Aggregation and gelation of bovine b-lactoglobulin, a-lactalbumin and serum albumin : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University

Gelation is one of the most important functional properties of whey proteins in food systems. The properties of whey protein gels are affected by the chemical and physical properties of its protein components, (β- lactoglobulin AB (β-Lg), α-lactalbumin (α-La) and bovine serum albumin (BSA). Heat-induced aggregation and gelation of individual whey proteins, (β-Lg, α-La and BSA and in mixture was studied by dynamic rheology and electrophoresis analysis. The proteins were dispersed in an ionic buffer containing 0.009 M CaCl , 0.012 M NaCl, 0.012 M K HPO and 0.007 M Nacitrate (pH 6.8) which was comparable to the ionic composition of 12% whey protein concentrate solution. Rheological properties of the protein solutions were measured using a Bohlin VOR rheometer after heating to 70, 75 and 80°C, holding at these temperatures for 60 min and after cooling to 25°C. Gel electrophoresis under non-dissociating (Native-PAGE in the absence of dissociating and reducing agents) and dissociating but non-reducing conditions (SDS-PAGE) was used to determine the extents of aggregation in some of the heated protein samples. Gelation temperatures of 10%, w/v, protein solutions were found to be in the range 82.5 - 84°C for β-Lg and 68 - 70°C for BSA while α-La did not gel even at 90°C. Gelation temperatures of protein mixtures containing β- Lg and BSA were dependent on the relative proportion of the two proteins in the mixture. In contrast, the protein mixtures containing β-Lg and α-La gelled at temperatures (~ 83°C) comparable to that of β-Lg alone. Rheological measurements on pure β-Lg and BSA showed that BSA solutions formed self-supporting gels at lower protein concentrations and lower temperatures. Increasing the heating temperature or protein concentration of either β-Lg or BSA resulted in higher values of the storage modulus (G'). It was apparent from the electrophoretic data that protein aggregates were formed as an intermediate prior to the formation of gel net-work. These aggregates appeared to be non-covalently linked initially and became increasingly disulphide-linked during heating. Analysis of mixtures containing β-Lg and BSA during heat treatment showed that at both 70 and 75°C the gelation time decreased with the increasing proportion of BSA. Similarly, the values of G' after 60 min of heating were greater for the gels containing more BSA. G' values of these mixtures were dependent on the heating temperature and the relative proportion of the two proteins. Gel electrophoresis data for a mixture of 5% β-Lg and 5% BSA heated at 70°C showed that prior to gelation most of the BSA had been transformed into aggregates while most of the β-Lg was essentially in the native form. Aggregates of both β-Lg and BSA were formed during heating at 75°C. At both temperatures, gelation commenced after most of the BSA had become covalently cross-linked but before all the β-Lg had become cross-linked. This effect was also apparent for other mixtures. Initially the aggregates appeared to be non-covalently linked and became increasingly disulphide linked with heating. From these results it is apparent that during heating at 70°C, BSA is the main protein forming the gel net-work and some β-Lg aggregates are probably attached to the net-work strand through either hydrophobic interactions or disulphide linkages. During heating at 75°C, two gel net-works are presumed to be formed independently, again with some interactions between the strands of the two net-works. The rheological properties of protein mixtures containing β-Lg and α-La showed that β-Lg was the dominant gelling protein. G' values decreased with increasing relative proportion of α-La in the mixture at both 75 and 80°C. Gelling times increased with increasing proportion of α-La in the mixture at both 75 and 80°C. No aggregate formation was observed during heating of α-La at 75 or 80°C. However, in the presence of β-Lg, α-La aggregated rapidly during heating. This aggregation appears to involve sulphydryl disulphide interchange reactions particulary when the mixtures were heated at 80°C. Almost all the proteins had aggregated through disulphide linkages before any significant increase in G'. It is suggested that during heating and prior to gelation co-polymers of both β-Lg and α-La were formed and this resulted in heterogeneous net-work strands being formed. The results presented in this study suggest that slight differences in the protein composition of WPC are unlikely to affect the gelation properties of WPC. Further studies into the effects of immunoglobulins (Igs) are needed in order to gain further understanding of the contributions of these proteins to rheological properties of WPC gels

Terahertz Data Extraction and Analysis Based on Deep Learning Techniques for Emerging Applications

Following the recent progress in the development of Terahertz (THz) generation and detection, THz technology is being widely used to characterize test sample properties in various applications including nondestructive testing, security inspection and medical applications. In this paper, we have presented a broad review of the recent usage of artificial intelligence (AI) particularly, deep learning techniques in various THz sensing, imaging, and spectroscopic applications with emphasis on their implementation for medical imaging of cancerous cells. Initially, the fundamentals principles and techniques for THz generation and detection, imaging and spectroscopy are introduced. Subsequently, a brief overview of AI – machine learning and deep learning techniques is summarized, and their performance is compared. Further, the usage of deep learning algorithms in various THz applications is reported, with focus on metamaterials design and classification, detection, reconstruction, segmentation, parameter extraction and denoising tasks. Moreover, we also report the metrics used to evaluate the performance of deep learning models and finally, the existing research challenges in the application of deep learning in THz cancer imaging applications are identified and possible solutions are suggested through emerging trends. With the continuous increase of acquired THz data – sensing, spectral and imaging, artificial intelligence has emerged as a dominant paradigm for embedded data extraction, understanding, perception, decision making and analysis. Towards this end, the integration of state-of-the-art machine learning techniques such as deep learning with THz applications enable detailed computational and theoretical analysis for better validation and verification than modelling techniques that precede the era of machine learning. The study will facilitate the large-scale clinical applications of deep learning enabled THz imaging systems for the development of smart and connected next generation healthcare systems as well as provide a roadmap for future research direction

Enzymatic Hydrolysis of Heat-induced Aggregates of Whey Protein Isolate

The work herein was funded by Enterprise Ireland as part of the Food for Health Ireland project, grant number; CC20080001. I. B. O’Loughlin was funded by Enterprise Ireland under the Teagasc Walsh Fellowship Scheme.peer-reviewedThe effects of heat induced denaturation and subsequent aggregation of Whey Protein Isolate (WPI) solutions on the rate of enzymatic hydrolysis was investigated. Denaturation of whey proteins was monitored by reversed-phase and size exclusion HPLC and observed by native- and SDS-PAGE. Treated and un-treated WPI solutions (100 g L-1 protein) were hydrolysed to a target degree of hydrolysis (DH) of 5 % with Corolase® PP. Aggregate formation was monitored using light microscopy, with size distribution determined by particle size. Viscosity and surface hydrophobicity exhibited large increases with heat-treatment and the major protein components in WPI showed differences in their rates of aggregation. Results revealed an increased rate of hydrolysis of protein solutions, which were subjected to a pre-hydrolysis heattreatment. Light and Confocal Laser Scanning Microscopy (CLSM) images illustrated the optical clarification of the solution, weakening of the gel network and disintegration of aggregates indicative of hydrolysis. Comparison of samples where there was a heat-treatment prior to hydrolysis and a control non-treated hydrolysis reaction, revealed significant differences in the time to reach 5 %DH (P < 0.001). The heat-treatments ≥ 75 ºC for 5 min produced significantly (P < 0.001) more rapid reactions than the other 5 heat-treatments and the control un-treated reaction. The viscosity, surface hydrophobicity, and insolubility of the heat-treated WPI solutions subsequently declined upon their hydrolysis. The extensive aggregation in some heattreated solutions was postulated to relate to the congruent increased rate of hydrolysis. This study demonstrated that prior thermal treatment of ≥ 75 ºC for 5 min can accelerate the enzymatic hydrolysis reaction of WPI with Corolase® PP.Teagasc Walsh Fellowship ProgrammeEnterprise Irelan