Browsing by Author "Bronlund, John"
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- ItemBrowning and blistering of Mozzarella during high temperature pizza baking : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemical and Bioprocess Engineering at Massey University, Manawatū, New Zealand(Massey University, 2022) Thornton, DanielMozzarella and pizza baking are large and growing industries, and manufacturers and commercial operators need to know how their cheese will function during baking. The aim of this research was to develop a kinetic model describing the Maillard browning reaction occurring at the surface of Mozzarella during high temperature cooking, and to develop a conceptual model for how blister formation and growth is influenced by baking conditions. Image analysis using lightness, L*, from the CIELAB colour space (L*a*b*) colour scale was used to measure the development of brown colour during baking. An experimental method was developed using a DSLR camera to record colour data and an Infrared (IR) camera to study the Maillard browning reaction. A first order kinetic model was fitted to the lightness data using non-linear regression, with the temperature dependence found to follow the Arrhenius Law. The activation energy (Ea) and the kinetic rate constant at 120°C (k120), were fitted to two data sets. One based on an average region of interest (Average ROI kinetics, Eₐ = 124 kJ.mol⁻¹ & k₁₂₀ = 5.0x10⁻⁴ s⁻¹); and the other based on a discrete localised region where blistering occurred (P1 kinetics, Eₐ = 101.3 kJ.mol⁻¹ and k₁₂₀ = 3 .65x10⁻⁴ s⁻¹). Predicted L* was used to create a visual representation of predicted browning for the whole cheese surface which matched well with the shape and the outlines of the browned regions of the experimental data. The goodness of fit was better based on the Average ROI kinetics with an R2 of 0.88, compared to 0.66 for the P1 kinetics. A modified commercial pizza oven (Lincoln Impinger II 1100 Series) was characterised to provide information and data for the development of experimental techniques and analysis of baked pizzas. The modifications to the oven allowed for accurate temperature measurement, bake time, mass logging, and variable air flow. Air flow measurements showed that most of the air comes from below, based on the impinger layout, and there was minimal change to air flow within the control limits. The heat transfer coefficient (HTC) within the oven was measured using two methods; heating an aluminium block (29.1 to 37.1 Wm⁻²K⁻¹), and water evaporation (43.4 to 45.7 Wm⁻²K⁻¹). To analyse pizzas baked in the modified oven, an image analysis method was developed to process post baking images. MATLAB was used to process images of pizzas baked under a range of conditions, which involved colour conversion and correction, thresholding and determining characteristics. A dynamic thresholding method was developed to account for the variation in overall surface colour and provided consistent and accurate identification of blistering and browning of baked pizzas. The blister analysis process was applied to the experimental and predicted data from the kinetics experiment to determine blister characteristics. A general trend was identified, where blister numbers increased to a maximum and then reduced over time. Blister size was found to increase with time, which can be attributed to blister growth and also the joining of adjacent blisters as they continue to grow. Overall, the P1 kinetics gave a better fit across all of the experimental trials with R2 values ranging from 0.94 to 0.99, compared to the fit for the average kinetics at 0.90 to 0.98. The overall process of cheese baking can be categorised into several stages; melt and flow, steam formation, bubbling, drying and blistering and browning. The conceptual model developed, proposed that low heat flux conditions trend towards fewer but larger blisters and high heat flux conditions trend towards a greater number of small blisters. Blister nucleation was found to be likely more affected by bake time and temperature, than from initial conditions. It was found that the initial form factor (shreds vs slices) of Mozzarella did not affect the nucleation of blisters. The effect of baking conditions on blister characteristics was studied by baking pizza at a range of time and temperature combinations, with temperatures from 220 to 288°C and bake times from 6 to 15 minutes. Baking repeatability was found to be reliable and reproducible, with the % mass loss consistent with a standard error of 0.2% and the level of browning with a standard error of less than 3% for each set of operating conditions assessed. Blister characteristics were assessed from binary images based on the dynamic thresholding process. Observations from the images showed that the size of blisters decreased as oven temperature increased and baking time decreased. It was found that a higher oven temperature, and hence higher heat flux, resulted in greater blister numbers where blister coverage was less than 50%. Above 50%, it was found that further blister growth and characteristics were not sensitive to oven temperature. Analysis of the time for the onset of moisture loss and blistering relative to oven temperature found that as oven temperature increased, the time difference between the initiation of moisture loss and blister formation reduced from approximately 5 minutes at 220°C down to approximately 2 minutes at 280°C. This indicated that heat flux has a greater effect on blister initiation than overall moisture loss which suggested that heat flux has a greater effect on surface moisture loss in comparison to bulk moisture loss. This connection suggested that the pizza surface dried out faster relative to the overall moisture loss as oven temperature increased, and as moisture is lost, the viscosity of the cheese increases. At high heat flux, there is limited time for bubbles to form before a stable skin forms and the surface dries out. In addition, an increased viscosity means that there would be more resistance to growth. The resulting blisters would be smaller than for low heat flux conditions. If the cheese surface dries slower, there is more time for bubble growth before viscosity increases and a stable skin and hence larger blisters are formed. This suggested that there is a critical moisture content where the cheese surface forms a stable skin where temperature can rise above 100°C. To further study the effects of baking conditions on blister formation and growth, a benchtop oven was modified to measure and record surface colour, surface temperature and mass loss in real time during baking. A series of trials were carried out to bake cheese within the modified oven at temperatures of 168°C, 175°C, and 185°C for a minimum of 25 minutes each. The 10th percentile, 90th percentile, minimum and maximum values showed a pattern where initially the overall range is wide but reduces as the average temperature approaches 100°C, and then variation increases beyond 110°C. This pattern was similar for the L* data. Across all oven temperatures the 90th percentile and maximum L* values were similar, which agreed with the observations of lower surface temperatures in the 10th percentile and minimums across all oven temperatures. In contrast, there was a significant decrease in 10th percentile and minimum L* values as oven temperature increases, due to the increased surface temperatures relative to oven temperature. It was found that the original dynamic threshold was not suitable for analysis of the benchtop oven data as a result of different lighting conditions, so a new dynamic threshold equation was developed based on sensory evaluation. The analysis of binary images created using the new equation showed that blisters formed in less time at higher temperatures and blister coverage increased linearly relative to bake time, which agreed with the earlier analysis. Heat flux was found to be significantly lower for the benchtop oven, with the time to achieve 10% blister coverage at the highest oven temperature taking approximately 6 minutes longer compared to the lowest oven temperature from the commercial oven trials. The heat flux to the cheese layer for the commercial oven experiments was estimated to compare the effect of heat flux on the average blister size between the two experiments. It was found that there was a linear correlation between heat flux and average blisters size for the combined results, which suggested that this correlation may hold true irrespective of differences in oven setup and operating conditions. For blister initiation, a similar trend was observed from the benchtop data analysis as for the commercial oven data. Combining the blister initiation data suggested that the onset of browning is highly correlated to oven temperature, which is consistent with the temperature dependence of the Maillard reaction. The developed kinetic parameters were applied to the integrated kinetic equation to assess the performance of the model in a different application. It was found that the predicted images and subsequent blister characteristics matched well with the experimental data, especially for blister coverage, with and R2 of 0.99. The findings from these experiments and analysis indicate that surface drying dynamics are fundamental to browning and blister development. Blister growth and size is governed by the moisture content and therefore viscosity, at the cheese surface. Oven temperature (and therefore heat flux) dictates how fast the surface will dry and therefore the general blister characteristics. Bake time determines the desired level of baking based on blister/browning coverage. Hence heat flux and cheese surface dynamics, in regard to the rate of moisture loss and viscosity, are the critical factors in determining browning and blistering characteristics. The experiments and methods developed, and the understanding of cheese behaviour and influential factors during baking have potential benefits for the high temperature food processing industry, especially cheese manufacture and applications. Benefits include improved accuracy and consistency of product assessment, control over baking characteristics and reduced production costs. The image analysis process developed provides an objective measure of blister characteristics, which are otherwise subject to individual interpretation. This process could be applied in a commercial setting give a robust, repeatable and consistent means of product quality and performance assessment. Given the developed understanding of the fundamentals that drive blister formation and browning it is possible to manipulate parameters that affect surface drying dynamics. This could be through external baking conditions, such as a multi-stage baking process, or adjusting the cheese composition itself to achieve a desired result. The findings from this study resulted in a kinetic model describing Maillard browning of Mozzarella during baking as well as a good insight into the fundamentals that affect blister formation and growth to better understand the Maillard reaction and its application in high temperature food processing.
- ItemCommercially scalable fish collagen processing : 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. EMBARGOED until 5 August 2025.(Massey University, 2023) Gonapinuwala, Suchima TharangiFish collagen has a potential for high-value applications in the biomedical industry due to its excellent biocompatibility, biodegradability and low antigenicity properties. It is also a viable alternative for mammalian collagen due to its high availability, having no risk of disease transmission or religious barriers and the low cost of raw material. However, its utilisation is limited due to the non-availability of industrial-scale processing methods. Maintaining the native triple-helical structure in collagen molecules and the native D-banding pattern in the collagen fibrils are the requisites for biomedical collagen, therefore the existing industrial fish collagen extraction methods for food or cosmetic applications cannot be used. Unlike mammalian-origin collagen, fish-origin collagen differs due to fish species differences, and it is not practical to develop by trial and error, collagen extraction methods for every individual fish species of interest. Therefore, this study was carried out to interpret how the fish skin structure and composition relate to the physico-chemical processes that occur during collagen extraction, to develop a biomedical collagen extraction method based on this understanding, and to present guidelines to use this method for other fish species at industrial-scale. This collagen extraction process was developed through three main steps: pretreatment, extraction, and fibrillogenesis, and important determinants at each step, in relation to the fish skin structure and composition were identified. The focus of the pretreatment step is to remove non-collagenous proteins and fats, and the swelling of the skin in the pretreatment medium was also found to be a critical aspect in this tissue due to the structure of fish skin. The focus of the extraction step is to solubilise collagen molecules into the extraction medium in its native triple-helical conformation . . . With this understanding of the behaviour of fish skin during the extraction process, and the knowledge on how it can be applied to any fish species of interest, the future processing of biomedical collagen from fish skin at the industrial level will be possible.--Shortened abstract
- ItemThe modelling of caking in bulk lactose : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Process and Environmental Technology at Massey University(Massey University, 1997) Bronlund, JohnCaking during storage is a serious problem for manufacturers of bulk lactose. This study was carried out to investigate the causes of caking and identify solutions as to how such problems can be eliminated. The mechanisms for caking in crystalline lactose powders were identified. Liquid bridging between adjacent particles was shown to occur in high relative humidity environments (>80% RH). These liquid bridges could form crystalline solid bridges if the material was subsequently dried out. The potential mechanism of amorphous lactose flow and bridging in conditions where the glass transition temperature is exceeded was shown to be insignificant in predominantly crystalline lactose powders (<5% amorphous lactose). The presence of amorphous lactose is still important as the amorphous matrix acts as a sink of moisture, which can be released upon crystallisation. This increases the moisture available in the system which can contribute to caking by the liquid bridging mechanism. Both of these mechanisms involve changes in the local temperature and moisture conditions within the bulk powder. Such changes were known to be caused by moisture migration under the influence of a temperature gradient. A model which describes the transport of moisture in one dimension as a result of temperature gradients was developed and validated. The microscopic scale processes of liquid bridging and amorphous lactose moisture relations were included into this model. The model predictions agreed well with experimental trials for completely crystalline lactose powders. Comparison of model predictions for the case where amorphous lactose was present on the surface of the particles showed some inadequacies exist in the model. These were the rate of amorphous lactose crystallisation and the assumption of instantaneous equilibrium between the crystallising amorphous matrix and the air present in the interstices of the bulk lactose. Using the model it was shown that for expected storage conditions, the product should be stored with a water activity below 0.57 aw if no amorphous lactose is present and below 0.25 aw if it is present. If these prescribed limits are met then the goal of producing caking free lactose powders can be achieved.
- ItemModelling of chewing and aroma release during oral processing : model development, model validation and comprehensive examples for food design : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemical and Bioprocess Engineering, Massey University, Palmerston North, New Zealand(Massey University, 2021) Mohd Firdaus How, Muhammad Syahmeer HowChewing is complex because of its sub-processes and interactions, and inter-individual differences between people. The development of mechanistic models can be a tool to explore these aspects and can lead to the development of foods with controlled digestion outcomes and improved sensory appeal. A mechanistic chewing model was developed based on selection and breakage processes and implemented using a discretised population balance to predict the changes in bolus particle size distribution during chewing. The model was successfully implemented on peanuts, which gave confidence for its implementation to cooked white rice, which is an aromatic food system and has strong correlations with in vitro digestion. The relationship between panellists physiological, chewing and aroma release parameters during mastication of white rice were investigated in vivo to provide insights for model development. The findings showed that the dynamic behaviour of aroma release of all five subjects followed a similar trend with the breakdown pathways where subjects with smaller particles size in their bolus had higher aroma release. The study paved the first step in understanding the role of chewing on aroma release of cooked white rice and provided a range of oral processing behaviours for model validation. A coupled chewing and aroma release model was developed and validated against experimental data. Adjusting the input parameters from the coupled model showed that the portion size, initial concentration of the studied aroma compound, initial liquid volume and the rice pasted fraction were the most sensitive product-related parameters. The oral cavity volume, pharynx volume, nasal cavity volume and the breathing frequency were the most sensitive physiological parameters. The physico-chemical parameter which had the most significant effect was the mass transfer coefficient in the saliva phase. Examples were also given to show the difference in aroma release when aroma compounds of varying partition coefficients were used. The work from this thesis constitutes the first step in the application of mechanistic chewing models as a tool for food design. The next step will be to expand these models to a wider range of food systems and to a larger number of individuals to improve the model reliability.
- ItemThe role of flute morphology in mechanical behaviour of corrugated fibreboard : a numerical, analytical and empirical study : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Palmerston North, New Zealand(Massey University, 2020) Jamsari, AimanCorrugated fibreboard (CFB) packaging is designed to protect its contents during the shipping and storage of goods – a role threatened by damage to the CFB. Damaged goods will not only make the customers unhappy but also cause significant loss to the suppliers. As different goods require different design of CFB box, there is no one solution fits all to overcome this issue. This thesis was focused on understanding the fundamentals of CFB damage, relating the damage with the strength loss, and including the damage in strength predictive tools such as finite element (FE) and analytical models to allow for faster design of CFB boxes and the possibility of finding optimal solutions for different requirements. The type of CFB damage that the research narrowed down into was changes to the flute profile that could arise. Such flute damage could be unintentional (crushing and indentation at any stage during the shelf life of the packaging) or intentional (accompanying perforation for instance – a design option to provide secondary functionality such as in shelf ready applications). There is currently no systematic way of observing and quantifying the structure of the flute profile to allow for a proper understanding of the morphology of the flute. Typically, this is done either through measuring the change in calliper or direct observation on the profiles at the edge of CFB blanks which suffers additional physical damage due indentation from the cutting process. A new technique was presented to be able to do this by laser cutting the samples and digitalising the flutes. The method also includes a statistical tool that can compare different flutes and quantify the change in morphology through a variable called the ‘Similarity Factor’. The technique was demonstrated for flute profiles with different extents of crushing, and also allowed for transferring the digitalised profile for FE modelling purposes. Developing a full box compression strength (BCT) FE model with the micro-geometry of the fluting structure can be very time consuming as it will involve a huge number of mesh element and result in a long simulation time. So to overcome this, smaller component models like the bending and crushing tests that have been shown to be the largest factor affecting the BCT were developed with micro-geometry structure that allowed for significantly less computation time and better understanding of the effect of flute profile. A new finding identified through the application of the bending model was that the orientation of the sample can be rotated to find an optimal orientation angle that gives the best bending stiffness and maximum bending force performance. Analytical models were also assembled, and their performance compared with the FE models. These provided accurate outcomes for bending but were limited in cases such as inability to predict the maximum bending force and determining the locus of failure. Global damage to the CFB was simulated through deliberately crushing samples to different extents experimentally. The effect of different levels of crushing on flute morphology and mechanical performance was measured through image analysis, torsional, compressive and bending tests. These tests showed that the torsional behaviour of CFB had the highest sensitivity to crushing at low levels. Since the flute morphology measurements showed negligible changes (the original flute geometry was recovered after crushing), it is suggested that the crushing could affect other localised damage to CFB components such as to the fibres in the constituent papers. Further investigation of the extent and nature of this damage could be an interesting extension to find out its relation to the BCT. On the other hand, the reduction in bending strength and edge crush test followed a similar tend to change in flute morphology with increasing crush levels. This shows that some of the loss in strength could be attributed to the change in flute geometry as well as the reduction in calliper (beyond a threshold where morphology was recoverable after compression). By combining the new tool to characterise the flute structure and with models of varying complexity, their ability to predict the strength of CFB at different extents of crushing could be compared (simulating unintentional damage). These models consisted of an actual flute geometry, idealized flute geometry and an equivalent flute geometry FE models along with analytical solution models. This comparison showed that the use of an actual flute geometry was useful to predict mechanical performance but that the dominant effect on bending strength is the calliper and the flute morphology is a secondary influence. The utility of the FE model was further demonstrated with inclusion of an intentional localised damage through perforation. The model accurately predicted the drop in the experimentally measured apparent bending stiffness. The findings of the localised perforation study also demonstrated that the bending force of the CFB can be significantly improved by avoiding punching through the peaks that rest on the compressive side of the liner. The key new contribution of this research was the development of new a way to accurately measure and describe the actual flute profile within CFB exposed to pre-test damage. The profile allowed geometric damage to be quantified and for the true profile to be included in detailed finite element modelling of mechanical behavior. The effect of flute damage on the mechanical behavior of CFB could therefore be determined and predicted and allowed the potential effects on the strength of CFB packages to be inferred.
- ItemA systematic approach for developing and manufacturing fruit simulators : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Engineering, Massey University, Palmerston North, New Zealand(Massey University, 2023) Huang, HuijianDue to the high cost, variable nature and seasonal availability of fruit, conducting large scale experiments for research purposes is not easy. A fruit simulator is a physical tool that mimics the mechanistic features and properties of the targeted fruit; hence, it can be used as a replacement for the fruit in research experiments. This study focuses on developing simulators for heat transfer experiments, especially in horticultural produce precooling. A framework for developing the simulator was established based on the importance of each mechanistic feature. Depending on the application's needs, the simulator can mimic different length scale levels of the targeted fruit, such as the individual fruit, the bulk stacking of the fruit or sub-units of the fruit (e.g., a punnet/bag of table grapes). The scale level determines whether certain mechanistic features are important and affects the values of the thermal properties that must be matched. For example, a simulator that mimics a punnet of fruit with enclosed air pockets has an effective thermal conductivity and volumetric heat capacity that includes contributions from the thermal properties of the fruit and air, which provides more room for material selection. Based on this framework, a systematic approach for the simulator manufacture and material selection was developed. Three different simulators were developed based on the framework: kiwifruit, apple and table grape simulators. The comparison of a simulator and real fruit precooling trials showed good agreement, validating the approach and demonstrating the feasibility of using simulators in postharvest research. The kiwifruit simulator was validated at different experimental scale levels, from individual kiwifruit to multiple kiwifruit boxes containing numerous individual kiwifruit simulators (which reflected pallet scale precooling). During the simulator development, the concept of a time-scaled approach was identified and was explored. In theory, if the volumetric heat capacity of a simulator becomes smaller while the Bi of the simulator remains the same, the heating/cooling time of the simulator in an experiment will decrease proportionally according to the Fourier number (Fo). This approach was validated via the three simulators developed in this study. The validation of the simulators confirms the feasibility of this time-scaled concept. This approach has a significant advantage in reducing the experimental time and easing the material selection process for the simulator manufacture. In the table grape simulator development, a process of using CT scans of the bulk packaged system to study the bulk shape and effective properties of the fruit subunits (bags) were developed, where the bulk shape and effective thermal properties of a bag of table grape were determined based on the process. A set of bag shaped fruit simulators was then manufactured with equivalent bulk thermal conductivity and used to validate the bulk simulator approach by comparison of cooling rates with real fruit. Overall, this study has successfully developed a generalised heat transfer simulator development framework. In addition, this study validated the feasibility and applicability of the time-scaling approach, which could be helpful for any future experiments. Furthermore, this study has developed a process to use CT scanning to determine a bulk object's bulk shape and effective property. The outcomes of the work pave the way for carrying out postharvest and packaging optimisation experimental trials with reduced variability, greater ease and without seasonal constraints. The simulator development framework provides a basis for further expansion of these concepts into other applications beyond the heat transfer focus that they were developed for in this work.