Dairy Processing Technology Centre

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Compositional and analytical factors affecting the stickiness of dairy powders
(University College Cork, 2019-10) O'Donoghue, Laura T.; O'Mahony, Seamus Anthony; Murphy, Eoin; Enterprise Ireland
Spray dying is a dehydration technique used in the dairy industry for the preservation and creation of a wide range of valuable dairy products. However, challenges associated with stickiness development are often encountered during spray drying, particularly with spray dryer feed streams containing high levels of lactose, which can lead to lower yields, reduced powder quality and shorter runs. Stickiness in lactose-containing powders is related to the glass transition phenomenon, in which a phase change occurs in the amorphous form of lactose, causing a decrease in the viscosity of the powder particle surface, leading to liquid bridging and ultimately stickiness between particles and/or to equipment surfaces. There is a wide variety of compositional and environmental factors that affect the rate and extent of stickiness development in dairy powders, such as the temperature and relative humidity of the air or the protein content of the powder. The first objective of this study was to investigate the influence of particle size on the physicochemical properties and stickiness behaviour of a selection of lactose-containing dairy powders. Using a fluidisation technique, this work demonstrated that stickiness increased with decreasing particle size for lactose-containing dairy powders. Stickiness may be characterised using a number of different instrumental approaches, which can be categorised as direct/indirect or static/dynamic techniques. However, most methods provide a binary definition of stickiness (i.e., sticky or non-sticky), which while pragmatic, does not provide information regarding the mechanical relaxations which contribute to stickiness. Therefore, the second objective of this study was to examine the use of dynamic mechanical analysis (DMA) to characterise temperature- and humidity-induced relaxation behaviour of whey protein concentrate (WPC) powders; results were also compared to two other established techniques, differential scanning calorimetry (DSC) and a fluidisation method. The results demonstrated that while DMA may not be an accurate method for stickiness determination, it could prove useful as a complementary method when combined with stickiness techniques (e.g., fluidisation) to provide more detailed information on the physical changes occurring during stickiness. Overall, the findings of this research will prove useful to dairy processors at minimising issues with stickiness during drying and may also potentially provide powder technologists with a new method for tracking the physical transitions that occur during stickiness development of dairy powders.
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.
Mechanical integrity and rehydration properties of agglomerated nutritional dairy ingredient powders
(University College Cork, 2019-12-22) Hazlett, Ryan; O'Mahony, Seamus Anthony
The functional properties of nutritional dairy powders are key in determining the ease at which they can be stored, handled and further applied in formulations or on direct consumer application. Powder agglomeration is a unit operation employed during the spray drying process, in order to obtain a greater control of the resulting powder’s physical, bulk handling and functional properties. The studies presented in this thesis explore the importance of maintaining agglomerate integrity on powder handling (i.e., powder conveying) post-spray drying, while presenting novel research findings in the application of agglomeration for the modification of commercially important, high-protein content dairy powders (e.g., milk protein isolate; MPI). Initially, a custom fabricated pressure dispersion rig was utilised to achieve breakdown of agglomerated powder particles, similar to that occurring in industrial powder conveying systems (i.e., lean phase conveying). Analysis of the resulting powders showed that the significant alterations in both powder physical and bulk properties (i.e., decreased particle size, increased bulk density and increased surface free fat concentrations), occurring on agglomerate breakdown, significantly impaired the functionality (i.e., flowability and rehydration) of a range of commercially agglomerated nutritional dairy powders (i.e., whey protein concentrate, fat-filled milk powder and an infant formula powder). In addition, the agglomeration of MPI was researched, focusing on the utilisation of novel protein-based binders to achieve agglomeration. The results demonstrated that the use of novel protein-based binder solutions achieved a greater extent of agglomeration in comparison to more traditional binder solutions (i.e., water or lactose), ultimately improving the flowability and wetting properties of MPI powders. The conclusions of this thesis demonstrate the importance of maintaining the mechanical integrity of agglomerated dairy powders and the potential for the further application of agglomeration using novel protein-based binder solutions to tailor the functionality of high-protein dairy powders, such as MPI.
A comparison of the use of whole milk and fat-filled milk powders for production of heat-stable long-life beverages
(University College Cork, 2020-04) Crotty, Aisling; Kelly, Alan; O'Mahony, Seamus Anthony; Enterprise Ireland; Dairy Processing Technology Centre
Commercial bovine milk is 3.5% fat, the level of which is affected by seasonality, stage of lactation, feed, health, breed, and even the individual teat. Milk (and other liquid dairy products) are highly perishable due to their nutritional quality, as they are the sole source of nutrition for the neonate. As a result, milk is often dehydrated into powder form, which enhances its shelf life, its storage stability, and the convenience. Another way to enhance the shelf life of milk is to subject it to heat to destroy pathogenic bacteria, enzymes, spores, and to enhance the shelf life of the product. As most dairy products are subjected to some form of heat treatment, their heat stability is integral to the overall quality of the product. In Chapter 2, two reconstituted dairy powders (fat-filled milk powder (FFMP) and whole milk powder (WMP)) were compared under two heat treatments (UHT-processing and retort sterilisation), and three protein contents (2.3, 3.3, and 5%). These variables significantly affected the apparent viscosity, the pH, the colour, the emulsion stability, and the average particle size of the samples. Chapter 3 investigated the influence of calcium-chelating salts on heat stability. These salts are an often-used ingredient in dairy products, as they enhance the heat stability of the system by binding the calcium ions, which are important for casein micelle integrity. The influence of trisodium citrate (TSC), disodium hydrogen phosphate (DSHP), and sodium hexametaphosphate (SHMP) on heat stability, colour, and apparent viscosity was examined. SHMP had the most significant effect on heat stability, colour, and apparent viscosity due to its chelating capacity and its influence on cross-linking between the casein micelles. DSHP had no significant effect on viscosity or colour, whereas the addition of 20 mmol/L of TSC significantly affected the colour of the solution.
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.
The influence of temperature on filtration performance and fouling during cold microfiltration of skim milk
(Elsevier B.V., 2021) France, Thomas C.; Bot, Francesca; Kelly, Alan L.; Crowley, Shane V.; O'Mahony, James A.; Enterprise Ireland; Dairy Processing Technology Centre
Changes in the physicochemical properties and distribution of constituents in skim milk during microfiltration (MF) at low temperature influence filtration performance and product composition. In this study, the influence of processing temperature within the cold MF range (4, 8 and 12°C) on filtration performance, fouling and partitioning of proteins was investigated. MF at 4°C required the greatest energy input due to the significantly higher (p< 0.05) viscosity of feed and retentate streams, compared to processing at 8 and 12 °C. The greatest and lowest extents of reversible and irreversible fouling during MF were observed on filtration at 12 and 4 °C, respectively. Chemical analysis of the cleaning solutions post-processing demonstrated that protein was the major foulant; the lowest protein content in the recovered cleaning solutions (50 °C water and 55 °C alkali) was measured after MF at 4 °C. The concentration of β-casein, β-lactoglobulin and α-lactalbumin in the permeate all decreased throughout MF, due to fouling of the membrane. The greatest decrease in concentration of β-casein in the permeate during MF was observed at 12 °C (18.1%) followed by 8 °C (17.1%) and 4 °C (13.6%). The results of this study provide valuable information on processing efficiency (i.e., energy consumption and protein yield) and membrane fouling during the processing of skim milk in the cold MF range.
Approaches for improving the flowability of high-protein dairy powders post spray drying - a review
(Elsevier B.V., 2021) Hazlett, Ryan; Schmidmeier, Christiane; O'Mahony, James A.; Enterprise Ireland; Dairy Processing Technology Centre
Challenges are commonly encountered in the bulk handling and application of high-protein dairy powders, and are strongly influenced by their poor flowability. Powder flowability can be defined as the ability of a powder to flow under set environmental or processing conditions and it is ultimately determined by the type and extent of interparticle interactions occurring in the bulk powder (e.g., van der Waals and electrostatic interactions). High-protein powders are particularly susceptible to the occurrence of interparticle interactions, resulting in increased cohesive forces being experienced in the bulk powder, thereby reducing powder flowability. This review summarises the major factors responsible for poor flowability in high-protein dairy powders and critiques traditional (e.g., agglomeration) and some of the more relevant novel approaches (e.g., dry- and wet-coating and roller compaction) available for improving the flowability of powders post-spray drying. This review material will be of considerable interest to dairy scientists, technologists and engineers challenged with understanding, predicting and controlling the bulk handling and flowability of high-value dairy protein powders.
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.
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.
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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