Food and Nutritional Sciences - Doctoral Theses

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    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; Teagasc
    The 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.
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    Formulation, processing and functionality of plant-based alternatives to cheese
    (University College Cork, 2023) Grasso, Nadia; O'Mahony, Seamus Anthony; Crowley, Shane; Lauritzson Foundation
    Numerous plant-based cheese alternatives developed using different raw materials, formulations, and processes are currently commercially-available. However, most of these products differ significantly from their dairy counterparts, and a lack of knowledge of the science underpinning development of plant-based cheese alternatives is evident in the scientific literature. This thesis investigates the physicochemical characteristics of commercially-available products against dairy benchmarks and studies the influence of different protein concentrations and profiles, ingredients, and calcium fortification strategies, to achieve the development of plant-based cheese alternative prototypes with enhanced nutritional profile and functionality than these types of products currently available. Chickpea protein ingredients were used to formulate samples with high protein contents and different texture and microstructure; however, such samples did not have acceptable melting behaviour. Binary blends of zein and chickpea protein ingredients allowed development of plant-based cheese alternatives with improved meltability and stretching properties, due to the unique rheological characteristics of zein. Different calcium fortification approaches were proposed to improve the nutritional profile of plant-based cheese alternatives; however, fortification resulted in changes in the physicochemical properties of the samples. The learnings obtained were used to develop a plant-based cheese alternative prototype with similar texture to processed cheese, and enhanced nutritional and physicochemical properties compared to the commercial plant-based cheese alternatives. However, further improvements of protein digestibility and sensory properties of the prototype are needed. The findings presented in this thesis represent significant advancements in our understanding of the ingredient, formulation and processing science required to develop plant-based cheese alternatives.
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    Development and optimisation of food products low in FODMAPs: an investigation of dietary fibres in low FODMAP products and the reduction of FODMAPs via bio-technological processes
    (University College Cork, 2023) Atzler, Jonas J.; Arendt, Elke K.; Gallagher, Eimear; Department of Agriculture, Food and the Marine, Ireland
    Cereal-based products – a stable food source in the western world- are high in fructans and α-galactooligosaccharides (GOS). These carbohydrates belong to the group of fermentable oligo-, di-, monosaccharides and polyol (FODMAP), which were shown to trigger symptoms of irritable bowel syndrome. A diet low in FODMAPs is reported to relieve symptoms in over 70 % of patients However, the availability of nutritious and appealing food products (e.g., sufficient dietary fibre content and good techno-functional quality) suitable for that diet is very limited. Therefore, this thesis investigated two approaches and their potential for overcoming this challenge. Firstly, three enzymes (invertase, inulinase and α-galactosidase) were used to investigate the targeted degradation of fructans and GOS. Inulinase and invertase degrade both fructans and GOS, while α-galactosidase only degrades GOS. Inulinase was the most efficient in degrading both fructans and GOS since it led to the degradation of 90 % of both oligosaccharide types. However, the use of inulinase and invertase resulted in the production of two degradation compounds – fructose in excess of glucose and melibiose and its higher homologues- which have the potential to act as FODMAPs. The second approach was to fortify products with dietary fibres (DFs) beneficial for IBS-patients, based on substituting wheat flour with wheat starch and gluten. The application of two insoluble (bamboo fibre and cellulose) and two soluble-viscous DFs (psyllium and guar gum) was tested in bread and pasta. Two different concentrations of these DFs (3 g/ 100g and 6 g/100 g) were used to produce a bread. The application of these DFs in a bread system, highlighted that the effects on the bread quality significantly depend on both the DFs' solubility and viscosity. All DFs decreased the specific volume of breads and increased the hardness after 0 h and 24 h. Despite these effects, the techno-functional quality was similar to wheat bread fortified with DF (3 g/100 g and 6 g/ 100 g of wheat bran). Additionally, a dose dependency of these effects was found: using the DFs in a concentration of 6 g/100 g resulted in an enhancement of the observed effects. Ultimately, the addition of all fibres led to an improvement in the nutritional quality with reduced in vitro starch digestibility. All four DFs mentioned above were added to a pasta system in a concentration of 6 g/100 g. The effects on the techno-functional properties depended on the DF's solubility, viscosity, and particle size. Both cellulose and guar gum showed the most potential with acceptable techno-functional properties (e.g., hardness, optimal cooking time, cooking loss). The application of highly viscous DFs (especially guar gum) positively influenced the in vitro starch digestibility. For all DF fortified pasta, no significant difference in the sensory properties compared to the unfortified pasta was found, suggesting an acceptable sensory quality. Finally, a combination of three different DFs (resistant starch, cellulose and corn fibre rich in arabinoxylans) was used to produce a fibre-enriched low FODMAP biscuit. Using the response surface method (RSM) for finding the best combination of the three ingredients resulted in a biscuit with a DF content of ~15 % and an improved quality compared to the unfortified biscuit. The sensory quality of the optimised biscuit was similar to a wholemeal biscuit and the unfortified low FODMAP control biscuit. Furthermore, the fibre-enriched biscuits showed an improved in vitro starch digestibility. Overall, the findings of this thesis offer a set of tools for the developments of low FODMAP products. On the one hand the suitability of IBS-beneficial fibre for developing nutritious and appealing products suitable for a low FODMAP diet is a reliable approach, without the need of any further FODMAP reduction techniques. On the other hand, also the targeted use of FODMAP degrading enzymes is a promising approach; if native fructans and GOS are present (e.g., whole wheat or rye-based products) these can be efficiently degraded in combination with fermentation-based techniques.
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    Upcycling of brewing by-products using lactic acid bacteria fermentation technology and analysis of their behaviour in a cereal-based applications
    (University College Cork, 2023-05-19) Neylon, Emma; Arendt, Elke K.; Horizon 2020
    Barley rootlets (BR) and brewers spent grain (BSG) are by-products of the malting and brewing industries and are primarily used in animal feed and landfill. Due to the beneficial nutritional composition of BR and BSG (high fibre/protein) the current uses underestimate their maximum potential. BR are a relatively under explored material and review of the literature available on BR revealed extensive knowledge on the formation, processing, compositional quality, and potential applications of BR. In regard BSG, literature suggests high prospects for BSG in widely available cereal-based applications. However, further processing of BSG such as using lactic acid bacteria (LAB) fermentation technology are required to improve food product quality and further valorise BSG as a food ingredient. The incorporation of BSG and fermented BSG (FBSG) in a pasta matrix revealed inclusion of BSG and FBSG induced changes in gluten properties which depreciated pasta quality (reduced firmness and tensile strength) compared to semolina pasta. However, both BSG and FBSG pasta formulations performed more favourably than the wholemeal control from a techno-functional perspective. A greater reduction in the predicted glycaemic index with FBSG fortification compared to BSG suggested fermentation further enhances nutritional properties of BSG. A follow up study on the application of BSG and FBSG in a bread revealed similar defects to bread quality. Nonetheless, comparing BSG and FBSG breads, FBSG addition improved bread characteristics resulting in increased specific volume, reduced crumb hardness; restricted microbial growth rate over time; and slowed the release in reducing sugars over time during in vitro starch digestion. The success observed in the capability of LAB technology to functionalise BSG sparked interest in the application of LAB fermentation in BR processing. As a result, 5 fermented BR ingredients were developed and produced using Lactiplantibacillus plantarum FST 1.7 (BR-FST1.7), Lactobacillus amylovorus FST2.11 (BR-FST2.11), Weissella cibaria MG1 (BR-MG1), Leuconostoc citreum TR116 (BR-TR116) and Limosilactobacillus reuteri R29 (BR-R29). The changes in sugar/FODMAP/acid compositions; microbial metabolites and techno-functional properties of the developed BR ingredients identified each LAB fermentation imparted a unique set of characteristics to the BR ingredient, further affirming LAB fermentation technology as a functionalising processing technique. The developed BR ingredients were applied to a bread matrix to explore if characteristics of the LAB fermentation translated to the bread product. Inclusion of the fermented BR ingredients improved bread specific volume/reduced crumb hardness (BR-MG1, BR-TR116); substantially slowed microbial spoilage of breads (BR-R29); and produced breads with improved nutritional characteristics and varied sensory flavour profile (BR-FST2.11, BR-FST1.7). The outcome of this research thesis provides extensive knowledge on the effects of BSG and BR on pasta/bread quality as well as showcasing the potential of LAB fermentation technology as a valorisation technique for BR and BSG processing.
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    Dietary quality of school-aged children and teenagers in Ireland by demographic characteristics and eating location
    (University College Cork, 2022-10) Rusu, Ioana; Kehoe, Laura; Flynn, Albert; Cashman, Kevin; Walton, Janette; O'Mahony, Jim; Department of Agriculture, Food and the Marine, Ireland
    Background: Childhood and the teenage years are distinctive life stages characterised by unique dietary needs. Data from nationally representative dietary surveys of children and teenagers across Europe have shown that intakes of key nutrients are not in line with recommendations. Furthermore, demographic characteristics such as sex, age, socio-economic status and weight status may have an influence on dietary quality in children and teenagers. It has also been shown that eating location can influence dietary quality, with some locations such as ‘home’ and ‘school’ being associated with better dietary quality than other locations, such as ‘restaurants’, ‘takeaways’ and ‘shops’. Objectives: The overall aim of this thesis was to examine the dietary quality of school-aged children and teenagers in Ireland by demographic characteristics and eating location using data from the National Children’s Food Survey II (NCFS II) (2017-18) and the National Teens’ Food Survey II (NTFS II) (2019-20). Methods: The analyses for this thesis were based on data from the NCFS II and the NTFS II which are two nationally representative dietary surveys of children (5-12 years, n 600) and teenagers (13-18 years, n 428) living in the Republic of Ireland. Dietary intake data were collected at brand level using a 4-day weighed food diary for both surveys. Dietary quality was determined using energy-adjusted (%E or /10MJ) intakes of nutrients and food groups. ‘Eating location’ was defined as the location where food was prepared or obtained, irrespective of where it was consumed. For eating location analysis, consumers were defined as those who consumed food at a given location at least once during the four-day recording period. Results: The overall dietary quality of children and teenagers in Ireland was found to be unfavourable and there were very few differences observed across sex, age groups, categories of socio-economic status and weight status. Intakes of key food groups were not in line with food-based dietary guidelines (FBDG) for either children or teenagers. In both children and teenagers, dietary intakes were driven by the ‘home’ location. While the majority of children (73%) and teenagers (78%) consumed food from ‘outside of the home’, most eating occasions took place at ‘home’ for both children (89%) and teenagers (85%), accounting for a large proportion of the energy consumed (88% in children and 81% in teenagers). The contribution of food consumed from ‘outside of the home’ was higher in teenagers than in children (19% vs. 12%). Younger children had higher intakes of energy from food consumed from ‘other homes’ than older children and both children and teenagers of parents with primary/intermediate education only had higher intakes of energy from food consumed from ‘fast food/takeaways’ than children and teenagers of parents with tertiary education. There were no other differences observed in these eating patterns across any other demographic characteristics examined. Food consumed from ‘home’ and the ‘participant’s own home’ was better in terms of dietary quality than food consumed from ‘outside of the home’ and ‘other homes’. Of all ‘out of home’ locations, ‘school’ provided the best dietary quality for children, but this was not seen in teenagers. Conclusion: This thesis has shown that the overall dietary quality of children and teenagers in Ireland was unfavourable and there were few differences found across demographic characteristics. Dietary intake was driven by the home environment, with ‘home’ and the ‘participant’s own home’ being associated with better dietary quality than ‘other homes’ and ‘outside of the home’. The findings of this thesis can be of use to policy makers when introducing healthy eating policies aimed at school-aged children and teenagers such as taxation on unhealthy foods and regulation around marketing of unhealthy foods.