potential to be used as hurdle technology. A packaging based on an edible coating, requires a second packaging component which can be a packaging film. Combining the edible coating and an outside layer should provide an optimal product protection over the required shelf life. A mathematical modelling approach was taken to estimate the required water barrier properties for the packaging film material. The water loss was identified as the remaining most critical quality parameter after a chitosan coating was applied. Film materials were selected based on their properties and end of life options, and the water vapour barrier properties at lower storage temperatures were tested. The water vapour transmission rate (WVTR) allowing a water loss of 10% within 21 days was calculated using the GAB model, and using a linear approximation of the isotherm was estimated to be 94 and 81 g/m2 day, respectively. The simplified linear model showed similar results to the GAB model approach for predicting moisture loss of a high moisture food product. When increasing the required shelf life only a small reduction of the WVTR was seen. Testing the WVTR at chilled storage conditions showed that depending on the material selected, the temperature can impact the water vapour barrier of the packaging film materials, especially for biobased materials. The recommended film material in combination with a chitosan edible coating for a RtE baked fish product was a cellulose based compostable film. Food packaging is essential but only with efficient solutions, an open mind and with various approaches the negative effects of food packaging on the environment can be tackled. Special emphasis should be given to food packaging that allows to use naturally available protection systems. It was highlighted that including circular economy aspects and environmental considerations during all development stages of a food packaging improves the sustainability of a packed food product. An integrated precision packaging, based on an edible coating and a film layer, for RtE seafood products can be an eco-packaging solution, without compromises in food safety and quality.
Dairy powder breakage: mechanisms, impact factors, and influences on powder properties
(University College Cork, 2022-05) Han, Jie; Miao, Song; Fitzpatrick, John J.; Cronin, Kevin; Teagasc; University College Cork
Dairy powders provide a good form for convenient and stable preservation and transportation of milk ingredients, and most commercial dairy powders are agglomerated to improve powder functionalities. However, particle breakage during production and transportation is an important issue for agglomerates and only a few studies on dairy powder breakage have been published. Therefore, there is limited information to understand this phenomenon and find ways to decrease it. The present study investigated the breakage mechanisms of dairy powders, the influence of dairy powder breakage on powder properties, and the impact of powder characteristics on dairy powder breakage. This provides more information to better understand and control dairy powder breakage in an effort to improve the functionalities of dairy powders. The main breakage mechanisms of agglomerated infant milk formula (IMF) during transportation and mixing included dispersion, chipping (surface breakage), and fragmentation (body breakage, which includes both disintegration and splitting), which correspond to an increasing extent of breakage. The breakage mechanism of whole samples was one or a combination of breakage mechanisms because the breakage behaviour of samples with different particle sizes at the same process condition was different. Dairy powder breakage significantly decreased the particle size and porosity of powders and increased the specific surface area, particle density, and bulk density of samples. It also changed the shapes and surface composition of particles as seen with the increase in lactose content and the decrease in protein and fat contents for most samples. These changes in physical properties significantly deteriorated the rehydration properties of dairy powders, including the wettability and dispersibility, while it had only a small influence on powder flowability. In addition, body breakage had greater influences on powder physical properties than surface breakage. Thus, surface breakage had no influence on water sorption and mechanical properties of powders but body breakage significantly deteriorated these properties as seen with the increase in water sorption rates and final water contents, the acceleration in the crystallization, and the decrease in the overall molecular mobility. Dairy powder breakage degree or mechanisms was determined by the process conditions and particle characteristics. Breakage increased with increasing intensity of processing conditions, such as the transportation velocity and air pressures. In addition, fatigue affected the breakage of agglomerates dairy powders. For powder characteristics, the breakage degree of dairy powders increased with increasing particle size and decreasing particle structural strength. Considering particle structure, the strength of crystals and continuum solids were the highest, followed by particles with numerous holes throughout the particle, followed by the hollow sphere particle with a very thin shell. Under the same spray drying conditions, the formulation of dairy powders significantly affects dairy powder breakage by influencing the physical properties of powder particles, especially for particle size and particle structure. For whey protein/lactose model agglomerated powders, the two higher whey-protein powders were smaller in particle size, were less irregular in shape and had higher particle densities, which resulted in less breakage in comparison to the two lower whey-protein powders. For agglomerated model IMF powders that contained different protein and carbohydrates, whey protein powders were bigger in particle size, weaker in structural strength, and more irregular in shape in comparison to pure casein powders. This resulted in the better rehydration properties of whey protein powders but more breakage. Similarly, sucrose IMF samples had better rehydration properties but suffered more breakage than maltodextrin and pure lactose powders because of their bigger particle size. Findings in this study indicate that body breakage significantly deteriorates powder properties, so breakage should be limited to surface breakage. Since powder breakage cannot be avoided, changes to processing conditions (using lower conveying speeds or air pressures) and powder physical properties (mainly particle size and particle structure by changing production conditions or formulations) should be done to reduce breakage intensity.
Electrochemical materials for integrated magnetics
(University College Cork, 2021-06-23) Smallwood, Daniel C.; Rohan, James; McCloskey, Paul; Science Foundation Ireland
Next generation microinductors with magnetically enhanced VIA technology hold great promise for power converter applications in broad technology domains such as automotive, space, high-end computing, mobile devices, radio frequency (RF), artificial intelligence (AI) and the internet of things (IoT). Microinductor VIAs enable monolithic 3D device topologies with reduced footprint, increased inductance density and minimal parasitics. These qualities are essential for emerging 2.5/3D packaging architectures that require granular point-of-load (PoL) power delivery to efficiently supply a multitude of heterogeneously integrated devices. This thesis addresses the challenges of 3D monolithic microinductor design and fabrication, inclusive of magnetically enhanced VIAs comprising a clad laminated soft magnetic core. The current state-of-the-art utilizes 2D microinductor topologies and 2D fabrication methods, therefore significant advancement is required to enable fabrication of a novel 3D monolithic microinductor device comprising vertically oriented integrated magnetics. The major challenges addressed in this thesis fall into two main categories: 1) predictive modeling with computational lithography and computational electrochemistry to enable optimization of the VIA formation process and 2) the design and fabrication of a novel magnetically enhanced monolithic 3D microinductor device. A major contribution from the computational lithography is the derivation of a novel polychromatic light attenuation equation that is used to produce a succinct formula comprising a complete coupling between resist photochemistry and light diffraction effects. Additionally, new photoresist exposure dose determination methods are presented that negate the need for time consuming and costly in-situ metrology. These equations and methods enable fast and accurate predictive modeling of 3D photoresist VIA latent images, which are verified by comparison to directly corresponding experimental work, with highly positive correlation. These formulas converge quickly on the average modern computer and can be readily integrated into lithography simulators. Photoresist development is then investigated, wherein spin development is identified as the optimal method for wet etching VIA latent images. With computational electrochemistry, the electroforming process of Cu VIAs is explored using the FEM in COMSOL Multiphysics to perform 2D and 3D time-dependent simulation studies. Simulations are then verified by comparison to experimental results, with highly positive correlation. Special attention is given to electroformed surface topographies, which is valuable for sensor and flip chip applications. The major contributions from the microinductor device design and fabrication first include designing a unique device that meets target specifications for reduced footprint, increased inductance density and minimized parasitics. A novel fabrication process flow is next engineered to enable a vertically meandering current path with a repeating unit cell comprising a bottom interconnect, a first Cu VIA, a top interconnect and a second Cu VIA. This process flow is compatible with conformal deposition of a soft magnetic laminate (e.g., CoZrTa) for formation of a vertically oriented magnetic core clad on the Cu VIAs. Next, a 5-tiered photomask stack is designed and the corresponding SOPs are engineered. This enables fully in-house microinductor device fabrication, after which vital metrology and characterization is performed. The measured inductance density of our prototype magnetically enhanced monolithic 3D microinductor devices is 16.85 nH/mm2, which is comparable to previously reported metrics for fabricated 3D microinductors. This metric could be significantly improved in future devices by increasing the magnetic core thickness and/or optimizing the magnetic anisotropy characteristic of the integrated magnetic material and/or reducing the pillar diameter, wherein the VIA fabrication research presented in this thesis will be essential. Therefore, this novel microinductor research holds great promise for applications in next generation power converters.
Sustainability analysis of biopharmaceuticals manufacturing
(University College Cork, 2020-04-30) Lalor, Fergal; Byrne, Edmond P.; Fitzpatrick, John J.; Sage, Colin
The production of biopharmaceutical treatments is increasing globally at a rapid pace, leading to the treatment of more and more disorders, many of which historically were untreatable and debilitating. This increase in production poses sustainability concerns, with economic unsustainability from erratic returns on investment, societal concerns around treatment cost and access, and a dearth of published research on pathways to environmentally sustainable production methods. Recombinant protein production by perfusion cell culture under stainless-steel and single-use technologies was investigated using life cycle assessment (LCA) to determine the impact on environmental factors. The ReCiPe for LCA method was utilised, and the single-use scenario was found to result in 40% impacts than stainless-steel alternative across all production volumes. Factors influencing the difference in environmental impacts include infrastructural variables, such as the electricity source to the facility, and process variables, such as the interval between ultrafiltration/diafiltration batches. The feasibility of environmentally sustainable manufacturing processes were investigated, with novel technologies such as water-for-injection (WFI) production by reverse osmosis, the use of biologically-sourced polymeric materials for single-use items and the benefits of increased containment using single-use equipment on cleanroom maintenance evaluated. The results of this analysis indicate reductions in environmental impacts across both single-use and stainless-steel scenarios of 60%, but with further research required to fully understand the process impacts resulting from adopting these technologies. A multiple-criteria decision-making framework was developed to evaluate the economic, environmental and social sustainability of biopharmaceutical manufacturing processes under varying value orientations, enabling the comparison of treatments produced under different modalities. This framework may be utilised to assess treatments for regulatory approval and governmental reimbursement in a holistic manner, as opposed to a reductionist economic standpoint. Further research is required to account for greater complexities in the biopharmaceutical industrial system such as feedback loops between various stakeholders and to provide and document indices from existing processes to be used for evaluation of prospective treatments.
Characterisation and improvement of the rehydration behaviour of high-protein milk powder
(University College Cork, 2020-08-03) Wu, Shaozong; Fitzpatrick, John J.; Cronin, Kevin; Miao, Song; University College Cork; Teagasc; China Scholarship Council
Milk protein isolate (MPI) has poor rehydration behaviours, particular in wetting and dissolution. The rehydration difficulty inhibited the achievement of MPI functionality. Methods were explored to solve rehydration difficulty. Agglomeration was a valid method for enhancing the wetting of dairy powder. Moreover, broadband acoustic resonance dissolution spectroscopy (BARDS) monitored gas release from powder through the alteration of speed of sound in solution. Thus, BARDS was utilised to study the gas release behaviour of agglomerated MPI, and MPI coated with emulsifiers. Meanwhile, as MPI composed mainly by casein, pH of solution affected the status of casein which possibility modify the rehydration process of MPI as well. Real-time measurement of particle size was applied to analyse the effect of pH on rehydrating MPI. Sodium carbonate, as an alkali food additive, was firstly studied at rehydrating dairy powder. However, alkalization of MPI followed by neutralization has been thoroughly investigated. Consequently, considering the effect of calcium chelation on MPI, citric acid was utilised to neutralise MPI from alkalization. Finally, the gelation behaviour of MPI was studied in a different sequence of neutralisation. Our results showed that as the porous structure modified the gas distribution in agglomerated MPI, interstitial air within agglomerates and vacuole air within agglomerates determined the gas release behaviour of agglomerated powder, while the vacuole air in primary powder particle became a crucial barrier for MPI dissolution. The BARDS profile showed that there was faster initial gas release from the agglomerates, indicating better wetting and dispersion ability of the agglomerates. The gas release of MPI during the wetting step was facilitated by lecithin and Tween 80 while the dissolution step was still poor. The wetting behaviour of MPI covered by the emulsifiers was greatly improved except for samples coated with 4% lecithin. The most instant wetting behaviour was observed when coating MPI with Tween at the larger size fractions. The swelling of the primary particle was observed in alkalization, which was ascribed to the swelling of casein micelle aggregates. This swelling of casein micelle aggregates indicates greater water penetration and loosening of the aggregate structure at higher pH, which facilitated the faster dissolution of MPI powder, especially at pH 8.4. As alkalization proved an excellent ability at the dissolution of MPI, sodium carbonate was utilised, which also showed improvement of MPI rehydration. Sodium carbonate was supposed as a calcium chelation as well to modifying the structure of casein micelle. The results showed that wettability worsened with higher sodium carbonate concentrations, due to strong films developing at the powder/water interfaces which inhibited water penetration into the MPI. However, appropriate agitation could effectively wet and disperse MPI. On the other hand, particle size and centrifugal sedimentation studies showed that increasing the sodium carbonate concentration greatly improved the dissolution ability of the MPI powder. The subsequent neutralisation process by citric acid enhanced the effects of calcium chelation due to reaction-product citrate. Besides, alkalization and neutralisation created larger colloidal particle size, which is hypothesised as being a dynamic balance between micellar casein and non-micellar casein. The sequence of neutralisation determined the process of rehydration, which in turn determine the gelation process. As for the gelation time and gel stiffness, performing alkalization firstly before neutralisation had a better result corresponding with increasing mobile casein molecule by improved rehydration, exhibiting homogeneous gel structure.

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