Food Institute - Doctoral Theses
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Item Investigating the drying kinetics, quality attributes, proteome profile and the generation of aroma compounds during dry-ageing of grass-fed beef(University College Cork, 2024) Álvarez Hernández, Sara; O'Neill, Eileen; Mullen, Anne Maria; Álvarez, Carlos; Instituto Nacional de Investigacion Agropecuaria, Uruguay; TeagascBeef quality influences the consumer’s eating experience and their purchase intentions. Eating quality is impacted by many factors, such as, genetics and production systems, slaughtering management, post-mortem interventions, meat ageing, and packaging of meat products (Álvarez, Mullen, et al., 2021). Ageing consists of a subsequent series of biochemical events that start once the rigor sets in (when the meat reaches its maximum toughness after the slaughter of the animal) and finishes once the beef is ready for consumption. During this tenderisation period, muscle proteolytic enzymes (e.g. calpains, cathepsins, caspases) break down myofibrillar and cytoskeletal proteins, contributing to the degradation of the muscle structure and the improvement of meat tenderness (Bhat et al., 2018a). This thesis focuses on the study of ageing or tenderisation phase, particularly on the process known as dry-ageing, which has been significantly investigated over the last two decades. Dry-ageing of beef consists of storing carcasses, primals or sub-primal cuts without protective packaging in a chamber or unit under controlled refrigerated air conditions (relative humidity of 70-80%, temperature of 0-4 °C, and airflow of 0.5-2.5 m/s) for 14-35 days (Koutsoumanis et al., 2023). However, restaurants and retailers may use longer ageing times than 35 days if safety of the meat is demonstrated (Point 2a of Chapter VII in Section I of Annex III, Regulation (EC) No 853/2004 amended on 14th of December 2023; See more details in Appendix I of this thesis). Dry-ageing is a value-adding process that improves meat tenderness and results in a product with unique flavour characteristics. For a long time, dry-ageing was the only method of ageing available to meat processors and was considered a craft process where each meat processor would use different ageing days and air conditions, developing unique dry-aged meat products. Following the development of new packaging and processing technologies in the 1970s, wet-ageing (where meat is vacuumed-packaged using water-impermeable films and aged) progressively replaced dry-ageing, since it overcame some of the disadvantages associated with dry-ageing (Savell, 2008), such as the higher moisture and trimming losses, longer processing times, and higher production costs (Terjung et al., 2021). There is a general agreement that dry-ageing generates tender beef with unique flavour nuances, for which niche markets are willing to pay premium (Berger et al., 2018; Sitz et al., 2006). This signature “dry-aged beef” flavour has been described as nutty, aged, beefy, and brown roasted, and obtained higher liking scores than wet-aged beef (Campbell et al., 2001; Kim et al., 2016; Li et al., 2014; Stenström et al., 2014; Warren & Kastner, 1992). The development of a dry-aged beef flavour is influenced by a number of factors, such as dehydration, endogenous proteolysis, lipid oxidation, and the enzymatic activity of microorganisms on the beef surface (Zhang et al., 2022). These factors contribute to the generation of taste- and aroma-related precursors during ageing, which can further take part in complex reactions during cooking, such as the Maillard reaction, the thermal oxidation/degradation of lipids, and the interaction of these two pathways to produce high flavour-impacting compounds (Zamora & Hidalgo, 2011;Zamora et al., 2015). In addition, dehydration during dry-ageing favours the concentration of the above-mentioned flavour-related compounds (Lee, Choe, et al., 2019) and the lower moisture content and water activity may also enhance the Maillard reaction during ageing (Gardner & Legako, 2018; Li et al., 2021). The potential of dry-ageing to produce a unique premium product has increased the interest of purveyors and retailers in dry-aged beef in recent years (Dashdorj et al., 2016). Likewise, research on dry-ageing has increased in recent years and focused on aspects such as its impact on the meat quality attributes (Berger et al., 2018), understanding the generation of flavour precursors and volatile compounds during dry-ageing (Setyabrata, Vierck, et al., 2022), as well as, the characterisation of the microbiome in dry-aged beef (Oh et al., 2019). Despite moisture evaporation being an intrinsic part of dry-ageing, research focusing on dehydration dynamics is scarce. There is also a lack of research in the proteomic changes occurring during dry-ageing and the impact of post-mortem interventions on the final product attributes. In this context, the present thesis addresses several aspects of dry-ageing in order to increase our fundamental understanding of the process with a view to facilitating improvements in the efficiency and sustainability of the process while maintaining product quality. Therefore, the main objectives of this research work are as follows: ▪ To investigate the drying dynamics during dry-ageing of grass-fed beef. The outcomes obtained from this research will help meat processors to understand how water evaporates during dry-ageing, and may assist in optimisation of the ageing time. ▪ To study the proteome evolution during dry-ageing and understand the biochemical changes that determine the development of dry-aged beef products. In addition, this project aims to identify potential biomarkers that may further help in tailoring ageing time and meat quality attributes of dry-aged beef products ▪ To assess the application of a post-mortem intervention, namely UV treatment prior dry-ageing to improve process efficiency (by influencing drying rate) while maintaining desirable quality attributes. ▪ To explore the flavour chemistry by identifying and quantifying the aroma compounds that contribute to the unique dry-aged flavour of grass-fed beef. This work also investigates the influence of UV treatment before dry-ageing on the aroma profile of dry-aged beef.Item Fractionation of β-casein, the formation of complex coacervates between β-casein preparations and lactoferrin, and an assessment of their digestion, technofunctional and biofunctional properties(University College Cork, 2024) van der Schaaf, Jasper Melle; Kelly, Alan; O'Mahony, James; O'Regan, Jonathan; Goulding, David A.; Fondation NestléLactoferrin (LF) and β-casein are major human milk proteins that have individually been recognized for their significant roles in infant health and nutrition. However, the impact of their complex coacervation, involving liquid-liquid phase separation, and the behavior of these structures during gastrointestinal digestion remains largely unexplored. This thesis aims to advance the fractionation and use of β-casein as a dairy ingredient and knowledge on the formation of LF:β-casein complex coacervates, their physicochemical properties, and biological functionalities within the context of infant in vitro gastrointestinal development. The commercial production of β-casein is limited, due to challenges with yield, associated costs, and industrial application of the final ingredients. Combining fractionation treatments may improve the overall composition and purity of these ingredients. A novel approach for β-casein isolation was developed in Chapter 1, that included membrane filtration combined with chymosin treatment, which removed the κ-casein fraction from the final enriched β-casein ingredient. The second chapter focused on the factors influencing the formation of complex coacervates, including pH, ionic strength, stoichiometry, temperature, protein concentration and protein profile, and demonstrated a strong interdependence of these factors. The coacervate yield varied based on the starting material, and optimal conditions at which the highest phase separation yield were identified. Understanding these factors, and their interactions, is essential for optimizing complex coacervate-based formulations for infant nutrition. The effects of spray-drying or freeze-drying on the stability and reformation of complex coacervates were also investigated. The complex coacervation of LF with β-casein increased the denaturation point of LF by 5 °C; however, this increase does not permit commercial thermal treatment of LF without anticipated denaturation and functional loss. Importantly, drying the complex coacervates and rehydrating them showed no significant impact on the rheological behavior and all complex coacervates exhibited a frequency-dependent viscoelastic behavior. Potentially, freeze-drying complexes formed under infant nutrition grade conditions and dry-blending coacervated ingredients into infant formula may avoid further thermal processing and ensure that bioactivity is retained. The final chapters investigated the stability of complex coacervates during infant in vitro digestion and their potential impact on gastrointestinal health. Complex coacervates showed altered gastric proteolysis, which resulted in different peptide profiles, and could potentially influence bioactivity. Additionally, the digested complex coacervates were studied for their anti-inflammatory properties using a cell T84 epithelial cell model. The bifidogenic properties were studied by stimulating Bifidobacterium longum ssp. infantis with digested complex coacervates; all digested samples exhibited bifidogenic effects, with undigested β-casein stimulating bifidogenesis the most. The findings of this research will further support the development of LF and β-casein complex coacervation as a potential way of producing novel ingredients, as their unique physicochemical properties, increased heat-stability, and altered peptide profiles upon digestion, potentially leading to different biological activities, make them interesting to consider for inclusion in infant nutrition.Item Plant protein structure design and its potential substitution of dairy proteins in gelation systems(University College Cork, 2023) Tang, Qi; Miao, Song; Roos, Yrjo; O'Sullivan, Maurice; China Scholarship Council; Horizon 2020Plant-based proteins are gain attention as versatile alternatives to dairy-derived proteins as functional ingredients in food formulations due to their greater sustainability and lower production costs, and health benefits. However, in-depth knowledge about the structural and functional knowledge of plant and dairy proteins under different pH conditions and the modifying technologies for binary plant and dairy proteins have rarely reported. The study investigated the pH-dependent behavior of structural, and functional properties, especially thermal gelation performance, of plant protein and dairy proteins. Moreover, the study also explored the modifying strategies on the gelation performance of lentil-dairy binary protein gels treated with by heating and microbial transglutaminase. The studies focused on the influence of different pH levels on the structural, surface properties and functional properties of different plant proteins and dairy proteins. Findings demonstrated that dairy proteins generally showed brighter color (higher L* and lower a* and b*), higher solubility, emulsification properties, and foaming capacity compared to plant proteins, whereas plant proteins displayed superior foaming stability and water holding capacity. The thermal gelation performance of plant proteins and dairy proteins are also showed that the disulfide bond formation was attributed to partial 11S acidic and basic subunits of plant proteins (soy, pea, lentil, and chickpea). The disulfide-bonded aggregation was attribute to partial β-Lg and α-La in WPI, which was inhibited at acidic conditions but facilized under higher pH conditions, whereas in CM, κ-casein and αs2-casein might involve in this process. Moreover, the highest gel performance of SPI and CPI were peaked at pH 9, but that of LPI at pH 3, whereas no self-standing gel formed for PPI at the same protein concentration (14%, w/w) over the test pH conditions. For dairy protein, whey protein showed the superior gel performance at pH 7, whereas that was observed optimum at pH 3 for casein micelles. The modification strategies were further explored by subjecting plant and dairy binary protein mixtures to heating and microbial transglutaminase treatment and demonstrated that only certain fractions (legumin acidic and basic subunits) in LPI involved in disulfide-mediated polymerization, whereas almost all fractions in WPI were involved, but that of CM was hindered during heating treatment. However, the 11S acidic subunit and 7S vicilins in LPI were involved in Gln-Lys isopeptide bond formation when subjected to MTGase treatment, whereas that was hindered in WPI but promoted in CM. The binary protein gel performance demonstrated that the application of heating treatment could result in the formation of self-standing gels when replacing whey protein with lentil protein. Nevertheless, when aiming to substitute casein micelles with lentil protein with good gel performance, microbial transglutaminase treatment was found to be a more effective modifying method. Furthermore, a higher ratio of casein micelles to lentil protein can lead to a significant enhancement in gel performance, resulting in improved mechanical properties, rheological properties, water-holding capacity, and the development of more homogeneous and compact microstructures. Remarkably, when substituting 25% casein with lentil protein, similar gel performance with casein alone was observed when mediated by microbial transglutaminase treatment. The findings of this study offer a profound comprehension of the distinctions between plant proteins and dairy proteins regarding their structural and functional properties under varying pH conditions. Furthermore, this research provides different modifying strategies for substituting dairy proteins with plant proteins, thereby broadening the potential applications of plant proteins in diverse food formulations.Item Evidence-based design, physiological efficacy testing and consumer analysis of an exemplar model of a fruit derived bioactive functional food for use in physical performance and exercise settings(University College Cork, 2023) Carey, Conor C.; Lucey, Alice; Doyle, Lorna; Department of Agriculture, Food and the Marine, IrelandThe overall aim of this thesis is to examine the new product development practices used within the scientific design, development and testing of new nutritional products in the performance nutrition sector. Despite recent growth in the area there is a general lack of publicly available information to guide the incorporation of nutritional science into the processes underpinning the design and development of new performance nutritional products. Performance nutrition provides a promising area for the creation of value-add products using Irish agrifood outputs, a key priority in Irelands Food Vision 2030 strategy (Gov.ie - Food Vision 2030 – A World Leader in Sustainable Food Systems, 2021). In chapter 1, frameworks that were created as part of this PhD thesis to inform and guide the incorporation of nutritional science in the development of new products are introduced. These frameworks are applied throughout the subsequent chapters in the design and development of an exemplar model of a functional food to support post exercise recovery and endurance exercise performance. This exemplar model took the form of a blackberry polyphenol enriched high protein milk. Chapter 2 reviews the literature on new product development and discusses the role of polyphenols and protein in post-exercise recovery and supporting endurance exercise performance. The review confirms the efficacy of dairy protein, particularly in the form of bovine milk, for muscle repair and regeneration post-exercise. RCTs have consistently shown the benefits of consuming between 1.2-1.6g/kg/day of high-quality protein for those undergoing frequent exercise. While there's growing evidence to support the use of plant-derived polyphenols for exercise-induced muscle damage (EIMD) recovery and endurance exercise performance, gaps remain in understanding their mechanisms, dosing, and optimal dietary sources. Chapter 3 presents an online survey that assesses the nutrition priorities, practices and preferences of athletes and active individuals. This survey was designed as part of this thesis following a series of focus group sessions with athletes of various levels and backgrounds. This survey provides key end-user insights into the nutritional wants and needs of athletes and active individuals. Key findings highlight muscle recovery as the primary nutritional priority among the athletic community and reveal a clear preference for food product forms over supplements. The data collected provides invaluable guidance for new product development in sports nutrition and allows the meaningful incorporation of end-user insights into the process. Chapter 4 bridges a crucial knowledge gap by conducting a systematic review and meta-analysis investigating the efficacy of flavonoid-rich polyphenols to support post-exercise recovery. The meta-analysis of 26 randomised controlled trials (RCTs) observed significant benefits in muscle strength and soreness recovery post intensive exercise. However, a notable limitation in the included studies was the inadequate characterisation of the polyphenol subclasses and dosages used, emphasising the need for more detailed reporting in future human studies. Chapter 5 presents an RCT assessing the efficacy of the RubusElite beverage prototype to support post-exercise recovery. Results suggest that this beverage augments recovery of muscle strength and reduces muscle soreness in comparison to both high protein and low protein milks. In collaboration with RubusElite project partners, this RCT includes detailed characterisation of the beverage's polyphenol content and a verification of polyphenol stability within the treatment beverage for the study duration. Chapter 6 further investigates the efficacy of the RubusElite prototype in relation to physical performance during a 15km cycling trial. In contrast to previous findings, no significant improvement in performance or exertion-related measures was observed. However, thorough polyphenol characterisation alongside these findings offers critical insights into the lack of observed benefits and provides direction for the reformulation of the prototype. This also provides considerable insights into future RCT design to reassess the efficacy of the reformulated prototype. In summary, this thesis offers a comprehensive investigation into the development of performance nutrition products through the creation of an exemplar model using novel frameworks which allow for the incorporation of scientific best practice. It provides innovative insights into the role of polyphenols and protein in supporting exercise and is one of the first undertakings to assess their efficacy in combination. By combining rigorous scientific evaluation, consumer insights, and product prototyping, the research offers a comprehensive roadmap for future product development in the rapidly evolving domain of performance nutrition.Item Investigations of the complex relationships between minerals, pH and heat stability in milk protein systems(University College Cork, 2023) Aydogdu, Tugce; O'Mahony, Seamus Anthony; McCarthy, Noel; TeagascThe complex composition of milk and derivatives therefrom, mean that its stability in respect to thermal treatment, while well studied, is ever evolving. Non-fat milk powders are rich in protein, of which there may be greater than 4500 different nitrogenous compounds, often present in conjunction with milk minerals. Variations in the total concentration and individual components of proteins and minerals makes dairy science a multifaceted system from which nutritional dairy products emerge, manipulated and produced by processing factors such as temperature, pressure, dehydration, shear and filtration. At the centre of dairy processing lies the most basic element fundamental to solvent chemistry; hydrogen, used as a measure of chemical reactions, but more often taken as a control parameter for physical and sensory properties. Therefore, the objective of this thesis was to advance considerably our knowledge on milk protein and milk mineral systems with regard to three main properties; heat stability, viscosity and pH changes, which have cumulative effects on dairy processing performance and finished product quality and functionality. A novel method of measuring pH at ultra-high temperatures was adapted from the pharmaceutical industry and used to examine the hydrogen ion concentration in dairy systems. For the first time, a non-linear decrease in skim milk pH was shown with increasing temperature from 25 to 140°C. The pH of skim milk decreased from 6.7 at 25°C to 6.1 at 140°C, with this reduction being reversible on cooling. This was not the case for milk permeate, where the pH remained low after sequential heating and cooling, due to irreversible calcium phosphate formation and precipitation. This highlights the stabilizing ability of micellar casein in skim milk against significant levels of calcium phosphate precipitation. However, while precipitation might be reduced, the addition of milk permeate to milk protein concentrate (MPC) resulted in substantial levels of age thickening after evaporation (45% dry matter), whereas MPC with added lactose showed no age related viscosity increase. The former system also had lower pH compared to the latter. Given the significant influence milk permeate had on viscosity of protein solutions, the heat coagulation time of commercial bulk skim milk obtained across the spring period was assessed to determine if the changes in milk composition from early lactation affected heat stability. Type B HCT-pH profiles were shown for bulk milk samples taken in February and March, compared to a type A profile for April milk, with this type A profile continuing for the remainder of the year. This is the first time that a change in HCT profile has been shown for commercial bulk milk samples; although there was no obvious difference in milk composition between any of the samples. Ultrafiltration of the skim milks was performed to obtain milk permeate fractions and was used to swap the retentate obtained in February with the permeate from April milk. This showed that a type B HCT-pH profile in February could be changed to a type A profile by simply swapping the serum phase. The outcomes of the research in this thesis are highly applicable to the thermal processing of complex nutritional formulations (e.g., infant formulas), where mineral additions and substitutions are common practice. The ability to measure pH during UHT processing is certainly a highlight of the work presented herein. In addition, a key new finding is that macro composition, specifically protein and mineral profile, is not always a good predictor of HCT, but that the serum phase of milk has the more substantial effect on heat stability than the colloidal phase on its own. The work presented in the thesis provides novel information to both the dairy industry and academia, in terms of process control through in-line pH measurement, and the fundamental effects of milk serum on protein heat stability.