Dairy Processing Technology Centre - Doctoral Theses

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    Sensorial, cultural and volatile properties of dairy powders, yoghurt and butter from pasture and non-pasture cow diets
    (University College Cork, 2022-12-14) Zeng, Cheng; O'Sullivan, Maurice; Kerry, Joseph; Kilcawley, Kieran N.; Teagasc
    Significant advances have occurred in the ability to extract and identify volatile aromatic dairy compounds that may influence sensory perception. In this Thesis volatile extraction techniques were optimised and evaluated in order to obtain a more representative volatile profile of selected dairy products, such as; whole milk powder, skim milk powder, yoghurt and salted butter. This information was also utilised with gas chromatography olfactometry (GC-O) and sensory analysis to determine which specific compounds are most likely influencing sensory perception. In addition the impact of cow diet was assessed in terms of the volatile and sensory profile on skim milk powder, whole milk powder and salted butter using milk from cows outdoors on pasture-fed diets (such as ryegrass, ryegrass and white clover) and cows indoors on trial mixed rations. Cross cultural sensory analysis was also undertaken on skim milk powder from these diets in order to determine if consumers and trained panellists perceived skim milk powder differently based on diet but also on product familiarity Chapter 1 provides an updated review of traditional and novel sensory methods used to evaluate milk, milk powders, yoghurt, and butter, as well as gas chromatography mass spectrometry and gas chromatography olfactometry extraction techniques to provide more complete profile of volatiles that impact sensory perception. Chapter 2 investigates the impact of pasture and non-pasture cow diets on the volatile cross cultural sensory perception of skim milk powder. The volatile profile and sensory properties of the skim milk powder were influenced by cow diet and Irish, Chinese and USA consumers as well as trained sensory panellists perceived products differently primarily based on familiarity. Chapter 3 investigated if yoghurt produced from three different starter cultures were perceived differently by Irish consumers, German consumers and trained assessors. German trained assessors found it more difficult to discern differences between some of the yoghurts than trained Irish assessors. Seventeen of the 24 volatiles compounds identified differed due to starter culture, which most directly or indirectly associated with lipid oxidation.The ability of headspace solid phase microextraction, thermal desorption, and high capacity sorptive extraction as a direct immersion and headspace extraction technique were compared with and without salting out and by a polar and non-polar gas chromatograph column for volatile profiling of whole milk powder in Chapter 4. The impact of three different diets on the sensory properties and volatile profile of whole milk powder was investigated in Chapter 5. Both the sensory perception and volatile profiles of whole milk powder differed significantly depending on the diet, with whole milk powder derived from rye-grass or rye-grass and white clover more similar than whole milk powder derived from total mixed ration. Most of the differences in volatiles due to diet were either directly or indirectly linked to fatty acid content. Chapter 6 outlines the development and optimisation of direct immersion high capacity sorptive extraction for the extraction, separation and identification of volatile compounds from salted butter from three different diets; rye-grass or rye-grass and white clover or from total mixed ration. This thesis has clearly demonstrated that cow diet influences the volatile and sensory characteristics of selected dairy products, which subsequently effects sensory perception on a cultural basis influenced by product familiarity. The benefits of optimising volatile extraction techniques on a product specific basis were clearly demonstrated along with using multiple techniques in order to achieve the most representative volatile profile as possible. Combining volatile analysis with olfactometry and / or sensory techniques enables a more comprehensive understanding of factors influencing sensory perception and choice that can be utilised for product quality, improvement and marketing.
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    3D printing of dairy-based ingredients and investigation into Irish consumer acceptance of 3D food printing applications
    (University College Cork, 2022-05-05) Ross, Megan M.; Kelly, Alan; Morrison, Alan P.; Crowley, Shane; Mccarthy, Mary; The Lauritzson Foundation
    Three-dimensional (3D) food printing is a type of additive manufacture in which foods with certain rheological characteristics are mechanically layered to create 3D structures from a digitally model. 3D food printing can potentially offer consumers a range of benefits, such as personalised nutrition, customisable textures and unique structures and shapes. This multidisciplinary thesis outlines research completed in three key areas: engineering, food science and consumer science, reflecting the importance of evaluating 3D food printing in this holistic manner. The primary objectives of this work was three-fold: (1) to develop a practical 3D food printer design suitable for printing dairy-based ingredients; (2) to identify and develop suitable dairy-based recipes and investigate factors affecting their printability; and (3) to explore determinants of Irish consumer willingness to try 3D food printing applications. The rationale behind two selected 3D food printer designs (Cartesian and Delta), as well as a brief comparison between the functionality of both designs, are reported. The effects of printing parameters (i.e., nozzle diameter, distance to print bed, print speed etc.) on print quality are also discussed. Certain physicochemical factors such as pH and structural protein content were found to significantly affect the printability and texture of a basic processed cheese recipe. Samples with a higher pH (pH 5.8) tended to print less accurate grids and were significantly softer and less gummy, chewy and resilient than those with lower pH (≤ pH 5.6). Printed processed cheese recipes formulated with fresh curd (high structural protein content) resulted in significantly harder prints, yet printed grids inaccurately due to the material dragging during printing. Viscosity profiles were created for each processed cheese recipe using rheological methods and correlated with absolute printing precision values to identify a range of suitable recipes for accurate printing. The effect of various factors on the printability and functionality of Micellar Casein Concentrate (MCC) suspensions was also investigated. Increasing calcium chloride concentration (5 mM) of suspensions lead to significantly harder printed samples, which had lower dissolution and solubility rates than control or printed samples with lower calcium chloride concentration (1 mM). MCC suspensions printed in porous lattice structures were found to dissolve at a quicker rate than those printed in a hemisphere structure due to a higher surface area to volume ratio. An example of possible 3D-printed product concepts demonstrating the potential of MCC as a printing material is presented. In order to achieve a balanced and comprehensive understanding of 3D food printing technology from a number of perspectives, consumer acceptance research was incorporated into this study to compliment the food science and engineering narrative. Using qualitative methods, a series of themes were identified as forming Irish consumers’ perceptions of 3D food printing applications. Consumers’ affinity for naturalness and a strong association for unprocessed, homemade meals were considered barriers to acceptance of 3D-printed foods. As an extension of this study, data from quantitative research further revealed perceived personal relevance as a significant determinant affecting the dependent variable (i.e., willingness to try 3D food printing applications in the food service sector). Trust in science was found to diminish the negative effects of novel food technology neophobia on willingness to try. Potential solutions for negating factors affecting consumer acceptance are also discussed, which may be of benefit to those looking to market 3D food printing applications in the Irish marketplace. The findings from these studies present an opportunity for food sector stakeholders to utilise this knowledge as part of their foundation to build upon and create novel 3D food printer designs and printable formulations which are suitable for acceptance in the consumer market.
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    Development of a process-based milk processing sector model for the Irish dairy industry
    (University College Cork, 2022-04-25) Parmar, Puneet; Kelly, Alan; Crowley, Shane; Shalloo, Laurence; Dairy Processing Technology Centre; Teagasc
    In recent times, the EU dairy industry has been hampered by volatility and uncertainty due to changes in the Common Agricultural Policy (CAP) introduced in 2015. Milk quotas, first introduced in 1984, have since been abolished, which has led to unhindered growth in milk production. The unhindered growth in milk production, combined with volatile supply and demand scenarios, has posed challenges to dairy processing sector. The dairy industry continues to face numerous opportunities and challenges, like seasonality, variation in milk composition, low profitability and idle processing capacity. There are several factors that impact the quality of milk and how it is processed in a dairy environment. The studies presented in this thesis provided information that can aid dairy suppliers and processors on making well-informed, business-critical decisions using information generated from the models and density parameters described in the studies.
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    Controlling the denaturation and aggregation of whey proteins using κ-casein and caseinomacropeptide
    (University College Cork, 2019-12) Gaspard, Sophie J.; O'Mahony, Seamus Anthony; Kelly, Alan; Brodkorb, Andre; Teagasc; Dairy Research Ireland
    Whey proteins ingredients are extensively used in a variety of product formulations such as dairy beverages, infant formula and sport nutritional beverages, due to their nutritional and functional properties. Dairy protein-containing beverages are thermally processed, typically to ensure microbiological safety. However, whey proteins denature and aggregate at temperatures greater than 60°C, which can lead to fouling of industrial equipment and/or uncontrolled gelation, depending on formulation and heating conditions. The presence of caseins has been previously reported to limit the extent of aggregation of whey proteins. The objective of this study was to investigate the effect of κ-casein and caseinomacropeptide (CMP) on the denaturation and aggregation of whey proteins, with a view to developing practical strategies for controlling whey protein denaturation and aggregation for ingredient applications. This study demonstrated that both κ-casein and CMP have the ability to improve the heat stability of whey proteins. The inclusion of κ-casein reduced the size of the aggregates of whey protein after a first heat treatment (90°C for 25 min at pH 7.2) and enhanced their solubility during subsequent heating (90°C for 1 h at pH 7.2). The presence of CMP during heating increased the temperatures of denaturation and gelation of whey proteins and prevented the formation of solid whey protein gels when combined with a low heating rate. The presence of CMP also resulted in a lower turbidity of whey protein solutions after heating and an enhanced solubility of whey protein aggregates. The effect of glycosylation of CMP on the denaturation and aggregation of whey proteins was pH-dependent; a transition occurred at pH 6, below which the glycosylation of CMP reduced its stabilizing properties. This thesis provides new insights into the interactions of whey proteins with κ-casein and CMP, with potential for novel applications in improving the heat-stability and solubility of whey proteins. The outcomes of this study have applications for the manufacture of clear, heat-stable beverages containing whey proteins.
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    Patterns of proteolysis in Danish blue, Camembert, smear-ripened and Cheddar cheeses
    (University College Cork, 2020-06-04) Mane, Anuya; McSweeney, Paul L. H.; Food for Health (Ireland)
    Patterns of proteolysis in Danish blue, Camembert, smear-ripened and Cheddar cheeses The overall aim of this thesis was to investigate patterns of proteolysis in Cheddar, Danish blue (normal and treated), Camembert and smear ripened cheeses at different stages of ripening. Proteolysis in Danish blue was studied during 9 weeks of ripening, specificities of Penicillium roqueforti proteinases on the caseins in milk hydrolysates were determined with a total of 91 and 118 cleavage sites identified in s1- and -casein, respectively. Proteolysis in an Irish farm-house Camembert cheese was studied during 10 weeks of ripening, specificities of Penicillium camemberti proteinases on the caseins in milk hydrolysates were determined and 64, 6, 28 and 2 cleavage sites were identified in s1-, s2-, - and -casein, respectively. Proteolytic, physico-chemical and lipolytic properties of Danish blue cheeses made from partially (73%) or fully homogenised milk (200 L) with or without whey cream were determined at 4 weeks and 8 weeks of ripening. The study showed that incorporation of the whey cream did not cause any major difference to the compositional, proteolytic or lipolytic properties of Danish blue cheese. Proteolysis in an Irish farmhouse smear-ripened cheese was studied by serial slicing (0.41 mm/slice) the first 2 cm from surface towards the center of the cheese. Peptides produced at depths 0.41 mm and 20.5 mm were 720 and 427 from αs1-casein; 691 and 337 from αs2-casein; 807 and 453 from-casein; 180 and 109 from -casein, respectively. The study confirmed higher proteolytic activity at the surface due to action of enzymes of the smear microbiota than at the center of the cheese. Secondary proteolytic changes of the chymosin-derived peptides s1-CN (f1-23) and -CN (193-209) were investigated in Cheddar cheeses made using single strains of Lactococcus lactis subsp. cremoris HP and SK11 during 6 months of ripening and proteolytic specificities of the cell-envelope proteinases of these strains on the caseins were determined. A large number of peptides were identified from mass spectrometric analysis of the soluble extracts of the individual cheesees and highest values of relative intensity from the mass spectrometric analyses were used to plot the cleavage sites that can be used for further understanding of peptides, cleavage site and similar research.