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The particle matter of wine is mainly composed of wine colloids and macromolecules. The present work develops a methodology using asymmetrical flow field-flow fractionation coupled with multi-angle light scattering, differential refractive index detector, and ultraviolet detector (AsFlFFF–MALS–dRI–UV) for the fractionation and determination of the molar mass, the hydrodynamic radius, and the apparent densities of the aggregates and macromolecules present in wine samples. The results from a set of six Argentinian high-altitude wines showed two main populations: the first population composed of wine colloids with higher UV-specific absorptivity and the second population composed of polysaccharides, such as arabinogalactans. The conformation results showed that population 1 consists of small and dense particles, while population 2 showed high molar masses and lower densities. The results demonstrated the use of AsFlFFF as a new, effective method for the fractionation and characterization of wine colloids and wine macromolecules in red wines with further potential applications.

In this review, starch behavior is described from molecules in solution to the use of starch in products. The determination of molecular characteristics with asymmetrical flow field-flow fractionation is described, and the behavior of starch in binary solutions is discussed. The organization of starch in granules and the changes in organization during gelatinization and retrogradation are then described. The role of starch retrogradation in bread staling is described in some detail, and the influence of water mobility and distribution is discussed in relation to amylopectin retrogradation. Finally, the use of starch as emulsifier is described. Hydrophobically modified starch is one possibility for emulsion stabilization; also, the starch granule as such can be used to stabilize emulsions (so-called Pickering emulsions).

The release of soluble dietary fiber is a prerequisite for viscous effects and hence beneficial health properties. A simple in vitro method was adapted to follow the release during gastrointestinal digestion, and the percentage of solubilized fiber was measured over time. ß-Glucan from oat bran was mainly released during gastric digestion while the release of pectin from sugar beet fiber continued in the small intestine. Unmilled fractions of sugar beet fiber released more soluble fiber than oat bran flakes, probably due to the porous structure of sugar beet fiber as a result of manufacturing processes, but also due to differences in source. Milling to smaller fiber particles significantly improved releasability (from 20 to 55% released ß-glucan and from 50 to 70% released pectin, respectively, after digestion). When milled fibers were included in individual food matrices, the release was reduced by protein and starch matrices (5% ß-glucan and 35% pectin released, respectively) and slowed by fat (45% ß-glucan and 60% pectin released). This may result in a too low or too late release in the upper small intestine to be able to interfere with macronutrient uptake. The method may be suitable for predicting the gastrointestinal release of soluble dietary fibers from food matrices in the development of healthy food products.

The hydrodynamics of the High Pressure Homogenizer has been investigated in order to increase the understanding of the emulsification process. Fragmentation of drops in the homogenizer is generally assumed to be caused by cavitation and/or turbulence. Both processes are investigated experimentally in order to find its location in the HPH valve region. Cavitation was visualized by investigating light scattered in a HPH valve model with optical access. Detailed measurements of the one phase flow turbulence were obtained by Particle Image Velocimetry (PIV) on a carefully scaled model. The effects of dispersed phase flow volume fraction on the continuous phase turbulence was studied with refractive index matched PIV. The experiments show cavitation being focused in the first half of the gap whereas turbulence intensities are very low inside the gap. The turbulence is most effective in the outlet chamber downstream of the narrow gap. This is even more evident for the turbulent eddies of sizes comparable to the drops that are well known to be most efficient for the fragmentation. Increasing the disperse phase volume fraction does not alter the conclusion of highest turbulence downstream in the gap, however, it leads to an increase in energy of large turbulent eddies and a decrease in the energy of small sale eddies. This would imply a relative increase of the strength of the turbulent viscous mechanism compared to the turbulent inertial mechanism when increasing the volume fraction of dispersed phase. When comparing these findings on with visualizations of drop break-up; turbulence rather than cavitation seems to be the dominant mechanism of fragmentation in these geometries.

Effects of various enzymes and extraction conditions on yield and molecular weight of ß-glucans extracted from two batches of commercial oat bran produced in Sweden are reported. Hot-water extraction with a thermostable a-amylase resulted in an extraction yield of ˜76% of the ß-glucans, while the high peak molecular weight was maintained (1.6 × 106). A subsequent protein hydrolysis significantly reduced the peak molecular weight of ß-glucans (by pancreatin to 908 × 103and by papain to 56 × 103). These results suggest that the protein hydrolyzing enzymes may not be pure enough for purifying ß-glucans. The isolation scheme consisted of removal of lipids with ethanol extraction, enzymatic digestion of starch with a-amylase, enzymatic digestion of protein using protease, centrifugation to remove insoluble material, removal of low molecular weight components using dialysis, precipitation of ß-glucans with ethanol, and air-drying.

Abstract: The microstructure of phase-segregated amylopectin (AP) and β-lactoglobulin (βlg) mixtures formed during drying from solutions with different concentrations and different polysaccharide and protein ratios have been studied using atomic force microscopy (AFM) and transmission electron microscopy (TEM). AFM was used as the main technique and TEM was used to confirm the results. Systems with only one of the components, AP or βlg, displayed even structures. When the polysaccharide and the protein were in the same system they phase segregated with a sharp boundary between the phases. According to the type of surface morphology of the phase-segregated samples, they were grouped into: domains wetting the air-water surface and domains appearing to be immersed in the solid film. The size range of the domains varied widely from about some nanometers to about a few micrometers which was determined by kinetic reasons or by restrictions given by the film structure of the sample. The two phase systems were AP-continuous phase at AP to βlg ratios above about 1:3 and βlg-continuous phase at ratios below about 1:6. Between these ratios, the systems appeared more or less bicontinuous. The morphology as well as its position in the phase diagram suggested a spinodal phase separation. Phase separation was also observed in the metastable region (AP to βlg ratio 3:1), although the domains were smaller and less developed and it was interpreted as binodal phase separation.

Abstract: Time-dependent rheological properties of three tomato paste suspensions in the concentration range of 200–1,000 g paste/kg suspension have been investigated by using the vane geometry at shear rates $$ {\mathop \gamma \limits^ \cdot } < 10\,{\text{s}}^{{ - 1}} $$. Creep tests were conducted to analyze the influence of the level of stress on the rheological behavior of the samples before and after homogenization. The experimental results indicate that the suspensions exhibit an elastic behavior at long times and relatively low stresses, which proves that this type of material can be characterized by a yield stress (σ y). Applying stresses just beyond the yield stress, an initial rheopectic behavior appeared. This increase in viscosity at low deformations was markedly larger after homogenization, and this difference was attributed to changes in the aspect ratio, shape, and orientation of the particles induced by homogenization. These structural changes were also reflected in the transient viscosity when the samples were subjected to larger stresses (σ >> σ y): before homogenization the suspensions exhibited a steady-state viscosity at large deformations, whereas after homogenization, the transient viscosity continuously decreased. That behavior was attributed to flocculation of the particles.

The adsorption of starch that had been hydrophobically modified with octenyl succinate anhydride (OSA) at the oil/water interface during emulsification was studied. The starch samples were of waxy barley origin and were varied in molar mass and degree of substitution (DS). The particle size of the emulsions was measured and the adsorbed amount of starch was determined through serum depletion. The results show that adsorption is governed by the relationship between interfacial area and OSA-starch concentration. The surface load of OSA-starch can in some cases become very high, reaching 16 mg/m2. The emulsification occurs under nonequilibrium and turbulent flow conditions. Under these conditions kinetic factors are likely to play an important role in the adsorption process. Turbulent flow favors transport to the interface of larger molecules over small ones, which could lead to higher surface loads by causing jamming at the interface. A model that treats the adsorption as a collision between particles in turbulent flow has been used, and it shows that the adsorption time of a polymer decreases with increasing polymer radius. It also shows that the time scale of adsorption is shorter than the time scales for configurational changes of macromolecules at interfaces and that emulsion droplet−droplet collisions are of similar time scales as adsorption, which gives further indications that kinetic factors are important during adsorption. The simulation results give a reasonable explanation to why large molecules such as OSA-starch can be efficient as emulsifiers.

Cross‐linked agarose particles (Sepharose CL‐6B) and baker's yeast cells were found to adhere to siliceous supports end‐grafted with boronate‐containing copolymers (BCCs) of N,N‐dimethylacrylamide at pH≥7.5, due to boronate interactions with surface carbohydrates of the particles and the cells. These interactions were registered both on macroscopic and on molecular levels: the BCCs spontaneously adsorbed on the agarose gel at pH≥7.5, with adsorption increasing with pH. Agarose particles and yeast cells stained with Procion Red HE‐3B formed stable, monolayer‐like structures at pH 8.0, whereas at pH 7.0–7.8 the structures on the copolymer‐grafted supports were less stable and more random. At pH 9.0, 50 % saturation of the surface with adhering cells was attained in 2 min. Stained cells formed denser and more stable layers on the copolymer‐grafted supports than they did on supports modified with self‐assembled organosilane layers derivatized with low‐molecular‐weight boronate, presumably due to a higher reactivity of the grafted BCCs. Quantitative detachment of adhered particles and cells could be achieved by addition of 20 mMfructose—a strong competitor for binding to boronates—at pH 7.0–9.0. Regeneration of the grafted supports allowed several sequential adhesion and detachment cycles with stained yeast cells. Affinity adhesion of micron‐sized carbohydrate particles to boronate‐containing polymer brushes fixed on solid supports is discussed as a possible model system suggesting a new approach to isolation and separation of living cells.

In this paper, we study the mechanical degradation and changes in conformation of a branched ultrahigh molar mass biomacromolecule, hydrophobically modified starch, as caused by high-pressure homogenization. The characterization was performed with asymmetrical flow field-flow fractionation (AsFlFFF) with multiangle light scattering (MALS) and refractive index detection. The starch which had been chemically modified with octenyl succinate anhydride (OSA) proved to be very large and polydisperse. Upon high-pressure homogenization, the molar mass and rms radius (rrms) decreased, and the extent of these changes was related to the turbulent flow conditions during homogenization. The treatment also induced an increase and scaling with size in the apparent density of the macromolecules. To further study the changes in conformation, it was necessary to calculate the hydrodynamic radii (rh). This can be determined numerically from the elution times in the analysis and the flow conditions in the AsFlFFF channel. The results showed that the treatment can cause a dramatic decrease in the quotient between rrmsand rh, suggesting major conformational changes. These results together could be interpreted as degradation and “crumpling” of the macromolecule, which would give a decrease in rrmsand an increase in apparent density, together with a “fraying” of more outer parts of the macromolecule, which could give rise to the increase in rh.

Macroporous polyacrylamide gels (MPAAGs) with unique elastic morphology and open porous structure are prepared at subzero temperatures. The porous structure of MPAAGs consisting of large, 1–100 µm-sized interconnected pores, is controlled by the freezing temperature, the content of the initiator system (ammonium persulfate and N,N,N′,N′-tetramethyl-ethylenediamine) in the initial reaction mixture and the solvent used. The initiator content, through its effects on the kinetics of polymerization, is an efficient tool of control allowing for the preparation of well defined macroporous elastic structures with either open interconnected pores or closed pores. In the semi-frozen reaction mixture, the dissolved monomers and initiators are concentrated in the unfrozen liquid microphase where the polymerization reaction proceeds. The final freezing temperature, Tf(defined as temperature fixed in a low temperature thermostat), as well as the solvent used affect the porous structure through their effect on the formation of the unfrozen liquid microphase.

This study has focused on structures formed through the release of lipid membrane material from milk fat globules. The aim of the study was to describe vesicles in the cream plasma and processing-induced vesicular structures in cream and buttermilk. The dairy samples were divided into three fractions through centrifugation, using D₂O for density control. These fractions were examined using cryogenic transmission electron microscopy (cryo-TEM). The cream layer contains submicron-sized emulsion droplets, which are spherical and partly covered with loosely associated protein aggregates. The structures of the coalescence-induced vesicles are mostly unilamellar but bilamellar and multilamellar vesicles are also present. Some spherical structures are observed but facetted particles dominate. In the buttermilk sample, spherical and slightly deformed vesicles are visible but no facetted structures are observed. The butter oil serum sample shows interesting membrane vesicle-fat globule aggregate. These types of structures were also visible in the skim milk sample. The results show that that vesicular material may be found in a range of dairy products. To our knowledge this is the first time that the existence of these types of structure has been unambiguously demonstrated in these systems.

This study has focused on structures formed through the release of lipid membrane material from milk fat globules. The aim of the study was to describe vesicles in the cream plasma and processing-induced vesicular structures in cream and buttermilk. The dairy samples were divided into three fractions through centrifugation, using D2O for density control. These fractions were examined using cryogenic transmission electron microscopy cryo-TEM. The cream layer contains submicron-sized emulsion droplets, which are spherical and partly covered with loosely associated protein aggregates. The structures of the coalescence-induced vesicles are mostly unilamellar but bilamellar and multilamellar vesicles are also present. Some spherical structures are observed but facetted particles dominate. In the buttermilk sample, spherical and slightly deformed vesicles are visible but no facetted structures are observed. The butter oil serum sample shows interesting membrane vesicle-fat globule aggregate. These types of structures were also visible in the skim milk sample. The results show that that vesicular material may be found in a range of dairy products. To our knowledge this is the first time that the existence of these types of structure has been unambiguously demonstrated in these systems.

Abstract: An NMR technique to measure exchange kinetics at thermal equilibrium in dispersions of moderately soluble crystalline material is presented. By monitoring the exchange of molecules between pools in solid and dissolved form, one can characterize the surface specific exchange rate. Illustrative experiments were performed in a model system with β-type crystals of tripalmitin as the solid phase and tripalmitin, a fraction of it deuterated, dissolved in a medium-chain TG oil as the liquid phase. The concentration of deuterated tripalmitin in the solvent was followed by 2H NMR after the crystals, which initially lack deuterated tripalmitin, were immersed in the liquid. The variation of the 2H concentration in the solvent provided the surface specific exchange rate. No systematic errors, due to the slight difference in properties of the deuterated tripalmitin compared to hydrogenated tripalmitin, were observed. The methodology worked well between crystal concentrations of 2 and 4 wt%.

This investigation describes a novel concept in the formulation of carrier systems for the spray-drying of biological materials. As carrier material a system composed of poly(vinyl pyrrolidone) (PVP) and dextran was used. This system yields an aqueous two-phase system in which each phase is enriched in one of the polymers. By varying the composition of the system, the effective structure of a “stirred” system can be varied, covering the entire range from dextran continuous to PVP continuous. This facilitates encapsulation of either of these polymers in a spray-drying operation. In an attempt to investigate the spray-drying from such a system, the surface composition of the spray-dried powder obtained from various compositions of the two-phase system was analyzed by electron spectroscopy for chemical analysis (ESCA), providing information on the distribution of the polymers in the powder and thus also in the spray droplets. The two-phase system was applied for the spray-drying of live bacteria. The survival rate of the bacteria depended on the composition of the two-phase system. The storage stability of the bacteria in these formulations was investigated after storage at room temperature under dry conditions for 4 weeks, and it was found that the survival rate was 10–45%. The results therefore show that this type of formulation holds promise for future applications for micro-organisms as well as other sensitive biological materials such as proteins.

Orthokinetic aggregation of colloids trapped at the air–liquid interface was studied by direct imaging in a couette cell. This method allowed us to follow the temporal evolution of both the cluster-mass distribution and the cluster structure at a shear rate where Brownian aggregation is suppressed. The interactions between the monodisperse latex particles floating at the air–liquid interface were controlled either by varying the electrolyte concentration or by creating a bidisperse system through the addition of small particles. The results show that the clusters in all of the systems are characterized by a high fractal dimension, indicating that the clusters are rearranged and densified by the shear. Kinetic analysis suggests that aggregation of monodisperse systems mainly proceeds through homogeneous aggregation, i.e., large clusters sticking to other large clusters. The bidisperse system, finally, with a size ratio around 10, favored a more heterogeneous aggregation among small and large clusters throughout the aggregation process; a slightly lower fractal dimension was observed compared to the strongly aggregated monodisperse system.

The properties of sphingomyelin obtained from bovine milk were investigated. In particular, the properties of liposomes and emulsions prepared from the spingomyelin, as well as the liquid crystalline behavior, were investigated and compared to those of related phosphatidylcholine systems. Like sphingomyelins from other sources, sphingomyelin from milk contains a large fraction of long and saturated acyl groups, which results in a high gel-to-liquid crystal transition temperature (Tc35–82°C, depending on the lipid concentration). At high sphingomyelin concentrations, a lamellar phase forms above Tc, while a swollen gel phase is obtained below Tc. The gel phase swells to about 20 wt% water, whereas the swelling continues to about 40 wt% water above Tc. The limiting areas per molecule are 51 and 68 Å2below and above Tc, respectively. Sphingomyelin from milk forms liposomes readily in the presence of cholesterol. The liposomes formed have a diameter of about 100 nm and are stable, even at 0.1 M NaCl or HCl. Materials entrapped in the liposomes are released rather slowly (typically 40% over 5 h). A comparison shows that the sphingomyelin liposomes behave similarly to those formed by phosphatidylcholine systems. Furthermore, sphingomyelin from milk forms stable oil-in-water emulsions with soybean oil. The size of the emulsion droplets obtained was about 200 nm. Both the size of the emulsion droplets and its dependence on electrolyte addition correlate closely with those of emulsions formed by the corresponding phosphatidylcholine system. Therefore, it is possible to use sphingomyelin as an alternative for saturated phosphatidylcholines, which may be advantageous for oral and dermal pharmaceutical applications, as well as in cosmetics.

Lecithin is a powerful emulsifier widely used in foods, feeds and pharmaceuticals. Several analytical methods have been proposed to characterize lecithins, but they are often inadequate to determine the industrial functionality. The purpose of this study was to find a relationship between the interfacial properties of lecithins (adsorption to oil/water and fat crystal/oil/water interfaces), phospholipid composition and functionality. Results show that all lecithins adsorb to fat crystals at the triglyceride oil/water interface, making their surface more polar (observed as an increase in the contact angle measured through the oil at the interface: fat crystal/oil/water). This adsorption process is quick (less than five minutes) for relatively polar lecithins, such as soybean phosphatidylcholine (PC), and results in highly polar surfaces (contact angle ~180°). Less polar lecithins give slow adsorption (some hours) and less polar crystals (contact angle =90°). The adsorption of different lecithins to the oil/water interface, observed as a decrease in interfacial tension, follows the adsorption pattern to the fat crystals. We found a relation between high-fat crystal polarity and poor lecithin functionality in margarine (margarines spatters during frying), and also between high-fat crystal polarity and a high polar to nonpolar phospholipids [S(PI + PA + LPC)/SPE; PI, phosphatidylinositol; PA, phosphatidic acid; LPC, lysoPC, PE, phosphatidylethanolamine] ratio in lecithin. The correlations might beviaaggregation properties of lecithin in the oil. We found also that monoolein shifted the adsorption kinetics of lecithin (soybean PC) to fat crystals and the hydrophilicity of adsorbed layers probably due to formation of mixed aggregates between monoolein and soybean PC.

The surface composition of spray-dried sodium caseinate/lactose emulsions having different oil phases were estimated using electron spectroscopy for chemical analysis (ESCA), and the particle structure was studied using scanning electron microscopy (SEM) both before and after storage under humid conditions. After spray-drying, powders in which the oil phases consisting of fats with intermediate melting points, such as hardened coconut oil and butter fat, had the highest surface coverage of fat, approximately 34%. The powder with soybean oil as the oil phase had a surface coverage of fat of approximately 15%. The high-melting hardened rapeseed oil was almost completely encapsulated after spray-drying. After storage in a humid atmosphere, fat was released onto all the powder surfaces (surface fat after storage, between 50–65%) except for those with hardened rapeseed oil in which the fat remained encapsulated. These observations are consistent with the powder structure observed by SEM. The surface composition estimated by ESCA for spray-dried sodium caseinate/lactose-containing emulsions with different amounts of soybean oil and a constant lactose/sodium caseinate ratio showed an almost completely encapsulated oil-phase after drying. Storage of these powders in a humid atmosphere leads to a release of fat onto the powder surface even if the soybean oil content is low (1% of the dry weight). Powders made from soybean oil emulsions with sodium caseinate alone exhibit a much lower degree of encapsulation than in the system where lactose is present.

Submicron organic particles are produced by precipitation in an emulsion. The poorly water soluble organic substance is dissolved in a non-polar solvent. This solution is dispersed in an aqueous phase in the presence of emulsifier. When the non-polar solvent is removed by evaporation, the organic substance precipitates and one particle is formed in each emulsion droplet. Experimental work are here reported on the rate and the influence of the evaporation rate on the formation of cholesteryl acetate particles. An introductory theoretical analysis of the conditions experienced by each droplet during the evaporation is given.

The adsorption of apolipoprotein B (Apo B) at a series of surfaces was investigated with in situellipsometry. For silica and methylated silica, the adsorbed amount (Γ), the adsorbed layer thickness (δe1), and the mean adsorbed layer refractive index (nf) were obtained by a procedure involving studies of the bare substrate at two different ambient refractive indices, as well as four-zone averaging. The adsorbed amount of Apo B at silica is much higher than that at methylated silica. Despite this, the adsorbed layer thickness is the same at the two surfaces, and the adsorbed layer formation proceeds similarly. In both cases, the adsorbed layer formation occurs through the adsorption of Apo B molecules in an essentially random orientation, the difference between silica and methylated silica being the number of molecules adsorbed per unit area. Furthermore, the adsorption of Apo B at phospholipid surfaces was investigated. It was found that the adsorption at phosphatidylcholine (PC) was quite limited, whereas that at phosphatidic acid (PA) was substantial. Studies with mixed PA/PC layers showed that the Apo B adsorption depends on the mixed phospholipid layer composition in an essentially linear fashion. Finally, mixed phospholipid layers of PC and ganglioside GM1, as well as phosphatidylinositol layers, showed a dramatic preferential adsorption of Apo B over e.g., human serum albumin, immunoglobulin G, fibronectin, and fibrinogen.

The effects of fat content and thickeners, propylene glycol alginate (PGA; 1.40%) and guar gum (1.55%), on sensory and instrumental quality descriptors on reducedfat mayonnaises ( 15 and 30% fat) with and without added aroma compounds, citral (semi-polar) and pyroligneous acid (polar), were investigated. One mayonnaise, 82% fat, without added thickener or aroma compounds, was used as reference. Sensory evaluation (quantitative descriptive analysis; QDA), rheological analysis (yield stress, maximum viscosity, G′ and G″), measurements of particle size and headspace GC-MS analyses were carried out. Correlations between the results were developed. Perceived and instrumental texture, and perceived smell and flavour, changed differently in magnitude and direction due to fat content and type of thickener.

The application of surface force measurements for modelling the behaviour of food colloid systems, in particular dispersions of hydrophilic particles in oil-continuous media, is discussed. Interactions between two mica surfaces across a triglyceride (triolein) in the anhydrous state, or containing different amounts of dissolved water, have been investigated. The water content influences the layering of triolein molecules at the surfaces and thereby their interactions. The relationship between surface force data (e.g. the magnitude of the force barrier and the adhesion force) and the properties of colloidal systems is discussed. Further, the importance of capillary condensation for particle interactions in triolein saturated with water is demonstrated.

Emulsions made of whey protein, lactose and soybean oil were spray-dried and the chemical surface composition of the dried powders estimated by electron spectroscopy for chemical analysis. In particular, the ability of whey protein to encapsulate fat was highlighted. Additionally, the structure of the spray-dried powder particles was studied by scanning electron microscopy. The powders were examined after storage in both dry and humid atmospheres (relative humidity 75%, 4 days). It was found that the ability of whey protein to encapsulate soybean oil is rather low compared with sodium caseinate, with a large part of the powder surface covered by fat after spray-drying. After storage in humid atmosphere there is a release of encapsulated oil onto the powder surface in most cases, and an increase in fat coverage. The release offat onto the powder surfaces causes the particle structure to change dramatically for powders containing a critical amount of lactose. Such powders agglomerate and lose structure completely. In comparison, powders containing no lactose storage under humid conditions also cause a release of fat onto the powder; however, in this case particle structure remains intact. Powders containing only a small amount of lactose, up to ~25% of emulsion dry weight, do not exhibit the release of fat onto the powder surfaces after storage under humid conditions and the structure of these powder particles does not change. The presence of lactose in whey protein-stabilized emulsions, however, does not increase fat encapsulation by whey protein, as reported earlier for sodium caseinate-stabilized emulsions that were spray-dried. During spray-drying of whey protein/lactose solutions there is a strong overrepresentation of surface-active whey protein on the powder surface. Whey protein coverage increases even further when the powders are stored under humid conditions, also making them lose structure.

In the present paper redispersion and wettability experiments of spray-dried whey protein-stabilized emulsions are presented. Emulsion droplet size after redispersion gives information about eventual coalescence between emulsion droplets in the powder matrix during drying or storage, resulting in an increase in emulsion droplet size after redispersion. Results from redispersion experiments are combined with previously presented knowledge about powder surface composition and particle structure to elucidate internal processes in the powder matrix and external processes on the powder surface during drying and storage of whey protein powder. The results show that with addition of lactose to whey protein-stabilized emulsions, emulsion droplet structure remains intact in the powder matrix during drying since the emulsion droplet size in the redispersed spray dried emulsion is unchanged. In the absence of lactose there is a growth in emulsion droplet size after redispersion of the spray-dried whey protein-stabilized emulsion, showing that a coalescense of emulsion droplets occurs during the drying or redispersion process. Storage of the whey protein-stabilized powders in a humid atmosphere (relative humidity 75%, 4 days) induces changes in some powders. When the powder contains a critical amount of lactose there is a remarkable increase in emulsion droplet size after redispersion of humid stored powders compared with the emulsion before drying and with the redispersed dry stored powder. In addition, there is a release of encapsulated fat after humid storage of lactose-containing powders detected by electron spectroscopy for chemical analysis. For powders which do not contain any lactose there is no increase in emulsion droplet size after storage in a humid atmosphere compared with the redispersed dry stored emulsion. Addition of only a small amount of lactose prevents coalescence of emulsion droplets and the subsequent increase in droplet size during drying. If the lactose content is kept rather low neither an effect on the droplet size after storage under humid conditions nor a release of fat onto powder surfaces is detected. Furthermore, wettability of the spray-dried whey protein-stabilized emulsions by water is presented. It is concluded that it is beneficial to wettability in water to have as high a coverage of lactose on the powder surface as possible. In addition, a review of particle structure for powders of various composition is presented.

Abstract: Several foods contain semi-solid fats that consist of solid crystals dispersed in a liquid oil. In oil-continuous margarine, butter, and chocolate, fat crystals determine properties such as consistency, stability against oiling-out, and emulsion stability. Trends toward foods with less fat and/or less saturated fat create a need for understanding and controlling the properties of fat crystal dispersions. Fat crystals form a network in oil due to mutual adhesion. One source of strong adhesion is formation of solid bridges (sintering), which has been studied in this work through sedimentation and rheological experiments. Results indicate that sintering may be created by crystallization of a fat phase with a melting point between that of the oil and the crystal. Generally speaking, β′ crystals were sintered by β′ fat bridges, favored by rapid cooling, and β crystals by β fat bridges, favored by slow cooling. The existence of the same polymorphic form of the crystal and bridge indicated that solid bridges, rather than bridges formed by small crystal nuclei, were formed. A maximum in sintering ability for an optimal sintering fat concentration occurred due to competition between bridge formation and other crystallization processes. Some emulsifiers influenced the sintering process. For example, monooolein made it more pronounced, while technical lecithin had the opposite effect.

Abstract: The influence of low concentrations (0.1-5%) of fat crystals on the stability of water-in-soybean oil emulsions was examined by light scattering and sedimentation experiments. Both the initial flocculation/coalescence rate and long-term stability against water separation were determined. The initial flocculation/coalescence rate increased upon addition of small amounts of fat crystals. When the crystal concentration was increased above a critical concentration (specific to a system), a decrease in the flocculation/coalescence rate occurred. The increased flocculation/coalescence rate is likely the effect of bridging of water droplets by fat crystals. Fat crystal wetting by water is an important criterion for this phenomenon to occur. Emulsion stabilization for crystal concentrations above critical is caused by a mechanical screening of water droplets. The presence of considerable amounts of crystals in oil also lowered the density difference between droplet and medium, and enhanced viscosity. The degree of increase in viscosity depended upon the emulsifier. Both a decrease in density difference and an increase in viscosity play a role in hindering flocculation/coalescence of droplets. In long-term studies of water separation, all concentrations of fat crystals stabilized the water-in-oil emulsions. The droplet size of these emulsions increased until the critical droplet size was approached where the screening effect of crystals on the droplets no longer stabilized the emulsions. The stabilizing effect for emulsions with monoolein was continuously improved by increasing the amount of crystals up to 5%. For lecithin-stabilized emulsions, an optimal effect was achieved for fact crystal concentrations of 1–2%.

Abstract: Fat crystals influence the stability of food emulsions, such as margarine, butter, or cream, if adsorbed to the oil/water interface. During the adsorption process, a new fat crystal/water interface is created, while the oil/water interface is lost. The driving force for adsorption is therefore the difference between the interactions between fat crystal/water and oil/water. In this work, we have estimated this interaction difference and compared it to the displacement energy for fat crystals from the oil/water interface to the oil. Our calculations have shown that fat crystal adsorption to the oil/water interface (expressed by contact angle ϑ) is determined by polar energy, excess of fat crystal/water over oil/water (I sw -I ow ). The interfacial tension constitutes the resistance force for crystal adsorption to the interface. Polar interaction energy for fat crystal/water is stronger than the polar interaction energy for oil/water in all cases examined (I sw -I ow >0). The difference corresponds to about 104–106 hydrogen bonds for a hypothetical fat crystal with a diameter of 1 m. The displacement energy for fat crystals to oil is lower than the polar energy excess in most cases examined. Thus, an additional interaction between fat crystals and oil makes it easy to displace the crystals to the oil. There is also a relationship between the adhesion tension (-γ ow • cos ϑ) for the crystals at the oil/water interface and the interfacial tension γ ow . A straight line of slope -1 is achieved for systems with low interfacial tensions (γ ow ) and low polar energy excess (I sw -I ow ).

Abstract: Wetting of fat crystals has been extensively examined in this work by contact angle (θ) measurements of fat crystal, oil, and water in three-phase contact. Contact angle was measured in oil. The crystals were nonpolar and wetted by oil for a contact angle equal to 0, and polar and wetted by water for an angle equal to 180. Fat crystals are expected to contribute to the stability of margarine emulsions if they are preferentially wetted by the oil phase (0<θ<90), but result in instability if they are preferentially wetted by the water phase (90<θ<180). In the absence of oil and water additives, fat crystals in α and β' polymorphs were introduced to the oil/water interface from the oil side (contact angle θ ∼ 30). β Polymorphs were completely wetted by oil (θ ≈ 0). The contact angle for β' crystals decreased with increasing temperature and was slightly lower in butter oil than in soybean oil. Emulsifiers in the oil phase (lecithins, monoglycerides and their esters, ethoxylated emulsifiers) and surface-active proteins in the water phase (milk proteins) made the crystals more polar (higher θ). Nonsurface-active proteins, sugar, and citric acid had no significant effect, although concentrations of salt lowered θ. Contact angle increased with temperature for emulsifiers of limited solubility in the oil, e.g., saturated monoglyceride.

Abstract: The surface composition of spray-dried sodium caseinate/lactose emulsions having different oil phases were estimated using electron spectroscopy for chemical analysis (ESCA), and the particle structure was studied using scanning electron microscopy (SEM) both before and after storage under humid conditions. After spray-drying, powders in which the oil phases consisting of fats with intermediate melting points, such as hardened coconut oil and butter fat, had the highest surface coverage of fat, approximately 34%. The powder with soybean oil as the oil phase had a surface coverage of fat of approximately 15%. The high-melting hardened rapeseed oil was almost completely encapsulated after spray-drying. After storage in a humid atmosphere, fat was released onto all the powder surfaces (surface fat after storage, between 50–65%) except for those with hardened rapeseed oil in which the fat remained encapsulated. These observations are consistent with the powder structure observed by SEM. The surface composition estimated by ESCA for spray-dried sodium caseinate/lactose-containing emulsions with different amounts of soybean oil and a constant lactose/sodium caseinate ratio showed an almost completely encapsulated oil-phase after drying. Storage of these powders in a humid atmosphere leads to a release of fat onto the powder surface even if the soybean oil content is low (1% of the dry weight). Powders made from soybean oil emulsions with sodium caseinate alone exhibit a much lower degree of encapsulation than in the system where lactose is present.

Abstract: Lecithin is a powerful emulsifier widely used in foods, feeds and pharmaceuticals. Several analytical methods have been proposed to characterize lecithins, but they are often inadequate to determine the industrial functionality. The purpose of this study was to find a relationship between the interfacial properties of lecithins (adsorption to oil/water and fat crystal/oil/water interfaces), phospholipid composition and functionality. Results show that all lecithins adsorb to fat crystals at the triglyceride oil/water interface, making their surface more polar (observed as an increase in the contact angle measured through the oil at the interface: fat crystal/oil/water). This adsorption process is quick (less than five minutes) for relatively polar lecithins, such as soybean phosphatidylcholine (PC), and results in highly polar surfaces (contact angle ∼180). Less polar lecithins give slow adsorption (some hours) and less polar crystals (contact angle ≤90). The adsorption of different lecithins to the oil/water interface, observed as a decrease in interfacial tension, follows the adsorption pattern to the fat crystals. We found a relation between high-fat crystal polarity and poor lecithin functionality in margarine (margarines spatters during frying), and also between high-fat crystal polarity and a high polar to nonpolar phospholipids [Σ(PI + PA + LPC)/ΣPE; PI, phosphatidylinositol; PA, phosphatidic acid; LPC, lysoPC, PE, phosphatidylethanolamine] ratio in lecithin. The correlations might bevia aggregation properties of lecithin in the oil. We found also that monoolein shifted the adsorption kinetics of lecithin (soybean PC) to fat crystals and the hydrophilicity of adsorbed layers probably due to formation of mixed aggregates between monoolein and soybean PC.

The properties of sphingomyelin obtained from bovine milk were investigated. In particular, the properties of liposomes and emulsions prepared from the spingomyelin, as well as the liquid crystalline behavior, were investigated and compared to those of related phosphatidylcholine systems. Like sphingomyelins from other sources, sphingomyelin from milk contains a large fraction of long and saturated acyl groups, which results in a high gel-to-liquid crystal transition temperature (Tc35–82°C, depending on the lipid concentration). At high sphingomyelin concentrations, a lamellar phase forms above Tc, while a swollen gel phase is obtained below Tc. The gel phase swells to about 20 wt% water, whereas the swelling continues to about 40 wt% water above Tc. The limiting areas per molecule are 51 and 68 Å2below and above Tc, respectively. Sphingomyelin from milk forms liposomes readily in the presence of cholesterol. The liposomes formed have a diameter of about 100 nm and are stable, even at 0.1 M NaCl or HCl. Materials entrapped in the liposomes are released rather slowly (typically 40% over 5 h). A comparison shows that the sphingomyelin liposomes behave similarly to those formed by phosphatidylcholine systems. Furthermore, sphingomyelin from milk forms stable oil-in-water emulsions with soybean oil. The size of the emulsion droplets obtained was about 200 nm. Both the size of the emulsion droplets and its dependence on electrolyte addition correlate closely with those of emulsions formed by the corresponding phosphatidylcholine system. Therefore, it is possible to use sphingomyelin as an alternative for saturated phosphatidylcholines, which may be advantageous for oral and dermal pharmaceutical applications, as well as in cosmetics.

Abstract: The influence of water on the interactions between fat and sugar crystals dispersed in triglyceride (vegetable) oils was qualitatively estimated from sedimentation and rheological experiments. The experiments were performed both with and without food emulsifiers (monoglycerides and lecithins) present in the oil. The effects of minor natural oil components (nontriglycerides) on the interactions and on emulsifier adsorption to the crystals were examined by comparing a commercial refined oil and a chromatographically purified oil. The results show that water generally increases the adhesion between fat and sugar crystals in oils and also increases the surface activity of the oil-soluble food emulsifiers. Minor oil components give a small increase in the adhesion between fat and sugar crystals in oils, but do not influence the adsorption of food emulsifiers in any systematic way.

Wetting of fat crystals has been extensively examined in this work by contact angle (?) measurements of fat crystal, oil, and water in three-phase contact. Contact angle was measured in oil. The crystals were nonpolar and wetted by oil for a contact angle equal to 0°, and polar and wetted by water for an angle equal to 180°. Fat crystals are expected to contribute to the stability of margarine emulsions if they are preferentially wetted by the oil phase (0°

The influence of low concentrations (0.1-5%) of fat crystals on the stability of water-in-soybean oil emulsions was examined by light scattering and sedimentation experiments. Both the initial flocculation/coalescence rate and long-term stability against water separation were determined. The initial flocculation/coalescence rate increased upon addition of small amounts of fat crystals. When the crystal concentration was increased above a critical concentration (specific to a system), a decrease in the flocculation/coalescence rate occurred. The increased flocculation/coalescence rate is likely the effect of bridging of water droplets by fat crystals. Fat crystal wetting by water is an important criterion for this phenomenon to occur. Emulsion stabilization for crystal concentrations above critical is caused by a mechanical screening of water droplets. The presence of considerable amounts of crystals in oil also lowered the density difference between droplet and medium, and enhanced viscosity. The degree of increase in viscosity depended upon the emulsifier. Both a decrease in density difference and an increase in viscosity play a role in hindering flocculation/coalescence of droplets. In long-term studies of water separation, all concentrations of fat crystals stabilized the water-in-oil emulsions. The droplet size of these emulsions increased until the critical droplet size was approached where the screening effect of crystals on the droplets no longer stabilized the emulsions. The stabilizing effect for emulsions with monoolein was continuously improved by increasing the amount of crystals up to 5%. For lecithin-stabilized emulsions, an optimal effect was achieved for fact crystal concentrations of 1–2%.

Fat crystals influence the stability of food emulsions, such as margarine, butter, or cream, if adsorbed to the oil/water interface. During the adsorption process, a new fat crystal/water interface is created, while the oil/water interface is lost. The driving force for adsorption is therefore the difference between the interactions between fat crystal/water and oil/water. In this work, we have estimated this interaction difference and compared it to the displacement energy for fat crystals from the oil/water interface to the oil. Our calculations have shown that fat crystal adsorption to the oil/water interface (expressed by contact angle ?) is determined by polar energy, excess of fat crystal/water over oil/water (Isw-Iow). The interfacial tension constitutes the resistance force for crystal adsorption to the interface. Polar interaction energy for fat crystal/water is stronger than the polar interaction energy for oil/water in all cases examined (Isw-Iow>0). The difference corresponds to about 104–106hydrogen bonds for a hypothetical fat crystal with a diameter of 1 µm. The displacement energy for fat crystals to oil is lower than the polar energy excess in most cases examined. Thus, an additional interaction between fat crystals and oil makes it easy to displace the crystals to the oil. There is also a relationship between the adhesion tension (-?ow• cos ?) for the crystals at the oil/water interface and the interfacial tension ?ow. A straight line of slope -1 is achieved for systems with low interfacial tensions (?ow) and low polar energy excess (Isw-Iow).

Several foods contain semi-solid fats that consist of solid crystals dispersed in a liquid oil. In oil-continuous margarine, butter, and chocolate, fat crystals determine properties such as consistency, stability against oiling-out, and emulsion stability. Trends toward foods with less fat and/or less saturated fat create a need for understanding and controlling the properties of fat crystal dispersions. Fat crystals form a network in oil due to mutual adhesion. One source of strong adhesion is formation of solid bridges (sintering), which has been studied in this work through sedimentation and rheological experiments. Results indicate that sintering may be created by crystallization of a fat phase with a melting point between that of the oil and the crystal. Generally speaking, ß' crystals were sintered by ß' fat bridges, favored by rapid cooling, and ß crystals by ß fat bridges, favored by slow cooling. The existence of the same polymorphic form of the crystal and bridge indicated that solid bridges, rather than bridges formed by small crystal nuclei, were formed. A maximum in sintering ability for an optimal sintering fat concentration occurred due to competition between bridge formation and other crystallization processes. Some emulsifiers influenced the sintering process. For example, monooolein made it more pronounced, while technical lecithin had the opposite effect.

The influence of water on the interactions between fat and sugar crystals dispersed in triglyceride (vegetable) oils was qualitatively estimated from sedimentation and rheological experiments. The experiments were performed both with and without food emulsifiers (monoglycerides and lecithins) present in the oil. The effects of minor natural oil components (nontriglycerides) on the interactions and on emulsifier adsorption to the crystals were examined by comparing a commercial refined oil and a chromatographically purified oil. The results show that water generally increases the adhesion between fat and sugar crystals in oils and also increases the surface activity of the oil-soluble food emulsifiers. Minor oil components give a small increase in the adhesion between fat and sugar crystals in oils, but do not influence the adsorption of food emulsifiers in any systematic way.

The alkyl chain order in the lamellar liquid-crystalline phase formed in the octylamine/octylammonium chloride/water system has been investigated by 2H N.M.R. at constant mole ratio water/amphiphile and varying charge of the lamellae. The results are correlated to the dimensions of the aggregate obtained from X-ray low angle diffraction measurements.

Polar lipids have an important role as emulsifiers and stability controlling agents in the food industry. The principal effects of the emulsifiers have been found to depend on the situation in which they are applied. They may act as stabilising additives, creating repulsive interactions between droplets. They may act as emulsifying agents, or they may destabilise emulsions by reducing protein adsorption at the oil/water interface. They may also destabilise emulsions by increasing wettability of fat crystals. Furthermore, they may form micellar or liposomal aggregates in the dispersion, influencing interactions and aggregation.

Small particles of two steroids, choiesteryl acetate and β3-sitosterol, were prepared by the following technique. The steroid was dissolved in an organic solvent, which was emulsified in water in the presence of surfactant, thus giving a water-continuous emulsion. As the organic solvent was evaporated, the steroid precipitated. One particle was found to form in each emulsion droplet. Particle sizes down to 25 nm were obtained by this method. Particles were prepared from emulsions containing different organic solvents and surfactants, and the effect on the size and the colloidal stability of the particles was examined. The final particle suspension is relatively stable provided the initial emulsion is stable. Furthermore, there is a close correlation between the initial droplet size and the final particle size. The particle size, therefore, can be varied in the same manner as the size of emulsion droplets; that is, by changing the emulsification process parameters and the amount and choice of surfactant and the oil-to-water ratio. Finally, the particle size depends on the choice of solvent and only slightly on the concentration of drug in the oil phase of the emulsion.

The hexagonal (E) liquid-crystalline phase in mixtures of sodium desoxycholate (NaDOC) with the cationic surfactant cetyltrimethylammonium bromide (CTAB) in water has been investigated by small-angle X-ray diffraction and optical polarizing microscopy. Large proportions of the dihydroxy bile salt can be incorporated in the E phase of the detergent and lead to a decreasing average radius from 22 Å for pure CTAB to 19.5 Å at 46 mole% of NaDOC. The introduction of the bile salt in the cylinders thus increases the curvature, whereas the same bile salt induces a transition to rod-like micelles when added to spherical CTAB micelles at low surfactant concentration. The mixed E phase was identified and characterized as a hexagonal mesophase by optical polarizing microscopy. The diffusion-limited fluorescence quenching of excited state pyrene by dimethylbenzophenone was investigated in the cylindrical mixed micelles of the micellar (L1) phase in the same system. The decay curves were evaluated using a model of excited state deactivation in infinitely long rod-like micelles without exchange of quenchers (Almgren, M., Alsins, J., Mukhtar, E., and van Stam, J.,J. Phys. Chem.92,4479 (1988)) and gave as results the relative diffusion coefficient of the excited probe and quencher. The addition of DOC−up to an equimolar concentration decreased the diffusion coefficient substantially, indicating an increased rigidity of the micelle.

An NMR technique to measure exchange kinetics at thermal equilibrium in dispersions of moderately soluble crystalline material is presented. By monitoring the exchange of molecules between pools in solid and dissolved form, one can characterize the surface specific exchange rate. Illustrative experiments were performed in a model system with ß-type crystals of tripalmitin as the solid phase and tripalmitin, a fraction of it deuterated, dissolved in a medium-chain TG oil as the liquid phase. The concentration of deuterated tripalmitin in the solvent was followed by 2H NMR after the crystals, which initially lack deuterated tripalmitin, were immersed in the liquid. The variation of the 2H concentration in the solvent provided the surface specific exchange rate. No systematic errors, due to the slight difference in properties of the deuterated tripalmitin compared to hydrogenated tripalmitin, were observed. The methodology worked well between crystal concentrations of 2 and 4 wt%.