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Oleogels needs still a lot of work to be a viable alternative for solid fats, however their potential is very promising, as those structures are versatile and can be formulated with tailored technological and nutritional benefits. This study analyzes the solid fat replacement potential of agar – canola oil based hydroleogels in shortbread-type cookies recipe. Three types of agar hydroleogels solidyfying canola oil (of 3 different manufacturing methods) were used to formulate shortbread type cookies using wheat flour:fat source:sugar proportion of 3:2:1. The bakeloss, spreadability, specific volume, colour and crispiness were evaluated 1 h after baking while the colour and crispiness were also checked after 10 days. Crispness analysis showed that biscuits based on hydrogels with cold pressed and bleached oil, refined oil and cold pressed oil were less crispy compared to cookies based on margarine by 70 %, 135 % and 180 %, respectively. The highest baking losses were observed for cookies with cold pressed and bleached, cold pressed and refined oil-based hydrogels: 39 %, 21 % and 20 %, respectively. An increase in cookie size was observed with decreasing baking losses. This study confirmed the feasibility of using hydrogels as a potential substitute for traditional solid fat in bakery products. [Display omitted] • Hydroleogels as fat substitutes. • The type of oil affects the parameters of cookies. • The type of hydrogels affects the texture. [ABSTRACT FROM AUTHOR]

In this study, agar/corn starch cryogels with different morphologies and characteristics were synthesized using sol, gel, and freeze-drying techniques. The addition of agar increased the gelatinization temperature of starch and decreased the gelatinization enthalpy, thereby inhibited the gelatinization process of starch. The rheological data revealed that the addition of agar accelerated the gelatinization process of the agar/starch binary system and significantly increased the storage modulus of the hydrogel. Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy demonstrated that agar disrupted the retrogradation and crystal structure of starch. A lower concentration of agar destroyed the network structure formed by starch and increased the pore size of cryogel. However, the fiber-bundle structure formed in the large pores after increasing the agar content made the cryogel network more compact. However, this led to marginal increase in cryogel density which endowed the cryogel with significantly improved compressive strength (5.01 MPa) and toughness. Therefore, the incorporation of agar into starch to prepare a composite cryogel is an effective approach for improving the properties of starch-based cryogels. [Display omitted] • Agar inhibited the gelatinization process of starch. • The large addition of agar disrupted the double helix structure of starch. • The addition of agar had a significant effect on the microstructure of the cryogel. • Starch/Agar cryogel had better compressive strength and toughness. [ABSTRACT FROM AUTHOR]

The minimalistic solidified form of oil, herein called hydroleogel, was elaborated via the emulsion oleogelation method by using agar hydrogel, as sole oleogelator. The rapeseed oils, originating from different manufacturing processes, were used as oil phase. The texture and rheological characteristics, weight loss, oil binding capacity, as well as color and appearance once solidified and after 24 h and 48 h of storage were studied. Texture profile revealed the dual dependance – the hardest hydroleogels were formed with 3 % agar and using refined rapeseed (canola) oil showing 14.16 ± 0.28 N and 14.11 ± 0.45 N after 2 h and 48 h, respectively. In contrast, hydrogels formed with cold pressed oil and 3% agar solution had an average of 50% lower hardness compared to the others. The oil retention capacity of the matrix was highest for hydroleogels with 3 % agar and cold pressed oil (98.3 ± 1.4 %), followed by cold pressed and bleached oil (97.0 ± 1.8 %) and refined oil (95.77 ± 2.4 %). The largest weight losses were observed for hydroleogels based on 1 % agar, with the exception of those formed from refined oil where a sub-weight loss of 0.5 % was recorded after 48h. The brightest were hydroleogels with pressed and bleached oil and 1 % (w/w) agar having after 2h the L* parameter equal to 98.95 ± 0.01, while the darkest one was cold pressed and bleached oil with 3 % (w/w) of agar (83.15 ± 0.25). The concentration of agar and the type of rapeseed oils used strongly impacted the physicochemical parameters of agar-based hydroleogels. Rapeseed oil hydroleogels with agar as the only structuring agent - an oleogelator in the composition, are a unique combination of two phases being hydrogel (aqueous phase) and rapeseed oil (oil phase) with promising physicochemical parameters. [Display omitted] • Agar can be used for oleogelation as a single oleogelato. • Hydroleogels based on rapeseed oil and agar have interesting physicochemical parameters. • The physicochemical parameters of hydrogels based on agar and rapeseed oil depend on the concentration of agar and the type of oil. [ABSTRACT FROM AUTHOR]

The plant-based meat market is growing due to concerns about the sustainability of the modern food system. Plant-based meats are often constructed from blends of food biopolymers, such as plant proteins and polysaccharides. This study characterizes the thermal setting properties of potato protein (10%) and polysaccharide (2 wt%) mixtures containing polysaccharides with different reversible gelling behaviors: agar (cold set); gellan gum (cold set); or methyl cellulose (heat set). Each sample was heated above the thermal denaturation temperature of the potato proteins to promote protein unfolding, aggregation, and network formation. The addition of the polysaccharides tended to increase the complex shear modulus of the biopolymer blends before heating but increase or decrease it after heating depending on polysaccharide type. The shear modulus and hardness of the gels formed after heating tended to increase after addition of the cold-set polysaccharides but decrease after the addition of the heat-set polysaccharides, especially at refrigerator temperatures. Differential scanning calorimetry data showed that the potato proteins underwent irreversible denaturation after heating for all samples. Zeta-potential analysis showed that the potato proteins and all polysaccharides were negatively charged under the pH conditions used. There was greater water loss during heating for the composite gels containing methyl cellulose, which may have been due to its increase hydrophobicity at high temperatures. Appearance and microstructure analysis showed that phase-separation occurred after mixing the polysaccharides with the potato proteins, which was attributed to a segregation mechanism. The knowledge obtained from this study may help the food industry to optimize protein-polysaccharide blends to create gels with characteristics and structures that can mimic different plant-based meat products. [Display omitted] • Composite gels were formed from potato protein and cold-set or heat-set gums. • Agar and gellan gum (cold-set) increased the shear modulus of potato protein gels. • Methylcellulose (heat-set) reduced the shear modulus of the potato protein gels. • Methylcellulose interfered with protein network formation at high temperatures. • The protein-polysaccharide composite gels consisted of semi-interpenetrating networks. [ABSTRACT FROM AUTHOR]

Agar is a valuable seaweed hydrocolloid that can form a high-firmness thermoreversible gel. With the increasing demand for vegetarian meals, agar can be used as a gelatin substitute with some modifications. In this study, we investigated the structural, mechanical, and rheological properties of a compound hydrogel using the agar/locust bean/xanthan gum (ALX). The different concentrations of hydrocolloids were optimized based on comparing the results of texture profile analysis of samples with high-bloom gelatin. Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy tests confirmed the interaction between agar, locust bean and xanthan gum. The textural analysis results showed that the addition of locust bean gum (LBG) and xanthan gum (XG) to agar could significantly increase the springiness of agar hydrogel (AG) from 0.92 ± 0.00 to 1.00 ± 0.00, also decrease its hardness from 702.11 ± 5.99 to 343.31 ± 20.23 g (p < 0.05). Moreover, a remarkable decrease was shown in the syneresis degree of AG from 2.33 ± 0.02% to 0.52 ± 0.00%. All behaviors of the optimum hydrogel indicated the effective interaction of LBG and XG with AG which made the final compound hydrogel a promising alternative to high-bloom gelatin. [Display omitted] • Modification of agar gel by forming a compound hydrogel. • Evaluation of agar/locust bean/xanthan gum compound hydrogel as an alternative to gelatin. • Xanthan and locust bean gum could change agar hydrogel's mechanical and physical properties. • Syneresis rate was reduced in the complex hydrogel. • Lower setting and melting temperatures of agar/locust bean/xanthan gum complex hydrogel than agar gel. [ABSTRACT FROM AUTHOR]

Three different red seaweed species, Gelidium corneum and two Gracilaria species (Agarophyton chilensis, and Gracilariopsis longissima), were used to produce agar-based fractions through conventional and simplified extraction methods and their composition and gel-forming properties were evaluated. The use of an alkaline pre-treatment was effective in removing impurities such as proteins, lipids, and ash, while the agarose/agaropectin ratio in agar was not affected. This led to the formation of hydrogels with higher stiffness and strength. Surprisingly, the presence of semi-crystalline agaropectin in the agar fractions from the two Gracilaria species, especially G. longissima , promoted the formation of more densely packed and stronger hydrogel networks, with higher gelling temperatures and superior mechanical properties. Thus, these results suggest that G. longissima has the potential to be used as an alternative to the more widespread use of G. corneum for the production of agar hydrogels for food applications. [Display omitted] • Agar-based extracts from three agarophytes were produced by a simplified protocol. • Alkaline pre-treatment removes impurities, preserving the agarose/agaropectin ratio. • The extracts from Gracilaria species contain semi-crystalline agaropectin. • Hydrogels derived from Gracilaria species exhibit superior mechanical properties. • G. longissima is a potential source for agar production for food applications. [ABSTRACT FROM AUTHOR]

The growth of the plant-based meat analogue market has prompted the need for new approaches to replace animal adipose tissue. In this study, we developed a novel solid emulsion gel system using a hybrid gel network to simulate the thermal behavior and texture of adipose tissue. At various concentrations, emulsion gels were prepared using soybean oil, soybean protein isolate, agar, and alginate. After mixing all solutions at appropriate concentrations, cold-set gelation of agar was followed by ion-induced alginate gelation by immersion in calcium chloride solution. The resulting emulsion gel contained a dense network that trapped oil droplets and exhibited elastic behavior at all temperatures, similar to porcine adipose tissue. Furthermore, the optimized hybrid emulsion gel showed increased hardness compared with the single-agar emulsion gel. Overall, our findings suggested that the developed emulsion gel system could enhance the quality of plant-based meat analogues by mimicking the physical and thermal properties of animal adipose tissue. [Display omitted] • A hybrid network-based emulsion gel was developed to simulate animal adipose tissue. • The strength and thermal stability of emulsion gels were increased by intermolecular bonds and gel network interactions. • The emulsion gel displayed thermal behavior similar to porcine adipose tissue and had a dense network. • This work has important implications for the development of durable and stable food products that simulate animal fat. [ABSTRACT FROM AUTHOR]

With the deepening of polysaccharide research, whether the real polysaccharide structure can be clearly observed directly affects researchers' understanding of polysaccharide structure and function. Therefore, the establishment of a suitable method to study polysaccharide structure is urgent. Konjac glucomannan (KGM), agar, and curdlan were selected in this paper to investigate the effects of drying temperature, plasticizer type and dosage on the molecular structure of polysaccharides in the preparation of polysaccharide samples for AFM testing. The experimental results showed that the molecular morphology changes of different polysaccharides varied at different drying temperatures. Adding a certain dose of plasticizer could relieve the shrinkage of the hydrophilic polysaccharide molecular chain during the drying process. Compared with Tween 20 and Tween 80, glycerol showed a superior effect on relieving molecular chain shrinkage with the same addition amount. Finally, a new polysaccharide sample preparation method for AFM was proposed, and the feasibility of the method was confirmed, which provided a new idea for better use of AFM to observe the morphology of polysaccharides. [Display omitted] • Methods of KGM, agar, and curdlan samples preparation for AFM observation were improved. • The shape of molecular chains varied with drying temperatures in sample preparation. • The addition of plasticizers could increase the spacing between molecular chains. • Glycerol had the best effect in resisting molecular chain shrink. [ABSTRACT FROM AUTHOR]

Packaging is a crucial tool for reducing food waste and enhancing product competitiveness. Fossil fuel-based plastics, mostly used for food packaging, account for nearly 40% of global plastic waste. To address this issue, this study developed a layer-by-layer casting technique to create novel bilayered plastic composites with distinct agar/chitosan and PVA/agar layers. Film's properties, such as thickness, plasticity, and tensile strength, were affected by adjusting the volume of the layers. The elongation at break was positively related to the presence of citric acid (up to 30 wt%) as a crosslinker. The chitosan-rich first layer provided better UV-light blocking potential and opacity, which were beneficial in the prevention of lipid oxidation. Increasing the second layer by 40–60% substantially reduced the light absorption, while the colors were proportional to the citric acid content. The FT-IR band at 1713 cm−1 indicated an increase in C=O ester groups with crosslinker content. The hydrophobicity of the films was enhanced by the chitosan-rich layer. XRD supported intramolecular and intermolecular hydrogen bonding, whereas the micrographs revealed tightly bound structure between layers. The results corroborated that the inclusion of agar in the formulations increased the stability of the film, making it ideal for various packaging applications. [Display omitted] • A layer-by-layer casting was used to develop films made up of agar-chitosan covered with a citric acid-crosslinked agar/PVA. • The physico-mechanical properties of the double layered films were affected by the different layers' formulations. • FT-IR and XRD supported molecular hydrogen bonding, and micrographs revealed tightly bound structure between layers. • Including agar in layers' formulations increased the stability and suitability of the film for packaging applications. • The higher hydrophobicity of the bilayer films could increase their potential use in the packaging of various food products. [ABSTRACT FROM AUTHOR]

Melanin nanoparticles (MNP) were isolated from the sepia ink using a centrifugation method and used as a functional filler for the preparation of agar-based functional films. The MNP were spherical with an average diameter of 95.6 ± 21.2 nm. Field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FTIR) test results indicated that the MNP were well dispersed in agar polymer to form free-standing composite films. The addition of MNP enhanced the UV-blocking, hydrophobicity, mechanical, and water vapor barrier properties of the agar film. Also, the agar/MNP composite films showed a high antioxidant activity comparable to ascorbic acid. The MNP separated from sepia ink can be used as a functional filler to develop antioxidant biopolymer films for food packaging and biomedical applications. Image 105 • Melanin nanoparticles (MNP) were prepared from sepia ink using the centrifugation method. • MNP were spherical with an average diameter of 95.6 ± 21.2 nm. • Agar/MNP nanocomposite film was prepared using solution casting method. • Reinforcement of MNP increased mechanical strength and water vapor barrier property of agar film. • Agar/MNP nanocomposite film exhibited high antioxidant activity. [ABSTRACT FROM AUTHOR]

Abstract Copper sulfide nanoparticles (CuS NP) were prepared using copper acetate and thiourea as a source of Cu2+ and S2−, respectively, cornstarch as a stabilizing agent and ammonia as a hydrolyzing agent under a mild condition of sulfidation (70 °C for 1 h). The present work describes the synthesis and preparation of bioactive agar/CuS NP nanocomposite film. CuS NP was characterized using UV-vis spectroscopy, X-ray diffraction pattern, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). CuS NP was roughly spherical and irregular with a size in the range of 2–10 nm with an average of 4.6 ± 1.3 nm. Agar-based films with different concentrations (0.25, 0.50, 1.0 and 2.0 wt%) of CuS NP were prepared and characterized using SEM and Fourier transforms infrared spectroscopy (FTIR), and the film properties such as UV-barrier, mechanical, water vapor barrier, swelling ratio, water solubility, hydrophobicity, thermal stability, antibacterial properties and cytotoxicity were investigated. The CuS NP was well dispersed in the polymer matrix to form compatible nanocomposite films. The swelling ratio and moisture content of the composite films decreased while the water solubility increased slightly after the addition of CuS NP. The composite films showed significantly increased UV-barrier without much sacrifice of transparency, and they also showed increased mechanical strength and water vapor barrier properties. Also, in vitro analysis showed excellent biocompatibility of CuS NP and nanocomposite films on skin fibroblast L929 cell lines with cell viability above 90%. Also, they exhibited distinctive antibacterial activity against food-borne pathogenic bacteria, E. coli and some activity against L. monocytogenes. Graphical abstract Image 109422 Highlights • CuS NP were prepared using copper acetate and thiourea as source of Cu2+ and S2−, respectively. • Agar/CuS NP nanocomposite film was prepared using solution casting method. • Incorporation of CuS NP increased mechanical strength and water vapor barrier property of agar film. • Agar/CuS NP composite film exhibited potent antibacterial activity against food-borne pathogens. [ABSTRACT FROM AUTHOR]

In this study, agar was chemically modified with C12–C18 anhydrides. The effects of anhydrides with different degrees of substitution (DSs) and carbon chain lengths on the physicochemical and emulsifying properties of agar were investigated. The gel properties of the esterified agar decreased as the DS and carbon chain length increased. The addition of long hydrophobic chains and carboxyl groups led to good surface activity (surface tension of 29.1 mN/m, interfacial tension of 6.6 mN/m, and contact angle of 108.67°) and high negative charge (−20.23 mV) of the esterified agar. Fourier transform infrared spectral results showed that as the DS and carbon chain length increased, the carboxyl groups and long hydrophobic chains of anhydrides affected the intermolecular and intramolecular hydrogen bonds of agar. Scanning electron microscopy showed that the esterified agar had larger pores and looser network structure than native agar. Thermal stability showed that the esterified agar had strong electrostatic repulsion and chain flexibility, thereby reducing thermal stability. Appropriate hydrophobicity and electrostatic interaction of the long-chain anhydride-esterified agar resulted in the small particle size (60.533 μm), high emulsifying stability, and other properties of the prepared emulsion. In addition, increasing the DS and carbon chain length enhanced the emulsifying properties. The structural and amphiphilic properties of agars esterified by anhydrides with different chain lengths were investigated to stabilize the ability of agar-based emulsions. [Display omitted] • Long-chain anhydride linked agar shows gel properties and surface activity transition. • Break of H-bonds in agar molecules results gel presents loose network structure. • Increased hydrophobic long carbon chain facilitates formation of agar-based emulsions. • Electrostatic repulsion produced by carboxyl groups makes stable agar emulsions. [ABSTRACT FROM AUTHOR]

Abstract This work aimed to develop and characterize a novel indicator film for monitoring fish freshness based on agar incorporated with natural dye extracted from Arnebia euchroma root (AEREs). The Fourier transform infrared spectroscopy results reflected that some new interactions have occurred between polymer matrix and natural dye. And the results of X-ray diffraction and scanning electron microscopy indicated that AEREs were well dispersed in the agar base film. A certain decrease was observed in water solubility, swelling ratio and elongation at break of colorimetric film but tensile strength, Young's modulus, water vapor permeability and water contact angle of colorimetric film were increased by addition of AEREs. The prepared indicator films were used as freshness labels in an application trial, which was conducted to monitor the freshness of Wuchang bream (Megalobrama amblycephala) under refrigeration (4 °C) and at room temperature (25 °C). The total volatile basic nitrogen (TVB-N) and total viable count (TVC) of fish sample were determined periodically, and the color change of freshness labels was recorded simultaneously. The results showed that the indicator film with lower content of AEREs demonstrated more conspicuous color change during fish spoilage. And the color response of freshness label was consistent with the spoilage threshold of TVC and TVB-N content in fish sample. Thus, these colorimetric indicator films could indicate the fish spoilage by visible color change. The developed colorimetric indicator film is expected to provide a convenient, non-destructive and visual method to estimate fish freshness during storage. Graphical abstract Image 1 Highlights • A novel colorimetric film based on polysaccharide was successfully developed. • The extract of Chinese herbal medicine was used as pH sensing dye in this system. • The colorimetric film with lower content of dye has better color response. • The developed colorimetric film is expected to apply in fish spoilage monitoring. [ABSTRACT FROM AUTHOR]

Abstract The present study aims to develop natural biopolymer bioactive edible films. Particularly, blend (F-Bl) and bilayer (F-Bi) films based on grey triggerfish skin gelatin (G) and agar (A), incorporated or not with vine leaves ethanolic extract (VLE), at 5 and 10 mg/mL, were prepared using the casting method. First, VLE presented an important antioxidant potential evaluated by the iron (Fe2+) chelating activity, ferric (Fe3+) reducing antioxidant power, β-carotene bleaching protection and DPPH•-radical scavenging activity. Furthermore, VLE presented interesting antibacterial and antifungal activities. On the other hand, the composite films were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), physicochemical, and thermal analyses. SEM micrographs showed that agar and gelatin were compatible. Moreover, the mechanical properties results showed that F-Bl and F-Bi were mechanically stronger and more deformable than control films. This change in mechanical properties can be explained by the formation of a dense network after agar addition, due to the interactions with the gelatin matrix. After their incorporation into polymer network, VLE increased slightly the thermal stability, while it improved greatly the antioxidant activity of the composite films (gelatin and agar) in a dose dependent manner. Thus, results encourage the further use of gelatin/agar/VLE films as active food packaging material. Graphical abstract Image Highlights • Bio-based blend films based on fish gelatin and agar were prepared. • Addition of agar resulted in more resistant films. • Antioxidant power of the films increased with the incorporation of vine leaves extract. • Cross section micrographs demonstrated the good compatibility between both polymers. • Fish gelatin-agar/VLE films can act as a biodegradable and bioactive packaging film. [ABSTRACT FROM AUTHOR]

Abstract Gracilaria tikvahiae , an endemic western North Atlantic red alga, was cultivated for nutrient bioextraction in urbanized estuarine waters in Long Island Sound and the Bronx River Estuary, USA. This study assesses the feasibility of an integrated approach of using G. tikvahiae produced in this bioextraction system as sustainable biomass source for agar production. Agars were extracted after alkaline pre-treatment and characterized in terms of gelling strength, chemical composition, chemical structure and gel structure. Results indicated that this seaweed performed similar to other cultivated Gracilaria in terms of extraction yield and gelling strength of the agar. Differences between sites were not significant in terms of agar gel strength, though yield was higher at Long Island Sound. The extracted agars were sulfated, methylated and with no detectable pyruvate substituents. It is possible to use an integrated strategy of nutrient bioextraction in urbanized estuarine waters and agar exploitation with G. tikvahiae. Graphical abstract Image 1 Highlights • Agar was successfully extracted from G. tikvahiae used in the nutrient bioextraction systems in urbanized coastal waters. • Extracted agar performance was similar to other Gracilaria agars. • There were no significant differences in the gelling strength between the two cultivation sites. • NMR profile and gel structure of the extracted agars was analyzed. [ABSTRACT FROM AUTHOR]

Abstract Agar/maltodextrin (A/M) emulsion films incorporated with beeswax (BW), shortening (SH), and liquid paraffin (LP), respectively, at different concentrations (0, 10%, 20%) were prepared using the solution casting method, and their physicochemical properties were investigated. Fourier transform infrared spectra indicated that the intermolecular hydrogen bonds weakened with the increase in the concentration of hydrophobic agents. Differential scanning calorimetry and scanning electron microscopy analyses revealed good compatibility between agar and maltodextrin. Phase separation occurred when the hydrophobic agents were incorporated in the A/M films. SEM images of the composite films showed incompatibility between the A/M matrix and hydrophobic agents, causing an irregular and heterogeneous structure. Incorporation of hydrophobic agents significantly improved the hydrophobicity of the A/M films. A/M-10% BW and A/M-10% LP films achieved the lowest water vapor permeability (6.86 × 10−13 g·m−1·s−1·Pa−1) and oxygen permeability (1.17 × 10−17 cm2·s−1 Pa−1), respectively. The tensile strength (TS), elongation at break (EAB) and Young's Modulus (YM) of the A/M films simultaneously increased in the presence of hydrophobic agents. The TS and YM of A/M-20% BW film was 112% and 179% higher than A/M film, respectively. The EAB of A/M-20% LP film was 240% higher than A/M film. These results revealed that the A/M-hydrophobic agent films with high barrier and mechanical properties show promising potential for food packaging. Graphical abstract Image Highlights • Agar/maltodextrin emulsion films were prepared. • Addition of lipids significantly improved the hydrophobicity of the films. • The TS and EAB of the films simultaneously increased in the presence of lipids. [ABSTRACT FROM AUTHOR]

Abstract Quantitative ultrasound (US) techniques have an attractive potential for the non-invasive and real-time characterization of the structural and mechanical properties of food. The objective of the present study is to unravel the determinants of the variations of US properties during sol-gel transition of emulsion filled gels of agar and gelatin, due to the relative contributions (i) of their individual components and (ii) of their combined interactions. Nine model foods were designed, accounting gradually for the complexity of an emulsion filled gel composed of water, sucrose, agar, gelatin and sunflower oil. A quantitative US device was designed to monitor the sol-gel transition of the model foods. US velocity, reflectivity and attenuation were measured at 50 °C (sol-state) and 20 °C (gel-state) with a 1 MHz transducer in pulse-echo mode. US data were then compared to visco-elastic shear moduli and density measurements. Bulk elastic modulus was shown to prevail over density for explaining the variations of US velocity and reflectivity during sol-gel transition, while high gelatin concentration and interactions between agar and gelatin had an impact on US attenuation. In addition to the fact demonstrated here that US reflectivity is easier to measure compared to velocity and attenuation, the literature reports that this parameter also highly depends on the mechanical coupling of interfaces. Therefore, this study is a baseline for future investigations on the potential of US reflectivity for the characterization of physical interactions between food and more complex surfaces, so that to mimic tongue-food interaction during oral processing. Graphical abstract Image Highlights • A quantitative ultrasound (US) device was developed to monitor sol-gel transition. • Complex emulsion filled gels were broken down in simple samples. • Contributions of individual compounds and of their interactions were investigated. • Velocity and reflectivity were mainly ruled by bulk elasticity of samples. • High gelatin concentration and agar/gelatin interactions had an impact on attenuation. [ABSTRACT FROM AUTHOR]

Abstract In this study, two eco-friendly methods for agar extraction, enzyme-assisted extraction and enzyme extraction, were developed to promote workers' health and provide environmental protection. The physicochemical properties of enzyme-assisted extracted agar (EAA) and enzyme-extracted agar (EA) were evaluated and compared with those of the traditional alkali-extracted agar (AA). Compared with EAA and EA, AA showed most ideal performances in the aspect of gel strength (1521 ± 54.5 g/cm2), sulfate content (0.84% ± 0.15%), and 3,6-anhydro- l -galactose content (29.2% ± 0.3%) (p < 0.05). EAA showed similar properties to and lower sewage discharge than AA; thus, enzyme-assisted extraction could be a promising alternative to the traditional method. Enzyme extraction supports sustainable development because this process requires less energy and generates fewer wastes than alkaline processes while offering advanced and promising features, including high viscosity, sulfate content, water retention, and low melting temperature. Graphical abstract Image 1 Highlights • Two eco-friendly agar extraction methods present distinctly lower sewage discharge. • Similar properties appear in both enzyme-assisted and alkali extracted agar. • Enzyme-assisted extraction technology of agar is an alternative to traditional method. • Enzyme extracted agar with intriguing properties has potential application in food. [ABSTRACT FROM AUTHOR]

Abstract The rising demand to reduce sugar in foods has resulted in the need to better understand its structuring properties and contribution to the overall microstructure of products. The effect of sugars on the microstructure of agar fluid gels and their novel foams, including stability, has therefore been studied. Gelation kinetics and material properties of agar fluid gels with added glucose, fructose and sucrose have been explored. The addition of sugar did not notably affect the temperature of ordering during gelation however, it did cause a reduction in fluid gel particle size through changes in solution viscosity during gelation. At high concentrations of sugar (above 50%), the conversion of an overall brittle agar gel network to a more rubbery-like structure was inferred through rheology, as the glass transition of sugar was approached. Below 50% sugar, shear viscosity and G′ increased with concentration due to an increase in particle gel strength (observed through initial Young's modulus). These changes in material properties were overall observed to be independent of sugar type. All systems showed good foaming properties where foam half-life increased with sugar concentration as a result of increased fluid gel yield stress. In order to increase understanding of the foam stability mechanism, fluid gel particle size was altered. When the continuous phase consisted of larger particles, the initial liquid drainage was considerably reduced as particles were more effective at accumulating in the foam channels preventing the flow of the bulk phase. However, foam half-life was ultimately dependent on fluid gel yield stress. This research has provided fundamental understanding of the effect of sugars on the microstructure of agar fluid gels and their use in foam stabilisation, allowing the development of an approach that can potentially be tailored to specific product requirements. Graphical abstract Image 1 Highlights • Agar fluid gel microstructure can be manipulated by sugars. • Increasing sugar concentration altered gelation mechanism, decreasing fluid gel particle size. • Viscosity, G′ and yield stress increased with sugar concentration due to gel strength. • Very stable foams were produced, half-life was dependent on fluid gel yield stress. • Foam liquid drainage was considerably reduced by increasing fluid gel particle size. [ABSTRACT FROM AUTHOR]

Agar is widely used in yogurt manufacture to improve the stability of milk gels. However, the formation and structural properties of acid-induced casein–agar gel have not been elucidated. In this study, different acidification temperatures were used to evaluate the evolution of acid-induced casein–agar double networks and their microstructure and penetration properties. Agar (0.25%, w/w) was mixed with a micellar casein dispersion (3%, w/w), acidified with glucono-δ-lactone at 30, 37, 42, or 45 °C, respectively, and then cooled to 10 °C. Compared with casein gel alone, the casein–agar gel had a higher firmness and water holding capacity (WHC). Moreover, these acid-induced casein–agar double networks formed different structures depending on the acidification temperature. When acidified below the agar transition temperature (at 30 or 37 °C), the agar formed a weak gel prior to casein network formation that hindered the movement of casein micelles. Therefore, the casein–agar mixtures formed double networks during the acidification stage with relatively low elasticity indexes (EIs). In contrast, casein–agar mixtures acidified above the agar transition temperature (at 42 or 45 °C) formed double networks during the cooling stage that exhibited higher EIs. Cryo-scanning electron microscopy showed denser networks in casein–agar gels acidified above the agar transition temperature. Furthermore, casein–agar gels acidified above the agar transition temperature showed a significantly higher firmness and WHC than those acidified below. Overall, acidification temperature significantly affected the gelation sequence and, thereby, the formation and structural properties of the acid-induced casein–agar double network. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of protein hydrolysate (PH) and clove essential oil (CEO) on agar film properties and the shelf-life improvement of flounder fillets. Firstly, Argentine croaker muscle protein was alkali-solubilised and recovered to obtain a stable substrate. This substrate was hydrolysed to 20% degree of hydrolysis, by Alcalase (A20) and Protamex (P20). The molecular weight (MW) distribution, amino acid and in vitro antimicrobial activity of these hydrolysates were tested. Agar films were prepared with and without (control) incorporation of PH (A20 hydrolysate) or CEO and characterised by mechanical properties, water vapour permeability, solubility and optical properties. The microbiological, physical and chemical properties of flounder fillets coated with these films were monitored during storage at 5 °C for 15 days. Compared to P20, A20 hydrolysate possessed lower MW, higher hydrophobic amino acid content and the most effective antimicrobial activity against selected pathogens, such as Staphylococcus aureus , Yersinia enterocolitica , Aeromonas hydrophila , Debaryomyces hansenii and Listeria innocua . The presence of PH increased the water solubility, water vapour permeability, elongation at break and yellowness of the films. The CEO films possessed less transparency than PH films and control films, due to the presence of oil in the formulations. Fillets covered with PH and CEO films, especially the latter, presented lower total volatile bases and pH values, and delayed considerably the growth of H 2 S-producing microorganisms compared to the control films. The CEO might be used as a natural biopreservative to extend the flounder shelf-life. However, further studies are necessary, to assess the antimicrobial effect of PH when used as food packaging. [ABSTRACT FROM AUTHOR]

This study investigated the influence of mechanical and physicochemical properties of semi-solid model foods on the detection and temporal perception of texture contrast. Gel-based model foods consisting of two layers were used to systematically vary mechanical contrast and physicochemical properties within bi-layer gels. Fracture stress (σ F ) and strain (ε F ) were modified by changing the concentration of various gelling agents (agar, к-carrageenan, and gelatine). The physicochemical properties of gels varied with respect to syneresis and melting behaviour depending on the type of gelling agent. The detection limit of perceived texture contrast of bi-layer gels was determined using ranking tests. Subjects ranked gels in order of increasing perceived heterogeneity as a measure of texture contrast. The detection limit of texture contrast varied between brittle and elastic gels and between soft (low σ F ) and hard (high σ F ) gels. In soft and brittle agar gels, heterogeneity was perceived already when the difference in fracture stress between layers was small (Δσ F ≥5 kPa). In soft and elastic gels (к-carrageenan, gelatine) and hard gels, heterogeneity was perceived only when the difference in fracture stress between the layers was large (Δσ F ≥12 kPa). The perceived heterogeneity intensity over time was investigated by time-intensity profiling. During mastication, gelatine gels were perceived for a longer period of time with a higher heterogeneity intensity than agar and к-carrageenan gels. We conclude that mainly mechanical properties of gels impact detectability of mechanical contrast as perceived texture contrast (heterogeneity), whereas a combination of mechanical and physicochemical properties influence the dynamic perception of heterogeneity over time. [ABSTRACT FROM AUTHOR]

The effects of different agar and/or carrageenan proportions as wall material and the core-to-wall material ratio on physicochemical properties, delivery and bioaccessibility of microencapsulated brewer's spent grain (BSG) bioactive peptides were evaluated. Also, peptides from BSG hydrolysate were identified by LC-MS/MS. Microencapsulation was carried out by spray drying. All microcapsules exhibited negative charge both, at pH 2.0 and 7.0. Peptide release was higher at pH 7.0 than pH 2.0, showing a higher release at the site of absorption. Higher proportion of agar in the formulation had a positive impact on both, spray drying yield and encapsulation efficiency. Moreover, higher core-to-wall material ratio (1:4) improved encapsulation efficiency and maintained and even increased ABTS scavenging, ACE-I and DPP-IV inhibition, after a simulated gastrointestinal digestion process. Peptides identified from BSG hydrolysate ranged from 8 to 21 residues, contained mostly glutamic and glutamine residues and were rich in hydrophobic amino acids. Using in silico predictions, 16 peptides identified could act as antihypertensive and antidiabetogenic compounds, showing a multifunctional potential of BSG. [Display omitted] • Agar and carrageenan could be used as wall material to obtained microcapsules (M). • M were effective to protected bioactive peptides during in vitro digestion. • Higher protein content improved physicochemical properties and bio-accessibility. • Peptides identified could act as antihypertensive and antidiabetogenic compounds. [ABSTRACT FROM AUTHOR]

This work investigated the rheological properties of oxidized yeast β-glucans (OYG) with three different oxidation degrees (15.2%, 47.3% and 71.2%). Firstly, the intrinsic viscosities of OYG2 and OYG3 calculated by Huggins and Kraemer equations were 104 and 214 mL/g, respectively. Steady-state shear test showed that the OYG solutions exhibited shear-thinning behavior of pseudoplastic non-Newtonian fluid when concentration (c) was greater than 5 mg/mL and OYG1 had the highest apparent viscosity. By fitting viscosity data to the Cross model, the critical overlap concentration (c*) were determined to be 4.69, 3.79 and 2.25 mg/mL for OYG1, OYG2 and OYG3, respectively. From the results of dynamic frequency sweep test, the storage modulus (G ′) and the loss modulus (G ″) were greatly dependent on frequency and concentration, and OYG solutions represented the feature of structural fluid, an entanglement network at c ≥ 5 mg/mL. Micro-rheological test revealed that the OYG1 solutions were dominated by viscoelasticity at c ≥ 13 mg/mL and the Fluidity Index (FI) decreased with increasing concentration, indicating the increase in elasticity and viscosity. Meanwhile, as the concentration increased from 13 to 20 mg/L, shorter time and lower temperature were required for OYG1 to form a gel, as indicated as they decreased from 53′21 ″ and 78.60 °C to 41′34 ″ and 67.40 °C, respectively. Results of temperature ramp test illustrated a thermo-irreversible characteristic of OYG1/water system. The findings suggest that OYGs can be potentially employed in food or cosmetic products for various applications as thickener, stabilizer and so on. [Display omitted] • OYG had shear-thinning behavior of pseudoplastic non-Newtonian fluid at c > 5 mg/mL. • The viscoelasticity of OYG/water system increased with increasing concentration. • Critical overlap concentrations of OYG1-3 were 4.69, 3.79 and 2.25 mg/mL respectively. • OYG showed the feature of structural fluid, an entanglement network at c ≥ 5 mg/mL. • OYG1/water system had a thermo-irreversible characteristic. [ABSTRACT FROM AUTHOR]

In the present work, the influence of agar oligosaccharide (AO) on the stability of directly acidified milk drinks (DAMDs) was investigated. The experimental results showed that the DAMDs stabilized by AO in combination with anionic polysaccharide had smaller particle diameter values and lower sedimentation fractions than that stabilized by the commercial reference under the same pH conditions. Cryo-SEM images showed a remarkable density porous network organized by agar oligosaccharides based polysaccharide mixtures. It revealed that the stabilizing mechanism of polysaccharide mixtures containing agar oligosaccharides was dominated not only by electrostatic interactions between casein particles and anionic polysaccharides, but also by the three-dimensional network structure provided by agar oligosaccharides molecules, which could separate casein micelles and hold particles in suspension for a long storage time. [ABSTRACT FROM AUTHOR]

The increasing consumer demand for low fat foods has resulted in a need to replace fat in whipped products with natural, readily available food ingredients. Agar fluid gels with the ability to stabilise foams are therefore presented. Gelled particles can be used to mimic fat droplets and also stabilise foams through localised jamming of the interstitial fluid in foam channels, which considerably slows drainage. Innovative processing has developed fluid gels for the functionality of aeration that has built upon this understanding. Novel particle shapes were manufactured, which enhanced particle interaction and ultimately improved their functionality when aerated. The properties of agar gelled particles were controlled by altering agar concentration. Foam stability at each concentration was assessed in terms of half-life measurements. While most exhibited a half-life of around 24 h, there was a dramatic increase at 3 wt% agar, which displayed a half-life of six days. A critical yield stress of the suspending fluid at 3 wt% had therefore been reached, which resulted in enhanced foam stability to drainage. Interestingly, the increased yield stress was attributed to increased particle elasticity at 3 wt% agar. Stability was provided through the fluid gel acting as a network of particles with a finite yield stress. Particles impeded the liquid flow in the foam, which resulted in the formation of localised plugs where particles were confined to foam channels. Examining the internal microstructure of this novel, exceedingly stable foam using X-ray tomography supported this mechanism. [ABSTRACT FROM AUTHOR]

Lignin was used to prepare silver nanoparticles (AgNPs), and they were incorporated into agar-based films. The composite films were characterized using UV–visible spectroscopy, FE-SEM, FTIR, XRD, and TGA. The color, mechanical, water vapor barrier, and antibacterial properties of the composite films were also evaluated. The composite films exhibited characteristic light absorption peaks at 250–300 nm and 430 nm due to the lignin and AgNPs, respectively. The interaction of lignin and AgNPs with agar biopolymer was analyzed using FTIR. XRD results showed the characteristic peaks of crystalline AgNPs. Incorporation of lignin and AgNPs increased the mechanical, UV-light barrier, and water vapor barrier properties of the composite films. The loading of 1 wt% of AgNPs was the optimum concentration to improve the mechanical and water vapor barrier properties of the films. The films containing AgNPs exhibited antibacterial activity against food-borne pathogenic bacteria, Escherichia coli and Listeria monocytogenes. [ABSTRACT FROM AUTHOR]

Yield, physico-chemical and gelling properties of agar from Gracilaria tenuistipitata as affected by alkaline treatments conditions at various levels were investigated. Agar with alkaline treatment, especially at higher alkali concentration, showed better gelling property as evidenced by higher gel strength (624.4–1250.8 g cm −2 ), gelling (28.1–43.2 °C) and melting (96.4–99.6 °C) temperatures with coincidentally increased 3,6-anhydrogalactose content (38.93%–44.78%) and decreased sulphate content (7.79%–3.48%), but reducing yield (22.34%–15.61%). Treatment temperature or time has a positive influence on agar properties in appropriate range, while higher temperature or longer time might result in yield reducing. Alkaline treatment with 6% alkali at 80 °C for 1.5 h was the optimal pretreatment process, with the gel strength reached to 1068.15 g cm −2 and obtained high yield (23.14%), which are higher than the earlier reports. Meanwhile, the study of the correlation between physico-chemical and gelling properties of agar confirmed that the gel strength has negative correlation relationship with sulphate content (p < 0.05), while positive correlation with 3,6-anhydrogalactose content (p < 0.01) and gelling (p > 0.05) or melting temperatures (p > 0.05). Overall, this work suggested the feasibility of the exploitation of G . tenuistipitata for production of superior quality agar, which are mainly from Gelidium species. [ABSTRACT FROM AUTHOR]

The risk of dysphagia in the elderly has gradually become a social problem. An important strategy is to modify the food texture to reduce aspiration risk. Microgel, a structured fluid usually prepared by Couette flow and jacketed stirring, has attracted much attention due to its unique rheological properties and complex microstructure. This study proposed a continuous production process of agar structured fluid through pipe wall laminar shear. The rheological properties and particle size distribution of the agar microgel were characterized. The morphology of microgel and its interaction with water molecules were examined through scanning electron microscopy (SEM) and low-field nuclear magnetic resonance (LF-NMR), and some positive feedback examples were obtained through the videofluorographic swallowing study (VFSS). A molecular model was proposed in which agar microgel is a supramolecular structure with a multidomain weak interaction, whose "hairy" structure is the site of domain-domain interaction. Agar microgel as a structured fluid can achieve higher yield stress and elastic modulus at the same concentration compared to xanthan gum solution, which is expected to be the next cost-effective and age-appropriate pre-thickened diet for older adults with dysphagia. [Display omitted] • A novel preparation method to obtain agar microgel with high efficiency is proposed. • The molecular model of agar microgel formation is developed. • The agar microgel is considered a multi-domain weak interaction supramolecular structure. • It deepened the understanding of the "hairy" structure, which is the site of domain-domain interaction. • The agar microgel is expected to become a new member of the dysphagia diet family. [ABSTRACT FROM AUTHOR]

Thermoreversible gels are commonly prepared by cooling down to ambient temperature, aqueous polymer solutions first brought to a boil for a short time. Here, we study the effect of the latter duration on the subsequent gelation of an agar solution. Increasing the incubation time at high temperature ( T = 80 °C) from hours to a few days leads to the hydrolysis and the oxidation of the polysaccharides, and results in the decrease of the viscosity and the pH of the solution. Samples withdrew at different incubation times are cooled down to form gels whose structure and mechanical properties are systematically determined. Cryoelectron microscopy and X-ray diffraction experiments reveal that agar gels formed from solutions of increasing incubation times, display a coarser microstructure composed of micron-sized foils which result from the condensation of the polysaccharides, and contrast with the fibrous-like microstructure of gels prepared from a fresh agar solution. Along with structural changes, a prolonged incubation time of the agar solution at T = 80 °C leads to weaker gels than those made from fresher solutions, and extensive macro-indentation experiments coupled to direct visualization show that the gel rupture scenario turns from brittle to ductile-like as the incubation time increases. Our study suggests that the incubation time of agar solutions at high temperature could be used as an external control parameter to tune the mechanical properties of agar-based gels. [ABSTRACT FROM AUTHOR]

Sweetness resulting from sucrose released from agar gels of varying concentrations of agar (0.5, 1.0, and 1.5% w/w) and sucrose (10%–50% w/w) was evaluated. The intensity of sweetness as perceived by subjects was investigated during consumption of the gels. A time–intensity method was applied: the maximum intensity and area under the time–intensity curve were higher in gels with lower concentrations of agar as expected from previous studies. The intensity of sweetness as estimated by the area under the time–intensity curve increased with sucrose concentration, but the maximum intensity tended to reach a plateau above a certain sucrose concentration. The manifestation of the maximum sweetness was delayed with increasing concentrations of sucrose and agar. The total duration of the perception of sweetness was longer in gels with higher sucrose concentrations but did not depend on the concentration of agar in the range examined. Instrumental characterization of these gels was also conducted. Young's modulus, fracture stress, fracture strain, and energy obtained from a conventional uniaxial compression test of sample gels increased with sucrose concentration and the modulus, stress, and energy were higher in gels with higher agar concentration. Although mechanical characteristics such as Young's modulus, fracture stress, strain, and energy, increased with increasing sucrose concentration, the sweetness intensity tended to a plateau; therefore, physiological and psychological factors experienced during oral processing should be taken into account to understand the perceived sweetness intensity. [ABSTRACT FROM AUTHOR]

Binary blend films of agar and banana powder (A/B) and A/B composite films reinforced with silver nanoparticles (A/B/AgNPs) were prepared using a solution casting method and their properties were characterized. The SEM micrographs and FT-IR results confirmed the formation of physical interactions between polymer matrices and nanofillers. Apparent surface color and transmittance of the composite film were greatly influenced not only by the mixing of banana powder with agar but also by the incorporation of AgNPs. The UV light absorption, water vapor barrier properties, and antioxidant activity of A/B blend films increased with the increase in the concentration of the banana powder, while the mechanical properties decreased. The A/B/AgNPs composite film exhibited distinctive antimicrobial activity against food-borne pathogenic bacteria, Escherichia coli and Listeria monocytogenes with stronger antibacterial activity against Gram-negative bacteria than Gram-positive bacteria. The binary blend of A/B films are expected to be used for the edible film or coating of foods and their nanocomposite films with antimicrobial activity have a potential to be used as food packaging material for maintaining the safety and extending the shelf life of packaged food. [ABSTRACT FROM AUTHOR]

The red seaweed Gelidium sesquipedale is recognized for its high-quality agar, a valued hydrocolloid with gelling capacity, an industrially desirable property strongly dependent on its structure and composition. Despite its importance, there is a lack of information regarding the effects of processing conditions, including alternative extraction technologies, on these properties. To shorten that gap, the present study aimed to evaluate the use of autohydrolysis for obtaining agar from this marine macroalgae. This was performed by assessing the effect of hydrothermal treatments' severity and time and temperature binomials (at the same severity factor) on the extraction yield, texturizing and rheological behaviour, structure, composition, and molecular weight of the polysaccharide. The results obtained indicated that the optimal processing severity for agar recovery is 2.1 ± 0.1. Not only does this condition preserve the extraction yield (ranging from 12.3 ± 3.4% to 23.4 ± 1.6%, depending on the time and temperature binomial chosen), but it also results in a gelling strength of 758 ± 44 g/cm2, all while allowing a sharp processing time reduction (e.g. 1 min at 150 °C and 7.5 min at 140 °C). Molecular weight, rheological behaviour, and texturizing capacity proved to be directly linked to treatment's severity, with no differences observed in time and temperature binomials (at the same severity factor). On the other hand, 3,6-anhydro-α- l -galactose content and overall structure appeared to be intrinsic to the biomass, and not affected by the extraction conditions. Overall, this work demonstrated that autohydrolysis can be used to quickly and efficiently obtain high-grade food-safe agars when properly tuned. [Display omitted] • Autohydrolysis can be applied for the extraction of agars from Gelidium sesquipedale. • Autohydrolysis allows for a reduction in high gel strength agar extraction time. • A hydrothermal treatment with 2.1 severity is optimal for agar's gelling strength. • At equal severity, time and temperature combinations do not impact the agars' traits. • Treatment's severity influences the composition, structure and behaviour of agars. [ABSTRACT FROM AUTHOR]

The properties (e.g., viscosity, sol-gel transition, and mechanical characteristics) of polysaccharides are crucial for their food applications. This work discloses how xanthan gum (XG) incorporation tailors the performance of an agar/konjac glucomannan (KGM) system. As reflected by rheological and thermal analyses, an increasing content of XG added could strengthen the chain entanglement in the resulting ternary solution with strong KGM-XG binding (an exothermic event). For example, a ternary system with a 16% XG content (AKX-16%) showed simultaneous increases in the zero-shear viscosity (about 5.5 times that of the binary counterpart AK), sol-gel transition point (about 48 °C; 10 °C higher than that of AK), and gel hardness (about 2300 g; 450 g higher than AK). Moreover, the AKX-16% composite showed lower crystallinity and enhanced hydrogen bonding and tensile strength (74 MPa) resulting from gel dehydration. Additionally, increasing the XG content showed a negligible effect on the morphology of the composite matrix, suggesting the excellent compatibility between these different polysaccharides. [Display omitted] • Xanthan inclusion (16% for instance) strengthened chain entanglements of agar/KGM system. • Xanthan inclusion increased the zero-shear viscosity of agar/KGM-based system. • Xanthan inclusion increased the sol-gel transition point of agar/KGM-based system. • Xanthan inclusion increased the gel hardness of agar/KGM-based system. • Xanthan inclusion enhanced the tensile strength of agar/KGM-based composite. [ABSTRACT FROM AUTHOR]

The potential of using pressurized hot water extraction to valorize the remaining crude agar in Gelidium sesquipedale waste stream after an initial industrial extraction was investigated. In this process, a four-factor Box-Behnken design was coupled with a response surface methodology. The impact of the operating temperature (°C), the internal pressure (bar), the extraction time (min), and the algae concentration (% w: v), as well as their quadratic effects and two-way interactions, on the physicochemical properties of the residual agar, was analyzed. The yield (%), gel strength (g/cm2), gelling temperature (°C), melting temperature (°C), 3,6-anhydrogalactose content (%), and the sulfate content (%) were all considered in the evaluation. A multiple regression statistical model was used to fit all the experimental responses to a second-order polynomial equation that confirmed the suitability of the approach. Temperature of 120 °C, low pressure of 3.28 bar, and an extended extraction time of 150 min along with a 3% (w: v) algae concentration were projected to be optimum conditions for a high extraction yield of 17.03%. The strength of the recovered agar hydrogel oscillated between a minimum of 25 g/cm2 and a maximum of 350 g/cm2. The key parameters impacting the fluctuation of the sulfate content in the recovered agar (2% ≤ sulfate content ≤10%, with R2 = 79.8%) appeared to be the temperature and the algae concentration, in addition to the quadratic effect of the solid concentration. By adjusting the parameters, the process can accommodate the physicochemical properties of agar for wider range of applications. [Display omitted] • An exploitable amount of residual agar was found in the industrial waste stream of Gelidium sesquipedale. • Pressurized hot water extraction (PHWE) was a performant green and time efficient technology for recovering value added agar. • Performing a response surface methodology analysis provided the optimal conditions for the PHWE assisted agar recovery. [ABSTRACT FROM AUTHOR]

Many highly palatable foods are composed of multiple components which can have considerably different mechanical properties leading to contrasting texture sensations. The aim of this study was to better understand the impact of contrasting mechanical properties in semi-solid gels on oral processing behaviour and dynamic texture perception. Four reference emulsion-filled gels without mechanical contrast were prepared using agar (1 or 2 wt%) or gelatine (2.5 or 5.5% wt). Six emulsion-filled gels with contrasting mechanical properties were obtained by combining two different gel layers. Agar reference gels displaying low fracture strain produced boli with many small particles and were perceived as grainy. Gelatine reference gels displaying high fracture strain produced boli with few large particles which melted in mouth and were perceived as creamy. Reference gels with large fracture stress were masticated for long times with a high chewing muscle activity and perceived as firm and grainy. Bolus properties, oral processing behaviour and dynamic sensory perception of the 6 contrasting gels were compared to the 4 reference gels using Principal Component Analysis. The presence of an agar layer in contrasting gels dominated bolus properties which contained many small particles and did not mix readily in mouth. The temporal sensory profiles and sensory trajectories of contrasting gels fell between the temporal sensory profiles and sensory trajectories of the two gel layers which they were composed of. We conclude that distinct features of dynamic texture perception in emulsion-filled gels with mechanical contrast are perceived separately in mouth. [ABSTRACT FROM AUTHOR]

Physico-chemical and gelling properties of agar extracted from Gracilaria tenuistipitata as affected by alkaline pretreatments using NaOH and KOH at various levels (3–7%, w/v) were investigated. Yield of native agar was 17.1%, whilst those of agars pretreated with NaOH and KOH ranged from 23.6% to 26.1%. Agar with alkaline pretreatment generally showed the better gelling property as evidenced by higher gel strength, gelling, melting temperatures and viscosity with coincidentally increased 3,6-anhydrogalactose (3,6-AG) content than did native agar. Additionally, native agar had a higher sulphate content with lower syneresis (P < 0.05) than those with alkaline pretreatment. Regardless of alkaline concentration, NaOH used for pretreatment rendered agar with a higher quality, compared with KOH. Agar (1.5%, w/v) pretreated with 5% NaOH exhibited the highest gel strength (482 g/cm 2 ) with high yield (25.3%). The decrease in total sulphate content and the increase in 3,6-AG content were observed in agar having 5% NaOH pretreatment as determined by FTIR spectroscopy. Finer and more compact network with smaller pores was visualised in gel from agar with 5% NaOH pretreatment. Therefore, the appropriate pretreatment by using 5% NaOH could increase yield and improve the gelling property of agar from G. tenuistipitata harvested from the lake of Songkhla, Thailand. [ABSTRACT FROM AUTHOR]

Native (NA) and alkali-modified (AA) agars from Gracilaria vermiculophylla , cultivated in integrated multi-trophic aquaculture (IMTA) systems, were mixed with locust bean gum (LBG) at different mass ratios ( i.e . 100/0, 75/25, 50/50, 25/75, 0/100 agar/LBG) to prepare hydrogels with a final polymer concentration of 1% wt. The rheological properties of pure and mixed systems were studied under small (SAOS) and large amplitude oscillatory shears (LAOS). NA and AA interacted differently when mixed with LBG. Chemically, NA was poorer in 3,6-anhydro-α-L-galactose (LA; gelling) and richer in sulfated and methylated (non-gelling) units. Gels prepared with AA were more rigid (higher G ′ and gel strength) than the ones made with NA. Under SAOS, addition of LBG led to a gradual decrease in gel rigidity ( G ′ decrease) and for gels made with NA, to a significant decrease in elasticity (tan δ increase). For both agars, the gelation point moved to lower temperatures and the thermal hysteresis was progressively widened upon increase of LBG content in the gels. This matched with less coarse networks imaged through cryoSEM, particularly for AA. In LAOS experiments (strain sweeps), differences observed in the shapes of the curves for NA and AA gels, in the non-linear region, seemed to suggest stronger interactions for the former, probably reflecting the very different microstructures of both type of gels. Agars from sustainably grown G. vermiculophylla can yield gels with various rheological profiles when mixed with LBG. This can be very appealing to manufacture new products with interesting textures and mouth feel for consumers. [ABSTRACT FROM AUTHOR]

The effect of sucrose addition prior to or following the dissolution of agar on sucrose release from 1 wt% agar gels was studied. The order of addition was found to affect the fracture stress, fracture strain and sucrose release ratio. At sucrose concentrations below 30%, the rheology (fracture stress and strain) and structure of the gels did not depend on the order of addition of sucrose and agar. At sucrose concentrations >40%, however, the network structure of gels where sucrose was dissolved before agar addition was weaker than that of gels where sucrose was added after agar dissolution. The weaker network structure resulted in lower fracture stress and strain values. For gels prepared by adding agar to sucrose solutions, both fracture stress and strain decreased with increasing sucrose concentration in the range 40–55%. The decrease in fracture stress and strain led to an increase in the sucrose release ratio. The sucrose release ratio decreased monotonously with increasing concentration of sucrose when agar was dissolved prior to sucrose addition. The findings are discussed in relation to recent publications on gel inhomogeneity. [ABSTRACT FROM AUTHOR]

The effect of sucrose and agar concentrations on sucrose release from agar gels was investigated. It was found that the sucrose release ratio decreased with increasing sucrose concentration and with increasing fracture stress, which is consistent with previous findings. High correlation was found between the fracture stress, sucrose concentration and the sucrose release ratio. The total amount of sucrose released showed a maximum at a certain sucrose concentration, indicating that sucrose addition to enhance sweetness intensity may be ineffective or even counterproductive beyond a certain limit. [ABSTRACT FROM AUTHOR]

Extruded and native wheat flours were combined with agars ( Gracilaria and Gelidium ) and carrageenans (κ-carrageenan and ι-carrageenan) to modify their paste and gel properties. Combinations of extruded flours with hydrocolloids produced an increase in the hydration properties (swelling volume and water holding and water binding capacities). All hydrocolloids (particularly ι-carrageenan) also produced an increase in hydration properties after combination with native flours. With regard to the pasting properties of native flours combinations, all hydrocolloids produced an increase in peak viscosity (particularly Gelidium agar), but only agars decreased the onset temperature of gelatinization and increased breakdown, indicating a different mechanism of action. In the presence of extruded flour, the incorporation of hydrocolloids increased the cold viscosity of flours in very different ways depending on the hydrocolloid. Both native and extruded flours exhibited higher G′ and G″ values and a lower tan δ after the incorporation of carrageenans, which, together with the lower dependence on frequency, would produce stiffer and more stable pastes/gels. Based on gel properties, greatest hardness with native and extruded flours was achieved by the incorporation of carrageenans. In general, carrageenans, besides producing stiffer and more stable pastes, gave rise to harder and clearer gels compared to those made with agar, for both their combination with extruded and native wheat flours. Meanwhile, pastes made with combinations of extruded flours and agar showed higher thixotropy. [ABSTRACT FROM AUTHOR]

Gelatin/agar-based smart and functional freshness indicator films were fabricated using blue anthocyanin and zinc oxide nanoparticles (ZnO). The anthocyanin was extracted from butterfly pea (Clitoria ternatea) flower, and ZnO was synthesized using a simple hydrothermal method. The butterfly pea anthocyanin (BA) and ZnO were evenly dispersed in the polymer matrix to form a compatible film with the gelatin/agar polymer. The addition of BA and ZnO significantly increased the UV blocking properties and surface hydrophobicity without significant changes in the film's mechanical, thermal stability, and water vapor barrier properties. The BA and BA-added films showed excellent pH-responsive color-change properties as well as good color stability and reversibility. In addition, the composite film showed strong antioxidant and strong bactericidal properties, and the antioxidant function was mainly attributed to the BA, and the antibacterial function was attributed to ZnO. The functional and color indicator film was tested to monitor the freshness of shrimp. It showed distinctive color changes during storage, indicating the degradation of the quality of shrimp accompanied by the total volatile basic nitrogen (TVB-N). [Display omitted] • Gelatin/agar-based color-indicator films integrated with butterfly anthocyanin and ZnO were developed. • The fabricated film showed excellent pH sensitivity and volatile gas sensitivity. • The film showed a significant UV-light barrier property with high transparency. • The film also exhibited good antioxidant and antibacterial activities. • The color indicator films have a high potential for monitoring the freshness of the seafood. [ABSTRACT FROM AUTHOR]

Active agar (AG) bilayer films with bioactive capability and electrochemical writing property were developed for improving the postharvest quality of the banana. The antioxidant and antimicrobial capacity of the films were enhanced with the incorporation of red radish extract (RRE) and neem essential oil (NEO) into AG lower layer. The barrier and mechanical properties, retention of total anthocyanin and NEO content in the bilayer films were effectively improved with addition of TiO 2 into the AG upper layer. Multicolor patterns were successfully written on the bilayer film containing RRE. The AG-TiO 2 +AG-RRE-NEO bilayer film exhibited the optimal preservations on banana fruits during the storage period, based on the characterization by fruits appearance, senescent spotting symptom, microbial analysis, weight loss and firmness. Thus, the AG-TiO 2 +AG-RRE-NEO bilayer film was expected to be a multifunction packaging material for banana preservation. [Display omitted] • Active agar bilayer films were developed successfully. • Red radish extract (RRE) and neem essential oil (NEO) improved the antioxidant and antimicrobial capacity of the films. • TiO 2 nanoparticles enhanced the retention of total anthocyanin and NEO content in the bilayer films. • Multicolor patterns were successfully written on the active agar bilayer film containing RRE. • Active agar bilayer film expected to be a multifunction packaging material for banana preservation. [ABSTRACT FROM AUTHOR]

Spiced edible gels and films were produced as part of a future technological strategy to improve the quality of pork from entire male by contributing to a decrease in boar taint and improving the texture of the meat. Each formulation, two types of hydrocolloids and two spice mixtures, were tested for their high masking power (mixtures 1 and 2). The thermoreversible hydrocolloids carrageenans (g-C) and agar-agar (g-A) were used in the production of the gels, and maltodextrin + sodium alginate (f-MA) and gelatin (f-G) for the films. The results showed that the films and gels edible had good physical-chemical and mechanical characteristics, providing sufficient stability to act as a vehicle to incorporate spices and condiments into entire male pork, being mixture 2 provided the highest values. While the use of hydrocolloids in the films improved the texture of the meat. [Display omitted] • Gels and films reached correct mechanical properties to act as vehicles of spices. • Films made with hydrocolloids improved the pork sensory texture. • Spice mixture 2 had the greatest sensorial impact on the meat matrix. • Spiced edible films and gels were an alternative to alleviate boar-tainted pork. [ABSTRACT FROM AUTHOR]

Core-shell structural capsules can encapsulate various food ingredients (e.g., nutrients), thus being highly potential for the design of many food products. This work reports how the gum (xanthan, locust bean or gellan) inclusion tailors the practical features of agar/konjac glucomannan (KGM) system for fabricating the core-shell structural capsules. The rheological and textural analyses revealed that xanthan gum inclusion could simultaneously increase the sol-gel transition point and gel strength (ca. 1.6 times higher) of agar/KGM system. The composite gels were dehydrated to generate shell materials. The materials including xanthan or locust bean gum showed stronger chain interactions than did that including gellan gum, accompanied by weakened crystalline features for the different shell materials. Again, compared to the agar/KGM counterpart, the shell materials including xanthan gum could display a similar tensile strength (close to 50 MPa) but an evidently increased elongation at break (ca. 2.5 times higher). Then, these agar/KGM based systems were used to prepare core-shell structural capsules. The capsules based on agar/KGM/xanthan gum materials exhibited the highest roundness and breaking stress. Regarding this, the increased sol-gel point reduced the time required for droplet hardening (to generate core-shell gel balls); such fact, together with the higher gel strength, weakened the deformation of gel balls and thus increased the roundness and breaking stress of capsules (resulting from drying of gel balls). [Display omitted] • Adding xanthan gum increased sol-gel point of agar/konjac glucomannan (KGM) system. • Adding xanthan gum increased gel strength of agar/KGM based system. • Adding xanthan gum increased elongation at break of agar/KGM based shell materials. • Adding xanthan gum increased roundness of agar/KGM based core-shell capsules. • Adding xanthan gum increased breaking stress of agar/KGM based core-shell capsules. [ABSTRACT FROM AUTHOR]

This study investigated the eco-friendly extraction of agar from Gelidium sesquipedale. Two extraction strategies namely ultrasonication combined with a controlled alkali pretreatment followed by enzyme-assisted extraction (EAE), and ultrasonication combined with EAE for agar extraction were employed in this study. Five typical enzymes classified in carbohydrase and proteinase groups were explored for the extraction uses. The EAE yields obtained were 2 to 6-fold higher compared to a non-enzyme extraction control method for a total extraction time of 2–3 h. Agar extracts were analysed using a cascade of characterisation methods. FT-IR spectroscopy and chemometrics was used to determine the promising extraction protocols. In addition, apparent viscosity, molecular weight, sulphate content, 3,6-anhydrogalactose content, gel strength, compositional analysis and thermogravimetric analysis were also carried out to profile the agar extracts and furtherly identify the most promising extraction protocols. Characterisation results showed that agar extracted using EAE with Viscozyme® most closely matched the measured properties of a high-quality agar product. Further scale-up studies of EAE combined with ultrasonication for agar extraction should be carried out to facilitate industrial adoption of this eco-friendly processing approach. [Display omitted] • Agar was extracted from Gelidium sesquipedale and characterised following a cascade approach. • Enzyme-assisted extraction (EAE) was investigated using ultrasonication combined with a controlled alkali pretreatment. • EAE combined with ultrasonication achieved high extraction yield in limited extraction time. [ABSTRACT FROM AUTHOR]

Pectin/agar blended multifunctional composite films were prepared by reinforcing with melanin nanoparticles (MNP) and grapefruit seed extract (GSE). The physical properties of composite films made by mixing pectin and agar have been improved. The MNP and GSE were well dispersed in the pectin/agar blend film. The addition of MNP and GSE significantly increased the composite film's UV-blocking property, with some sacrificing transparency. The addition of MNP increased the mechanical strength of the agar/pectin film over GSE, but the addition of MNP and GSE together synergistically increased the film's strength. The film's thermal stability was not affected by the addition of MNP and GSE, but the water vapor barrier property was significantly increased. The water resistance and water swelling properties were increased considerably by the addition of MNP and GSE. The pectin/agar composite film showed intense antioxidant activity and excellent antibacterial activity against foodborne pathogens by adding MNP and GSE. [Display omitted] • MNP and GSE incorporated pectin/agar-based functional composite film was developed. • MNP and GSE improved mechanical properties without changing the thermal stability of the film. • The UV-light barrier property of the film increased without losing transparency. • Water resistance of the film has been improved, but water vapor barrier properties have been reduced. • The composite film exhibited distinctive antioxidant and antibacterial properties. [ABSTRACT FROM AUTHOR]

Food texture is one of the intangible properties of food which consumers are aware of without specifically identifying it. Texture in food has seen some dramatic changes not only on the technological side but also in consumer perception and concerns. This $7 billion dollar market has attracted the attention of global multinational companies. IMR International has been covering the technical and market developments of these ingredients since 1984. The two principals of IMR are Dennis Seisun (Founder) and Nesha Zalesny (Partner). [ABSTRACT FROM AUTHOR]

Gelatin is a commonly used gelling agent in many confectionery gel (CG) products such as gummy candies. The rheological behaviors of gelatin in gummy products are still poorly understood. The objective of this study was to investigate how gummy formulation affects rheological behaviors of the gelatin network in both linear and nonlinear viscoelastic regions. The effects of °Brix, acids, hydrocolloids, and nutrients on gelatin gelation in gummies were investigated using both small amplitude oscillatory shear (SAOS) tests and large amplitude oscillatory shear (LAOS) tests. °Brix appeared not to impact the gelling temperature of the gelatin gummy until it reached 80 or higher when the gelling temperature decreased probably due to the extrusion of sugar from the gelatin network. Both citric acid and malic acid weakened the gelatin gummy network due to their restrictive effect on the formation of hydrogen bonds. Incorporating hydrocolloids, such as pectin and agar-agar, into the gelatin gummy showed synergistic effect on the gel network due to the nature of hydrocolloids and the ratio to gelatin in the formulation. Incorporating inulin into gelatin gummy enhanced the gel network through hydrogen bonding between inulin and gelatin. As indicated by the frequency sweep tests, incorporating whey protein isolate caused a whey protein dominated bi-continuous gel network which was enhanced by the presence of gelatin. Large deformation rheological tests showed that the gelatin gummy with 81 °Brix had greater nonlinear behaviors under large shear strains, whereas gelatin gummy with 78 °Brix was more resistant to the large deformation. These gelation and stability differences of gelatin gummy network can contribute to the differences in texture and stability of gummies during processing and storage. Image 1 • Rheological tests are useful to study the gelling properties of gelatin gummies. • Citric and malic acids each weakened the gelatin gummy network. • Incorporating pectin and agar-agar into gelatin gummy showed a synergistic effect. • Incorporating inulin into the gelatin gummy enhanced the gel network. • Gelatin enhanced whey protein dominated gel structure. [ABSTRACT FROM AUTHOR]

Agar that has been extracted via traditional alkaline pretreatment always appears yellowish because it contains pigments. This characteristic adversely affects the food and biotechnological applications of agar. In this work, agar was bleached with hydrogen peroxide. The whiteness of high-whiteness agar reached 74.4%, which was 32% higher than that of raw agar (56.48%). The high-whiteness agar bleached with hydrogen peroxide exhibited several other excellent qualities over raw agar. These characteristics included, low sulfate content (0.67%), low ash content (1.01%), and high transparency (64.4%). In particular, the transparency of the high-whiteness agar was 13% higher than that of raw agar (56.8%). By contrast, the gel strengths of the two agars did not significantly differ. The structures of raw and high-whiteness agar were characterized by using thermogravimetric (TG)–differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). TG–DSC analysis indicated that the high-whiteness agar had better thermal stability, hygroscopicity, and water-holding capacity than raw agar. SEM images showed that the surface of the high-whiteness agar had imperfections or fissures that were caused by the oxidative degradation of hydrogen peroxide. The diversified application of the high-whiteness agar was explored on the basis of the promotion of agar quality. Results indicated that the visual appearance of the jelly prepared with the high-whiteness agar was better than that of the jelly prepared with raw agar. Moreover, the high-whiteness agar medium was easier to observe and use for colony counting than biochemical medium. Image 1 • Agar bleaching with hydrogen peroxide presents eco-friendly and efficient merits. • The whiteness and transparency of agar improves distinctly after bleaching. • High-whiteness agar has diversified application in food and biotechnology industries. [ABSTRACT FROM AUTHOR]