Allan T. Paulson

Effects of lipids on mechanical and moisture barrier properties of edible gellan film

Abstract Beeswax or a 1:1 blend of stearic–palmitic acids (S–P) were incorporated into gellan films through emulsification to form gellan/lipid composite films. The films, containing 0–25% lipid (dry film basis) were examined for mechanical properties, water vapor permeability (WVP) and opacity. Addition of the lipids to gellan films significantly improved the WVP (P

Mechanical and water vapour barrier properties of edible gellan films

Abstract Edible films based on gellan were developed. Of the plasticizers tested, glycerol was found to be the most suitable with respect to mechanical properties and transparency. The mechanical properties (tensile and puncture), water vapour permeability (WVP) and glass transition temperature ( T g ) were examined for gellan films as a function of glycerol concentration. The lowest effective glycerol concentration was ∼60% (film dry weight basis); below this concentration, the films tended to be brittle and difficult to handle, whereas films with more than ∼75% glycerol tended to be sticky. Addition of glycerol to gellan films increased extensibility (tensile elongation and puncture deformation) moderately, but decreased tensile strength, elastic modulus and T g , and increased WVP of the films. Increasing the a w caused marked decreases in tensile strength and elastic modulus, but decreased tensile elongation only slightly. In general, tensile strength and elastic modulus appeared to be more sensitive to changes in glycerol content and a w than puncture strength.

Texture profile and turbidity of gellan/gelatin mixed gels

Abstract The effect of gellan (1.6–0.2%) to gelatin (0–1.4%) ratio and calcium ion concentration (0–30 mM) on the textural properties and turbidity of gellan/gelatin mixed gels was examined using instrumental Texture Profile Analysis (TPA) and spectrophotometry. Hardness of the mixed gels decreased as the proportion of gellan decreased. Hardness increased with increasing calcium ions until calcium concentration reached a critical level, after which further increases in calcium resulted in a reduction of hardness. Brittleness, springiness and cohesiveness were very sensitive to low levels of added calcium (0–10 mM), but less sensitive to higher calcium concentrations and gellan/gelatin ratio. In general, the addition of calcium ions caused gels to be more brittle and less cohesive and springy. Decreasing gellan to gelatin ratio caused an increase in gel turbidity at lower calcium ion levels (2–4 mM) and a decrease in turbidity at high calcium levels (20–30 mM). Maximum turbidity was observed in 0.6% gellan–1.0% gelatin gels without added calcium. The results of this study suggested a weak positive interaction between gellan and gelatin when no calcium was added, whereas at higher calcium levels gellan formed a continuous network and gelatin a discontinuous phase.

Effect of polymer ratio and calcium concentration on gelation properties of gellan/gelatin mixed gels

Abstract Gelation properties of gellan/gelatin mixed solutions were studied using dynamic viscoelastic testing at eight different ratios of gellan (1.6–0.2% w/v) to gelatin (0–1.4% w/v) and seven different calcium levels (0–30 mM). The gelation temperature and gelation rate of the mixed gels were significantly affected by the ratio of gellan to gelatin as well as concentration of calcium. Addition of calcium at low levels resulted in an increase in gelation temperature and gelation rate compared to gels with no added calcium. Further increases in calcium increased the gelation temperature, but caused a decrease in gelation rate of the mixed gels. In addition, the presence of gelatin generally had a negative influence on gelation rate, especially at high proportions and when the solution had a high gelling temperature, probably by physically hindering the growth and development of gellan crosslinks. It appeared that in the presence of calcium, gellan formed the continuous gel matrix, with gelatin present as a discontinuous phase. Gellan/gelatin mixtures can form gels over a wide temperature range by varying the ratio of the two polymers as well as the calcium concentration.

Biopolymers in Controlled-Release Delivery Systems

Publisher Summary The flexibility in polymer processing plays an important role in the development of controlled delivery devices for a range of applications related to drugs, food-related bioactive ingredients, and genes. Biopolymers are generally synthesized by an organism or plant and have a more complex chemical structure than that of synthetic polymers. Many pharmaceutical companies now use controlled-/sustained-delivery technologies to improve existing therapeutic agents simply by controlling the rate at which they enter the bloodstream, thus reducing and ideally avoiding under- or overdosing. Temperature-sensitive hydrogels are probably the most commonly studied class of sensitive polymer systems in drug delivery research. They have gained considerable attention in the pharmaceuticals field due to their ability to swell or shrink as a result of changes in temperature. The tanning of biological materials with quinones alters their mechanical and solubility properties, making them insoluble in water, detergents, organic solvents, and strong acids and alkalies. The use of ionic cross-linking has recently gained importance in medical and pharmaceutical applications. The importance of biopolymers in the development of matrices for the controlled release of drugs and other bioactive compounds will continue to increase.

Microencapsulation in genipin cross-linked gelatine-maltodextrin improves survival of Bifidobacterium adolescentis during exposure to in vitro gastrointestinal conditions

To improve survival during exposure to adverse conditions, probiotic Bifidobacterium adolescentis 15703T cells were encapsulated in novel mono-core and multi-core phase-separated gelatine-maltodextrin (GMD) microspheres where the gelatine (G) phase was cross-linked with genipin (GP). Microscopy showed that encapsulated cells were exclusively associated with maltodextrin (MD) core(s). Small (average diameter 37 µm) and large (70 µm) GMD and G microspheres were produced by modulating factors (e.g. mixing speed, surfactant, GP and G concentrations) affecting the size, structural stability and phase-separation. In vitro sequential gastro-intestinal (GI) juice challenge experiments revealed increased survival of cells encapsulated in GMD (∼106–7 cfu mL−1) and G (∼105 cfu mL−1) microspheres as compared to free cells (∼104 cfu mL−1). In GMD microspheres, the bacteria derive energy from MD to survive during exposure to acid and bile salts. In conclusion, the novel food grade GMD microencapsulation formulation was shown to protect probiotic bifidobacteria from adverse conditions.

Modeling of orthokinetic flocculation of Saccharomyces cerevisiae

This study examined the flocculation behavior of two Saccharomyces cerevisiae strains expressing either Flo1 (LCC1209) genotype or NewFlo (LCC125) phenotype in a laminar flow field by measurement of the fundamental flocculation parameter, the orthokinetic capture coefficient. This orthokinetic capture coefficient was measured as a function of shear rate (5.95-223 s(-1)) and temperature (5-45 degrees C). The capture coefficients of these suspensions were directly proportional to the inverse of shear rate, and exhibited an increase as the temperature was increased to 45 degrees C. The capture coefficient of pronase-treated cells was also measured over similar shear rate and temperature range. A theory, which predicts capture coefficient values due to zymolectin interactions, was simplified from that developed by Long et al. [Biophys. J. 76: (1999) 1112]. This new modified theory uses estimates of: (1) cell wall densities of zymolectins and carbohydrate ligands; (2) cell wall collision contact area; and (3) the forward rate coefficient of binding to predict theoretical capture coefficients. A second model that involves both zymolectin interactions and DLVO forces was used to describe the phenomenon of yeast flocculation at intermediate shear ranges, to explain yeast flocculation in laminar flow.

Formation of Calcium‐Mediated Junction Zones at the Onset of the Sol‐Gel Transition of Commercial κ‐Carrageenan Solutions

Gelling temperatures of commercial kappa-carrageenan solutions were measured using dynamic oscillatory shear rheometry, in response to varying polymer (0.4% to 1.6%, w/w) and added Ca(2+) (5 to 20 mM) salts. Gelling temperatures were found to shift to higher temperatures with increased polymer and Ca(2+) concentration. The Tang model was used to estimate the number of Ca(2+)-mediated cross-links formed with kappa-carrageenan at the onset of junction zone formation. Based on this model, 6 kappa-carrageenan double helices were estimated to be cross-linked by 5 Ca(2+) ions through ionic bridging and electrostatic attraction, within a cross-linking region equivalent to one pitch of the double helix.

CHAPTER 16 – Biopolymers in Controlled-Release Delivery Systems

Publisher Summary The flexibility in polymer processing plays an important role in the development of controlled delivery devices for a range of applications related to drugs, food-related bioactive ingredients, and genes. Biopolymers are generally synthesized by an organism or plant and have a more complex chemical structure than that of synthetic polymers. Many pharmaceutical companies now use controlled-/sustained-delivery technologies to improve existing therapeutic agents simply by controlling the rate at which they enter the bloodstream, thus reducing and ideally avoiding under- or overdosing. Temperature-sensitive hydrogels are probably the most commonly studied class of sensitive polymer systems in drug delivery research. They have gained considerable attention in the pharmaceuticals field due to their ability to swell or shrink as a result of changes in temperature. The tanning of biological materials with quinones alters their mechanical and solubility properties, making them insoluble in water, detergents, organic solvents, and strong acids and alkalies. The use of ionic cross-linking has recently gained importance in medical and pharmaceutical applications. The importance of biopolymers in the development of matrices for the controlled release of drugs and other bioactive compounds will continue to increase.

Entrapment of basic fibroblast growth factor (bFGF) in a succinylated chitosan nanoparticle delivery system and release profile

Abstract Basic fibroblast growth factor (bFGF) helps to regulate the proliferation and migration of fibroblasts, the proliferation of endothelial cells, and aids the development of angiogenesis. Its in vivo half-life is on the order of minutes due to extensive degradation and inactivation, which could be potentially reduced by controlled release vehicles. In this study, bFGF was entrapped into chitosan (CS) and N-succinyl-chitosan (SC) nanoparticles, with and without heparin, at two levels of initial loading, followed by further characterization of the particles. Release studies were conducted using radiolabeled bFGF-loaded nanoparticles. Both types of nanoparticles loaded similar amounts of bFGF (60.2 and 68.6% for CS and SC, respectively). The release profile varied greatly among the samples, and a burst release was observed in most cases, with the release amount approaching its final value in the first 6 h. The final amount released varied from 1.5 to 18% of the amount of bFGF-entrapped. The concomitant encapsulation of heparin and the use of SC as a nanoparticle matrix contributed to the largest amount of bFGF release (18%) over the time investigated.