[Show abstract][Hide abstract] ABSTRACT: Mid-infrared (MIR) spectrometry was used to estimate the fatty acid (FA) composition in cow, ewe, and goat milk. The objectives were to compare different statistical approaches with wavelength selection to predict the milk FA composition from MIR spectra, and to develop equations for FA in cow, goat, and ewe milk. In total, a set of 349 cow milk samples, 200 ewe milk samples, and 332 goat milk samples were both analyzed by MIR and by gas chromatography, the reference method. A broad FA variability was ensured by using milk from different breeds and feeding systems. The methods studied were partial least squares regression (PLS), first-derivative pretreatment + PLS, genetic algorithm + PLS, wavelets + PLS, least absolute shrinkage and selection operator method (LASSO), and elastic net. The best results were obtained with PLS, genetic algorithm + PLS and first derivative + PLS. The residual standard deviation and the coefficient of determination in external validation were used to characterize the equations and to retain the best for each FA in each species. In all cases, the predictions were of better quality for FA found at medium to high concentrations (i.e., for saturated FA and some monounsaturated FA with a coefficient of determination in external validation >0.90). The conversion of the FA expressed in grams per 100 mL of milk to grams per 100 g of FA was possible with a small loss of accuracy for some FA.
Journal of Dairy Science 11/2013; · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Milk oligosaccharides (OS)—free complex carbohydrates—confer unique health benefits to the nursing neonate. Though human digestive enzymes cannot degrade these sugars, they provide nourishment to specific commensal microbes and act as decoys to prevent the adhesion of pathogenic micro-organisms to gastrointestinal cells. At present, the limited quantities of human milk oligosaccharides (HMO) impede research on these molecules and their potential applications in functional food formulations. Considerable progress has been made in the study of OS structures; however, the synthetic pathways leading to their synthesis in the mammary gland are poorly understood. Recent studies show that complex OS with fucose and N-acetyl neuraminic acid (key structural elements of HMO bioactivity) exist in goat milk. Polymorphisms in the CSN1S1 locus, which is responsible for synthesis of αs1-casein, affect lipid and casein micelle structure in goat milk. The present study sought to determine whether CSN1S1 polymorphisms also influence goat milk oligosaccharide (GMO) production and secretion. The GMO compositions of thirty-two goat milk samples, half of which were from genotype A/A (αs1-casein producers) and half from genotype O/O (αs1-casein non-producers), were determined with nanoflow liquid chromatography high-accuracy mass spectrometry. This study represents the most exhaustive characterization of GMO to date. A systematic and comprehensive GMO library was created, consolidating information available in the literature with the new findings. Nearly 30 GMO, 11 of which were novel, were confirmed via tandem mass spectrometric analyses. Six fucosylated OS were identified; 4 of these matched HMO compositions and three were identified for the first time in goat milk. Importantly, multivariate statistical analysis demonstrated that the OS profiles of the A/A and O/O genotype milks could be discriminated by the fucosylated OS. Quantitative analysis revealed that the goat milk samples contained 1.17 g/L of OS; however, their concentration in milks from A/A and O/O genotypes was not different. This study provides evidence of a genetic influence on specific OS biosynthesis but not total OS production. The presence of fucosylated GMO suggests that goat milk represents a potential source of bioactive milk OS suitable as a functional food ingredient.
Small Ruminant Research 04/2013; · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Milk fat secretion is a complex process that initiates in the endoplasmic reticulum of the mammary epithelial cell by the budding of lipid droplets. Lipid droplets are finally released as fat globules in milk enveloped by the apical plasma membrane of the mammary epithelial cell. The milk fat globule membrane (MFGM) thus comprises membrane-specific proteins and polar lipids (glycerophospholipids and sphingolipids) surrounding a core of neutral lipids (mainly triacylglycerols and cholesterol esters). We have recently described major proteins of the MFGM in the goat and we have highlighted prominent differences between goats and bovine species, especially regarding lactadherin, a major MFGM protein. Here, we show that, in the goat species, the well-documented genetic polymorphism at the α(s1)-casein (CSN1S1) locus affects both structure and composition of milk fat globules. We first evidenced that both milk fat globule size and ζ-potential are related to the α(s1)-casein genotype. At midlactation, goats displaying strong genotypes for α(s1)-casein (A/A goats) produce larger fat globules than goats with a null genotype at the CSN1S1 locus (O/O goats). A linear relationship (R(2)=0.75) between fat content (g/kg) in the milk and diameter of fat globules (μm) was established. Moreover, we found significant differences with regard to MFGM composition (including both polar lipids and MFGM proteins) from goats with extreme genotype at the CSN1S1 locus. At midlactation, the amount of polar lipids is significantly higher in the MFGM from goats with null genotypes for α(s1)-casein (O/O goats; 5.97±0.11mg/g of fat; mean ± standard deviation) than in the MFGM from goats with strong genotypes for α(s1)-casein (A/A goats; 3.96±0.12mg/g of fat; mean ± standard deviation). Two MFGM-associated proteins, namely lactadherin and stomatin, are also significantly upregulated in the MFGM from goats with null genotype for α(s1)-casein at early lactation. Our findings are discussed with regard to techno-functional properties and nutritional value of goat milk. In addition, the genetic polymorphism in the goat species appears to be a tool to provide clues to the lipid secretion pathways in the mammary epithelial cell.
Journal of Dairy Science 08/2012; 95(11):6215-29. · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Fat is present in milk as droplets of triglycerides surrounded by a complex membrane derived from the mammary epithelial cell called milk fat globule membrane (MFGM). Although numerous studies have been published on human or bovine MFGM proteins, to date few studies exist on MFGM proteins from goat milk. The objective of this study was thus to investigate the protein composition of the goat MFGM. Milk fat globule membrane proteins from goat milk were separated by 6% and 10% sodium dodecyl sulfate-PAGE and were Coomassie or periodic acid-Schiff stained. Most of MFGM proteins [mucin-1, fatty acid synthase, xanthine oxidase, butyrophilin, lactadherin (MFG EGF-8, MFG-E8), and adipophilin] already described in cow milk were identified in goat milk using peptide mass fingerprinting. In addition, lectin staining provided a preliminary characterization of carbohydrate structures occurring on MFGM proteins from goat milk depending on alpha(S1)-casein genotype and lactation stage. We provide here first evidence of the presence of O-glycans on fatty acid synthase and xanthine oxidase from goat milk. A prominent difference between the cow and the goat species was demonstrated for lactadherin. Indeed, whereas 2 polypeptide chains were easily identified by peptide mass fingerprinting matrix-assisted laser desorption/ionization-time of flight analysis within bovine MFGM proteins, lactadherin from goat milk consisted of a single polypeptide chain. Another striking observation was the presence of caseins associated with MFGM preparations from goat milk, whereas virtually no caseins were found in MFGM extracts from bovine milk. Taken together, these observations strongly support the existence of a singular secretion mode previously hypothesized in the goat.
Journal of Dairy Science 03/2010; 93(3):868-76. · 2.57 Impact Factor