Britta Folmer

Low‐density lipoprotein analysis in microchip capillary electrophoresis systems

Due to the mounting evidence for altered lipoprotein and cholesterol‐lipoprotein content in several disease states, there has been an increasing interest in analytical methods for lipoprotein profiling for diagnosis. The separation of low‐ and high‐density lipoproteins (LDL and HDL, respectively) has been recently demonstrated using a microchip capillary electrophoresis (CE) system [1]. In contrast to this previous study, the present report demonstrates that LDL analysis can be performed in an uncoated glass microchannel. Moreover, by adding sodium dodecyl sulfate (SDS) to the sample at a concentration well below the critical micellar concentration prior to injection, the LDL peak undergoes a focusing effect and exhibits an apparent efficiency of 2.2×107 plates/m. Laser light scattering experiments demonstrate that the low concentration of SDS used does not significantly alter lipoprotein particle size distribution within the time course that the analysis is performed. It is thus hypothesized that SDS nondisruptively coats LDL particles. The peak sharpening effect, observed only when SDS is added solely to the sample, is probably due to a mobility gradient created between the sample and the running buffer. The chip‐based method demonstrated here has the potential for rapid analysis and sensitive detection of different LDL forms of clinical relevance.

Influence of Foam Structure on the Release Kinetics of Volatiles from Espresso Coffee Prior to Consumption

The relationship between the physical structure of espresso coffee foam, called crema, and the above-the-cup aroma release was studied. Espresso coffee samples were produced using the Nespresso extraction system. The samples were extracted with water with different levels of mineral content, which resulted in liquid phases with similar volatile profiles but foams with different structure properties. The structure parameters foam volume, foam drainage, and lamella film thickness at the foam surface were quantified using computer-assisted microscopic image analysis and a digital caliper. The above-the-cup volatile concentration was measured online by using PTR-MS and headspace sampling. A correlation study was done between crema structure parameters and above-the-cup volatile concentration. In the first 2.5 min after the start of the coffee extraction, the presence of foam induced an increase of concentration of selected volatile markers, independently if the crema was of high or low stability. At times longer than 2.5 min, the aroma marker concentration depends on both the stability of the crema and the volatility of the specific aroma compounds. Mechanisms of above-the-cup volatile release involved gas bubble stability, evaporation, and diffusion. It was concluded that after the initial aroma burst (during the first 2-3 min after the beginning of extraction), for the present sample space a crema of high stability provides a stronger aroma barrier over several minutes.

Monocomponent hexa- and dodecaethylene glycol succinyl-tocopherol esters: Self-assembly structures, cellular uptake and sensitivity to enzyme hydrolysis

We have chemically synthesized two water-soluble forms of tocopherol succinate linked via an ester bond to hexaethylene glycol and dodecaethylene glycol. The self-assembly structure of the former in water is vesicular, whereas the latter forms elongated micelles. We treated Caco-2 cells with these compounds in these physical forms, in addition to a mixed micelle form. The intact compounds were taken up into the cells, influenced by both the chain length and the physical structure. In addition, the tocopherol derivatives were also metabolized into tocopherol succinate and tocopherol inside the cell. The total hydrolysis and uptake into the cells was two-fold higher from tocopherol hexaethylene glycol succinate in the form of mixed micelles than in vesicular form as assessed by analyzing intracellular tocopherol and tocopherol succinate. The longer polyethylene glycol chain gave a higher intracellular tocopherol succinate/tocopherol ratio. The major intracellular esterase in Caco-2 cells is carboxyl esterase 1 (EC 3.1.1.1), and in silico modelling studies show that the position of docking and hence the site of hydrolysis is influenced by the chain length. The in silico prediction is consistent with the in vitro data, since a longer chain length is predicted to favour hydrolysis of the ester bond between the succinate and polyethylene glycol moieties.

The cross-sectional headgroup area of nonionic surfactants; the influence of polydispersity

Abstract In this work, we have measured surface tension as a function of concentration of pure and technical nonionic ethoxylated surfactants. Critical micelle concentration(CMC) values, surface tension at the CMC and the cross-sectional headgroup areas are compared. It is shown that the CMC does not depend significantly on the polydispersity of the polyoxyethylene chain. However, the surfactant headgroup area, as determined from the surface tension plots, is much smaller for polydisperse surfactants than for homologue pure surfactants. This is proposed to be due to selective adsorption of the shorter polyoxyethylene species at the surface. For the same reason, the surface tension at the CMC is lower for technical surfactants than for homologue pure species.

Structure and Dynamics of Micelles and Cubic Phase Structures with Ethoxylated Phytosterol Surfactant in Water

The self-assembly of a sterol ethoxylate surfactant with 30 oxyethylene units in water was studied by 1H NMR self-diffusion measurements in a wide concentration range in the micellar region (0-25 wt %). The data showed that the surfactant aggregates do not interact by hard sphere interactions but rather a strong concentration dependence of the diffusion coefficient was noted which was explained by polymer scaling theory. In the cubic phase (30-65 wt %), the self-diffusion data from water, from surfactant, and from free polyoxyethylene suggest spherical micelles, although water diffusion was much restricted due to binding to the surfactant headgroup. From X-ray measurements in the cubic phase, the unit cell size was calculated, and together with surfactant self-diffusion measurements the exchange dynamics between free and aggregated surfactant was obtained.

Crema—Formation, Stabilization, and Sensation

The signature of a good quality espresso coffee is a nice dense brown crema layer that covers the liquid extract. Although some work has been done on the mechanism of formation, the molecular science on the stabilization of the crema is still shrouded in mystery. This chapter gives an overview of the mechanisms of formation and some recent data on the compounds in charge of the stabilization. Further to these physical–chemical aspects, an overview of the role the crema plays in the sensorial perception of espresso coffee is given. We end with the conclusion that to further develop products with optimal crema, a holistic approach needs to be considered, taking into account physics, chemistry, sensory, and consumer science.

Human Wellbeing—Sociability, Performance, and Health

Abstract It is well known that coffee is one of the most widely consumed beverages worldwide. Since its discovery, it has played an important role in the life of many people, even though throughout history people have debated the consequences of drinking coffee to the human body and mind. The pleasurable taste and stimulating properties have been worshiped and hated. But along with these love and hate waves science has evolved and revealed that coffee is a complex mixture of substances that may act together to prevent diseases. Today the debate around the stimulating properties of caffeine has moved from “good versus bad” to the quantities needed for a beneficial impact, and amounts corresponding safe consumption. This chapter will explore these aspects bringing an overview of the evolution of coffees role in the well-being of people through history.