Showing papers on "Gelatin published in 1997"

Gelatin from cod skins as affected by chemical treatments

Abstract: Concentrations of sodium hydroxide, sulfuric and citric acids used in processing gelatin from cod skins affected both yield and quality. The highest yield of gelatin was obtained when low concentrations [0.1–0.2% (w/v)] of sulfuric acid and sodium hydroxide were applied to the skins followed by treatment with 0.7% (w/v) citric acid. The effects on bloom value, viscosity, odor, clarity, color and pH of the gelatin varied. However, the use of 0.7% (w/v) citric acid in different combinations with sodium hydroxide and sulfuric acid usually gave best results. Freezedried gelatin had considerably higher bloom value than air-dried gelatin.

Rheological and DSC study of sol-gel transition in aqueous dispersions of industrially important polymers and colloids

Abstract: Gelation kinetics, mechanical spectra, thermal scanning rheology (TSR), and differential scanning calorimetry (DSC) in aqueous solutions of gelling polymers and colloids such as seaweed polysaccharides (agarose, carrageenans), microbial polysaccharides (gellan, curdlan), plant polysaccharides (methylcellulose), globular proteins (casein, glycinin, β-conglycinin), fibrous proteins (gelatin, fibrin), and polyvinyl alcohol, which are related to foods, cosmetics, biomedical and pharmaceutical applications, are described. Some gelation processes at a constant temperature have been treated successfully by an equation of first order kinetics or by other modified equations, and the molecular mechanism of gel formation is discussed briefly. For water-soluble polymers, the criterion of the gel or sol based on the frequency dependence of storage and loss moduli gives valuable informations. TSR and DSC are complementary, and the combination of these methods has been proved to be useful.

Potential efficacy of basic fibroblast growth factor incorporated in biodegradable hydrogels for skull bone regeneration.

Abstract: Biodegradable gelatin hydrogels incorporating basic fibroblast growth factor (bFGF) were evaluated for their efficacy in bone regeneration using a rabbit model. Hydrogels with water contents of 85% and 98% were prepared using chemical crosslinking of gelatin with an isoelectric point of 4.9 in aqueous solution and, after freeze drying, were impregnated with an aqueous solution of bFGF to obtain bFGF-incorporated gelatin hydrogels. When they were implanted into bone defects measuring 6 mm in diameter in rabbit skulls (six animals/group), complete closure of the defect was observed at 12 weeks after implantation, regardless of the water content of the hydrogels. In contrast, bFGF did not enhance bone regeneration when applied to the skull defect in solution with phosphate-buffered saline (PBS). Also, gelatin hydrogels lacking bFGF were not effective in inducing bone formation, with fibrous tissue growing into the defect instead, similar to the skull defect seen in control rabbits treated with PBS. This indicates that the presence of hydrogels did not interfere with bone regeneration at the skull defect, probably because of their disappearance during biodegradation. It is concluded that the gelatin hydrogel is a promising matrix for effective induction of biological activity of bFGF for bone regeneration in skull and sinus defects.

Cross-linked protein gels and methods of making them

Abstract: Enzymatically cross-linked protein gels and methods for preparing them are disclosed. The methods comprise adding a transglutaminase, such as factor XIII, to a composition of a temperature-sensitive gel-forming protein, such as gelatin or collagen, and incubating the composition and transglutaminase under gel-forming conditions. The resulting gels have superior strength and thermal stability, and can be used within a variety of medical and industrial applications.

Polyelectrolyte-gelatin complexation : Light-scattering study

Abstract: Complex formation between negatively charged polyelectrolytes and a net negatively charged polyampholyte (gelatin) has been characterized by light scattering. The two polyanions studied are sodium ...

Dynamic–Mechanical Properties of Bioartificial Polymeric Materials

Abstract: Bioartificial polymeric materials represent a new class of polymeric materials based on blends of synthetic and natural polymers, designed with the purpose of producing new materials with enhanced properties with respect to the single components. The mechanical properties of bioartificial materials prepared using poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) as synthetic components, and collagen (SC), gelatin, starch, hyaluronic acid (HA) and dextran as biological components, were investigated by dynamic mechanical thermal analysis. The materials were prepared in the form of films or hydrogels and treated by glutaraldehyde (GTA) vapour or thermal dehydration in order to reduce their solubility in water. The results indicate that SC/PVA, gelatin/PVA and starch/PVA films behave as biphasic systems, showing good mechanical properties over a wide range of temperature. It was observed that the GTA procedure affects only the biological component of the SC/PVA and gelatin/PVA blends, whilst the thermal treatment influences mainly the synthetic polymer. In the case of HA/PVA hydrogels, a modulus variation was found with the HA content related to the organization degree and perfection of the PVA network structure. It seems evident that, in the experimental conditions used, dextran/PAA mixtures behave as miscible blends showing a glass transition intermediate between those of the pure components. With both untreated and GTA-treated gelatin/PMAA blends, it was not possible to evaluate the miscibility of the systems; it could only be affirmed that these materials show good mechanical properties over a wide range of temperature. © 1997 SCI.

Physical gelation under shear for gelatin gels

Abstract: Physical gelation is the process of crosslinking which reversibly transforms a solution of polymers into a gel. The crosslinks of the network have a physical origin (hydrogen bonding, Van der Waals forces... ) and therefore are sensitive to variations of temperature, pH, ionic content, etc. (non-permanent crosslinks). Physical and chemical gelation have been extensively studied in quiescent conditions, where rheology experiments have been performed to follow the network formation without disturbing the process. In this study we consider gelation of a well known physical, thermoreversible, gel (gelatin gel), which proceeds under flowing conditions. The gelling solution is submitted to a shearing, with imposed, permanent shear stresses or imposed, permanent, shear rates. Under flow, a competition arises between the formation of clusters by physical crosslinking and their disruption by the shear forces. This investigation defines the flowing conditions which either allow or impede gel formation. In particular, a critical shear rate \(\dot \gamma *\), related to the gelation temperature and gelatin concentration, is identified which separates the two regimes. A microscopic model is proposed, based on the analysis of flow curves and dynamic measurements, which describes the structure of the gelling solution: microgel particles grow to a maximum size which depends on the flow. When the volume fraction of particles is high enough, percolation between particles occurs suddenly and a yield stress fluid is formed (particulate gel). The differences between gels made in quiescent conditions and gels made under flow are underlined.

Hydrogels prepared by crosslinking of gelatin with dextran dialdehyde

Abstract: Hydrogels were prepared by reaction of gelatin with partial periodate oxidized dextran. It was found that the rate of gelation depends on the molecular weight and on the degree of oxidation of dextran, the type of gelatin and on the reaction conditions. Rheological measurements demonstrate that the gel strength is governed by two factors: chemical crosslinking by reaction with polyaldehyde and physical structuring of the gelatin. By proper selection of the reaction conditions, in particular storage temperature, the contribution of both processes to the final material strength can be varied. It was observed that short cryogenic treatment significantly enhances the chemical crosslinking.

Polymeric particles having a biodegradable gelatin or aminodextran coating and processes for making same

Abstract: Gelatin and aminodextran coated polymer core particles useful in immunoassays and methods of making the same are disclosed. The preparation of aminodextrans having varying amounts of amine groups is also described, as is a method of crosslinking gelatin and aminodextran without the use of a stabilizer.

Structure and rheology of gelatin gels

Abstract: This paper is essentially a review of past work, including structural and rheologicai studies on gelatin gels and progress made in the last decade or so. Now many aspects of gelatin gelation are unchallenged. For example, it seems clear that the helical junction zones do not have a large cross-sectional radius of gyration, and both the gel modulus, and the absolute optical rotation appear to increase slowly, but without limit, even when plotted on a log time axis. The implications of such work are summarized.Other topics of current interest include the nature of gelatin gels at very long times (creep vs. dynamic measurements), large deformation measurements, mixed chemically and physically cross-linked samples, and also the future of bovine gelatin and the development of novel sources following the BSE crisis. These topics are discussed in terms of the author’s view of recent progress in, and future prospects for, gelatin research.

Mechanical properties and transition temperatures of crosslinked-oriented gelatin

Abstract: This second part of a systematic study of the properties of crosslinked-oriented gelatin involves the effects of orientation and water content on the glass transition temperature Tgand on the melting behavior. The samples were the same as those in the preceding study, and their transition temperatures were determined by both differential scanning calorimetry and dynamic mechanical thermal analysis. The crosslinked gelatin which had been room-conditioned showed two transition temperatures: the lower one was attributed to Tg of the water-plasticized gelatin, and the higher one was interpreted as Tg of dried gelatin superimposed by melting. A rather unusual situation arose because of the fact that the Tg and melting temperatures Tm (217 and 230°C, respectively) are so similar. Using water as plasticizer not only decreases Tg but produces imperfect crystallites which melt below the Tg of the system. The presence of the amorphous phase in the glassy state would presumably make it essentially impossible to define a melting point or crystallization temperature in the normal manner, as an equilibrium between crystalline and amorphous phases.

Prion-free collagen and collagen-derived products and implants for multiple biomedical applications; methods of making thereof

Abstract: The use of collagen as a biomedical implant raises safety issues towards viruses and prions The physicochemical changes and the in vitro and in vivo biocompatibility of collagen treated with heat, and by formic acid (FA), trifluoroacetic acid (TFA), tetrafluoroethanol (TFE) and hexafluoroiso-propanol (HFIP) were investigated FA and TFA resulted in extensive depurination of nucleic acids while HFIP and TFE did so to a lesser degree The molecules of FA, and most importantly of TFA, remained within collagen Although these two acids induced modification in the secondary structure of collagen, resistance to collagenase was not affected and, in vitro, cell growth was not impaired Severe dehydrothermal treatment, for example 110 °C for 1-3 days under high vacuum, also succeeded in removing completely nucleic acids Since this treatment also leads to slight cross-linking, it could be advantageously used to eliminate prion and to stabilize gelatin products Finally, prolonged treatment with TFA provides a transparent collagen, which transparency is further enhanced by adding glycosaminoglycans or proteoglycans, particularly hyaluronic acid All the above treatments could offer a safe and biocompatible collagen-derived material for diverse biomedical uses, by providing a virus or prion-free product

A Comparison of the Biocompatibility of three Absorbable Hemostatic Agents in the Rat Middle Ear

Abstract: Absorbable gelatin sponge (Gelfoam) has been used for many years in middle ear surgery. Although the sponge is generally well tolerated, fibrosis occasionally forms in the mesotympanum; some studies indicated that the absorbable gelatin sponge may be responsible. Many of these studies lack statistical analysis. We prospectively studied three absorbable hemostatic agents in the middle ear of adult male Sprague-Dawley rats to determine which promotes fibrosis to the greatest degree: absorbable gelatin sponge (Gelfoam), absorbable gelatin sheet (Gelfilm), or absorbable collagen sheet (Instat). The materials were implanted in the middle ear through a post-auricular approach and the temporal bones were serially harvested at different time intervals so we could examine histologic changes. The nonimplanted ear served as surgical control. Examination of the specimens at 6, 8, and 10 weeks by light microscopy revealed that although absorbable gelatin film and collagen-absorbable hemostat are well tolerated in this animal model, absorbable gelatin sponge promoted the presence of fibrosis to a significantly greater degree, (p = 0.0344). We conclude that absorbable gelatin sponge promotes fibrosis more frequently than do collagen-absorbable hemostat and absorbable gelatin film in this animal model.

Viscosity of Emulsions of Polydisperse Droplets with a Thick Adsorbed Layer

Abstract: Three oil-in-water dispersions stabilized by the anionic surfactant Alkanol-XC and adsorbed gelatin have been isolated by centrifugation, resuspended in water, and characterized with respect to particle size and gelatin binding. The viscosities of these resuspended dispersions were measured as a function of applied shear rate and dilution with the aim of understanding the rheological role of the adsorbed gelatin shell. The emulsions are polydisperse (weight:number mean size ∼3) with the number-mean diameter ∼50−90 nm. The low-shear behavior (from the Newtonian plateau to the critical shear stress) can be described using a simple hard-sphere model using an estimated length-mean size for the oil droplets with an adsorbed gelatin layer of effective thickness from 25 to 39 nm, increasing with mean oil particle size. At high shear the model breaks down because there is no second Newtonian plateau. Instead, power-law thinning continues to the highest rates (∼105 s-1) and stresses (∼500 Pa) measured. We attribut...

Swelling behaviour and elastic properties of gelatin gels

Abstract: The swelling behaviour and elastic properties of gelatin gels are reported. Ampholytic swelling properties have been investigated. Antipolyelectrolyte performance is observed when gels are swollen in different salt solutions. Swelling behaviour in high salt solutions is different from that in low salt solutions; this may be attributed to the formation of ion pairs. The elastic properties of the gel and their relationship with swelling character are also discussed. ©1997 SCI

Haze‐Active Protein and Polyphenols in Apple Juice Assessed by Turbidimetry

Abstract: The amount of haze-active protein in apple juice was determined by adding tannic acid to induce haze followed by turbidimetry. Turbidity was essentially linear with protein concentration. PVPP treatment prior to tannic acid addition appeared to remove endogenous polyphenols and resulted in slightly weaker response. Adding gelatin to apple juices or clarified ciders induced hazes in response to content of haze-active polyphenols. At an appropriate gelatin concentration turbidity was nearly linear with polyphenol concentration. Treatment with bentonite prior to gelatin addition appeared to remove endogenous protein. Temperature control during the induction period was critical to reproducibility.

Determination of extent of formaldehyde-induced crosslinking in hard gelatin capsules by near-infrared spectrophotometry.

Abstract: Purpose To predict the degree of crosslinking from formaldehyde-stressed hard gelatin capsules (HGCs) using near-infrared spectrophotometry (NIR)

Gelling Temperature of Gellan Solutions Containing Calcium Ions

Abstract: Gelling temperatures were measured using a dynamic rheological testing method, a spectrophotometric method and direct visual examination combined with use of a thermocouple. Results from the dynamic testing method were most consistent. Gelling temperatures of gellan solutions increased from 30 to 72°C, as polymer concentrations increased from 0.4 to 2.0% w/v and Ca ++ concentrations increased from 2 to 40 mM. A mathematical model was developed based on the van't Hoff equation to relate gelling temperatures to composition and polymer molecular weight. The heat of cross-linking in Ca-gellan gels was estimated to be 428.6 kJ/mole, about 1.4 to 2.1 times greater than for gelatin gels.