Comprehensive characterization of neutral and polar lipids of buttermilk from different sources and its milk fat globule membrane isolates

Buttermilk (BM) has recently received much attention as a source of milk fat globule membrane (MFGM) due to its high polar lipid (PL) content, which gives it functional properties and health benefits. Nevertheless BM can be obtained from two different technological processes, i) the BM from the butter oil industry (BM1) and ii) BM from the butter manufacture (BM2). Neutral lipids (NL) and PL characterization from both BM and their MFGM isolated fractions have been qualitatively and quantitatively characterized including the individual phospho- and sphingolipids by HPLC-ELSD as well as triacylglycerols (TAG) and cholesterol and FAME by GC-FID. The results revealed that while BM (either from BM1 or BM2) had a PL fraction of 12–16 %, the MFGM isolated fraction contained about 40 % of PL with major presence of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM). Besides, MFGM showed a significant increase in the medium molecular weight TAG and cholesterol and almost two fold amount of PUFA content than BM due mainly to linoleic acid. The results of this study provide deeper information on the lipid composition of BM and MFGM isolated fractions of great importance for the design of dietary supplements with potential beneficial effects on human health.     

Profiling gangliosides from milk products and other biological membranes using LC/MS

Gangliosides are an important class of glycosphingolipids involved in numerous biological processes such as neuronal development, host–pathogen interactions and gastrointestinal health. Due to the highly heterogeneous nature and relatively low abundance of gangliosides, characterization of gangliosides in biological membranes is challenging. Existing methods for ganglioside analysis are quite time consuming and require expensive high resolution mass spectrometers. A rapid method combining reversed phase chromatography and mass spectrometry was developed using a triple-quadrupole mass spectrometer operating in multiple reaction monitoring mode. The ganglioside species were separated with a Poroshell 120 EC-C18 column and analysed under the negative ion mode. This method allows a sensitive, specific, and quantitative assay for profiling gangliosides. The method is developed for analysis of gangliosides in the milk fat globule membrane of whole milk and applied to other biological membranes. Application includes the cellular membrane of prostate cancer cells. In summary, the method allows various biological membranes to be screened for over 600 gangliosides from 12 classes (GM1, GM2, GM3, GM4, GD1, GD2, GD3, GD4, GT1, GT2, GT3, and GT4) in less than three hours. In summary, expressed as % of relative amounts: 1.5% GM3, 80.2% GD3, 14.4% GT3, 1.5% GM1, 2.4% GD1 were observed in whole milk; 2.5% GD1, 88.2% GD3, 2.5% GM1, 2.2% GM3, 0.2% GT2, 4.2% GT3 were observed in buttermilk and 10.6% GD1, 55.6% GD3, 1.6% GM1, 12.2% GM3, 19.2% GT3, 0.9% GT4 were observed in colostrum.     

Impact of buttermilk consumption on plasma lipids and surrogate markers of cholesterol homeostasis in men and women

Background and aimsSphingolipids (SL) are important components of the milk fat globule membrane (MFGM) found in buttermilk. While studies in animal models suggest that dietary SL may have cholesterol-lowering properties, data in human are lacking. The aim of this study was to investigate the impact of buttermilk consumption on plasma lipids and surrogate markers of cholesterol (C) homeostasis in humans.Methods and resultsMen and women (n = 34) with serum LDL-C <5.0 mmol/L at screening (mean LDL-C = 3.8 mmol/L) were recruited in this double-blinded randomized crossover placebo controlled study. Their diets were supplemented with 45 g/d of buttermilk and with 45 g/d of a macro/micronutrient matched placebo (4 weeks each in random order). Serum lipid concentrations and surrogate markers of cholesterol homeostasis were measured post diet and compared using mixed models for repeated measures. Consumption of buttermilk led to reduction in serum cholesterol (?3.1%, P = 0.019), LDL-C (?3.1%, P = 0.057) and triacylglycerol (?10.7%, P = 0.007). Buttermilk consumption increased plasma lathosterol concentrations (+12.1%, P = 0.001), but multiple regression analysis indicated that variations in β-sitosterol concentrations (P = 0.002) were the only significant predictor of the LDL-C response to buttermilk consumption.ConclusionButtermilk consumption may be associated with reduced cholesterol concentrations in men and women, primarily through inhibition of intestinal absorption of cholesterol.Registration numberThis trial is registered at clinicaltrials.gov as NCT01248026.     

Quantification of MFGM proteins in buttermilk and butter serum by means of a stain free SDS-PAGE method

In comparison to skim milk and whey, buttermilk and butter serum contain high amounts of functional milk fat globule membrane (MFGM) proteins. Quantification of MFGM proteins is difficult because no analytical standard material is available. By means of conventional SDS-PAGE with subsequent staining, MFGM proteins are analytically separated. However, due to various protein structures (e.g., glycosylation) the affinity to the dye is inconsistent. A direct correlation between measured band intensity and protein concentration and, therefore, absolute protein quantification is not possible. The purpose of this study was to apply a novel stain free SDS-PAGE technique that relies on measuring UV light fluorescence of tryptophan in order to quantify MFGM proteins. Thus, proteins can be quantified without the need for analytical standards, provided that the relative tryptophan content relative to the molecular weight is known. In this study, buttermilk and butter serum obtained from raw cream were examined and the three most abundant membrane proteins were absolutely quantified. Higher amounts of peripheral MFGM proteins were determined in buttermilk (0.9 g/L) and butter serum (2.7 g/L), in comparison to integral MFGM proteins (0.3–0.5 g/L). Conclusions were drawn regarding the absolute protein amount of MFGM material surrounding native milk fat globules.     

Echogenicity caused by stable microbubbles in a protein-lipid emulsion

Some investigators have hypothesized that the echogenicity of natural emulsions is due to protein-lipid interfaces. An in vitro investigation of these phenomena indicates that the observed echoes are the result of entrapped microbubbles that can remain relativelystable in certain naturally occurring products, such as buttermilk.     

Effect of buttermilk consumption on blood pressure in moderately hypercholesterolemic men and women

ObjectivesMilk fat globule membrane (MFGM) found in buttermilk is rich in unique bioactive proteins. Several studies suggest that MFGM proteins possess biological activities such as cholesterol-lowering, antiviral, antibacterial, and anticancer properties, but data in humans are lacking. Furthermore, to our knowledge, no study has yet investigated the antihypertensive potential of MFGM proteins from buttermilk. The aim of this study was to investigate the effects of buttermilk consumption on blood pressure and on markers of the renin–angiotensin–aldosterone (RAS) system in humans.MethodsMen and women (N = 34) with plasma low-density lipoprotein cholesterol < 5 mmol/L and normal blood pressure (< 140 mm Hg) were recruited in this randomized, double-blind, placebo-controlled, crossover study. Their diets were supplemented with 45 g/d of buttermilk and with 45 g/d of a macro-/micronutrient-matched placebo in random order (4 wk for each diet).ResultsButtermilk consumption significantly reduced systolic blood pressure (−2.6 mm Hg; P = 0.009), mean arterial blood pressure (−1.7 mm Hg; P = 0.015), and plasma levels of the angiotensin I-converting enzyme (−10.9%; P = 0.003) compared with the placebo, but had no effect on plasma concentrations of angiotensin II and aldosterone.ConclusionShort-term buttermilk consumption reduces blood pressure in normotensive individuals.