Influence of maltodextrin addition on the freeze-dry stability of β-lactoglobulin-based emulsions with controlled electrostatic and/or steric interactions

Three types of emulsions (β-Lg-, β-Lg-pectin-, and β-Lg-ι-carrageenan-coated emulsions) with controlled electrostatic and/or steric interactions were prepared, and then examined for their freeze-dry stability in the absence or presence of 6% maltodextrin (MD). In the absence of MD, all emulsions were highly unstable to freeze-drying, nevertheless, the β-Lg-pectin-coated emulsions (d ₃₂ =5.37, d ₄₃ =35.11 μm) that were stabilized mostly by steric repulsion showed better stability than the other 2 emulsions (no dried power was obtained). The freeze-dry instability of all emulsions was improved with MD addition, particularly in the β-Lg- (d ₄₃ =1.10 μm) and β-Lg-ι-carrageenan-coated emulsions (d ₄₃ =0.58 μm) that were stabilized by electrostatic repulsive force. In the presence of MD, the β-Lg-ι-carrageenan-coated emulsions showed the highest stability to freeze-drying, which was attributed to the cooperative impact of steric and electrostatic repulsion. This study implicates that the major mechanism for stabilizing emulsions against freeze-drying could be different depending on the absence or presence of MD.     

Impact of cosolvents (polyols) on globular protein functionality: Ultrasonic velocity, density, surface tension and solubility study

The objective of this study was to understand how cosolvents influence the molecular and functional properties of globular proteins in aqueous solutions. The ultrasonic velocity, density and adiabatic compressibility of cosolvent solutions (0–50 wt% sorbitol or glycerol) were measured in the absence and presence of a globular protein (1 wt% β-lactoglobulin) at 30 °C. These measurements were used to calculate the partial specific apparent volume and adiabatic compressibility of the protein. The protein's volume decreased and its compressibility increased in the presence of high cosolvent concentrations, which were attributed to changes in the properties of the protein interior and solvation layer. Sorbitol was more effective than glycerol at decreasing the protein volume at high cosolvent concentrations, which may be because glycerol has some surface activity and may therefore accumulate around hydrophobic regions on the protein surface. Our data were used to account for the observation that sorbitol is more effective than glycerol at increasing the thermal stability and self-association of the β-lactoglobulin. A better understanding of the influence of protein–cosolvent–solvent interactions on the functionality of globular proteins may facilitate the design of protein-based products.     

Application of multi-component biopolymer layers to improve the freeze–thaw stability of oil-in-water emulsions: β-Lactoglobulin–ι-carrageenan–gelatin

This study examines the influence of interfacial composition on the freeze–thaw stability of oil-in-water emulsions. Three 5% w/w oil-in-water emulsions (5 mM phosphate buffer, pH 6.0) were prepared using the layer-by-layer electrostatic deposition method that had different interfacial compositions: (i) primary emulsion (β-Lg); secondary emulsion (β-Lg–ι-carrageenan); (iii) tertiary emulsion (β-Lg–ι-carrageenan–gelatin). The primary, secondary and tertiary emulsions were subjected to from one to three freeze–thaw cycles (−20 °C for 22 h, +40 °C for 2 h) in the absence or presence of sucrose (10% w/w), and then their stability was assessed by ζ-potential, particle size, microstructure and creaming stability measurements. In the absence of sucrose, the primary and secondary emulsions were highly unstable to droplet aggregation and creaming after three freeze–thaw cycles, whereas the tertiary emulsion was stable, which was attributed to the relatively thick biopolymer layer surrounding the oil droplets. In the presence of 10% w/w sucrose, all of the emulsions were much more stable, which can be attributed to the ability of sucrose to increase the amount of non-frozen aqueous phase in the emulsions. The interfacial engineering technology used in the study could therefore lead to the creation of food emulsions with improved stability to freezing and thawing.     

Modulation of thermal stability and heat-induced gelation of β-lactoglobulin by high glycerol and sorbitol levels

The influence of glycerol and sorbitol on the thermal stability and heat-induced gelation of β-lactoglobulin (β-lg) in aqueous solutions was investigated. The thermal stability of β-lg was characterized by measuring the thermal denaturation temperature (T_m) using differential scanning calorimetry, while its gelation properties were characterized by measuring the gelation temperature (T_gel) and final gel rigidity (G^∗) using dynamic shear rheology. All experiments were carried out using aqueous solutions containing 10% (w/w) β-lg, glycerol (0–70% w/w) or sorbitol (0–55% w/w), and 5 mM phosphate buffer (pH 7.0). No salt was added to these solutions so that there was a relatively strong electrostatic repulsion between the protein molecules, which usually prevents gelation. When the cosolvent concentration was increased from 0% to 50%, T_m increased from 74 to 86 °C for sorbitol, but only from 74 to 76 °C for glycerol, which indicated that sorbitol was much more effective at stabilizing the native state of the globular protein than glycerol. Protein solutions containing sorbitol (0–55%) did not form a gel after heating, but those containing glycerol formed gels when the cosolvent concentration exceeded about 10%, with G^∗ increasing with increasing glycerol concentration. We attribute these effects to differences in the preferential interactions of polyols and water with the surfaces of native and heat-denatured proteins, and their influence on the protein–protein collision frequency.     

Nanoscale Nutrient Delivery Systems for Food Applications: Improving Bioactive Dispersibility,Stability, and Bioavailability

There has been a surge of interest in the development of nanoscale systems for the encapsulation, protection, and delivery of lipophilic nutrients, vitamins, and nutraceuticals. This review article highlights the challenges associated with incorporating these lipophilic bioactive components into foods, and then discusses potential nanoscale delivery systems that can be used to overcome these challenges. In particular, the desirable characteristics required for any nanoscale delivery system are presented, as well as methods of fabricating them and of characterizing them. An overview of different delivery systems is given, such as microemulsions, nanoemulsions, emulsions, microgels, and biopolymer nanoparticles, and their potential applications are discussed. Nanoscale delivery systems have considerable potential within the food industry, but they must be carefully formulated to ensure that they are safe, economically viable, and effective.     

The first panic attack: A neurobiological theory.

The authors extend a neurodevelopmental model of specific phobias (W. J. Jacobs and L. Nadel, 1985) to the etiology of an initial panic attack and its elaboration into panic disorder. An important difference between the initial panic attack and specific phobia is the developmental timing of critical emotional experience: Those occurring early in development lead to panic; those occurring later in development lead to specific phobia. By this account, sensory and emotional experiences that occur early in development are stored in a set of modules, each with a unique developmental trajectory. Reinstatement, which occurs during hormonal stress, produces an aggregate of sensory and emotional memories and the first experience of an unexplained panic attack. Panic disorder, which evolves from unexplained panic attacks, involves retrieval of a disaggregate set of sensory and emotional memory fragments supplemented by an inferential fitting of an explanatory context to this incomplete aggregate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of encapsulation of emulsified lipids with chitosan on their in vivo digestibility

The influence of interfacial composition on the in vivo digestibility of emulsified and encapsulated lipids was investigated. An electrostatic layer-by-layer deposition technique was used to prepare soybean oil-in-water emulsions that contained lipid droplets coated by lecithin or by lecithin–chitosan. Thirty six 4-week-old male mice were divided into four groups and fed treatment diets for 4 weeks; atherogenic diets supplemented with (A) non-emulsified fat, without chitosan (control), (B) non-emulsified fat, with chitosan, (C) emulsified fat, without chitosan, or (D) emulsified fat encapsulated by chitosan. There were no differences in body weights, food intake, major organ weights, or fecal fat contents between all treatment groups, where total fat absorption was >90%. The results suggest that encapsulation of lipids by chitosan does not inhibit their in vivo digestibility, even though previous studies indicate that chitosan does inhibit their in vitro digestibility. Consequently, it should be possible to use chitosan to microencapsulate lipids and lipid-soluble components without compromising their bioavailability, although further human studies are needed to confirm this.     

The effect of binary cosolvent systems (glycerol–sucrose mixtures) on the heat-induced gelation mechanism of bovine serum albumin

The influence of cosolvent composition on the thermal denaturation and gelation of bovine serum albumin (BSA) has been studied. Cosolvent composition was varied by changing the ratio of glycerol to sucrose in 40 wt% cosolvent solutions containing BSA. Differential scanning calorimetry measurements on 0.5 wt% BSA solutions showed that the thermal denaturation temperature of the protein increased with increasing sucrose content. Temperature scanning dynamic shear rheology and turbidity measurements on 4 wt% BSA solutions showed that the gelation temperature and final gel strength increased with increasing sucrose concentration. These observations were attributed to the fact that sucrose was more effective than glycerol at increasing the thermal stability and attraction between globular BSA molecules through a steric exclusion effect. The molecular origin of these effects is the tendency for the system to minimize the contact area of the protein molecules with the surrounding cosolvent solution.     

Characterization and optimization of Yb-doped photonic-crystal fiber rod amplifiers using spatially resolved spectral interferometry

Spatially resolved spectral interferometry is used to measure the mode content of a Yb-doped photonic-crystal fiber rod amplifier with a 2300 μm(2) mode area. The technique, known as S(2) imaging, was adapted for the short fiber amplifier at full power and revealed a small amount of a copolarized LP(11) mode. Simulations illustrate the potential for weak mode suppression in this fiber and agree qualitatively with the measurements of S(2) and M(2). Higher-order-mode content depends on the alignment of the input signal at injection and ranged from -18 dB for optimized alignment to -13 dB when the injection alignment was offset along the LP(11) axis by 30% of the 55 μm mode-field diameter.     

Inflammatory Mechanism of Brucella Infection in Placental Trophoblast Cells

Brucellosis is a severe zoonotic infectious disease caused by the infection of the Brucella, which is widespread and causes considerable economic losses in underdeveloped areas. Brucella is a facultative intracellular bacteria whose main target cells for infection are macrophages, placental trophoblast cells and dendritic cells. The main clinical signs of Brucella infection in livestock are reproductive disorders and abortion. At present, the pathogenesis of placentitis or abortion caused by Brucella in livestock is not fully understood, and further research on the effect of Brucella on placental development is still necessary. This review will mainly introduce the research progress of Brucella infection of placental trophoblast cells as well as the inflammatory response caused by it, explaining the molecular regulation mechanism of Brucella leading to reproductive system disorders and abortion, and also to provide the scientific basis for revealing the pathogenesis and infection mechanism of Brucella.