Food and Nutritional Sciences - Doctoral Theses
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Item Investigating casein-polymer interactions as a platform technology for cheese for Asian consumers(University College Cork, 2024) Ouyang, Hao; Kelly, Alan; Sheehan, Diarmuid (JJ); Dairy Research Ireland; TeagascThe focus of the global cheese industry on accessing new markets for cheese is driving a greater need for innovation in cheese products. Increasing opportunities for cheese have been identified in many Asian countries, due to factors such as rising income and a change away from traditional lifestyles (e.g., appeal of fast-food chains to young people). The objectives of the work presented in this thesis were: to gain a better understanding of consumers in emerging markets; to identify texture or flavour characteristics of cheese that may be preferred by such consumers; and to explore the potential of incorporation of different non-dairy polymers in different processing steps of cheese manufacturing to achieve such sensory properties. Consumer focus group methodology was applied to understand the preference for, and consumer behaviour towards, cheese products by a cohort of young, internationally mobile Chinese consumers. Participants in the focus groups had general positive expectations towards cheese due to associations with western-style foods and nostalgia; however, many participants had low perceived ability to select cheese and had limited motivation to engage with cheese due to low perceived relevance of cheese to their daily food life. Innovative cheese products such as cheese snacks or cheese energy bars may be developed to better fulfil important choice motives. Participants generally preferred cheese with a mild and milky flavour and a soft texture, which agreed with trends emerged from a parallel literature review. The effects of addition of konjac glucomannan (KG, neutral charge), soy soluble polysaccharides (SP, negatively charged), or chitosan (CH, positively charged) on rennet coagulation and rennet-induced casein gels were investigated to assess the potential of incorporating these polysaccharides prior to rennet coagulation to modify cheese texture. Addition of either KG (0.02%, 0.04%) or SP (0.25%, 0.5%) enhanced rennet coagulation properties by reducing rennet coagulation time (RCT) and promoting development of gel firmness. The addition of CH, on the other hand, hindered rennet coagulation by decreasing the maximum gel firming rate. The two non-interactive polysaccharides (KG and SP) affected rennet coagulation by a depletion flocculation mechanism, and hydrated KG or SP particles may act as inactive filler particles in rennet-induced gels. Larger hydrated KG particles provided weak points in the gels, while smaller SP particles did not significantly affect microstructure or properties of rennet-induced casein gels at the concentrations studied, which, combined with relatively low retention rate in curd, limits its use for modification of cheese texture. Interactions of CH with caseins hindered aggregation of hydrolysed caseins, and gave less interconnected gel structures. The incorporation of KG or CH affected rennet coagulation and gel structure through different mechanisms, but could both result in a casein matrix that is softer and more easily broken down, which may be harnessed to develop cheese preferred by Asian consumers. The effects of addition of SP/KG/CH (0.5%) at dry salting of Cheddar-style cheese manufacture on characteristics of the cheeses were examined. Addition of KG at dry salting resulted in formation of a KG gel at milled curd junctions, retaining significantly (p<0.05) higher levels of moisture and salt, and higher salt-in-moisture (S/M) level compared to the control without polysaccharide addition. A significant (P<0.05) reduction in salty whey level was also observed with addition of CH, although to a lesser extent compared to KG addition, with a concurrent significant (p<0.05) increase in salt and S/M levels. The changes in compositions of these cheeses also impacted texture and volatile compound profiles over a ripening period of 90 d, although no difference in overall consumer acceptability was observed by a cohort of Chinese consumers. Dry salting is thus a promising step to incorporate different polysaccharides into Cheddar-style cheese, which could also help with salt retention and reduction in salty whey production, as well as modifying cheese characteristics (e.g., composition and texture), which may be of interest to manufacturers and researchers from sustainability and/or product development perspective. Cheese puffs (manufactured using microwave vacuum drying: MVD) produced from Cheddar curds with or without polysaccharide addition at dry salting were characterised. MVD was shown to be a promising technology to produce dried cheese snacks with minimal changes in properties such as colour and volatile compounds. The volumetric expansion during puffing process was significantly (p<0.05) decreased by addition of KG, and increased by addition of CH, respectively; this showed that polysaccharides may be used in modifying texture of cheese puffs. Overall, the work undertaken provides a technological platform for industry to help access Asian markets and contributes to the understanding of use of polysaccharides in development of novel cheese products.Item Impact of a transition to diets from sustainable sources on micronutrient intakes and status(University College Cork, 2024) Leonard, Ursula; Kiely, Mairead; Arranz, Elena; Department of Agriculture, Food and the Marine, Ireland; Food Institutional Research MeasureBackground: A global transition to diets from sustainable sources is required for planetary health. This transition will result in greater reliance on plant-based protein sources coupled with reductions in animal source foods. The evidence base underpinning the formulation of nutrition policy lacks data on the feasibility, safety and effectiveness of translating sustainable dietary guidelines into practice in the population, which could pose risks to nutrition for large sectors, including females of reproductive age and children. Objective: The aim of this thesis was to explore of the impact of a transition to diets from sustainable sources on micronutrient (MN) intakes and status. Objectives were to systematically review the existing evidence assessing the impact of following environmentally protective diets on MN intakes and status (Chapter 2); design and conduct a first-of-its-kind dietary intervention trial of an environmentally protective diet (Chapter 3); assess the impact of the intervention on MN intakes (Chapter 4) and status (Chapter 5); and explore the potential for dietary modelling to assist the development of MN adequate diets from sustainable sources (Chapter 6). Methods: PRISMA guidelines were followed to conduct a systematic literature review (SLR) of studies reporting MN and environmental outcomes, searching seven databases from January 2011 to October 2022 (Chapter 2). Chapters 3 to 5 describe a 12-week, three-centre, single-blind, parallel, randomised controlled trial (RCT) among 355 healthy participants aged 18-64 years, known as MyPlanetDiet. The intervention provided participants with personalised dietary advice based on their dietary habits, in line with sustainable healthy principles (intervention arm) or dietary guidance based on the Irish and Northern Irish healthy eating guidelines (control arm). Outcomes included changes in dietary environmental impacts, energy, protein, MN intakes, the prevalence of inadequate intakes and changes in MN status throughout the intervention. Chapter 6 describes a narrative review of diet optimisation studies that design diets considering nutritional, environmental and context-specific constraints. Results: The SLR (Leonard et al., 2024) included 56 studies; one RCT which provided the only biomarker data; 10 dietary intake studies, and 45 dietary modelling studies, including 29 diet optimisation studies. Most studies suggested that intakes of zinc, calcium, iodine, and vitamins A, B12 and D would decrease, and total iron and folate would increase in a dietary transition to reduce environmental impacts, with similar findings for the prevalence of inadequate intakes, reported in only 10 studies. In the MyPlanetDiet RCT, dietary GHGE decreased from baseline to endpoint in both arms and was lower in the intervention arm at endpoint. There were changes in MN intakes in both arms over the 12-weeks, and at endpoint, the intervention arm had lower intakes of energy, protein, thiamin, riboflavin, niacin, vitamins D, B6, B12 and C, calcium, zinc, potassium, selenium and iodine, and higher intakes of vitamins A, E and K1 (P < 0.05) compared with controls. The prevalence of inadequate intakes of riboflavin, calcium, zinc, vitamins B6, B12 and C was higher, and of vitamin E and copper was lower (P < 0.05) among females in the intervention arm than controls. Among males, the prevalence of inadequate intakes of riboflavin, selenium and iodine was higher in the intervention arm than controls (P < 0.05). Changes in biomarkers of nutritional status analysed for this thesis were minimal over the 12 weeks. Our narrative review of diet optimisation studies (Leonard & Kiely, 2024) identified a range of diets that meet individual MN requirements, have reduced environmental impacts, and minimise deviation from culturally acceptable dietary practices. Although these are theoretical solutions, opportunities arising from the results of diet optimisation studies include supporting the development of food-based dietary guidelines and exploring food-based strategies to increase nutrient supply, such as fortification. Conclusions: The findings from our SLR, mainly based on observational data, and the MyPlanetDiet RCT aligned, identifying several key MNs that are at risk in the transition to diets from sustainable sources, particularly among females. Greater emphasis on meeting diverse MN requirements from appropriate dietary sources is required in the global discussion around developing diets from sustainable sources. Dietary modelling techniques, such as diet optimisation, can be a useful tool in the generation of hypotheses and diet solutions for testing in further intervention studies among diverse populations.Item Reconstruction of milk fat globules/membrane (MFGs/MFGM) and characterization of its physicochemical properties and techno-functionalities(University College Cork, 2024) Sun, Yanjun; Miao, Song; Roos, Yrjo; O'Sullivan, Maurice; Teagasc; China Scholarship Council; State Key Laboratory of Dairy BiotechnologyMost commercially available infant formulas (IFs) lack phospholipids and milk fat globule membrane (MFGM) proteins. To mimic human milk's lipid profile, MFGs/MFGM ingredients from sweet whey or buttermilk are fortified in IF. Understanding the structural and compositional, and techno-functionalities changes of MFGs/MFGM is crucial for their application. The MFGs/MFGM has been reconstructed by the mostly used processing methods in dairy industry, acidification (pH 6.30 and 5.30, 25℃), and novel non-thermal treatment, ultrasonic treatments with different intensities. Additionally, anionic polysaccharide- high-methoxyl pectin (HMP) was incorporated to the raw milk before the cream separation, examining the resulting physicochemical properties and techno-functionalities. Results indicated that pH adjustment affected the MFGs structure and MFGM protein compositions, particularly at pH 5.30, causing protein loss such as butyrophilin (BTN) and Periodic Acid Schiff 6/7 (PAS 6/7) and particle size changes. Fourier Transform Infrared Spectroscopy (FTIR) spectra revealed more proteins compositions in MFGs/MFGM prepared from sweet whey (MFGM-C) compared to bovine raw milk, showing lower interfacial tension and ζ- potential. In addition, there were no apparent polymorphs in MFGM-C, and lower exothermic or endothermic enthalpy was needed during the heating and quenching procedures. Acidification, especially pH 6.30 conditions, led to the adsorption of non-membrane milk proteins on the MFGs or MFGM fragments and formed more types of conjugate detected by FTIR. Consequently, this induced changes in the crystal form proportion and thermal behaviour of MFGs/MFGM at pH 6.30. Different acoustic powers generated by the 20 kHz and 40 kHz independently or synchronously working conditions, affected the interfacial properties and thermal behaviour of MFGs/MFGM samples. 20 kHz treatments led to a relatively even particle distribution in MFGs/MFGM compared to 40 kHz and 20 + 40 kHz treated MFGs/MFGM. Ultrasound treatment significantly resulted in the decrease of interfacial tension (π) in all MFGs/MFGM (p0.05). Three typical crystal forms, α-crystal, β-form and β'-form, were observed in control and ultrasonicated 5 min MFGs/MFGM, but α-crystal disappeared in all the 15 min treated MFGs/MFGM. Ultrasonic duration has a more profound effect on the increase of β'- crystal than the intensity. Ultrasonic treatments promoted the crystallisation of MFGs/MFGM fat at higher temperature but increased the melting temperature of MFGs/MFGM. Additionally, the 15 min treatments caused more pronounced changes in the intramolecular β-sheet, random coil, and α-helix structures compared to the 5 min treatments. 20 + 40 kHz/ 15 min treatment led to aggregated membrane proteins indicated by the confocal laser scanning microscopy (CLSM) images. All the MFGs/MFGM exhibited shear-thinning behaviour, except for the 40 kHz treated MFGs/MFGM, which displayed non-Newtonian behaviour at the lower shear rate. The preliminary investigation on the effects of HMP incorporation on the MFGs/MFGM materials showed the enhanced absorbance at the Amide I and Amide II bands and altered fingerprint regions among all the MFGs/MFGM. Larger particle sizes ranging from 10 to 100 μm presented in the 0.30% HMP MFGs/MFGM, suggesting the formation of conjugates between HMP and milk proteins. These structural and compositional changes induced by HMP affected the physical stability and rheological properties of MFGs/MFGM. Notably, MFGs/MFGM with 0.30% HMP exhibited the poorest stability, a significant increase in apparent viscosity, and shear-thinning behavior throughout the analysis. In summary, acidification, ultrasonic treatments, and HMP incorporation significantly impact the structural, compositional, and functional properties of MFGs/MFGM ingredients.Item Upcycling of brewing by-products using bio-processing technology and an analysis of their functional and nutritional characteristics(University College Cork, 2024) Jaeger, Alice; Arendt, Elke K.; Sahin, AylinThis thesis focuses on the upcycling of brewing by-products; specifically brewer’s spent yeast (BSY) and a protein isolate produced from brewer’s spent grain (BSG). Although high in nutrients, the unappealing sensory characteristics and unstable nature of these products has made it difficult to valorise these materials to date. Spent yeast was extensively characterised and a process was developed focused on alcohol removal, standardisation, autolysis, and lactic acid bacteria fermentation using L. amylovorus FST 2.11. As a result of this process, sensory characteristics were significantly improved regarding reduced bitterness and an increase in fruity flavours. Techno-functional properties were also altered, with major changes in pH and protein composition. In addition, the effects of this processing on protein digestion, using the in-vitro INFOGEST protocol, and on the gut microbiome, using an in-vitro colon model were examined, yielding increased amino acid bio-availability and indicators of prebiotic potential. As well as BSY, the potential of BSG as a sustainable nutrition source was examined, particularly regarding the functional and digestive properties of a spent grain protein isolate (BRP). BRP was shown to have superior functionality to many plant proteins, in particular regarding solubility, and also displayed good digestibility characteristics as determined using the tiny-TIM in-vitro model. This research explores the enormous potential to be found within brewing by-products and the benefits of processing to achieve palatable, functional and highly nutritious food ingredients to form a part of a more sustainable and circular future food system.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.