Κ-carrageenan Concentration Research Articles

The impact of κ-carrageenan on the pea protein gelation by high pressure processing and the gelling mechanisms study

The transition toward sustainable and health-conscious diets has intensified plant-based proteins, particularly pea protein. This research explored the gelation mechanisms of pea protein with κ-carrageenan by high-pressure processing (HPP) as an alternative to traditional thermal methods. Suspensions containing 15% pea protein with 0.1–1% κ-carrageenan were subjected to HPP at 100–600 MPa for 5–30 min. Increasing κ-carrageenan concentration reduced the pressure required to obtain good gels, rendering HPP more energy efficient. Pea protein gels with 1% κ-carrageenan at 600 MPa demonstrated a 27-fold increase in compressive strength compared to 15% pea protein alone by HPP and over 5 times the strength of heat-induced counterparts. Gel textures could be tailored by modulating HPP conditions and κ-carrageenan concentrations. Fourier transform infrared spectroscopy, confocal laser scanning microscopy, and scanning electron microscopy characterized protein unfolding, phase separation, and network formation to study the gelation mechanisms. Results revealed that HPP induced protein tertiary structure unfolding, facilitating phase separation and uniform submicron κ-carrageenan particle distribution in the protein matrix. This, along with a more compact protein network induced by HPP, enhanced gel strength, compensating for limited cysteine in pea protein for disulfide bonds. Higher pressures intensified protein unfolding and aggregation, with κ-carrageenan particles evenly distributing into smaller particles, further strengthening gel structures. Conversely, heating-induced gelation caused more random protein aggregation, leading to coarser and weaker gel networks. This research highlights HPP's effectiveness over traditional heating methods in preparing strong pea protein gels with minimal κ-carrageenan and provides preliminary insights into tailoring HPP and κ-carrageenan for desirable gel textures.

Underlying the mechanisms of incorporation of κ-carrageenan on the formation of low-salt myofibrillar protein gels during heating process: Perspective on the dynamic changes of protein structures and molecular interactions

This study aimed to systematacially investigate the effects of κ-carrageenan (KC) concentration on the formation of myofibrillar protein (MP) gels under low-salt condition based on the dynamic changes of protein structures and molecular interactions during heating process. The results indicated that incorporating KC markedly improved the water holding capacity (WHC) and gel strength of MP gels (P < 0.05). Those properties were most improved by adding 0.4% KC with WHC of 71.44% and gel strength of 1.62 N. During the heating process, when the temperature was above 50 °C, KC addition significantly increased the turbidity and particle size and decreased solubility of MP in a concentration-dependent manner, as well as exhibiting higher surface hydrophobicity at 0.2% KC concentration (P < 0.05), indicating that KC accelerated the rate of aggregation of MP during heating process. The dynamic rheological behaviors indicated that the addition of KC promoted the early unfolding and aggregation of MP at a relatively lower temperature, which was verified by the fluorescence denaturation mechanism results. Moreover, the addition of KC significantly promoted the heat-induced conformational transition of MP from α-helix companied with β-sheet and β-turn, which was due to the interaction between MP and KC accelerating the formation of MP gels during the heating process. Intermolecular forces results revealed that the aggregation of myosin head and cross-linking of myosin tail of MP added KC was enhanced by ionic bonds, hydrophobic interactions, and disulfide bonds, which facilitated the better gel performance. Our present results provided a comprehensive understanding of gelation mechanism of MP-KC mixed gels under low-salt condition, with implications for the practical application of KC in meat processing.

The Effect of κ-Carrageenan on Porcine Sperm Cryo-Survival.

κ-Carrageenan is a sulfated polysaccharide from red seaweed with substantial antioxidant activities. This study aimed to investigate the effect of κ-Carrageenan treatment on frozen-thawed (FT) porcine semen quality. Therefore, the spermatozoa were diluted and cryopreserved in a freezing extender supplemented with 0 (control), 0.2, 0.4, 0.6, and 0.8 mg/mL κ-Carrageenan. Sperm kinematics were assessed immediately after thawing (AT) and post-incubation for 120 min. The viability, acrosome integrity, lipid peroxidation, mitochondrial membrane potential (MMP), and intracellular caspase activity were measured AT. The results indicated that 0.2 mg/mL κ-Carrageenan increased total and progressive motility AT and post-incubation for 120 min (p < 0.05). Moreover, the viable sperm percentage and MMP after 0.2 mg/mL treatment were higher than those after control and other κ-Carrageenan concentration treatments. The proportion of acrosome-intact spermatozoa was significantly higher after 0.2 and 0.4 mg/mL κ-Carrageenan treatment than that after control and other κ-Carrageenan concentration treatments. The intracellular caspase activity was not significantly different among the experimental groups. However, the MDA concentration after 0.2 mg/mL κ-Carrageenan treatment was lower (p < 0.05) than that after the control treatment. Taken together, adding κ-Carrageenan to the porcine semen freezing extender improved the FT sperm quality mainly by influencing membrane stability and protecting against oxidative stress.

Impact of κ-Carrageenan on the Cold-Set Pea Protein Isolate Emulsion-Filled Gels: Mechanical Property, Microstructure, and In Vitro Digestive Behavior

More understanding of the relationship among the microstructure, mechanical property, and digestive behavior is essential for the application of emulsion gels in the food industry. In this study, heat-denatured pea protein isolate particles and κ-carrageenan were used to fabricate cold-set emulsion gels induced by CaCl2, and the effect of κ-carrageenan concentration on the gel formation mechanism, microstructure, texture, and digestive properties was investigated. Microstructure analysis obtained by confocal microscopy and scanning electron microscopy revealed that pea protein/κ-carrageenan coupled gel networks formed at the polysaccharide concentration ranged from 0.25% to 0.75%, while the higher κ-carrageenan concentration resulted in the formation of continuous and homogenous κ-carrageenan gel networks comprised of protein enriched microdomains. The hydrophobic interactions and hydrogen bonds played an important role in maintaining the gel structure. The water holding capacity and gel hardness of pea protein emulsion gels increased by 37% and 75 fold, respectively, through increasing κ-carrageenan concentration up to 1.5%. Moreover, in vitro digestion experiments based on the INFOGEST guidelines suggested that the presence of 0.25% κ-carrageenan could promote the digestion of lipids, but the increased κ-carrageenan concentration could delay the lipid and protein hydrolysis under gastrointestinal conditions. These results may provide theoretical guidance for the development of innovative pea protein isolate-based emulsion gel formulations with diverse textures and digestive properties.

Physicochemical and release properties of anthocyanin gastric floating tablets colloidized with κ-carrageenan/metal ions

Gastro-retentive carriers have recently been used to improve the quality of biologically active components and their controlled-release. Anthocyanins are biologically active compounds that are absorbed and digested in the stomach. In this study, κ-carrageenan, sodium bicarbonate, calcium carbonate, and potassium chloride were used to produce anthocyanin gastric floating tablets (GFTs). The GFTs had a hardness of 6.63–8.58 kgf and friability of 0.02–0.05%. Differential scanning calorimetry and X-ray diffraction revealed a good excipient stability. Metal ions changed the κ-carrageenan type and concentration, which influenced composite hydrogel film production and anthocyanin release. An increase in potassium ions increased –OH stretching (3600–3000 cm−1) and calcium ions improved hydrogel properties, lowering the tablet swelling ratio from 80.48 to 66.67%, thereby facilitating the formation of a stable κ-carrageenan gel structure. This also increased the duration of anthocyanin release in the simulated gastric fluids from 180 to 300 min. GFTs can be used as gastro-retentive carriers for the delivery of pharmaceuticals and functional supplements.

Rheological properties and microstructure of rennet-induced casein micelle/κ-carrageenan composite gels

This study aimed to investigate effects of kappa-carrageenan (κ-carrageenan) concentration and storage temperature on the rheological and texture properties of casein micelle/κ-carrageenan composite gels. The particle size, zeta potential, Fourier transform infrared spectroscopy of the mixture, and microstructure of the composite gels were measured. The movement of κ-carrageenan characteristic bond showed that the casein micelle and κ-carrageenan formed a complex with larger particle size through electrostatic adsorption. The electrostatic repulsion between molecules increased with the increase of κ-carrageenan concentration, which stabilized the mixed system. It was found that both κ-carrageenan concentration and storage conditions affected the gel's rheological properties and microstructure. As the concentration of κ-carrageenan increased, the storage modulus (G′) of the composite gels increased, the rennet coagulation time (RCT) decreased, and the water holding capacity (WHC) increased at 25 °C. Microstructure results showed that a more uniform and denser gel network structure with smaller pore sizes was formed after the addition of κ-carrageenan compared with the control. G′ and RCT were reduced and microscopic phase separation occurred after storage at 4 °C, resulting in a porous structure with large pore sizes. Thus, the addition of κ-carrageenan could enrich the diversity of food gel structure to obtain an ideal gel.

Design of glucono-δ-lactone-induced pinto bean protein isolate/κ-carrageenan mixed gels with various microstructures: fabrication, characterization, and release behavior.

Protein gels are used for different purposes, such as providing good texture, serving as fat replacers, and enhancing the nutritional and functional characteristics of foods. They can also deliver controlled release agents for sensitive drugs. The objective of this study was to investigate the impact of κ-carrageenan (kcr) concentration (0, 1.5, 3, and 4.5mg g-1 ) on the morphological and physicochemical properties and release behavior of glucono-δ-lactone (GDL)-induced pinto bean protein aggregate (PBA) gels. When κ-carrageenan concentration increased from 0 to 1.5 and 3mg.g-1 , the firmness of the samples increased significantly, by 2.04 and 3.7 fold, respectively (P< 0.05). A compact and homogenous network with considerable strength and maximum water-holding capacity (97.52 ± 1.17%) was obtained with the addition of 3mg g-1 κ-carrageenan to the gel system. Further increasing the κ-carrageenan concentration to 4.5mg g-1 produced a coarse gel structure with higher storage modulus (G'), firmness (6.30-fold), thermal stability, and entrapment efficiency (85.6%). Depending on the κ-carrageenan concentration, various microstructures from protein continuous phase to κ-carrageenan continuous phase were observed. The release test indicated that 70.25% of the loaded curcumin was released in the simulated gastrointestinal tract for pure PBA gels. In contrast, for binary gels containing 4.5mg g-1 κ-carrageenan, curcumin was protected in the upper gastrointestinal tract, and 64.45% of loaded curcumin was delivered to the colon. Our study showed that κ-carrageenan/PBA gels had high entrapment efficiency and could protect curcumin in the upper gastrointestinal tract. The hydrogels are therefore very valuable for colon-targeting delivery purposes. © 2022 Society of Chemical Industry.

Effects of gelation concentration on cyclic deformation behavior of κ-carrageenan hydrogels

The aim of this study is to elucidate the relationship between the network structure of κ-carrageenan hydrogels and their mechanical properties. First κ-carrageenan hydrogels have been prepared at different gelation concentrations, and then the mechanical behavior during four cyclic deformations has been examined at the same κ-carrageenan concentration. Young's modulus is higher for the gel prepared at 5 gL−1 (C05) compared to that for the gel prepared at 30 gL−1 (C30). C30 shows almost linear relation between the stress and the strain like an ideal rubber, while a residual strain appears in each cyclic deformation for C05. The extent of the residual strain depends on the maximum strain and the deformation speed, indicating that C05 deforms plastically to some extent. The residual strain for C05 decreases gradually even after a cyclic deformation and disappears in the case of a small strain as if there were a memory of the structure. The effects of the gelation concentration on the mechanical properties have been explained based on the network structure specific to κ-carrageenan hydrogels. The higher modulus for C05 has been attributed to the higher helix content and the plastic deformation of C05 to the loosely-aggregated crosslinks.

Nanoemulsions with sea buckthorn oil and κ-carrageenan

The structure, stability, and rheological properties of nanoemulsions with droplets of sea buckthorn oil stabilized with Tween 80 and Span 80 and κ-carrageenan in the aqueous phase were investigated. The fast flocculation and coalescence of oil droplets occurred in nanoemulsions without κ-carrageenan. The nanoemulsion stability was significantly improved in the presence of the gel network at κ-carrageenan concentrations ≥ 0.5 mass%. TEM analysis showed that oil droplet flocs were trapped in the polymer gel network, so the further floc compaction and creaming were prevented. Nanoemulsions without κ-carrageenan and 0.25 mass% κ-carrageenan displayed the Newtonian-like rheological behavior whereas nanoemulsions with 0.5–5.0 mass% κ-carrageenan demonstrated the non-Newtonian flow of the pseudoplastic type. Oscillatory measurements showed that the values of G′ were higher than the corresponding G″ for nanoemulsions with 0.5 and 2 mass% κ-carrageenan in the investigated range of angular frequencies. However, the G′/G″ crossover was detected for nanoemulsion with 5 mass% κ-carrageenan. The structure relaxation was not observed for this nanoemulsion because the gel in the aqueous phase was irreversibly broken under shear. In nanoemulsions with lower κ-carrageenan concentration, the disintegrated structure was recovered with time after shearing. Apparently, the destruction of the oil droplet flocs under the shear was reversible and the elastic structure of the gel was not destroyed.

Interfacial viscoelastic moduli in a weak gel

HypothesisThe measurement of interfacial viscoelastic moduli provides information on the ability of surface-active agents to texture the interface. However, the contribution of the bulk rheology cannot be ignored in particular when the continuous phase exhibits a gel-like behavior, even with low modulus. ExperimentsBetween 2 and 6 g/L, κ-carrageenan aqueous solutions have no significant activities at interfaces. At low concentrations or high temperatures, they behave like Newtonian liquids. Upon heating or cooling, a reversible liquid/gel transition appears with a hysteresis where the rheological behavior can be easily modulated by adjusting κ-carrageenan concentration. The frequency dependence of bulk and interfacial viscoelastic moduli are determined using a conventional shear rheometer and a drop tensiometer with a polyisobutene oil, respectively. FindingsThe effect of concentration and temperature is analyzed and the frequency dependence of interfacial moduli is correlated with those of the bulk. In presence of a gelled κ-carrageenan solutions, an elastic behavior of the interface appears and strengthens as the elastic modulus of the suspended phase is high. It turns out that the oscillating pendant drop method could be a sensitive indicator of the presence of very weak gels, even hardly detected by a shear classical rheometry.

Utilization of κ-carrageenan as stabilizer and thickener of honey pineapple (Ananas comosus [L. Merr]) jam

Honey pineapple jam is an intermediate moisture food that often has low stability; hence it is not strong enough to hold the fruit tissue sugar in position during storage. Therefore, it is necessary to add hydrocolloid in fruit jam processing to increase stability and consistency, one of which is κ-carrageenan. The purpose of this study was to determine the effect of adding κ-carrageenan towards stability and preference for honey pineapple jam. The κ-carrageenan concentrations used were 0%, 0.5%, 1%, and 1.5% (w/w) of total ingredients. The ratio of honey pineapple pulp and sugar was 4:1 (w/w). The results showed that the addition of κ-carrageenan had a significant effect (p&lt;0.05) on the hedonic evaluation of colour, smearing ability, and texture; moisture content, water activity (Aw), syneresis and texture (hardness, cohesiveness, and adhesiveness). The addition of κcarrageenan had no significant effect (p&gt;0.05) on the hedonic evaluation (preference) of aroma and taste. Increasing the κ-carrageenan concentration can increase the hedonic value for colour and decrease the hedonic value for smearing ability and texture. Increasing the concentration of κ-carrageenan can also increase the value of hardness and cohesiveness but decrease water activity, syneresis, and adhesiveness. The addition of κcarrageenan 0.5% was more efficient in shortening the cooking time until 25%, inhibiting syneresis by 30%, and improving the colour of honey pineapple jam.

Structure-property relations of β-lactoglobulin/κ-carrageenan mixtures in aqueous foam

There is a great interest in mixed protein/polysaccharide layers at air-water interfaces due to their ability to stabilize aqueous foams. Properties of β-lactoglobulin (BLG)/κ-carrageenan mixtures at different κ-carrageenan concentrations were studied using foam analysis and molecular-level characterizations at the air-water interface. Because air-water interfaces are a major element in aqueous foams, they were investigated with a combination of interface-sensitive methods such as sum-frequency generation (SFG) as well as surface tensiometry. Using SFG spectroscopy we provide new information on the changes in the interfacial charging state and composition when the BLG/κ-carrageenan mixing ratio changes. κ-carrageenan is only weakly surface active as it does not lower the surface tension to a large extend. However, BLG/κ-carrageenan mixtures showed a synergistic effect because the formation of complexes at the air-water interface and in the bulk solution can favorably influence foam stability. BLG (7.5 µM) was mixed with different κ-carrageenan concentrations from 0 to 1 mM while the bulk pH was adjusted to pH values which are below (4.5), slightly above (5.6) and well above (7.0) the isoelectric point of BLG. At pH 4.5, the positive ζ-potential of BLG was drastically reduced to negative values and large aggregates in the bulk formed that showed a reduced surface activity and caused also a reduced net charging state at the air-water interface. The interfacial and bulk properties at pH 4.5, resulted in a poor stability of foams that were likely only stabilized by the weak electrostatic disjoining forces in the foam lamella. At pH 5.6 and 7, cooperative effects of BLG and κ-carrageenan dominate and, in particular, at pH 5.6 give rise to an increase in BLG surface coverage when the κ-carrageenan concentration increases. This resulted in a substantially improved foam stability.

EFFECT OF K-CARRAGEENAN ON MECHANICAL, THERMAL AND BIODEGRADABLE PROPERTIES OF STARCH–CARBOXYMETHYL CELLULOSE (CMC) BIOPLASTIC

Starch–carboxymethyl cellulose (CMC) bioplastics have limited mechanical properties. Carrageenan from seaweed is a potential reinforcement material for improving the mechanical properties of bioplastics. This study aimed to determine the effect of Kappa (κ)-carrageenan on the mechanical and thermal properties and biodegradability of starch–CMC bioplastics. In this study, carrageenan at concentrations of 0%, 10%, 15%, 20%, 25% and 30% was used. The melt-mixing process was conducted at 130 °C for 4 min, using a mixer and then hot-pressing (30 kgf/cm2) at 150 °C for 5 min. The results indicated that the higher κ-carrageenan concentration increased the strength of bioplastics up to 15.7 MPa. The fracture analysis via scanning electron microscopy–energy-dispersive X-ray spectroscopy indicated the distribution of sulfur (S) elements that described the dispersion of κ-carrageenan. The Fourier transform infrared spectroscopy spectra revealed that the interaction between the starch–CMC matrix and κ-carrageenan formed a tight hydrogen bond network. The lowest mass reduction observed by thermogravimetric analysis occurred in bioplastics with 25% carrageenan, decreasing by 48% compared with bioplastics without κ-carrageenan. The addition of κ-carrageenan was identified as not affecting the biodegradability of the bioplastics.

Polysaccharide-based skin scaffolds with enhanced mechanical compatibility with native human skin

We report a custom-made technique to synthesize process-convenient skin scaffolds by tuning the mechanical properties of hydrogels based on a few naturally occurring polysaccharides to match the rheological properties of previously established benchmarks, i.e., the ex vivo native human skins. We studied the mechanical parameters using oscillatory shear rheology. At small strain amplitudes, the intrinsic elastic modulus showed an almost linear dependence in the middle and a changing rate profile at the two ends with concentration of the principal hydrogel component variant, i.e., kappa (κ)-carrageenan. At large strain amplitudes, the hydrogels demonstrated intercycle strain-softening behavior, the onset of which was directly proportional to the κ-carrageenan concentration. We observed a concentration match for the intrinsic elastic modulus of the benchmark within this sigmoidal curve fit. Contextually, we need to explore other potent polymeric hydrogel systems to achieve mechanical affinity in terms of multiple rheological parameters derived from both strain amplitude and angular frequency sweeps. Additionally, we carried out diffusion experiments to study caffeine permeation attributes. The hydrogels show improved barrier features with increasing κ-carrageenan concentration. In terms of the penetration flux and total cumulative amount of permeated caffeine, this enhanced mechanical adherence demonstrates comparable penetration features with the commercial 3D skin model.

Formulation of alginate/carrageenan microgels to encapsulate, protect and release immunoglobulins: Egg Yolk IgY

In this study, alginate/κ-carrageenan hydrogel beads were developed to encapsulate and release egg yolk immunoglobulin Y (IgY) under simulated gastrointestinal conditions. The effects of κ-carrageenan concentration on the encapsulation and loading efficiency of the hydrogel beads was assessed, as well as on their swelling and release behavior in a simulated human gut. An κ-carrageenan concentration of 0.30% gave the optimum encapsulation and loading efficiency. After incubation in simulated gastric fluids, there was no loss in IgY activity when it was encapsulated within alginate/carrageenan beads but around 35% loss when it was encapsulated in pure alginate beads. This effect was attributed to a stronger electrostatic attraction and a more closely packed biopolymer network formed within the composite beads, based on measurements of their electrical and microstructural properties. The composite beads were resistant to swelling in the stomach phase, but not in the intestine phase. The kinetics of swelling under simulated gastric conditions was found to follow Schott's second-order model. The gastrointestinal digestion of the IgY was slower in the composite beads than in the pure alginate beads. The release kinetics of IgY from the composite beads was fitted by an irregular release model. Our results suggest that alginate/κ-carrageenan composite beads are efficient carriers for the delivery systems of hydrophilic immunoglobins.

Ultra-high temperature (UHT) stability of chocolate flavored high protein beverages.

The effects of two milk protein formulations and κ-carrageenan concentration (0, 0.01, 0.03, and 0.05%) on UHT (145 °C) fouling behavior and physical properties of chocolate flavored high protein beverages were studied. These two beverage formulations were: (i) reconstituted milk protein concentrate (RMPC-Choco) and (ii) RMPC and reconstituted whey protein concentrate (C:W-Choco). The UHT run times for samples prepared without κ-carrageenan were very short (9.5 ± 0.71 and 26.5 ± 2.12 min for RMPC-Choco-0 and C:W-Choco-0, respectively) due to settlement of cocoa powder particles inside the UHT plant leading to severe fouling. The κ-carrageenan requirement for UHT stable (UHT run times >120 min) RMPC-Choco and C:W-Choco was 0.03 and 0.01%, respectively. The presence of higher amounts of whey proteins in C:W-Choco lowered its κ-carrageenan requirement to render it UHT stable due to additional gelation of whey proteins. This additional gelation was evident from larger average particle sizes and higher viscosity of UHT treated C:W-Choco samples at κ-carrageenan concentrations similar to RMPC-Choco samples. PRACTICAL APPLICATION: This research can be helpful to the food industry when formulating chocolate flavored high protein beverages; their protein profiles can be modified to lower the amount of stabilizers required to make them UHT stable.

Microbeads of Sodium Caseinate and κ-Carrageenan as a β-Carotene Carrier in Aqueous Systems

β-Carotene was encapsulated in microbeads formed by ionotropic gelation of multilayered emulsions containing sodium caseinate (Na-CAS) and κ-carrageenan at pH 7 and 3.5. The influence of κ-carrageenan concentration on the morphology of microbeads was studied, as well as the effect of pH on the encapsulation efficiency and rheological properties of microbead suspensions. Most of the microbeads showed monomodal size distribution with a mean particle diameter between 25.3 and 176.1 μm. Microbead morphology was influenced by the κ-carrageenan concentration, as microbeads tended to be larger and more spherical at higher κ-carrageenan concentrations. On the other hand, microbeads were slightly affected by pH, showing similar results for encapsulation efficiency and rheological properties of microbead suspensions in salt solution. The encapsulation efficiency was higher than 60% at both pH values. In addition, rheological measurements indicated that the incorporation of microbeads exerted a slight influence on the viscosity of aqueous solutions, mainly up to the 40% volume fraction. Therefore, these microbeads are promising systems for β-carotene vehiculation in food products without compromising their texture.

Effect of hydrocolloids on gel properties and protein secondary structure of silver carp surimi.

Hydrocolloids are the most commonly used additive in the processing of surimi products. However, the effect of hydrocolloids on surimi protein conformation has not been reported, and the level of hydrocolloids may be a key factor influencing the quality of surimi. Therefore, this study investigated the effect of curdlan, xanthan gum, κ-carrageenan, and gelatin at various levels on gel properties and protein conformation of surimi from silver carp. Addition of curdlan, κ-carrageenan, or gelatin at lower level could significantly promote gel strength, textural profiles, and water holding capacity (WHC) of the surimi gels. However, gel strength and WHC gradually decreased with increasing amount of xanthan gum added. The addition of curdlan or κ-carrageenan remarkably increased the whiteness of surimi gel, but the whiteness decreased when the concentration of κ-carrageenan reached 5 g kg-1 . Along with the increase of curdlan, κ-carrageenan, or gelatin concentration, the index of hydrophobic interaction and hydrogen bonds first increased and then decreased, whereas index of ionic bonds first decreased and then increased. According to Raman spectroscopy data, a small content of curdlan or κ-carrageenan promoted the conformational transition of surimi protein from α-helix to β-sheet, leading to the changes in gel properties of surimi gels. Scanning electron microscopy photographs showed surimi gels added with 4 g kg-1 curdlan or 2 g kg-1 κ-carrageenan had a finer and denser network structure. Curdlan or κ-carrageenan at an appropriate concentration is a potential modifier to effectively improve the quality of surimi products. © 2020 Society of Chemical Industry.

Properties of a commercial κ-carrageenan food ingredient and its durable superabsorbent hydrogels

Physical kappa-carrageenan-based hydrogels are often prepared from dilute aqueous kappa-carrageenan (κ-carrageenan) solutions at the presence of metallic ions or by mixing these solutions with proteins and other polysaccharides. The κ-carrageenan hydrogels have been used for technological purposes; however, there are no reports about the properties of a commercial GENUGEL® κ-carrageenan produced by the CP Kelco. The flame atomic absorption spectrometry shows that the commercial κ-carrageenan comprises a high content of metallic ions (K+ = 216.1 g kg−1, Na+ = 6.3 g kg−1 and Ca2+ = 12.5 g kg−1). The X-ray photoelectron spectroscopy (XPS) indicates the presence of sodium, calcium, and potassium atoms on the as-received κ-carrageenan and its physical hydrogel surfaces. XPS supports the occurrence of a low protein content onto the sample surfaces, as well. The metallic level (especially for K+) in the commercial κ-carrageenan plays an essential role in the preparation of durable hydrogels. These materials are prepared by cooling aqueous κ-carrageenan solutions at 4.0 and 5.0 wt%. The gelation temperature is determined by measuring G′ &G″ as a function of the temperature. The gelation behavior depends on the κ-carrageenan concentration, as well as the metallic content in the commercial sample. Scanning electron microscopy shows that hydrogels have porous and smooth surfaces. The dried materials swell from 2400 to 3100%, while the disintegration/dissolution test confirms that the samples present high stability in distilled water throughout 14 days. These hydrogels are superabsorbent materials and can be applied in agriculture as soil conditioners.

Rheological, thermal and microstructural properties of casein/κ-carrageenan mixed systems

The thermal, linear and non-linear rheological as well as microstructural properties of casein/κ-carrageenan mixtures were investigated. The results showed that the addition of κ-carrageenan greatly affected the rheological behavior of casein. The storage (G′) and loss (G″) moduli, and apparent viscosity (η) values were positively associated with κ-carrageenan concentration. Casein/κ-carrageenan mixtures showed the typical type Ⅳ (strong strain overshoot) network behavior in the large amplitude oscillatory shear tests. Lissajous plots of casein/κ-carrageenan mixtures appeared stronger nonlinear behavior by adding of κ-carrageenan. The existence of κ-carrageenan also increased the thermal denaturation temperature of casein in the mixture and produced a significant microstructural change within the network entanglements of casein. These changes of casein/κ-carrageenan mixed systems were due to associative interaction between casein and κ-carrageenan caused by electrostatic forces and hydrogen bonding.