Darius Hummel¹ and Jörg Hinrichs^{1
1 University of Hohenheim, Garbenstraße 21, 70599 Stuttgart, Germany}

Abstract
In recent years, the frothing capacity of milk, explicitly shelf stable milk, has become more important. Beverages as latte macchiato and cappuccino - especially latte art - have become increasingly popular. The main reason for decreased frothing capacity of milk is known to be based on elevated levels of free fatty acids. They originate from mechanical shear stress and growth of certain bacteria. Regarding induced lipolysis caused by mechanical stress, various processing steps during dairy processing seem to be critical. The present study focuses on the entire process of milk processing regarding the influence of cow breed, storage time of fresh raw milk as well as variations during milk processing as septic and aseptic homogenization and their influence on the concentration of free fatty acids and frothing capacity of shelf stable milk. Furthermore, critical values for frothing of shelf stable milk were determined.

Practical relevance
Milk processing companies face the problem that some UHT milk batches show poor frothing capacities and are complained about by the retail trade. By examining the entire process of UHT milk preparation, particularly critical process steps for the quality are to be identified and critical values for the content of free fatty acids for good foaming behavior are to be defined.    

Yuan Jiang¹, Xiao-Chen Liu¹, Lilia M. Ahrné¹ and Leif H. Skibsted^{1
1 Department of Food Science, University of Copenhagen, Rolighedsvej 26, DK, 1958, Frederiksberg C, Denmark}

Abstract
Calcium binding to lactose, inulin, fructose, galactose and glucose has been investigated using electrochemical, calorimetric and solubility methods. Calcium binding to milk saccharides was athermal and binding in 1:1 complexes accordingly entropy controlled with Ka = 10 L/mol for lactose, Ka = 8 L/mol for galactose, Ka = 6 L/mol for fructose and Ka = 4 L/mol for glucose. For inulin, binding has Ka = 35 L/mol for each of two calcium bound by each inulin in a moderately endothermic process corresponding to ΔH > 0 for calcium association. Quantum mechanical calculations using  Density Functional Theory show increased binding of β-anomers of lactose compared with α-anomers of lactose, which was confirmed experimentally and assigned to 3-coordination versus 2-coordination with hydroxyl groups with ΔS = 19 J/(mol·K) for the dicoordinated α-anomer and ΔS = 20 J/(mol·K)  for the tricoordinated β-anomer. Calcium binding to lactose is expected to be independent of pH and lactose might accordingly prevent precipitation of calcium in the intestines and thus increase absorption of calcium as was previously found by others in human intervention studies.

Practical relevance
Understanding of the binding of calcium to the milk sugars lactose, galactose and glucose and to the plant oligosaccharide inulin often used as an ingredient in dairy products will help in a rational use of oligosaccharides in the design of novel dairy products with enhanced calcium bioaccessibility.    

Xiao-Chen Liu¹, Jacob J. K. Kirkensgaard¹ and Leif H. Skibsted^{1
1 Department of Food Science, University of Copenhagen, Rolighedsvej 26, DK, 1958, Frederiksberg C, Denmark}

Abstract
The calcium citrate complex (CaCitr-) accounts for 70% of the soluble calcium species in milk. Understanding effects of acidification and heat treatment on calcium citrate speciation in milk is accordingly crucial for process development in the dairy industry. Especially the effect of changes in pH on speciation during digestion is important for optimizing calcium absorption in intestine from functional foods based on milk, since CaCitr- prevents calcium from precipitation and formation of calcium citrate hexahydrate (CCH). Three hydrates of calcium citrate were detected during dehydration of the thermodynamic stable CCH with the enthalpies of dehydration of ΔH (hexa to tetrahydrate) = 43.6, ΔH (tetra to dihydrate) = 43.8, and ΔH (di to anhydrate) = 88.1 kJ/mol as measured by DSC. The more soluble, less stable but more robust calcium citrate tetrahydrate is not converted into the thermodynamic stable CCH with lower solubility during the pH-changes typical for digestion explaining the positive effect of citrate on calcium bioavailability, in agreement with Ostwards phase law.

Practical relevance
The effects of acidification and heat treatment on calcium citrate speciation in milk is important for dairy industry development. The effect of changes in pH on calcium species during digestion is important for understanding calcium absorption in intestine from milk based foods.       

Pernille Lund¹, Mie R. Bechshøft², Colin A. Ray² and Marianne N. Lund^{1
1 University of Copenhagen, Frederiksberg, Denmark
2 Arla Foods Ingredients Group P/S, Videbæk, Denmark}

Abstract
When breastmilk is not an option, newborns rely on getting their nutritional needs fully covered by infant formula (IF) and it becomes crucial to manufacture IF with high nutritional quality. The most widely used whey protein ingredient in IF is whey protein concentrate (WPC). Various processing steps are included in manufacturing of both powdered IF and WPC, which introduce protein modifications. A gently processed whey protein ingredient (SPC) was manufactured and used for production of a powdered IF, which was compared to a powdered WPC-based IF. In addition, casein ingredients were included. Structural protein modifications and Maillard reaction products were quantified in ingredients and IFs. Overall, IF processing was responsible for several protein modifications, where this contribution generally outweighed the differences between ingredients. Quantification of α-dicarbonyls revealed the importance of considering other aspects than thermal processing. Surprisingly, SPC had a higher methylglyoxal level than WPC. Different trends in formation of Maillard reaction products were observed, challenging the idea of using a single marker for evaluating the Maillard reaction.

Practical relevance
Quantification of protein modifications and their precursors are important for development of tailored manufacturing leading to improved IF that ensures a healthy diet for newborns. Innovative processing has allowed production of a sustainable whey protein ingredient, but it was revealed that processing steps in addition to heat load must be considered.    

Martin Nørmark Thesbjerg^1,2, Søren Drud-Heydary Nielsen¹, Ulrik Kræmer Sundekilde¹, Nina Aagaard Poulsen¹ and Lotte Bach Larsen^{1
1 Department of Food Science, Aarhus University, Denmark
2 Sino-Danish College (SDC), University of Chinese Academy of Science}

Abstract
In bovine milk it has long been known that the formation of cysteine-bridges plays an important role for the tertiary organizations of the caseins and as such presumably for casein micelle organization. In bovine milk, both αs2-CN and κ-CN has two Cys residues each, which can engage in cysteine-bridges. Bovine κ-CN forms homomultimers, while αs2-CN is present as dimers, linked with interchain disulfide bridges. In contrast, human αs1-CN and κ-CN contains one and three Cys residues, respectively, and hetromultimers between κ-CN and αs1-CN have been reported. Comparing the O-glycosylations of κ-CN in human and bovine milks, the O-glycosylations on human κ-CN are more extensive and consists of larger and more complex glycans. From an analytical point of view, these features possess a set of challenges, as the caseins in human milk are tightly linked into large multimeric structures requiring specific treatments prior to proteomic analysis. As part of an ongoing PhD project, protein profiles of human milk protein were investigated by various proteomic approaches and revealed that cysteine-bridges and O-glycosylations of κ-CN play a major role in relation to analytical performance.

Practical relevance
Understanding the complexity of the κ-/αs1-CN heteromultimers in human milk is necessary for establishing Top-Down Mass Spectrometry methods for further analysis of the proteomic footprint in relation to e.g., genotypes and other biologic variation in profiles of the major human milk proteins. 

Megan M. Ross¹, Shane V. Crowley¹, Alan P. Morrison², Jorge Oliveira, Suzanne Crotty³ and Alan L. Kelly^{1
1 School of Food and Nutritional Sciences, University College Cork, Cork, Ireland
2 School of Engineering and Architecture, University College Cork, Cork, Ireland
3 BioSciences Imaging Centre, Department of Anatomy and Neuroscience, BioSciences Institute, University College Cork, Cork, Ireland}

Abstract
3D printing is an Additive Manufacturing technology that is used to make complex structures and geometries using a diverse range of materials, including food. To achieve this, a greater understanding of the fundamental printability of food materials is required. The objective of this study was to develop rheological methods to characterise the ‘printability’ of processed cheese formulations. The pH and casein content of processed cheese formulations significantly (p > 0.05) affected its printability. Printing temperature had a large effect on the microstructure and texture of printed processed cheese; processed cheese printed at 65°C showed larger fat droplets and harder texture than cheese printed at lower temperatures (45°C). Subsequently, the effect of various factors (i.e., calcium concentration and printed geometries) on 3D-printed Micellar Casein Concentrate (MCC) was studied. It was found that these factors all had an effect on the structure and properties (e.g., melting rate) of 3D-printed MCC gels. In conclusion, the formulation and technology of 3D-printed dairy materials can influence its suitability as a printing material and the applications of that product thereafter.

Practical relevance
3D food printing has potential to give consumers the freedom to design personalized meals and snacks. Foods suitable for 3D food printing (e.g., dairy-based ingredients) could act as a basic structural foundation for nutrients and flavours to be incorporated into, thereby, creating a customised snack or meal to suit the nutritional requirements and personal taste preferences of individual users.