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.     

Formation of nanoemulsions stabilized by model food-grade emulsifiers using high-pressure homogenization: Factors affecting particle size

Nanoemulsions are finding increasing utilization in the food and beverage industries for certain applications because of their unique physicochemical and functional properties: high encapsulation efficiency; low turbidity; high bioavailability; high physical stability. In this study, we examined the impact of system composition and homogenization conditions on the formation of nanoemulsions using a high-pressure homogenizer (microfluidizer). The mean particle diameter decreased with increasing homogenization pressure and number of passes, with a linear log–log relationship between mean particle diameter and homogenization pressure. The minimum droplet diameter that could be produced after 6 passes at 14 kbar depended strongly on emulsifier type and concentration: SDS < Tween 20 < β-lactoglobulin < sodium caseinate. Small-molecule surfactants formed smaller droplets than proteins, which was attributed to their ability to rapidly adsorb to the droplet surfaces during homogenization. The impact of phase viscosity was examined by using different octadecane-to-corn oil ratios in the oil phase and different glycerol-to-water ratios in the aqueous phase. The minimum droplet size achievable decreased as the ratio of disperse phase to continuous phase viscosities (η_D/η_C) decreased for SDS-stabilized emulsions, but was relatively independent of η_D/η_C for β-lactoglobulin-stabilized emulsions. At low viscosity ratios, much smaller mean droplet diameters could be achieved for SDS (d ∼ 60 nm) than for β-lactoglobulin (d ∼ 150 nm). The information reported in this study will facilitate the rational design of food-grade nanoemulsions using high-pressure homogenization methods.     

Impact of dietary fiber coatings on behavior of protein-stabilized lipid droplets under simulated gastrointestinal conditions

Multilayer emulsions containing lipid droplets coated by lactoferrin (LF) - anionic polysaccharide layers have improved resistance to environmental stresses (such as pH, salt, and temperature), but their behavior within the gastrointestinal tract (GIT) is currently unknown. The objective of this research was therefore to monitor changes in the physicochemical properties and digestibility of these systems under simulated GIT conditions. Primary emulsions (5% corn oil, 0.5% LF) were prepared using a high-pressure homogenizer. Secondary emulsions (5% corn oil, 0.5% LF, 0.5% polysaccharide) were prepared by incorporating alginate, low methoxyl pectin (LMP) or high methoxyl pectin (HMP) into primary emulsions. Emulsions were then subjected to simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) conditions in sequence. LF, LF-LMP and LF-HMP emulsions were stable to droplet aggregation in the stomach but aggregated in the small intestine, whereas LF-alginate emulsions aggregated in both the stomach and small intestine. The presence of a dietary fiber coating around the initial lipid droplets had little influence on the total extent of lipid digestion in SIF, but LF-alginate emulsions had a slower initial digestion rate than the other emulsions. These results suggest that the dietary fiber coatings may become detached in the small intestine, or that they were permeable to digestive enzymes. Pepsin was found to have little influence on the physical stability or digestibility of the emulsions. The knowledge obtained from this study is important for the design of delivery systems for encapsulation and release of lipophilic bioactive ingredients.     

Nanoemulsion-based delivery systems for poorly water-soluble bioactive compounds: Influence of formulation parameters on Polymethoxyflavone crystallization

Polymethoxyflavones (PMFs) extracted from citrus peel exhibit potent anti-cancer activity, but are highly hydrophobic molecules with poor solubility in both water and oil at ambient and body temperature, which limits their bioavailability. The possibility of encapsulating PMFs within nanoemulsion-based delivery systems to facilitate their application in nutraceutical and pharmaceutical products was investigated. The influence of oil type (corn oil, MCT, orange oil), emulsifier type (β-lactoglobulin, lyso-lecithin, Tween, and DTAB), and neutral cosolvents (glycerol and ethanol) on the formation and stability of PMF-loaded nanoemulsions was examined. Nanoemulsions (r < 100 nm) could be formed using high pressure homogenization for all emulsifier types, except DTAB. Lipid droplet charge could be altered from highly cationic (DTAB), to near neutral (Tween), to highly anionic (β-lactoglobulin, lyso-lecithin) by varying emulsifier type. PMF crystals formed in all nanoemulsions after preparation, which had a tendency to sediment during storage. The size, morphology, and aggregation of PMF crystals depended on preparation method, emulsifier type, oil type, and cosolvent addition. These results have important implications for the development of delivery systems for bioactive components that have poor oil and water solubility at application temperatures.     

Influence of chitosan on stability and lipase digestibility of lecithin-stabilized tuna oil-in-water emulsions

The influence of chitosan concentration (0–0.3 wt%) and molecular weight (120, 250 and 342.5 kDa) on the physical stability and lipase digestibility of lecithin-stabilized tuna oil-in-water emulsions was studied. The ζ-potential, droplet size, creaming stability, free fatty acids and glucosamine released was measured for the emulsions when they were subjected to an in vitro digestion model. The ζ-potential of the oil droplets in lecithin-chitosan stabilized emulsions changed from positive (≈+53 mV) to negative and the emulsions were unstable to droplet aggregation for all chitosan concentrations and molecular weights used after being subjected to the digestion model. The amount of free fatty acid and glucosamine released per unit amount of emulsion was higher when pancreatic lipase was included in the digestion model. These results suggest that lecithin-chitosan coated droplets can be degraded by lipase under simulated gastrointestinal conditions. Consequently, chitosan coated lipid droplets may serve as useful carriers for the delivery of bioactive lipophilic nutraceuticals.     

Kinetically controlled siloxane ring-opening polymerization

Some basic aspects of the kinetics and mechanisms of anionic and cationic ring-opening polymerization of cyclic siloxanes are discussed in connection with their use in polymer synthesis. The emphasis is put on the polymerization of strained ring monomers, such as cyclic trisiloxanes, since these provide the possibility of tailoring the polymer structure. Much attention is devoted to association phenomena and to oligomer formation processes.This review is from the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

Gel permeation chromatography: The effect of flow rate on efficiency. II

The effect of flow rate on efficiency in gel permeation chromatoraphy has been examined over wide ranges of flow rate, i.e., linear flow velocities using columns of different diameters using both organic and inorganic packings. The results indicate a considerable increase in efficiency at flow velocities below 0.02 cm/s. No lower limit to this increase could be determined due to experimental difficulties. Between flow velocities of 0.02–0.2 cm/s little efficiency is lost.     

Gel permeation chromatography: The effect of treatment with hexamethyldisilazane on porous glass packings

Porous glass column packings have been shown to be an effective substrate for gel permeation chromatography. When carbon tetrachloride is used as a solvent in conjuction with infrared detection, the porous glass exhibits adsorptive properties with polystyrene and polyisobutene. A procedure to eliminate these undesirable properties by treatment with hexamethyldisilazane has been developed. Experiments showed complete elution of all injected polymer. The treatment thus permits quantitative fractionation studies using infrared detection.     

Inhibition of protein synthesis in lettuce (Latuca sativa L.) by allelopathic compounds

The effects of ferulic, cinnamic, and ellagic acids on the development of roots and protein synthesis in lettuce seedlings (Latuca sativa L., variety of Black Seeded Simpson) are reported here. Both ferulic and cinnamic acids were found to inhibit protein synthesis of the seedlings either when added from the beginning of the germination period, or when added for a short period of time to seedlings which had already germinated under control conditions. Ellagic acid, at the same pH and osmotic concentrations as the effective inhibitors, was completely ineffective in inhibiting either growth of roots or protein synthesis. It is shown that utilization of [¹⁴C] amino acid incorporation into seedlings appears to be a sensitive, reliable, and appropriate indicator of allelopathic inhibition of plant growth. Utilizing this method, it should be possible to determine if the effect on protein synthesis by putative allelopathic compounds is a general phenomenon and may, in turn, help to elucidate the role of these compounds.     

Polymer degradation. V. Changes in molecular weight distributions during sonic irradiation of polyisobutene

Gel permeation chromatography was used to follow changes in the molecular weight distribution of a polyisobutene, initial M _v = 466,000, during degradation induced by sonic irradiation. Seven samples taken at times of 200–163,500 sec. were studied. In general, a steady decrease in molecular weight was observed, although a bimodal distribution was present after 20,000 sec. irradiation. Various measures of inhomogeneity, M _w/M _n, U, etc., were examined. The function, σ_n/M _w, where σ_n is the standard deviation of the number distribution, is considered as a measure of the relative distribution. It is shown to be almost constant throughout the degradation.