The effects of selenium-containing green tea (SGT; 1.4mgselenium/kg) and China green tea (CGT; 0.13mgselenium/kg) on the in vitro growth of lactobacilli and bifidobacteria were investigated using pure and mixed cultures. SGT had significantly higher phenolic contents (TPC), higher reducing activity, higher DPPH free-radical scavenging activity, and higher ferrous-ion chelating activity (P<0.05–0.0001) than CGT. The addition of aqueous extracts from CGT to Mann-Rogosa-Sharpe (MRS) broth at 10% and 25% (v/v) resulted in small but nonsignificant (P>0.05) increases in the numbers of Lactobacillus rhamnosus and Bifidobacterium breve over the control incubations (without tea). Addition of 10% and 25% of SGT extract resulted in a significant increase (P< 0.05–0.0001) in the number of lactobacilli and bifidobacteria recovered from batch fermentation while CGT did not increase the number of bifidobacteria. The higher prebiotic activity of SGT over CGT may be related to the higher TPC or minerals, notably selenium or a combination of these factors. To test whether selenium itself has an effect on bacterial growth, Na-selenite and Na-selenate were added alone or in combination with CGT to the MRS broth containing pure culture of L. rhamnosus. Growth of this bacterium was enhanced relative to the control incubation of MRS only. When added in combination with CGT, Na-selenate was more effective at enhancing the growth of L. rhamnosus than Na-selenite. The prebiotic effect of SGT could be largely explained by its selenium content.

This article discusses the nature and extent of collaboration between two labour unions in the North-East which was aimed at establishing a permanent alliance in order to further perceived joint aims. Chartist-inspired, if not formally aligned to the movement, the proposed union was very much in tune with the principles of the 'Charter and Something More' espoused by G. J. Harney in 1851. Moreover, the leadership of the joint union saw that working-class solidarity was an important long-term aim and in that sense the organization anticipated the kind of affiliative strategies promoted by the Labour Parliament of 1854. This article proposes that the fragmentation of Chartism was an experience mirrored by the miners' and seamen's movement. The problems of maintaining mass support from an industry in which trade unionists were unwelcome, as well as differences over tactical aims, proved impossible to overcome.

Intermacromolecular complexation between chitosan and sodium caseinate in aqueous solutions was studied as a function of pH (3-6.5), using absorbance measurements (at 600 nm), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The chitosan-caseinate complexes formed were stable and soluble in the pH range 4.8-6.0. In this pH range, the biopolymers had opposite charges. At higher concentrations of chitosan (0.15 wt%), the soluble complexes associated to form larger particles. DLS data showed that, between pH 4.8 and 6.0, the particles formed by the complexation of chitosan and caseinate had sizes between 250 and 350 nm and these nanoparticles were visualized using negative staining TEM. Above pH 6.0, the nanoparticles associated to form larger particles, causing phase separation. Addition of NaCl increased the particle size. The pH dependence of the zeta potential of the mixture solutions was appreciably different from that of the pure protein and pure chitosan solutions.

A matured gum arabic, (Acacia (sen) SUPER GUM™) was investigated as an emulsifier to aid in the stabilisation of water-in-oil-in-water (W/O/W) emulsions. Emulsions were characterised by phase separation, confocal microscopy, droplet sizing, and encapsulation efficiencies (EE). Initial results showed that some precipitates were observed when SUPER GUM™ was dissolved in a 0.1M sodium phosphate buffer and this necessitated the preparation of emulsions in distilled water systems. Interestingly, the ionic environment had an effect on the emulsifying ability of the synthetic hydrophobic emulsifier, polyglycerol ester of polyricinoleic acid (PGPR). The concentration of PGPR could be reduced to 2wt% in distilled water systems with an EE>90%, while in buffered systems, 4wt% PGPR was required to maintain a similar EE. SUPER GUM™ was added as an emulsifier to replace sodium caseinate either in the internal or external aqueous phase of W/O/W emulsions over a range of concentrations. It was found that SUPER GUM™ destabilised the W/O/W emulsions prepared with low PGPR concentration when added to the internal aqueous phase. On the other hand, addition of 10wt% SUPER GUM™ to the external aqueous phase allowed further reduction in the PGPR concentration to 0.5wt% whilst an EE>90% was maintained. W/O/W emulsions formed with SUPER GUM™ were also found to be stable over a wide pH range, compared to W/O/W emulsions stabilised with sodium caseinate, and thus, may be suitable for applications over a wide range of pH values, as may occur during ingestion or incorporation into different food systems.

Microemulsions (so-called due to their small particle size; 5-100 nm) are thermodynamically stable, transparent, low viscosity and isotropic properties of microemulsions and gelled microemulsions, called organogels. Specific emphasis is placed on the ability of microemulsions and organogels to improve the solubilisation and bioavailability of food- derived bioactives and drugs, and recent advances in the food and pharmacological fields are presented.

Microemulsions are transparent, isotropic solutions of oil, water and surfactant (and possibly cosurfactant) which are thermodynamically stable, and have been much studied in terms of pharmaceutical and cosmetic applications. However, the application of microemulsions in foods has been limited both due to toxic or irritant nature of ionic surfactants and the difficulty of solubilising large triglycerides. Three surfactants, food-grade ethoxylated mono- and diglycerides (EMD) and phospholipids, and non-food-grade polyoxyethylene oleyl ether (POE) were examined for their ability to form microemulsions using soybean oil, and their areas of formation expressed on phase diagrams. Microemulsions prepared with EMD and phospholipids required the presence of a short-chain alcohol for formation. Both oil/water (o/w) and water/oil (w/o) microemulsions could be formed using EMD, and the microemulsion area of the phase diagram increased on addition of sucrose and increase in temperature. Depending on sucrose and ethanol concentrations, microemulsions formed with EMD were found to retain their integrity at temperatures below which they formed. Microemulsions could be formed using phospholipids, but only at high surfactant concentration and in the presence of a short-chain alcohol. O/w microemulsions containing 10% oil (w/w) were prepared with POE at surfactant concentrations of >20% (w/w). Dynamic light scattering of microemulsion samples diluted with water indicated particle radii of 6.5nm. Freeze-fracture SEM showed the structures to be of a droplet type, however, this was more evident at higher surfactant/oil concentrations. The results indicated that it is possible to formulate microemulsions at low EMD and POE surfactant concentration. These microemulsions systems may potentially be used for encapsulation of oil-soluble bioactives, e.g. α-tocopherol, in food systems.

Antioxidants may be utilised for two main purposes, to protect the sensory and nutritive quality of the food and/or to protect the body against chronic and age-related diseases. Generally, antioxidants are subject to process degradation and, when given to the body in their free form, cannot pass cell membranes and are rapidly cleared from the general circulation. Because of their unique properties, lipid-based nanoencapsulation systems enhance the performance of antioxidants by improving their solubility and bioavailability, in vitro and in vivo stability, and preventing their unwanted interactions with other food components. This paper reviews nanoliposomes, archaeosomes and nanocochleates with respect to their potential applications as antioxidant carriers in foods. (c) 2006 Society of Chemical Industry

Microemulsions are thermodynamically stable, transparent, low viscosity, and isotropic dispersions consisting of oil and water stabilized by an interfacial film of surfactant molecules, typically in conjunction with a cosurfactant. Microemulsions (so-called due to their small particle size; 5–100 nm) have found application in a wide variety of systems, such as pharmaceutical and oil recovery, but their application in food systems has been hindered by the types of surfactant permissible for use in food. The objective of this review is to provide an overview of the structures and phase behavior of microemulsions, methods of microemulsion formation, and techniques which may be used for characterization. A comprehensive review of previous work on both food-grade microemulsion systems, and non-food-grade systems of specific food interest is included. The application of microemulsions as reaction media, their ability to solubilize proteins and hence their use as a separation technique is also documented. In addition, attention is focused on the application of microemulsions as delivery systems for delivery of bioactive compounds, and the links between microemulsions and increased bioavailability. Future research, both applied and fundamental, should focus on surfactants which are not restricted for use in foods.

Conjugation of the milk protein sodium caseinate and a protein-containing polysaccharide, gum arabic, was achieved through the use of the cross-linking enzyme transglutaminase. The extent of conjugation was monitored by size exclusion separation coupled with a multiangle laser light scattering detector. The elution times of gum arabic solutions incubated with transglutaminase were unchanged over time, whereas incubation of sodium caseinate with transglutaminase resulted in shorter elution times as reaction time increased, indicating the formation of cross-linked caseinate polymers. However, when mixtures of caseinate and gum arabic were incubated with transglutaminase, the elution times were decreased markedly, indicating conjugation between the protein and polysaccharide. The molecular masses of the conjugates increased from approximately 950 to 1600 kDa. This method of protein-polysaccharide conjugation offers noticeable advantages over previously used methods, and the conjugates produced may exhibit unique functional properties.

The formation of electrostatic complexes between sodium caseinate and gum arabic (GA) was studied as a function of pH (2.0-7.0), using slow acidification in situ with glucono-delta-lactone (GDL) or titration with HCl. The colloidal behavior of the complexes under specific conditions was investigated using absorbance measurements (at 515 or 810 nm) and dynamic light scattering (DLS). In contrast to the sudden increase in absorbance and subsequent precipitation of sodium caseinate solutions at pH < 5.4, the absorbance values of mixtures of sodium caseinate and GA increased to a level that was dependent on GA concentration at pH 5.4 (pH(c)). The absorbance values remained constant with further decreases in pH until a sudden increase in absorbance was observed (at pH(phi)). The pH(phi) was also dependent upon the GA concentration. Dynamic light scattering (DLS) data showed that the sizes of the particles formed by the complexation of sodium caseinate and GA between pH(c) and pH(phi) were between 100 and 150 nm and these nanoparticles were visualized using negative staining transmission electron microscopy (TEM). Below pH(phi), the nanoparticles associated to form larger particles, causing phase separation. zeta-Potential measurements of the nanoparticles and chemical analysis after phase separation showed that phase separation was a consequence of charge neutralization. The formation of complexes between sodium caseinate and GA was inhibited at high ionic strength (>50 mM NaCl). It is postulated that the structure of the nanoparticles comprises an aggregated caseinate core, protected from further aggregation by steric repulsion of one, or more, electrostatically attached GA molecules.

The inherent thermodynamic instability of water–oil–water (W/O/W) emulsions has restrictions for their application in food systems. The objective of this study was to develop a food grade W/O/W emulsions with high yield and stability using minimal concentrations of surfactants. Emulsions were prepared using soybean oil, polyglycerol ester of polyricinoleic acid (PGPR) alone or in combination with sodium caseinate (NaCN) as emulsifier(s) for primary water-in-oil (W/O) emulsions and NaCN as the sole emulsifier for secondary W/O/W emulsions. Increasing the concentration of PGPR (0.5–8%w/v) had no effect on the droplet sizes of the resulting W/O/W emulsions. However, significant increases in droplet sizes of W/O/W emulsions were observed when the concentration of NaCN in external phase was reduced from 0.5 to 0.03% (w/v) (p<0.05). Percentage yields of emulsions (using a water-soluble dye) improved when PGPR concentration in the inner phase was increased from 0.5 to 8% (w/v). A stable W/O/W emulsion with a yield >90% could be prepared with 4% (w/v) PGPR alone as primary hydrophobic emulsifier and 0.5% (w/v) NaCN as external hydrophilic emulsifier. The concentration of PGPR in the inner phase could be reduced to 2% (w/v) without affecting the yield and stability of the W/O/W emulsion by partially replacing PGPR with 0.5% (w/v) NaCN, which was added to the aqueous phase of the primary W/O emulsion. The results indicate that a possible synergistic effect may exist between PGPR and NaCN, thus allowing formulation of double emulsions with reduced surfactant concentration.

Presented is a novel application of pulsed field gradient (PFG)-NMR to the analysis of intercompartment exchange and the inner compartment droplet size distribution of a W/O/W multiple emulsion. The method involves monitoring the diffusional behavior of different components of the emulsion. Pfeuffer et al. [Pfeuffer, J.; Flogel, U.; Dreher, W.; Leibfritz, D. NMR Biomed. 1998, 11(1), 19-31.](1) and Price et al. [Price, W. S.; Barzykin, A. V.; Hayamizu, K.; Tachiya, M. Biophys. J. 1998, 74(5), 2259-2271.](2) proposed methods to extend Kärger's PFG-NMR model of exchange between two compartments to accommodate spherical inner compartments. Each model enables the prediction of the oil membrane permeability, the inner compartment volume fraction, and a representation of the inner compartment droplet size distribution. The models were fitted to PFG-NMR experimental data of W/O/W emulsions. The Pfeuffer et al. model provided the best description of the observed experimental data. Predicted values of permeability and swelling were consistent with those reported in the literature for W/O/W emulsions. The addition of sorbitol to either the inner or outer water compartment resulted in an increase in the oil membrane permeability. Inner compartment droplet size distribution measurements indicate that swelling, rupture, and coalescence are likely to have occurred during the secondary emulsification and emulsion ripening. In its present form, the method still constitutes a fast, noninvasive (no addition of a tracer), and in situ method for comparative analysis of the permeability, stability, and yield of different formulations of multiple emulsions with a single PFG-NMR experiment.

The potential application of the o-phthaldialdehyde (OPA) reagent for quantification of the type and extent of the reaction(s) catalysed by transglutaminase (TGase) during incubation with sodium caseinate (NaCN) was investigated. Initial studies were performed to ensure that NH3, a by-product of TGase activity, could be determined with the OPA reagent in trichloroacetic acid (TCA) supernatants of NaCN solutions. The detectable concentration of exogenously added NH3 (at NH3 concentrations > 10 mM) was found to decrease during extended incubation at 23, 37 and 50 degrees C and at either pH 7.0 or 8.0 in 4% w/v NaCN solutions, even when taking into account the evaporation of water from the sample. The recovery of NH3 from 12% w/v TCA supernatants of NaCN solutions spiked with 5 mm NH3 at 23 degrees C and pH 7.0 was found to be 88%. The release of NH3 and the decrease in epsilon-amino groups on incubating NaCN with TGase was subsequently quantified using the OPA reagent. Incubation of NaCN (4% w/v) with TGase at 23 degrees C resulted in progressive increases and decreases, respectively, in NH3 and -amino group concentration with increased incubation time. These changes were dependent on TGase:NaCN. It was estimated that approximately 20% of the available Lys residues in NaCN were involved in TGase-catalysed cross-links. However, the observed decrease in epsilon-amino group concentration was higher than expected. This may be due to concealment of noncross-linked amino groups in polymerised NaCN, making them unavailable for reaction with the OPA reagent.

The effect of heating (140 degreesC, 0-60 min between pH 6.0 and 7.0) on the turbidity, pH 4.6 soluble amino group content and urea PAGE profiles of sodium caseinate (NaCN) and transglutaminase (TGase)-treated NaCN was determined. pH-dependent heat-induced changes in the turbidity and urea PAGE profiles of NaCN were initially attributed to casein aggregation followed by subsequent degradation on extended heating. Cross-linked NaCN samples (incubated with TGase at 20 degreesC, [E:S] of 1:50 and 1:20 for 185 min) were generally less turbid and had lower pH 4.6 soluble amino group content on heating than unmodified NaCN. The nitrogen solubility of cross-linked NaCN was improved at pH 2.0, 3.0 and 5.0. Some improvements in emulsifying activity index and stability of cross-linked NaCN were observed at pH 5.0 and 10.0. The improved heat stability and nitrogen solubility observed after TGase cross-linking may help extend the range of applications for NaCN. (C) 2002 Elsevier Science Ltd. All rights reserved.

The effects of hydrolysis with Protamex (a Bacillus proteinase), cross-linking with microbial transglutaminase, and combinations of these treatments on the functional properties of sodium caseinate (NaCN) were investigated. Higher (P<0.005) emulsifying activity index (EAI) values were observed between pH 4.0 and 10.0 on hydrolysis of transglutaminase cross-linked NaCN to 0.5% degree of hydrolysis (DH) compared to either the 0.5% DH hydrolysate, the cross-linked NaCN or unmodified NaCN control. Reversing the order of modification (cross-linking after hydrolysis to 0.5% DH) generated a product which displayed 1433% foam expansion (FE) at pH 6.0, compared to 735% FE for the control. Cross-linking with transglutaminase after hydrolysis to 1.3% DH resulted in significant improvements (P<0.005) in EAI at low pH, compared to control. In addition, the latter sample exhibited greater FE than the control between pH 3.0 and 10.0 (P<0.005). Extensive transglutaminase-catalysed cross-linking of NaCN per se resulted in increased viscosity (P<0.005) at alkaline pH.

Sodium caseinate (NaCN) was digested with Protamex, a Bacillus proteinase, at 40°C and pH 7.0 to degree of hydrolysis (DH) values of 2.7%, 5.3% and 13.3%. The solubility, emulsifying, foaming and viscosity properties of the hydrolysates were investigated between pH 2.0 and 10.0. Foam expansion of >1300% was observed for the 5.3% DH hydrolysate at pH 4.0, compared to 670% for unheated NaCN. Significantly improved foam expansion properties (P<0.005) were observed over the entire pH range examined for the 13.3% DH hydrolysate compared to unheated or heat-treated NaCN. Hydrolysis resulted in significantly improved solubility (P<0.005) around the isoelectric point and significant improvements in the emulsifying activity and stability (P<0.005) at alkaline pH compared to unheated NaCN. Hydrolysis with Protamex increased the apparent viscosity of NaCN at the isoelectric point. Reversed-phase HPLC profiles showed that high DH samples contained high levels of hydrophilic peptides.

Sodium caseinate (NaCN), hydrolyzed with Protamex, a Bacillus proteinase preparation, to 0.5, 1.3, and 17.5% degrees of hydrolysis, was incubated with transglutaminase (TGase) for 3, 42, and 290 min at enzyme/substrate ratios of 1, 1, and 10% (w/w), respectively, pre- and post-hydrolysis. The electrophoretic, reversed-phase high-performance liquid chromatography (RP-HPLC) and nitrogen solubility profiles of the modified products were investigated. Combinations of hydrolysis and incubation with TGase generated products displaying novel physicochemical and nitrogen solubility properties. Significant changes in sodium dodecyl sulfate (SDS) and urea polyacrylamide gel electrophoresis profiles were apparent in the modified caseinate samples. Extensive TGase cross-linking resulted in polymers that were unable to enter the resolving gel during SDS polyacrylamide gradient gel electrophoresis. Extensive combined enzymatic modification resulted in peptides eluting earlier on RP-HPLC than limited combined enzymatic modification or limited hydrolysis. Combination of enzymatic treatments resulted in significantly (P < 0.005) improved solubility around pH 4.6, compared to incubation with TGase or hydrolysis of NaCN alone.