Milk Fat Content and DGAT1 Genotype Determine Lipid Composition of the Milk Fat Globule Membrane

During secretion of milk fat globules, triacylglycerol (TAG) droplets are enveloped by a phospholipid (PL) trilayer. Globule size has been found to be related to polar lipid composition and fat content, and milk fat content and fatty acid composition have been associated with the diacylglycerol acyltransferase 1 (DGAT1) K232A polymorphism; however, the association between the DGAT1 polymorphism and fat globule size and polar lipid composition has not been studied. The ratio between polar and neutral lipids as well as the composition of the polar lipids in milk has industrial as well as nutritional and health implications. Understanding phenotypic and genotypic factors influencing these parameters could contribute to improving milk lipid composition for dairy products. The focus of the present study was to determine the effect of both fat content and DGAT1 polymorphism on PL/TAG ratio, as a marker for milk fat globule size, and detailed PL composition. Milk samples were selected from 200 cows such that there were equal numbers of samples for the different fat contents as well as per DGAT1 genotype. Samples were analyzed for neutral and polar lipid concentration and composition. PL/TAG ratio was significantly associated with both fat content and DGAT1 genotype. Phosphatidylinositol and phosphatidylserine concentrations were associated with fat content*DGAT1 genotype with a stronger association for the AA than the KK genotype. Sphingomyelin concentration tended to interact with fat content*DGAT1 genotype. Phosphatidylethanolamine (PE) concentration showed a biphasic response to fat content, suggesting that multiple biological processes influence its concentration. These results provide a new direction for controlling polar lipid concentration and composition in milk through selective breeding of cows

Binding of CML-Modified as Well as Heat-Glycated beta-lactoglobulin to Receptors for AGEs Is Determined by Charge and Hydrophobicity

Intake of dietary advanced glycation end products (AGEs) is associated with inflammation-related health problems. Nε-carboxymethyl lysine (CML) is one of the best characterised AGEs in processed food. AGEs have been described as ligands for receptors present on antigen presenting cells. However, changes in protein secondary and tertiary structure also induce binding to AGE receptors. We aimed to discriminate the role of different protein modifications in binding to AGE receptors. Therefore, β-lactoglobulin was chemically modified with glyoxylic acid to produce CML and compared to β-lactoglobulin glycated with lactose. Secondary structure was monitored with circular dichroism, while hydrophobicity and formation of β-sheet structures was measured with ANS-assay and ThT-assay, respectively. Aggregation was monitored using native-PAGE. Binding to sRAGE, CD36, and galectin-3 was measured using inhibition ELISA. Even though no changes in secondary structure were observed in all tested samples, binding to AGE receptors increased with CML concentration of CML-modified β-lactoglobulin. The negative charge of CML was a crucial determinant for the binding of protein bound CML, while binding of glycated BLG was determined by increasing hydrophobicity. This shows that sRAGE, galectin-3, and CD36 bind to protein bound CML and points out the role of negatively charged AGEs in binding to AGE receptors

Mechanisms underlying the skin-gut cross talk in the development of ige-mediated food allergy

Immune-globulin E (IgE)-mediated food allergy is characterized by a variety of clinical entities within the gastrointestinal tract, skin and lungs, and systemically as anaphylaxis. The default response to food antigens, which is antigen specific immune tolerance, requires exposure to the antigen and is already initiated during pregnancy. After birth, tolerance is mostly acquired in the gut after oral ingestion of dietary proteins, whilst exposure to these same proteins via the skin, especially when it is inflamed and has a disrupted barrier, can lead to allergic sensitization. The crosstalk between the skin and the gut, which is involved in the induction of food allergy, is still incompletely understood. In this review, we will focus on mechanisms underlying allergic sensitization (to food antigens) via the skin, leading to gastrointestinal inflammation, and the development of IgE-mediated food allergy. Better understanding of these processes will eventually help to develop new preventive and therapeutic strategies in children

Invloed van natuurkorst op ontwikkeling van geur tijdens kaasrijping

In de afgelopen jaren deden wij bij Wageningen University & Research onderzoek als onderdeel van de ‘proeftuin natuurlijke kaasrijping’ bij Remeker in Lunteren, in de vorm van afstudeeronderzoeken. In totaal deden zeven studenten levensmiddelentechnologie hun afstudeeronderzoek in het kader van de proeftuin. De onderliggende vraag van al deze onderzoeken was: wat bepaalt de geur van Remeker- kaas. Daarbij lag de focus op zowel het begrijpen van de geurstofvorming als het effect van de veranderende rijpingsomstandigheden in de proeftuin. Een belangrijk onderdeel van de proeftuin was namelijk om de kazen op een stabiele temperatuur (16 °C) en een relatieve hoge luchtvochtigheid (90%) te rijpen, waarbij het belangrijk was om na te gaan of dit een verandering zou veroorzaken in de geurstofvorming

Letters: Milk and Mortality : Study used wrong assumption about galactose content of fermented dairy products

Michaëlsson and colleagues’ proposed mechanism for the effect of milk intake on the risk of mortality and fractures is based on the assumption that fermented dairy products (which had the opposite effects to those of non-fermented milk) are free of galactose.1 For most fermented dairy products, however, this is untrue. The paper quoted by the authors shows a decrease in lactose from 4.8 g/100 g to 2.3 g/100 g (loss of 2.5 g/100 g) in yoghurt compared with milk,2 with an increase in galactose of 1.3 g/100 g. Because lactose is composed of glucose and galactose, which have equal molecular weight, this decrease in lactose would lead to 1.25 g/100 g of galactose formed (equal to the 1.3 g/100 g in the quoted paper). Yoghurt therefore contains the same amount of galactose as milk (and in lactase non-persistent people may lead to even higher galactose intakes). The galactose content of (semi)hard cheeses is somewhat lower because the curd is washed during production, but cheese is not usually free from galactose. Overall, the galactose intake from fermented dairy products (soured milk and yoghurt in the paper) is equal to that from regular dairy products, which makes the authors’ proposed mechanism highly unlikely

Quality control of raw cows' milk by headspace analysis : a new approach to mastitis diagnosis

In de levensmiddelenindustrie wordt veelvuldig de kwaliteit van levensmiddelen getest met behulp van apparaten die aan het voedsel ruiken. Dit is ook op melk toegepast. Hierbij bleek dat melk van goede kwaliteit slechts zeven verschillende geurstoffen bevat (ter vergelijking, in kaas worden meer dan honderd verschillende geurstoffen aangetroffen). Na analyse van de geurpatronen in melk met verschillende gebreken bleek dat in melk onder andere residuen van reinigingsmiddelen en de mate van vetafbraak gedetecteerd konden worden. Vervolgens is onderzoek gedaan naar melk van koeien met uierontsteking (mastitis), één van de belangrijkste ziekten bij melkkoeien. In een eerste experiment bleek dat de geurstoffen in mastitis melkmonsters een bijzonder patroon vertoonden, waarbij een statistisch model op basis van het patroon aan geurstoffen kon voorspellen welke bacterie de veroorzaker van de uierontsteking was. Vervolgens is bepaald dat de geurstoffen gevormd werden door de bacterie zelf. Uit het laatste experiment bleek dat 4 tot 8 uur incubatietijd nodig was voorafgaand aan de identificatie van geurstoffen

Smediger kaas door juiste voer

Veel kaasmakers willen smedige (zachte, smeuïge) kaas maken, want de gemiddelde consument vindt die kaas het lekkerst. Kasper Hettinga en Jan Dijkstra van Wageningen Universiteit vertellen hoe de smedigheid van kaas kan worden beïnvloed door de samenstelling van het veevoer

Dairy in a sustainable diet: a question of balance

The demand for dairy products is growing rapidly, especially in emerging markets. Dairy products are nutrient rich and, therefore, an important food group for ensuring nutrient security in the future. In many countries, dairy contributes significantly to nutrient intake. Meta-analyses have shown that consumption of dairy may reduce the risk of chronic diseases and thereby lower healthcare costs. Milk production and processing contribute to greenhouse gas emissions, estimated at 2.7% (cradle-to-retail) of the world’s total. Evaluating the position of dairy in the diet should take into account the impact of both nutritional and environmental factors. Local conditions are also important; in many parts of the world, the cow is an efficient converter of human-inedible resources into nutrient-dense food. Increased productivity of cows is a decisive factor in realizing sufficient milk production with optimal resource efficiency and minimal greenhouse gas emission. Models that optimize total diets, rather than individual food products, for their nutritional and environmental impact are the preferred approach for developing realistic alternative consumption strategies

Short communication: Practical issues in implementing volatile metabolite analysis for identifying mastitis pathogens

Several parameters for improving volatile metabolite analysis using headspace gas chromatography-mass spectrometry (GC-MS) analysis of volatile metabolites were evaluated in the framework of identification of mastitis-causing pathogens. Previous research showed that the results of such volatile metabolites analysis were comparable with those based on bacteriological culturing. The aim of this study was to evaluate the effect of several method changes on the applicability and potential implementation of this method in practice. The use of a relatively polar column is advantageous, resulting in a faster and less complex chromatographic setup with a higher resolving power yielding higher-quality data. Before volatile metabolite analysis is applied, a minimum incubation of 8 h is advised, as reducing incubation time leads to less reliable pathogen identification. Application of GC-MS remained favorable compared with regular gas chromatography. The complexity and cost of a GC-MS system are such that this limits the application of the method in practice for identification of mastitis-causing pathogens