Lower Gel Strength Research Articles

Autolysis of bovine skin, its endogenous proteases, protease inhibitors and their effects on quality characteristics of extracted gelatin

The autolysis of pretreated bovine skin (PBS) (treated with 0.1 M NaOH and 1% HCl), its endogenous proteases, inhibitors and their effects on quality attributes of gelatin were examined. PBS was subjected to different temperatures (20–90 °C) and pH (2–9) and treated with different protease inhibitors. Maximum autolytic activity of PBS was observed at 40 °C and pH 5. Ethylene-bis (oxyethylenenitrilo) tetraacetic acid (EGTA) was the most effective in impeding the degradation of γ-, β- and α- chains of PBS protein indicating that metallocollagenases were the predominant endogenous proteases in bovine skin. Gelatin was extracted in the absence (GAE) and presence (GPE) of EGTA, and EGTA with papain enzyme (GPEP). GPEP had a higher yield and lower gel strength than GEA and GPE. Metallocollagenases partook in the degradation of gelatin thereby affecting its functional properties. Pretreating PBS with or without EGTA, and papain influenced the quality attributes of gelatin.

Tuning hydrophobicity of zein nanoparticles to control rheological behavior of Pickering emulsions

In the present work, the influence of hydrophobicity of zein/tannic acid complex particles (ZTPs) on the rheological behavior of ZTP-stabilized emulsion gels is described. The hydrophobicity of the particles was controlled by the incorporation of different amounts of hydrophilic tannic acid, while retaining a similar particle size. The resulting ZTPs with varying hydrophobicity were successfully used to form emulsion gels with similar oil droplet size. With a decrease in the hydrophobicity of ZTPs, the storage modulus (G′) of emulsion gels increased, while tan δ and the frequency dependence decreased, indicating the formation of a stronger gel network. The crossover strain, γco, increased with a decrease in the hydrophobicity of ZTPs, indicating the gel network becomes more resistance against breakdown. In all cases, G′ increased in a power-law manner with an increase in protein concentration (G' ∼ cpn) and oil content (G' ∼ φm). The exponent n and m decreased with decreasing particle hydrophobicity, indicating that hydrophobic interactions between particles within the particle network in the continuous phase and the oil droplets provide a relatively larger contribution to the gel strength for emulsion gels stabilized by ZTPs with higher hydrophobicity. Increasing the oil polarity provided a lower gel strength for emulsions stabilized by particles with high hydrophobicity, while it increased the gel strength for particles with low hydrophobicity. The results show that the rheological behavior of ZTP-stabilized emulsion gels can be tuned by changing the particle hydrophobicity and oil polarity, which provide interesting features for various applications in the food industry.

“Effect of process variables on solubility and recovery yields of proteins from pangas (Pangasius pangasius) frames obtained by alkaline solubilization method: Characteristics of isolates”

Proteins from pangas (Pangasius pangasius) fillet frame were recovered using alkaline solubilization method. Effect of process variables like pH, time, weight of paste to extractant volume ratio, temperature, centrifugation speed and stirring frequency on concentration and recoveries were studied. pH, weight of paste to extractant volume ratio, temperature and centrifugation speed were found to have significant effect (p<0.05) on protein solubility as well as on recoveries. The optimum extraction conditions found were pH-13.0, extraction time – 60min, temperature – 50°C, weight of paste to extractant volume ratio-1:6, centrifugation speed – 8000rpm and continuous stirring, with a total recovery of 68.52%. During alkaline processing lipids, myoglobin and pigment contents were reduced by 90.33, 97.65 and 58.27%, respectively. Despite of improving the color of the isolates and gel, alkaline processing could cause some denaturation resulting in low gel strength and water holding capacity of gels. Alkaline processing did not affect the amino acid profiling substantially, resulting in maximum recovery of all the amino acids. Glutamic acid (GLU), aspartic acid (ASP), leucine (LEU) and lysine (LYS) were found to be the major amino acids in isolates. Alkaline processing could cause enrichment of the essential amino acids in isolates.

Dose-dependent effects of rosmarinic acid on formation of oxidatively stressed myofibrillar protein emulsion gel at different NaCl concentrations

The effects of rosmarinic acid (RA) (12, 60 and 300μM/g protein) on the textural properties and stability of oxidized myofibrillar protein (MP) emulsion gels were investigated. A low dose (12µM/g) of RA significantly prevented the loss of thiol and ε-NH2 groups and the unfolding of the oxidized MP. However, a high dose of RA (300µM/g) covalently and non-covalently interacted with the MPs, which induced a significant loss of thiol and ε-NH2 groups and aggregation of the MPs, causing decreased solubility, resulting in a poor three-dimensional emulsion gel network, and hence, higher cooking loss and lower gel strength. Moreover, the emulsifying properties of the MP emulsion gel were jeopardized by 300µM/g RA. A high concentration of NaCl (0.6M) enhanced the interaction between RA and MPs, increasing deterioration of the internal structure and leading to extremely unstable emulsifying properties of the MP emulsion gel.

Gelation Behavior Study of a Resorcinol–Hexamethyleneteramine Crosslinked Polymer Gel for Water Shut-Off Treatment in Low Temperature and High Salinity Reservoirs

Mature oilfields usually encounter the problem of high watercut. It is practical to use chemical methods for water-shutoff in production wells, however conventional water-shutoff agents have problems of long gelation time, low gel strength, and poor stability under low temperature and high salinity conditions. In this work a novel polymer gel for low temperature and high salinity reservoirs was developed. This water-shutoff agent had controllable gelation time, adjustable gel strength and good stability performance. The crosslinking process of this polymer gel was studied by rheological experiments. The process could be divided into an induction period, a fast crosslinking period, and a stable period. Its gelation behaviors were investigated in detail. According to the Gel Strength Code (GSC) and vacuum breakthrough method, the gel strength was displayed in contour maps. The composition of the polymer gel was optimized to 0.25~0.3% YG100 + 0.6~0.9% resorcinol + 0.2~0.4% hexamethylenetetramine (HMTA) + 0.08~0.27% conditioner (oxalic acid). With the concentration increase of the polymer gel and temperature, the decrease of pH, the induction period became shorter and the crosslinking was more efficient, resulting in better stability performance. Various factors of the gelation behavior which have an impact on the crosslinking reaction process were examined. The relationships between each impact factor and the initial crosslinking time were described with mathematical equations.

Experimental Investigation of Limonene-based Environmental-Friendly Emulsion Drilling Mud

The use of emulsion drilling mud in the oil and gas industry has gained wide acceptance. However, the disposal of drill cuttings and the waste of such emulsion drilling mud usually poses environmental concern. Hence, there is the need to seek oil from biodegradable sources as an alternative to the current conventional diesel oil which constitute environmental threat. In this study, limonene obtained from dried peel of sweet orange was used as the dispersed phase in the formulation of nano-modified emulsion drilling mud. A Design Of Experiment (DOE) approach was employed to investigate the extraction of limonene and the results analysed. Three different mud samples were formulated; the conventional water-based drilling mud, nano-modified emulsion drilling mud with diesel oil and limonene as the dispersed phase respectively. The rheological properties, density, sand content, PH and filtration loss of the formulated mud samples were tested and compared. The results of the experiment showed that the formulated nano-modified emulsion drilling mud with limonene as the dispersed phase followed Herschel-Bulkley rheological Model with low gel strength and yield point which are desirable mud property for turbulent flow at low pump pressure for effective hole cleaning. Also, there is reduction in filtration loss and mud cake compared to the conventional water-based drilling mud which will lead to reduction in torque and drag, reduction in pipe sticking, reduction in hole enlargement and less bit balling.

Efficient encapsulation and release of RNA molecules from gelatin-based nanoparticles

The design of synthetic carriers for nucleic acid delivery has become a research field of increasing interest. Studies on the delivery of DNA have brought up a variety of gene delivery vehicles. Recent studies in our group have demonstrated the preparation of new gelatin-based nanoparticles for the sustainable intracellular DNA delivery. Furthermore, the more recently emerged strategy by the intracellular delivery of RNA takes benefit from existing expertise in DNA transfer. In this work, the preparation and physicochemical characterization of new nucleic acid-based particles for the sustainable RNA delivery have been demonstrated. Gelatin (either high or low gel strength) and protamine sulfate have been selected to form particles by interaction of oppositely charged compounds. Particles in the absence of RNA (binary system) and in the presence of RNA (ternary system) have been prepared. The physicochemical characterization (particle size, polydispersity index, degree of RNA entrapment and RNA binding efficiency) has been evaluated as a function of the nature of the RNA derivative (acid form, diethylaminoethanol salt or core form) from torula yeast. The pH-dependent response of nanoparticles co-incubated in buffers at defined pHs that mimic late endo-lysosomal environment has demonstrated that the nanoparticles tend to destabilize and RNA can be successfully released as a consequence of changes in the intracellular pHs. Among the different systems, gelatin B (RNA)-PS nanoparticles using RNA acid form from torula yeast has proved to be the best system, from an effective and economic point of view.

Effect of high pressure treatment on the structural, mechanical and rheological properties of glucomannan gels

The influence of high hydrostatic pressure (HHP) of 100 (C100), 200 (C200), 400 (C400) and 600 MPa (C600) on the structural, physicochemical, and thermo-rheological properties of aqueous glucomannan dispersions (AGD) was studied. Each AGD was prepared with a 5% concentration of deacetylated glucomannan (GM) at pH = 11 for use in the preparation of restructured fish products. The control (0 MPa) AGD (C0) exhibited a partially crystalline GM network with a glass transition temperature (Tg) of ∼75 °C. C0 gels at 25 °C were rigid, with high breaking force (BF), fracture constant (Kf) and complex modulus (G*) and low tanδ values due to the large number of physical junctions produced by complete deacetylation of the GM chains. This structural response was reflected in high water binding capacity (WBC) and colour (L*) and low cooking loss (CL). Specifically, 200 MPa reduced close packing ability in the crystalline regions, evidenced in the lower Tg∼65 °C and resulting in lower gel strength (S), Kf, G* and a higher viscous component (high tanδ), thus reducing the L* value. Conversely, 600 MPa increased the degree of cross-linking in C600, reinforcing the number and extent of crystalline regions, resulting in the broadening of the O–H stretching band in the FT-IR spectrum and producing a thermoset physical network with no glass transition region. Thus, C600 gel was firmer (higher G*) with greater S, and less flexible (lower strain amplitude-γmax). Consequently, depending on the textural properties desired in the final restructured fish product, the most appropriate pressure would be 200 MPa for softer final gels and 600 MPa for firmer and less deformable gels.

Use of freezing techniques for increasing the output of ultralow density laser targets

Self-supporting ultralow density laser targets with an apparent density as low as 1 mg/cm3, a porous layer thickness of 60–500 μm, and a window diameter of 2.5 mm were prepared by thermally induced gelation of cellulose acetate solution in a mixture solvent between two glass slides using the mold casting method. In view of the low mechanical gel strength at a concentration of <0.2 wt %, supercritical drying of molded targets is carried out without separating the glass slides. For the target output to be radically increased, a new procedure has been developed based on rapid freezing of the solution on a metal brick from room temperature to–60°C and lower, down to–190°C, without initial gelation.

Nonlinear rheology and pressure wave propagation in a thixotropic elasto-viscoplastic fluids, in the context of flow restart

A new continuous nonlinear rheological model is established to quantify, correlate, and predict the thixotropic viscoelastic and visco-plastic properties of waxy crude oil gels. A complete rheological description of the gel is afforded by quantification of the maximum stress point (so called static yield stress) in conjunction with viscosity of the pristine gel and final slurry. Extraneous parameters are derived from the maximum stress condition. In order to develop an understanding of flow restart processes within gelled pipelines, direct numerical simulation of pressure propagation in weakly compressible thixotropic elasto-viscoplastic gel (Oldroyd-B fluid model) is performed using the rheological correlations. Deficiencies associated with conventional Bingham yield stress and conventional shear thinning methodologies are concomitantly revealed by the present elasto-viscoplastic model. Depending on parametric values, pressure may propagate and flow may commence for pipeline lengths larger than the critical length, Lc=ΔpR/2τy, (where Lc is the flow restart length for a yielding gel without microstructure breakage, Δp is the applied pressure, R is the pipe radius, and τy is the yield stress). Prior to attaining the critical length, the nature of the pressure wave is shown to be either inertial or viscous, depending on the initial gel viscosity. Upon approaching the critical length, the nature of the pressure wave is governed by gel degradation, except at extreme compressibility values. At high compressibility, the nature of the pressure wave is controlled by gel degradation, even prior to reaching Lc, facilitating flow commencement in long pipes via a sequential breakage process. At very low compressibility, the pressure wave propagates until the force exerted by the fluid on the wall evenly balances the applied pressure. Hence, the pressure wave may propagate beyond the critical length but sustained flow does not commence. At intermediate compressibility values, if propagation of pressure to the critical length causes mean near-wall gel deformation on a similar magnitude as the static yield strain value (γ≡χΘΔp2/2τy∼γs, where χΘ is the isothermal compressibility) then the pressure wave does not propagate substantially beyond Lc and flow does not restart in the pipeline. For intermediate compressibility when γ > >γs, then flow restarts via the high compressibility mechanism (e.g. low gel strength cases) and when γ < <γs then the pressure wave propagates without flow restart (e.g. high gel strength cases), similar to the low compressibility regime. For validation of numerical results, a case with only a viscous term is compared with literature results. Furthermore, large scale flow loop experiments were performed to measure pressure propagation. Experimental results are consistent with the mechanism of pressure propagation and flow restart determined numerically.

Rheological, thermal, and gelling properties of azuki bean starch with sucrose

Rheological, thermal, and gelling properties of 5% (w/w) Korean azuki bean starch (ABS)‐sucrose mixtures at different sucrose concentrations (0, 10, 20, and 30% w/w) were investigated. Flow properties of ABS‐sucrose mixtures were determined from rheological parameters for power law and Casson flow models. All mixture pastes exhibited a pseudoplastic shear‐thinning characteristic (n = 0.30–0.34) with yield stress. Consistency index (K), apparent viscosity (ηa,50), and Casson yield stress (σoc) values decreased with an increase in sucrose concentration. Dynamic moduli (G′ and G″) values of ABS‐sucrose mixtures increased with increasing sucrose concentration, indicating that their viscoelastic properties were greatly affected by the addition of sucrose. The addition of sucrose had little impact on tan δ (ratio of G″/G′) values. Differential scanning calorimetry of ABS‐sucrose mixtures showed an increase in the onset (To), peak (Tp), and conclusion (Tc) temperatures of gelatinization and a decrease in the enthalpy (ΔH) of gelatinization with a corresponding increase in sucrose concentration. The ABS‐sucrose mixture gels showed much lower gel strength values compared to the control (0% sucrose). In general, these results suggest that the presence of sucrose in ABS modifies physical and rheological properties, depending on the sucrose concentration. In addition, these results could facilitate the development of sweetened ABS‐based products with improved physical and rheological properties.

Gelatin-based nanoparticles as DNA delivery systems: Synthesis, physicochemical and biocompatible characterization

The rapidly rising demand for therapeutic grade DNA molecules requires associated improvements in encapsulation and delivery technologies. One of the challenges for the efficient intracellular delivery of therapeutic biomolecules after their cell internalization by endocytosis is to manipulate the non-productive trafficking from endosomes to lysosomes, where degradation may occur. The combination of the endosomal acidity with the endosomolytic capability of the nanocarrier can increase the intracellular delivery of many drugs, genes and proteins, which, therefore, might enhance their therapeutic efficacy. Among the suitable compounds, the gelification properties of gelatin as well as the strong dependence of gelatin ionization with pH makes this compound an interesting candidate to be used to the effective intracellular delivery of active biomacromolecules. In the present work, gelatin (either high or low gel strength) and protamine sulfate has been selected to form particles by interaction of oppositely charged compounds. Particles in the absence of DNA (binary system) and in the presence of DNA (ternary system) have been prepared. The physicochemical characterization (particle size, polydispersity index and degree of DNA entrapment) have been evaluated. Cytotoxicity experiments have shown that the isolated systems and the resulting gelatin-based nanoparticles are essentially non-toxic. The pH-dependent hemolysis assay and the response of the nanoparticles co-incubated in buffers at defined pHs that mimic extracellular, early endosomal and late endo-lysosomal environments demonstrated that the nanoparticles tend to destabilize and DNA can be successfully released. It was found that, in addition to the imposed compositions, the gel strength of gelatin is a controlling parameter of the final properties of these nanoparticles. The results indicate that these gelatin-based nanoparticles have excellent properties as highly potent and non-toxic intracellular delivery systems, rendering them promising DNA vehicles to be used as non-viral gene delivery systems.

Reduced functionality of PSE-like chicken breast meat batter resulting from alterations in protein conformation

The objectives of this study were to evaluate protein thermal stability, water-protein interaction, microstructure, and protein conformation between PSE-like and normal chicken breast meat batters. Sixty pale, soft, and exudative (PSE)-like (L*>53, pH24 h<5.7) and 60 normal (46<L*<53, 5.7<pH24 h<6.1) chicken breast meats were selected from 3 different occasions in a major Chinese commercial plant. Two different meat batters were formulated to 14% meat protein and 2% salt, and they were analyzed for the protein changes and the microstructure using differential scanning calorimetry, low-field (LF)-NMR, SEM, and Raman spectroscopy. PSE-like meat batter had lower gel strength, water-holding capacity, and salt-soluble protein extraction (P < 0.05). Heated PSE-like meat batter formed an aggregated gel matrix, while normal meat batter produced a compact gel network with fine, cross-linked strands by many protein filaments. LF-NMR revealed an increase in the water mobility in heated PSE-like meat batter with an increasing amount of loosely bound water (P < 0.05). No significant changes were observed in the electrophoretic patterns of salt-soluble protein extracts by SDS-PAGE. However, differential scanning calorimetry showed that PSE-like meat had greater myosin and sarcoplasmic proteins/collagen denaturation (P < 0.05). In PSE-like meat, actin denaturation was particular evident after salt addition (P < 0.05) using differential scanning calorimetry. Moreover, Raman spectroscopy indicated that PSE-like meat batter had less unfolded α-helix and β-sheet structure formation, reduced exposure of hydrophobic and tyrosine residues (P < 0.05), and changes in the microenvironment of aliphatic residues and tryptophan, which affected salt-soluble protein extraction, gel properties, and water-holding capacity. In conclusion, the inferior functional properties of PSE-like meat were attributed to not only myosin denaturation, but also actin denaturation after salt addition and different protein structural states.

Chemical and biophysical properties of gelatins extracted from the skin of octopus (Octopus vulgaris)

Gelatins from alkali-pre-treated skin of Octopus (Octopus vulgaris) were extracted with different concentrations of pepsin at pH 2.0. The resulting octopus skin gelatins OSG0, OSG5, OSG10 and OSG15, extracted, respectively, without enzyme treatment or with 5, 10 and 15 U of pepsin/g alkaline treated skin were evaluated for gel strength, textural parameters, thermal and gelling properties. The yield of gelatin extracted without enzymatic pretreatment was only 3.21% and the addition of pepsin (15 U/g) increased the yield of gelatin extraction to 7.78%. Molecular weight distribution of gelatins indicates that OSG10 and OSG15 contain peptides with molecular weights less than 10 kDa (>40%). In addition, Fourier transform infrared (FTIR) spectra of extracted gelatins were slightly different, indicating that the triple helical structure of gelatins was affected by pepsin treatment. Compared to OSG0, pepsin gelatins exhibited lower gel strength, hardness, adhesiveness, transition, gelling and melting temperatures and all of the values decreased with increasing enzyme concentration. In addition foam expansion (FE) was affected by enzyme treatment, and the values decreased as pepsin increased. However, the emulsifying activity index (EAI) values of all gelatins were the same. Further, FE and EAI increased with increasing concentrations (1–3%, w/v). The results showed that octopus skin can be a good source for gelatin.

Preparation and gel properties of low molecular weight curdlan by hydrolysis of curdlan with commercial α-amylase

Low molecular weight curdlan (LMWC) was prepared by hydrolysis of curdlan with commercial α-amylase. The hydrolysis reaction was conducted using 31.94mg α-amylase per 500mL reaction mixture, which contained 5g curdlan. The hydrolysis was performed at pH 5.98 and 55.92°C for 10min. The molecular weight and structure of LMWC were characterized by high-performance liquid chromatography and Fourier transform infrared spectroscopy, respectively. Generally, LMWC showed lower gel strength than high molecular weight curdlan (HMWC). Unlike HMWC, LMWC could form into a gel at 50°C. By contrast, HMWC could form into a gel at pH 11, but LMWC gel failed to form at this pH level. The strength of LMWC and HMWC gels increased with increasing temperature and decreased with increasing pH level.

Rheology of Yanang solution: Effect of temperature, pH and divalent cation

The main objective of this work was to study rheological properties of Yanang (Tiliacora triandra) solution; a kind of food that derived from plants is being widely used in many countries in South East Asia and East Asia. Experiments were conducted to evaluate the impact of temperature on the viscosity and then build rheological curves of products. The results showed that viscosity of Yanang solutions changes with temperature in the shear - thinning models. These solutions formed gel at low temperature and gel strength can be improved by adjusting pH and adding Ca2+ due to the presence of uronic axit residues on the backbone of Yanang gums.

Effects of high pressure processing on the thermal gelling properties of chicken breast myosin containing κ-carrageenan

The effects of high pressure processing (HPP) (0–400 MPa for 10 min, 0–20 min under 300 MPa) on the water holding capacity (WHC) and gel strength of chicken breast myosin containing 0.225% κ-carrageenan (W/V, 2.25 g/L relative to myosin solution) (myosin-K) and the thermal gelling mechanism were investigated. The results revealed that HPP at 100–400 MPa could significantly increase the WHC of myosin-K gels while decreasing the gel strength (P < 0.05). The turbidity, surface hydrophobicity and reactive sulfhydryl contents of the pressurized myosin-K increased significantly at 200–400 MPa (P < 0.05). Dynamic rheological measurements indicated that the thermal gelling ability of the pressurized myosin-K matrix gradually decreased as the pressure increased (100–400 MPa). Low-field nuclear magnetic resonance data suggested that HPP at 100–400 MPa might shorten the water relaxation time of the gel. The Fourier transform infrared spectroscopy data revealed that the hydrogen bonding interactions in the gels might weaken when subjected to 100–300 MPa but could be enhanced at 400 MPa. The scanning electron microscopy images revealed that HPP (300 MPa, 10 min) produced a dense, networked myosin-K gel structure with small cavities and thin cross-linked strands. Moreover, pressure levels were responsible for the above results. The protein in myosin-K could denature, unfold and aggregate under HPP (100–400 MPa), thus decreasing the thermal gelling ability of myosin-K matrix. The high WHC of the pressurized myosin-K gel was attributed to the enhanced hydrogen bonding and hydrophobic interactions, as well as the uniform and dense networked structure; the low gel strength might be ascribed to the low thermal gelling ability of pressurized myosin-K.

Modifying the flocculation of microfibrillated cellulose suspensions by soluble polysaccharides under conditions unfavorable to adsorption

Carboxymethylcellulose (CMC) and xanthan gum were studied as dispersants for microfibrillated cellulose (MFC) suspension using a rotational rheometer and imaging methods. The imaging was a combination of photography and optical coherence tomography (OCT). Both polymers dispersed MFC fibers, although CMC was more effective than xanthan gum. The negatively charged polymer chains increased the viscosity of the suspending medium and acted as buffers in between the negatively charged fibers. This behavior decreased the number and strength of contacts between the fibers and subsequently dispersed the flocs. The stronger separation of the fibers was reflected in the frequency sweep where the MFC/polymer suspensions had lower gel strength than pure MFC suspension. Dispersing effect was also observed in the flow measurements, where the floc size was more uniform with polymers in the decelerating flow and after long, slow constant shear, which normally induces a heterogeneous structure with large flocs into the MFC suspension.

Physico-chemical properties of gelatin from bighead carp (Hypophthalmichthys nobilis) scales by ultrasound-assisted extraction.

In this study, gelatin was extracted from bighead carp (Hypophthalmichthys nobilis) scales by water bath (WB) and ultrasound bath (UB) at 60°C for 1h, 3h and 5h, named WB1, WB3, WB5, UB1, UB3 and UB5, respectively. The physicochemical properties of gelatin were investigated. The result indicated that gelatin extracted from bighead carp scales had a high protein content (84.15 ~ 91.85%) with moisture (7.11 ~ 13.65%), low ash content (0.31 ~ 0.97%). All extracted gelatin contained α-and β-chains as the predominant components. Gelatin extracted by UB obtained much higher yield (30.94-46.67%) than that of WB (19.15-36.39%). More voids and less sheets of gelatin structure were observed, when the gelatin was extracted by UB for longer time. Gelatin of UB-assisted extraction normally exhibited lower gel strength and melting points than that of WB, which may be resulted from the protein degradation reflected by the FTIR spectra and higher free amino group content. However, there was no significant difference between WB1 and UB1. Therefore, the ultrasound assisted extraction in a short time was a promising method to enhance the yield and obtain gelatin with high quality.

Effect of epiphyte infection on physical and chemical properties of carrageenan produced by Kappaphycus alvarezii Doty (Soliericeae, Gigartinales, Rhodophyta)

Epiphytism of filamentous red algae is a serious problem in Kappaphycus farms in the Philippines, Indonesia, Malaysia, and Tanzania. The causative organism of epiphyte outbreak has been identified as Neosiphonia apiculata (Hollenberg) Masuda and Kogame, but its actual effect on carrageenan quality has not yet been established. Therefore, yield and quality of carrageenan from healthy and infected specimens were examined. Infected specimens showed 20.5 ± 2.5 % DW lower carrageenan yield compared with the healthy seaweed (65.5 ± 4.2 % DW). Infected specimens also had a higher phenolic and fatty acid content, compared with healthy specimens. The carrageenan from the infected seaweed showed 74.5 ± 2.8 % lower viscosity, 52.6 ± 3.6 % lower gel strength, 22.9 ± 1.5 % higher syneresis, and 5 °C higher melting temperature as compared with carrageenan from healthy specimens. FTIR and 13C-NMR analysis of carrageenan from infected seaweed did not show any differences in their functionality or carbon atom chemical shift as compared with healthy and standard k-carrageenan. However, size exclusion chromatography showed the infected carrageenan molecular size to be 80 kDa as compared with 800 kDa for the healthy and standard k-carrageenan. These findings prove that infection of Kappaphycus by the filamentous red algae epiphyte, N. apiculata, reduces carrageenan molecular size and affects the physical properties of the carrageenan.