Ana-Isabel Mulet-Cabero¹, Alan Mackie², Pete Wilde¹ and André Brodkorb^{3
1 Quadram Institute Bioscience, Norwich, UK
2 School of Food Science and Nutrition, University of Leeds, Leeds, UK
3 Teagasc Food Research Centre, Moorepark, Cork, Ireland}

Abstract
The aim of this study was to unravel the mechanisms of the digestion of caseins and whey proteins by which they are denominated as ‘slow’ and ‘fast’ proteins, respectively.

Formulations were designed differing in the ratio of caseins to whey proteins at 8% total protein with and without the addition of lipid. The samples were digested in a semi-dynamic adult digestion model, which simulated the main dynamics of the human stomach. Selected emptied aliquots went through an in vitro small intestinal digestion while nutrient absorption was assessed by the ex vivo methodology of Ussing chamber, using murine intestinal tissue.

The casein-rich samples showed the formation of mozzarella-like coagula that were persistent throughout gastric digestion. In contrast, whey proteins presented soluble aggregates that dissipated over time resulting in a clear solution by the end of the gastric digestion. This intragastric behaviour was supported by a preliminary human study, using capsule endoscopy. The different gastric re-structuring of the milk proteins critically modulated the nutrient emptying and the subsequent amino acid bioaccessible and absorbed.

Practical relevance
The modulation of gastric behaviour can be further exploited to develop food structures with tailored rates of nutrient digestion, exerting specific physiological functionalities. For instance, foods with fast protein uptake will promote protein synthesis, which can be beneficial for sports nutrition or treating sarcopenia in the elderly.    

David A. Goulding¹, Jonathan O’Regan², Nora M. O’Brien¹ and James A. O’Mahony^{1
1 School of Food and Nutritional Sciences, University College Cork, Ireland
2 Nestlé Development Centre Nutrition, Wyeth Nutritionals Ireland, Askeaton, Co. Limerick, Ireland}

Abstract
Lactoferrin (LF) is a bioactive iron-binding glycoprotein. When thermally processed, LF undergoes significant physicochemical changes. The link between such changes and the bioactivity of LF is not well characterised. In this work, thermal processing (72, 80, 85 or 95°C for 15 s) of LF solutions (1%, w/v, pH 7) was simulated. Heat-induced disulfide-linked aggregates were formed. This was accompanied by increases in surface hydrophobicity, ζ-potential and changes to the secondary structure of the protein. The red colour of LF was also lost. LF samples were irreversibly denatured, with endotherms detected at 58.7°C (apo-LF) and 89.6°C (holo-LF). Using the same samples, it was shown that LF and heat induced LF aggregates were largely resistant to simulated infant gastric, but not intestinal, digestion. Also, the efficacy of LF bactericidal activity, and inhibition of lipopolysaccharide-induced NF-κB activation were negatively impacted by thermal processing. LF physicochemical structure and bioactive efficacy was affected by the extent of heat-induced changes in protein structure whereby processing conditions of least severity (i.e. pasteurisation) had the least impact on bioactivity.

Practical relevance
To avoid thermal processing with other formula components, LF is typically dry blended into infant formula. Thermal processing is typically required for manufacture of LF ingredients suitable for dry blending to infant formula. This research conveys the link between processing intensity and LF structure, digestion, and bioactivity. Pasteurisation retains LF bioactivity causing least impact.     

Shuo Mu¹, Sanne Boesveldt¹ and Markus Stieger^{1  
1 Division of Human Nutrition and Health, Wageningen University, Wageningen, the Netherlands}

Abstract
Previous studies indicated that humans have the ability to detect fatty acids by their odor and to discriminate olfactorily between milks differing in fat content. Researchers argue that volatile aroma composition may contribute to the discrimination, but the detailed mechanisms behind this remain unknown. The aims of this study were (a) to compare olfactory fat discrimination capability of pasteurized and UHT milks (0.5, 1.5, 3.5% fat content) and (b) to link volatile aroma composition (volatile odor compounds) to olfactory fat discrimination capability.  Triangle tests were performed (n=33) to determine olfactory fat discrimination capability. Aroma intensity and liking were quantified using line scale ratings (1-100). SPME-GC-MS analysis were performed to quantify volatile composition of the headspace of milks. Participants were capable of discriminating the smell between all fat levels for pasteurized milks (significant differences (p<0.05) between 0.5 vs. 1.5%; 0.5 vs. 3.5%; 1.5 vs. 3.5%).  In contrast, participants were not capable of olfactory discriminating between any fat levels for UHT milks. When comparing milks with same fat content, aroma intensity.

Practical relevance
This study indicated why people can or cannot distinguish fat content in pasteurized and UHT milks. The mechanism can be applied to optimize the flavour of pasteurized and UHT milk products. Besides, this result also can be helpful when keeping the consistency of milk flavour.

María Ayelén Vélez¹, Erica Rut Hynes¹, María Cristina Perotti^{1
1 Instituto de Lactología Industrial (INLAIN, Universidad Nacional del Litoral/CONICET). Santa Fe, Argentina}

Abstract
Addition of beneficial unsaturated fatty acids into dairy food provides relevant health properties. However, they are unstable and susceptible to environmental conditions such as oxygen, light, temperature, pH and ionic charge, and can decrease both food functionality and quality. Our research focuses on two approaches to achieve stability of bioactive fatty acids: encapsulation and homogenization.  For the first approach we have studied liposome delivery, formulating CLA-liposomes as ingredients for dairy applications. We characterized the vesicles morphologically (TEM microscopy), in size (by DLS), for encapsulation efficiency (GC) and resistance to freeze-drying. Besides, we assessed the performance of the liposomes as an ingredient in yoghurt. They showed resistance to thermal treatment, oxidation stability and high CLA recoveries. No detrimental effects were found. For the second approach, we used a homogenization step to incorporate CLA in yoghurt milk. We studied the effect of CLA at two levels on fermentation, particle size distribution, CLA content, fatty acids profiles, oxidative stability and physicochemical properties. We successfully increased CLA in all formulations.

Practical relevance
Our research is an innovative and feasible option to produce functional foods with high bioavailability of beneficial fatty acids. Liposomes are versatile vesicles, with high biocompatibility and biodegradability which makes them suitable for diverse fields. As for homogenization, it is a technology commonly applied in dairy industry and could be easily adapted to prepare biolipid-enriched foods.

Natalie Ahlborn^1,2,3, Carlos Montoya^1,3, Aiqian Ye^1,2, Linda Samuelsson³, Nicole Roy^1,4,5 and Warren McNabb^1,4

^{1 Riddet Institute, Massey University, Private Bag 11222, Palmerston North, New Zealand
2 School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand
3 Smart Foods Innovation Centre of Excellence, AgResearch Ltd, Te Ohu Rangahau Kai, Palmerston North, New Zealand
4 High-Value Nutrition National Science Challenge, Auckland, New Zealand
5 Department of Human Nutrition, University of Otago, Dunedin, New Zealand}

Abstract
Milk is a worldwide staple food, consumed from infancy to late adulthood. Globally, bovine milk is mainly processed using heat and pressure to improve safety and preservation. Differences in processing can affect nutrient structural assemblies, with downstream implications for gastric digestion. Growing pigs (n=180) were fed either raw or processed (pasteurised-homogenised, pasteurised non-homogenised and ultra-high-temperature) bovine milk for ten days. Gastric contents were collected at six timepoints postprandially to analyse rheological and microstructural properties of the gastric curd, and the gastric emptying rate. Preliminary data analysis showed that heat treatment and homogenisation of bovine milk decreased (P<0.05) the curd strength and influenced pH of the curd over time, while ultra-high temperature treatment resulted in a faster gastric empty rate during the first two post-prandial hours. In conclusion, this data indicated that both heat treatment and homogenisation impact in vivo gastric digestion. Ongoing analyses will determine the impacts of varied curd and whey fraction formation on the release and absorption of amino acids and lipids from the small intestine.

Practical relevance
This work will add to our understanding of how the digestion and absorption of processed milk contribute to their nutritional outcomes. The knowledge gained from this work can then be used to develop milk-based foods able to deliver superior nutritional value to consumer populations with specific requirements, such as the elderly, athletes or the ill.     

Shruti Lalwani¹, Andreas Håkansson¹, Marie Paulsson¹ and Maria Glantz^{1
1 Department of Food Technology, Engineering and Nutrition, Lund University, Sweden}

Abstract
Consumer trends are focused on minimal processing of milk. Process technologies for heat treatment used within the dairy industry today probably have smaller effects on the nutritional quality and functionality of milk than older technologies that are the basis for the calculations of nutritional values declared to consumers. This PhD-project focuses on what effects different heat treatments have on the nutritional quality and functionality of milk and dairy products. In a first study, the temperature gradient of fluid was investigated in a lab-scale setup, both experimentally and with Computational Fluid Dynamics (CFD) simulations, to get unbiased kinetic parameters of fluids when heat-treated. When a fluid is subjected to heat, an axial temperature gradient will be formed as a consequence of free convection. This temperature gradient will have no effect on water-soluble vitamins, however effects may arise for fat-soluble vitamins in milk. Further, HPLC methods are developed for the simultaneous elution and quantification of vitamins. Degradation of vitamins present in heated milk are quantified and reaction kinetics of the vitamins during heat treatment is evaluated.

Practical relevance
The results have practical implications for studies aiming to estimate the degradation kinetics parameters for vitamins in milk. The data resulting from the project will be further used to develop new calculation models for the nutritional quality of milk which could further be applied to various processing technologies used in the dairy industry.