Effect of Thermal Treatment on the Physicochemical Properties of Emulsion Stabilized by Gelatin from Black Tilapia (Oreochromis mossambicus) Skin

This study investigated the influence of thermal treatment (30 °C to 110 °C, 30 min) on the physicochemical and rheological properties of an emulsion stabilized by black tilapia (Oreochromis mossambicus) skin at pH 4. The protein pattern of tilapia gelatin did not have any significant difference after the gelatin was heated within a temperature range of 30 °C to 70 °C. However, at 90 °C and 110 °C, denaturation occurred where α-, β- and γ-chains of the gelatin were degraded, leading to a concomitant increase in low molecular peptides. The emulsion stability was investigated through a particle size analyzer, zeta potential, microscopic observation and creaming index. The gelatin emulsion was physically stable at 30 °C to 70 °C with a mean droplet size of less than 13 μm. When the heating temperature was increased to 90 °C and 110 °C, the emulsion showed a pronounced increase in droplet size due to coalescence. The gelatin emulsion heated at 90 °C and 110 °C also displayed instability against creaming after storage at room temperature for 7 days. As the heating temperature increased, the gelatin emulsion exhibited a decrease in apparent viscosity and the flow behavior changed from shear thinning to Newtonian. The rheological data also showed that the storage modulus (G′) of emulsion became more frequency dependent as the heating temperature increased, indicating weak droplet interactions. The tilapia gelatin emulsion was physically unstable when subjected to thermal treatment above 70 °C. The data reported in this study provides useful insight into the formulation of acidic food emulsions that require thermal treatment.

     

Mechanical,Optical, Thermal,and Barrier Properties of Poly (Lactic Acid)/Curcumin Composite Films Prepared Using Twin-Screw Extruder

In this present work, we synthesized poly (lactic acid) (PLA)/curcumin composite films using a twin-screw extruder and evaluated their mechanical, optical, thermal, and barrier properties. The composite films were characterized using Fourier transform infrared spectroscopy (FTIR), Universal testing machine (UTM), thermogravimetric analysis (TGA), ultraviolet-visible spectrometry (UV-visible), colorimetry, goniometry, and oxygen permeation analysis. The results confirmed that, the composite films exhibited better ultraviolet radiation-blocking properties and hydrophobicities than did the reference PLA film. The oxygen and water vapor permeabilities of the composite films were also lower than those of the reference PLA film.

     

Properties,Microstructure and Heat Seal Ability of Bilayer Films Based on Fish Gelatin and Emulsified Gelatin Films

Bilayer films prepared by the lamination of fish gelatin film (GF) and its corresponding emulsified film (EF) with different thickness ratios (7:3, 5:5 and 3:7) were characterized. Bilayer films had the similar tensile strength (TS) to EF (p > 0.05) but showed lower elongation at break (EAB) (p < 0.05). All bilayer films showed the lower water vapor permeability (WVP) but higher oxygen permeability (OP) than GF. Bilayer films had varying ΔE* (total color different), where the highest value was observed in that laminated with higher thickness ratio of EF (p < 0.05). Lower light transmission and higher transparency value were obtained for bilayer films, compared to GF (p < 0.05). Based on scanning electron microscopic (SEM) cross-section micrographs, all bilayer films consisted of two layers. Differential scanning calorimetric (DSC) analysis revealed that the bilayer films had the higher glass transition temperature (T _g) than GF but lower than EF. All bilayer films were heat sealable, however their seal strength and seal efficiency were lower than those of GF (p < 0.05). Therefore, the thickness ratios of GF and EF had a marked effect on the mechanical and barrier properties as well as heat sealing ability of resulting bilayer films.     

Effect of Transglutaminase on the Properties of Films Prepared from Chitosan and Gelatin

Applied Biochemistry and Microbiology - The production conditions were optimized, and the characteristics of biodegradable chitosan-gelatin films crosslinked with various microbial...     

Antioxidant Properties of Lactic Acid Bacteria

Microbiology - Lactic acid bacteria (LAB) are widely used in fermentation processes for the preparation of various foodstuffs, including dairy, meat and vegetable products. In the course of...     

The Ultrastructure of Erythrophores and Melanophores from the Skin of Tilapia mossambica (Peters)

Abstract The ultrastructure of erythrophores and melanophores present in the skin of adult Tilapia mossambica is described. A comparison of the two types of chromatophores indicates that both show a smooth endoplasmic reticulum, pinocytotic vesicles, microtubules and complexly branching cell processes. However, differences in the form, consistency and distribution of erythrosomes and melanosomes are noted. It is suggested that erythrophores be defined as chromatophores including carotenoid derivatives as the main pigment in their erythrosomes.     

Characteristics and Gel Properties of Gelatin from Skin of Asian Bullfrog (<Emphasis Type="Italic">Rana tigerina</Emphasis>)

Characteristics and gel properties of gelatin from frog skin as influenced by extraction temperatures (45–75 °C) were investigated. Yield of gelatin increased as the extraction temperature increased (P < 0.05). All gelatins contained α- and β-chains as the predominant components and showed a high imino acid content (215 residues/1000 residues). Fourier transform infrared (FTIR) spectra indicated that all gelatin samples had major peaks in amide regions. Gelatin extracted at 55 °C exhibited the highest gel strength (P < 0.05), which was similar to that of commercial bovine gelatin (P > 0.05). Gelling and melting temperatures of frog skin gelatin were 23.47–24.87 and 33.22–34.66 °C, respectively. Gels became more yellowish with increasing extraction temperatures (P < 0.05). All gelatin gels were sponge or coral-like in structure but varied in patterns as visualized by scanning electron microscopy (SEM). Gelatin from frog skin could be used as a replacement for land animal counterpart.     

Effects of Cellulose Nanofibers Filling and Palmitic Acid Emulsions Coating on the Physical Properties of Fish Gelatin Films

In this preliminary study, fish gelatin films with improved strength and water resistance were prepared from a dispersion of fish gelatin and carboxylated cellulose nanofibrils (CNF) by using the casting method, followed by subsequent coating with palmitic acid emulsion. The surface topography displayed a uniform distribution of the CNF particles in the gelatin films, but aggregation occurred at a CNF dosage of 4 wt% or higher. Due to the reinforcing effect of CNF, a dosage-dependent increase in the Young’s modulus and tensile strength was observed for the CNF-reinforced films. The addition of CNF also led to an obvious increase in thermal stability. Via surface coating, the emulsion at the 60:40 (w/w) ratio of palmitic acid to water showed excellent layer-forming and high adhesion properties, contributing to the significant improvement of water resistance. The enhanced properties of these fish gelatin films would promote their practical applications in edible packaging.     

Probiotic Properties of Lactic Acid Bacteria Isolated from Water-Buffalo Mozzarella Cheese

This study evaluated the probiotic properties (stability at different pH values and bile salt concentration, auto-aggregation and co-aggregation, survival in the presence of antibiotics and commercial drugs, study of β-galactosidase production, evaluation of the presence of genes encoding MapA and Mub adhesion proteins and EF-Tu elongation factor, and the presence of genes encoding virulence factor) of four LAB strains (Lactobacillus casei SJRP35, Leuconostoc citreum SJRP44, Lactobacillus delbrueckii subsp. bulgaricus SJRP57 and Leuconostoc mesenteroides subsp. mesenteroides SJRP58) which produced antimicrobial substances (antimicrobial peptides). The strains survived the simulated GIT modeled in MRS broth, whole and skim milk. In addition, auto-aggregation and the cell surface hydrophobicity of all strains were high, and various degrees of co-aggregation were observed with indicator strains. All strains presented low resistance to several antibiotics and survived in the presence of commercial drugs. Only the strain SJRP44 did not produce the β-galactosidase enzyme. Moreover, the strain SJRP57 did not show the presence of any genes encoding virulence factors; however, the strain SJRP35 presented vancomycin resistance and adhesion of collagen genes, the strain SJRP44 harbored the ornithine decarboxylase gene and the strain SJRP58 generated positive results for aggregation substance and histidine decarboxylase genes. In conclusion, the strain SJRP57 was considered the best candidate as probiotic cultures for further in vivo studies and functional food products development.     

猪源乳酸菌产乳酸及其抑菌特性研究

研究了5株(L1、12、L3、L5和L7)分离自仔猪肠道的乳酸菌的产乳酸能力及抑菌特性。结果表明：L5菌株产乳酸的速度最快,培养液中乳酸含量最高,L5菌株培养液pH值的下降速度最快,终末pH值最低,而L1菌株产乳酸的速度最慢,培养液乳酸含量最低。5株乳酸菌对大肠杆菌K88、K99、987P、O141和大肠杆菌E1及金黄色葡萄球菌均有不同程度的抑制作用;排除酸的影响后仍有22％～53％抑菌效果;经热处理后保持有92％以上的抑菌效果;蛋白酶处理后保持85％以上的抑菌效果。     

一组鸡源乳酸菌产乳酸及其耐受特性研究*

研究了12株（K9、D17、C1、C12、D11、D14、C2、D9、K6、C21、D1和D7）分离自肉鸡肠道的乳酸菌的产乳酸能力及其中3株产酸能力强的菌株的耐受特性。12株乳酸菌产乳酸结果表明：12h内,K6产乳酸速度最快,其次为K9和C1,24h时,D17乳酸浓度最高,48h时C1终乳酸浓度最高。K9、D17和C1的耐受试验结果表明：C1菌株耐酸能力最强,pH2时,C1菌株培养3h后还能检测到活菌,D17和K9菌株培养1h后就已经检测不到活菌。在胆盐浓度0．08％-0．40％范围内,C1、D17和K9均有一定的耐受能力,随着胆盐浓度的升高,C1、D17和K9的存活数呈现缓慢的下降趋势。3株菌中D17耐热能力最强,经80％处理后仍有10^4.9／mL存活数,而K9和C1已检测不到活菌;C1对热最敏感,65℃处理后存活数由10^8／mL降为10^3／mL。     

产黏乳酸菌的发酵特性研究

通过对2株产黏乳酸球菌的发酵特性比较研究,以感观、酸度、活菌数对数值、培养时间、粘度及乳清析出率为考察指标,结果表明:乳酸球菌Q26具备较好的产黏、产香特性,遗传性质较稳定.通过与乳酸杆菌G18进行发酵应用试验,确定G18和Q26存在共生关系,混合发酵的酸牛乳乳清析出率为0.1％,粘度为4 528mPa·s.通过保质期试验,产品在28、20、4℃下保质期分别为3、6、15d.确定Q26和G18为最佳酸牛乳生产用菌种.     

Functional Electrospun Poly (Lactic Acid) Scaffolds for Biomedical Applications: Experimental Conditions,Degradation and Biocompatibility Study

The electrospinning technique is a method used to produce nano and microfibers using the influence of electrostatic forces. Porous three dimensional networks of continuous and interconnected fibers as scaffolds were obtained from a poly (lactic acid) solution. The concentration of the polymeric solution, 12.5% m/w, as well as the conditions of voltage (V=11kV) and tip-metallic collector distance (H=13cm) were established to develop these scaffolds through the electrospinning process. The characteristics of the scaffolds, such as fiber diameter, sintering and the biomimetics of the characteristics of a native extra cellular matrix were verified by Scanning Electron Microscopy (SEM). The orientation induced in the material as a consequence of the electrospinning forces was studied by Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD).The same techniques were used to study the hydrolytic degradation of samples in a ringer solution (pH=7-7.4 at 37oC) for 12 weeks and showed evidences of superficial degradation on the microfibers. The suitability of these scaffolds for tissue engineering was studied through the primary cell culture of chondrocytes, by observing adhesion and cellular proliferation developed during 14 days of assay.     

Purification and Properties of Poly(A) Polymerase from Vigna unguiculata

Poly(A) polymerase was purified from germinating Vigna unguiculataseeds by successive column chromatography on phosphocellulose,Toyopearl HW-55S, heparin-Sepharose and TSKgel phenyl-5PW, whichyielded two activity fractions. The first fraction was purifiedas a single polypeptide with a mol wt of 63,000 as estimatedby SDS-PAGE. The enzyme activity was highly specific for ATPand required Mn²⁺ ion; an ATP-Mn complex may be the actual substrate.The polymerization reaction required a primer, with varioustypes of RNAs, poly(A) as well as dinucleoside phosphates having3'—OH, serving as efficient primers. The two forms ofthe enzyme had very similar properties with respect to divalentcation requirement and dependency on ion strength, but theyshowed some difference in primer preference. (Received March 4, 1988; Accepted May 2, 1988)     

乳酸菌Enterococcuse faecalis TN-9低温蛋白酶的提纯及性质

对产自乳酸菌Enterococcuze fecalis TN-9的蛋白酶,进行了硫酸铵沉淀,DEAE—Sephadex A-25以及DEAE Cellulofine A-500离子交换层析的3步纯化和特性研究。纯化酶Native PAGE显示1条蛋白带。SDSPAGE和凝胶层析分子量分别为30ku及69ku。纯化酶最适作用温度为30℃,最适作用PH为7．5～8．0,在pH6．0～9．5和45℃以下条件下稳定,在0℃下显示了6．1％的相对活性,60℃以上热处理完全失去酶活。该酶被EDTA-2Na,Hg^2＋、Cu^2＋、Ni^2＋、Ag^2＋、Co^2＋及Pepstatin A不完全抑制。Zn^2＋对蛋白酶具有明显的激活作用。纯化酶作用于偶氮酪蛋白的Km和Vmax分别为0．098％和72mg／（h·mg）。该酶为N末端VGSEVTLKNS的明胶酶（Gelatinase）的一种,性质属于低温蛋白酶。     

Physical Properties of Lactic Dehydrogenase-Elevating Virus and Its Ribonucleic Acid

Infectious lactic dehydrogenase-elevating virus propagated in primary cultures of mouse peritoneal macrophages in the presence of ³H-uridine and isolated by isopycnic centrifugation was found to have a density of 1.12 g/cm³. Ribonucleic acid extracted from the virus by treatment with sodium dodecyl sulfate was single stranded with a sedimentation coefficient of approximately 48S.     

Biopreservation of Brined Shrimp (Pandalus borealis) by Bacteriocins from Lactic Acid Bacteria

In brined shrimp (ca. 3% NaCl), the effects of three different lactic acid bacteria bacteriocins (crude [6.54 x 10(sup10) U of bacteriocin activity {BU}/g] and purified [8.13 x 10(sup23) BU/g] nisin Z, carnocin UI49 [2.32 x 10(sup4) BU/g], and crude bavaricin A [2.78 BU/g]) on bacterial growth and shelf life were compared with those of a benzoate-sorbate solution (0.1% each [wt/wt]) and a control with no preservatives. The shelf life of shrimp subjected to the control treatment was found to be 10 days. Carnocin UI49 did not extend the shelf life, while crude bavaricin A (a cell-free supernatant of Lactobacillus bavaricus MI 401) resulted in a shelf life of 16 days, as opposed to 31 days with nisin Z for both its crude and purified forms. The benzoate-sorbate solution preserved the brined shrimp for the whole storage period (59 days). In the control, carnocin UI49, and crude bavaricin A treatments, a gram-positive flora dominated towards the end of the storage period while in the nisin Z treatment a gram-negative flora was more pronounced.     

Evaluation of Physical and Mechanical Properties of Porous Poly (Ethylene Glycol)-co-(L-Lactic Acid) Hydrogels during Degradation

Porous hydrogels of poly(ethylene glycol) (PEG) have been shown to facilitate vascularized tissue formation. However, PEG hydrogels exhibit limited degradation under physiological conditions which hinders their ultimate applicability for tissue engineering therapies. Introduction of poly(_L-lactic acid) (PLLA) chains into the PEG backbone results in copolymers that exhibit degradation via hydrolysis that can be controlled, in part, by the copolymer conditions. In this study, porous, PEG-PLLA hydrogels were generated by solvent casting/particulate leaching and photopolymerization. The influence of polymer conditions on hydrogel architecture, degradation and mechanical properties was investigated. Autofluorescence exhibited by the hydrogels allowed for three-dimensional, non-destructive monitoring of hydrogel structure under fully swelled conditions. The initial pore size depended on particulate size but not polymer concentration, while degradation time was dependent on polymer concentration. Compressive modulus was a function of polymer concentration and decreased as the hydrogels degraded. Interestingly, pore size did not vary during degradation contrary to what has been observed in other polymer systems. These results provide a technique for generating porous, degradable PEG-PLLA hydrogels and insight into how the degradation, structure, and mechanical properties depend on synthesis conditions.