The influence of amylose and amylopectin on water retention capacity and texture properties of frozen-thawed konjac glucomannan gel

Konjac glucomannan: A comprehensive review of its extraction, health benefits, and pharmaceutical applications

Konjac glucomannan (KG) is a dietary fiber hydrocolloid derived from Amorphophallus konjac tubers and is widely utilized as a food additive and dietary supplement. As a health-conscious choice, purified KG, along with konjac flour and KG-infused diets, have gained widespread acceptance in Asian and European markets. An overview of the chemical composition and structure of KG is given in this review, along with thorough explanations of the processes used in its extraction, production, and purification. KG has been shown to promote health by reducing glucose, cholesterol, triglyceride levels, and blood pressure, thereby offering significant weight loss advantages. Furthermore, this review delves into the extensive health benefits and pharmaceutical applications of KG and its derivatives, emphasizing its prebiotic, anti-inflammatory, and antitumor activities. This study highlights how these natural polysaccharides can positively influence health, underscoring their potential in various biomedical applications.

Effect of pretreatment with electron beam irradiation on the deacetylation efficiency of konjac glucomannan and its structural, physicochemical and gel properties

Due to its emulsifying and thickening properties, konjac glucomannan (KGM) is widely used in the food, medicine, and materials industries. Nevertheless, its high viscosity and significant water absorption limit its application range. Therefore, electron beam (e-beam) irradiation pretreatment was carried out to improve the deacetylation efficiency of KGM, and the physicochemical and gel properties of KGM were investigated. The results show that e-beam irradiation and deacetylation decrease the water absorption, solubility, transparency, molecular weight, and viscosity of KGM. Conversely, the moisture content, thermal stability, and water-binding capacity increase. FTIR and X-ray diffraction analysis revealed no significant changes in the chemical and crystalline structure of KGM before and after modification. However, modification weakens the intermolecular interaction of KGM hydrosols, which affects their rheology. Furthermore, deacetylation improves the mechanical properties and water retention capacity of KGM gels. Overall, the e-beam irradiation pretreatment provides a method to increase the efficiency of KGM deacetylation and improve the physical and chemical properties of KGM, thus expanding its potential applications in the food and chemical industries, among others.

Investigation into the fabrication of plant-based simulant connective tissue utilizing algae polysaccharide-derived hydrogel

Connective tissue is an important component of meat products that provides support to animal muscles. Hydrogels are considered a promising alternative to connective tissues and simulate actual products by adjusting the gel texture and mouthfeel. This study used soybean protein isolate (SPI), corn starch (CS), konjac glucomannan (KGM), and seaweed powder (SP) as raw materials to examine the effect of different added SP and KGM concentrations on the gel texture. The G' of the gel increased five-fold when the SP and KGM concentration was increased from 1 % to 3 %. The results of mechanical property tests showed that with the addition of SP, the gel hardness increased from 316.00 g to 1827.23 g and the tensile strength increased from 0.027 MPa to 0.089 MPa. Sensory evaluation showed that the samples with 2 % SP and KGM presented the highest overall acceptability score and the most significant similarity to real connective tissue. The connective tissue simulants exhibited excellent water-holding capacity (>90 %), significantly increasing their juiciness. SEM indicated that 2 % KGM addition improved gel network structure stability. The results demonstrate the potential of seaweed polysaccharide-derived hydrogels as connective tissue mimics. This provides a new strategy for the preparation of high mechanical strength hydrogels and lays the foundation for structural diversification of plant-based meat.

Constructing gellan gum/konjac glucomannan/wheat fiber composite hydrogel to simulate edible cartilage by ionic cross-link and moisture regulation

The utilization of non-animal-derived materials to imitate cartilage is critical for the advancement of plant-based simulated meat. In this study, gellan gum (GG), konjac glucomannan (KGM), and wheat fiber (WF) were used to construct hydrogel, and the mechanical strength, water properties, and microstructure were regulated by constructing Ca2+ cross-links and moisture control. The hardness, chewiness, resilience, shear force, and shear energy of the Ca2+ cross-linked samples were significantly improved. Extrusion dehydration further changes the related mechanical properties of the hydrogel and results in a tighter microstructure. The findings suggest that the establishment of Ca2+ cross-links and water regulation are efficacious techniques for modifying the texture of the GG/KGM/WF composite hydrogel. Correlation analysis and sensory evaluation showed that the test indexes and sensory scores of the samples with Ca2+ crosslinking and 80 % moisture content were similar to chicken breast cartilage, and the samples with Ca2+ crosslinking and 70 % moisture content were similar to pig crescent bone. This study presents a framework for designing edible cartilage simulators using polysaccharide hydrogels, with implications for enhancing the resemblance of plant-based meat products to real meat and expanding the range of vegetarian offerings available.

Enzymatic modification lowers syneresis in corn starch gels during freeze-thaw cycles through 1,4-α-glucan branching enzyme

The current research in the food industry regarding enzymatic modification to enhance the freeze-thaw (FT) stability of starch is limited. The present study aimed to investigate the FT stability of normal corn starch (NCS) modified using 1,4-α-glucan branching enzyme (GBE) derived from Geobacillus thermoglucosidans STB02. Comprehensive analyses, including syneresis, scanning electron microscopy, and low-field nuclear magnetic resonance, collectively demonstrated the enhanced FT stability of GBE-modified corn starch (GT-NCS-30) in comparison to its native form. Its syneresis was 66.4 % lower than that of NCS after three FT cycles. Notably, GBE treatment induced changes in the pasting properties and thermal resistance of corn starch, while simultaneously enhancing the mechanical strength of the starch gel. Moreover, X-ray diffractograms and microstructural assessments of freeze-thawed gels indicated that GBE treatment effectively hindered the association of corn starch molecules, particularly amylose retrogradation. The enhanced FT stability of GBE-modified starch can be attributed to alterations in the starch structure induced by GBE. This investigation establishes a foundation for further exploration into the influence of GBE treatment on the FT stability of starch and provides a theoretical basis for further research in this area.

Salt ions improve soybean protein isolate/curdlan complex fat substitutes: Effect of molecular interactions on freeze-thaw stability

Although emulsion gels show significant potential as fat substitutes, they are vulnerable to degreasing, delamination, and other undesirable processes during freezing, storage, and thawing, leading to commercial value loss in terms of juiciness, flavor, and texture. This study investigated the gel strength and freeze-thaw stability of soybean protein isolate (SPI)/curdlan (CL) composite emulsion gels after adding sodium chloride (NaCl). Analysis revealed that adding low salt ion concentrations promoted the hardness and water-holding capacity (WHC) of fat substitutes, while high levels displayed an inhibitory effect. With 40 mM NaCl as the optimum concentration, the hardness increased from 259.33 g (0 mM) to 418.67 g, the WHC increased from 90.59 % to 93.18 %, exhibiting good freeze-thaw stability. Confocal laser scanning microscopy (CLSM) and particle size distribution were used to examine the impact of salt ion concentrations on protein particle aggregation and the damaging effect of freezing and thawing on the proteoglycan complex network structure. Fourier-transform infrared spectroscopy (FTIR) and protein solubility evaluation indicated that the composite gel network structure consisted of covalent contacts between the proteoglycan molecules and hydrogen bonds, playing a predominant role in non-covalent interaction. This study showed that the salt ion concentration in the emulsion gel affected its molecular interactions.

Preparation of a novel expandable konjac fiber at different freezing temperatures and exploration of its digestion regulation functions

A new form of konjac fiber was successfully prepared, and it could instantaneously expand when in contact with the digestive fluid. The expanded konjac fiber could inhibit the digestion of the ingested food by competing with the substrate for digestive enzymes and space. The konjac fiber with desirable physical properties was obtained at 4 different freezing temperatures (-20 °C, -40 °C, -80 °C, and -196 °C), and the digestion regulation mechanisms of these fibers were systematically explored. The results showed that the konjac fiber prepared at -20 °C displayed an outstanding performance in delaying gastric emptying and preventing intestinal starch hydrolysis, while the fiber prepared under liquid nitrogen conditions (-196 °C) showed the weakest digestion regulation ability. However, the digestion regulation ability of this novel fiber was highly related to the food rheological property, and it exhibited a stronger interference effect on high-viscosity food. Our novel konjac fibers exhibited a great digestion regulation potential. Our findings provide valuable references for the development of dietary fiber-based satiety-enhancing functional foods.

Investigation of the effect and mechanism of nanocellulose on soy protein isolate- konjac glucomannan composite hydrogel system

To enrich the application of nanocomposite hydrogels, we introduced two types of nanocellulose (CNC, cellulose nanocrystals; CNF, cellulose nanofibers) into the soy protein isolate(SPI)- konjac glucomannan (KGM) composite hydrogel system, respectively. The similarities and differences between the two types of nanocellulose as textural improvers of composite gels were successfully explored, and a model was developed to elaborate their interaction mechanisms. Appropriate levels of CNC (1.0 %) and CNF (0.75 %) prolonged SPI denaturation within the system, exposed more buried functional groups, improved molecular interactions, and strengthened the honeycomb structural skeleton formed by KGM. The addition of CNC resulted in greater gel strength (SKC1 2708.53 g vs. Control 810.35 g), while the addition of CNF improved the elasticity (SKF0.75 1940.24 g vs. Control 405.34 g). This was mainly attributed to the reinforcement of the honeycomb-structured, water binding and trapping, and the synergistic effect of covalent (disulfide bonds) and non-covalent interactions (hydrogen bonds, ionic bonds) within the gel network. However, the balance and interactions between proteins and polysaccharides were disrupted in the composite system with excessive CNF addition (≥0.75 %), which broken the stability of the honeycomb-like structure. We expect this study will draw attention on potential applications of CNC and CNF in protein-polysaccharide binary systems and facilitate the creation of novel, superior, mechanically strength-regulated nanofiber composite gels.

Mastering textural control in multi-polysaccharide gels: Effect of κ-carrageenan, konjac glucomannan, locust bean gum, low-acyl gellan gum, and sodium alginate

To comprehend the intricate interplay of five common food polysaccharides, κ-Carrageenan (KC), konjac glucomannan (KGM), locust bean gum (LBG), low-acyl gellan gum (LAG), and sodium alginate (SA), within composite polysaccharide gels, widely employed for textural modulation and flavor enhancement. This study systematically modulates the quantities of these five polysaccharides to yield six distinct multi-polysaccharide gels. The unique impact of each polysaccharide on the overall quality of composite gels were studied by thermostability, microstructure, water-holding capacity (WHC), texture, and sensory attributes. The findings unequivocally manifest the phenomenon of thermoreversible gelation in all composite gels, except for the KC-devoid sample, which displayed an inability to solidify. Notably, KGM, LBG, and LAG emerged as pivotal enhancers of the network structure in these composite gels, while SA was identified as a promotor of layered structure, resulting in a reduction of surface hardness. Leveraging principal component analysis (PCA) to analyzed 14 critical evaluation parameters of the five multi-polysaccharide gels, revealing the order as follows: KC > KGM > SA > LAG > LBG. These findings would imparts valuable insights into the pragmatic utilization of multi-polysaccharide gels for the development of food products (e.g. Bobo balls in milk tea) with tailored textural and sensory attributes.

Regulate structure and properties of κ-carrageenan/konjac glucomannan composite hydrogel by filling effects of Quillaja saponin-stabilized solid lipid nanostructure

κ-Carrageenan/konjac glucomannan (κ-CA/KGM) composite hydrogels often fail to meet industrial requirements due to their low gel strength and poor mechanical properties, while solid lipid nanoparticles are potential materials to address this challenge due to their good biocompatibility. In the study, we propose using Quillaja saponin-stabilized solid lipid nanoparticle (QSLN) as nanofillers to enhance properties of κ-carrageenan/konjac glucan (κ-CA/KGM) composite hydrogels, and with emphasis on the effect of QSLN filling concentration on the structure and properties of composite hydrogels and the possible mechanisms were investigated. The best performance of QSLN-filled composite hydrogels was achieved at the QSLN concentration of 2.4 %. QSLN was uniformly distributed in the hydrogel matrix and formed electrostatic interactions and hydrogen bonding interactions with the matrix at an appropriate filling level, which enhanced the textural and rheological properties of the hydrogel greatly. In addition, the results of low-field NMR experiments showed that the filling of QSLN reduced the water mobility by enhancing the entanglement of polymer chains in the hydrogel matrix, which improved the freeze-thaw stability and regulated the swelling and deswelling behavior of the composite hydrogel. However, with the increasing of QSLN filling concentration, the above improvements were weakened by the depletion of van der Waals interactions due to the large amount of QSLN aggregation and the weakening of electrostatic interaction. In turn, the hydrogel was found to modulate the crystalline behavior of QSLN by X-ray diffraction and differential scanning calorimeter monitoring. Overall, the optimal synergistic effect between structure and properties could be achieved when the QSLN filling concentration was 2.4 %. These results provide a basis for the development of products that require excellent gel properties and structure.

The alleviative effect of curdlan on the quality deterioration of konjac glucomannan thermo-irreversible gels after commercial sterilization at 121 °C

This work employed different curdlan concentrations (0.00 %, 1.00 %, 1.50 %, 2.00 %, and 2.50 %) to alleviate the quality degradation of konjac glucomannan (KGM) gels after commercial sterilization at 121 °C for 15 min. The results showed that all levels of curdlan could retard the deterioration of KGM gels, with the best effect at 2.00 %. After commercial sterilization, incorporating curdlan into KGM gels greatly reduced the Tan σ (G"/ G'), total relaxation time and half-free water from 0.52, 89.85 ms and 98.26 % to 0.27, 38.48 ms and 21.42 %, respectively. Moreover, the addition of curdlan imparted a better texture to KGM gels, as reflected in the increase of hardness, springiness, water-holding capacity and whiteness value from 1400.85 g, 0.42, 87.92 % and 33.33 to 3461.68 g, 0.80, 96.50 % and 49.27, respectively. Furthermore, SEM images revealed that curdlan endowed KGM gels with a tighter structure and smaller pores, and the pore size distribution was reduced from 113.46 μm to17.91 μm, indicating a stronger interaction among molecules, as evidenced by XRD and FTIR results. KGM gels with curdlan possessed less proportion of complete crystallites and crystalline region. These findings suggested that curdlan can be the potently protectant for improving the quality of commercially sterilized KGM gel-based products.

Effects of lactic acid bacteria fermentation on the physicochemical and structural characteristics of starch in blends of glutinous and japonica rice

In this study, the effects of lactic acid bacteria (LAB) fermentation on the physicochemical and structural characteristics of mixed starches in blends of glutinous and japonica rice were investigated. Five starter cultures improved in varying degrees the hydration ability, transparency, and freeze-thaw stability of the mixed starches. Mixed starch I, prepared by fermentation of Lactobacillus acidophilus HSP001, exhibited optimal water-holding capacity, solubility, and swelling power. In comparison, mixed starches V and III involved fermentation of L. acidophilus HSP001 and Latilactobacillus sakei HSP002, using ratios of 2:1 and 1:1 to achieve higher transparency and freeze-thaw stability, respectively. The LAB-fermented, mixed starches exhibited excellent pasting properties due to their high peak viscosities and low setback values. Moreover, the viscoelasticity of mixed starches III-V, prepared by compound fermentation of L. acidophilus HSP001 and L. sakei HSP002 in ratios of 1:1, 1:2, and 2:1, respectively, proved superior to their single strain fermentation counterparts. Meanwhile, LAB fermentation resulted in reduced gelatinization enthalpy, relative crystallinity, and short-range ordered degree. Thus, the effects of five LAB starter cultures on mixed starches were inconsistent, but these results provide a theoretical basis for the application of mixed starches. PRACTICAL APPLICATION: Lactic acid bacteria was used to ferment blends of glutinous and japonica rice. Fermented mixed starch had better hydration, transparency, and freeze-thaw stability. Fermented mixed starch exhibited nice pasting properties and viscoelasticity. LAB fermentation corroded starch granules, leading to the decrease of ΔH. Relative crystallinity and short-range order of fermented mixed starch decreased.

Konjac glucomannan/xanthan gum/sodium alginate composite hydrogel simulates fascial tissue by pre-stretching and moisture regulation

Improving the mechanical strength and creating an anisotropic structure of edible macromolecular hydrogels is crucial to accurately simulate the texture of connective tissues. In this study, konjac glucomannan (KGM), xanthan gum (XG), and sodium alginate (SA) were used to construct hydrogels, and the effects of different pre-stretching degrees and moisture control on the composite gels were investigated. The results of the mechanical property tests and microstructure tests indicate that pre-stretching and moisture control can significantly enhance the strength of the gels and induce anisotropic structures. In addition, the feasibility of the composite gel structure in simulating brisket fascia was investigated, and it was concluded that 1.5 × -DR samples were most suitable for simulating connective tissue. This study provides compelling evidence for the potential of macromolecular hydrogels in simulating connective tissue and provides theoretical guidance for regulating gel texture.

Effects of Physical Properties of Konjac Glucomannan on Appetite Response of Rats

Dietary fiber has been widely used in designing foods with a high satiating capacity, as the use of satiety-enhancing food is considered to be a promising strategy for combating obesity and the overweight condition. In the present study, partially degraded konjac glucomannan (DKGM) diets with different water-holding capacities, swelling capacities, and viscosities were used to feed rats to investigate the effects of the fiber's physical properties in regulating the appetite response of the animals. The results showed that the mass and water content of the gastrointestinal chyme increased as the diet's physical properties were enhanced by the DKGM, which increased the stomach distention of the rats and promoted satiation. Besides, the hydrated DKGM elevated the chyme's viscosity, and the retention time of the digesta in the small intestine was prolonged significantly, which resulted in an increased concentration of cholecystokinin-8, glucagon-like peptide 1, and peptide tyrosine-tyrosine in the plasma, thus helping to maintain the satiety of rats. Furthermore, the results of the behavioral satiety sequence and meal pattern analysis showed that DKGM in the diets is more likely to reduce the food intake of rats by enhancing satiety rather than satiation, and will finally inhibit excessive weight gain. In conclusion, the physical properties of dietary fiber are highly related to the appetite response, which is a powerful tool in designing food with a high satiating capacity.

The Effect of Different Ratios of Starch and Freeze-Thaw Treatment on the Properties of Konjac Glucomannan Gels

The composite gels of konjac glucomannan (KGM) and corn starch (CS) were prepared and treated by the freeze-thaw method. For KGM-CS gels, as the starch ratio rose from 0 to 100%, storage modulus (G') decreased by 97.7% (from 3875.69 Pa to 87.72 Pa), degradation temperature decreased from 313.32 °C to 293.95 °C, and crystallinity decreased by 16.7%. For F-KGM-CS gels, G' decreased by 99.0% (from 20,568.10 Pa to 204.09 Pa), degradation temperature increased from 289.68 °C to 298.07 °C, and crystallinity decreased by 17.1% with more starch content. The peak in infrared spectroscopy shifted to a higher wavenumber with more starch and to a lower wavenumber by freezing the corresponding composite gels. The detected retrogradation of the composite gels appeared for KGM-CS with 80% starch and F-KGM-CS with 40% starch. The endothermic enthalpy of free water rose by 10.6% and 10.1% with the increase in starch for KGM-CS and F-KGM-CS, respectively. The results of moisture distribution found that bound water migrated to free water and the water-binding capacity reduced with more starch. The results demonstrated that the molecular interaction in composite gels was weakened by starch and strengthened by freezing.

Binary Hydrogels: Induction Methods and Recent Application Progress as Food Matrices for Bioactive Compounds Delivery-A Bibliometric Review

Food hydrogels are biopolymeric materials made from food-grade biopolymers with gelling properties (proteins and polysaccharides) and a 3D network capable of incorporating large amounts of water. They have sparked considerable interest because of their potential and broad application range in the biomedical and pharmaceutical sectors. However, hydrogel research in the field of food science is still limited. This knowledge gap provides numerous opportunities for implementing their unique properties, such as high water-holding capacity, moderated texture, compatibility with other substances, cell biocompatibility, biodegradability, and high resemblance to living tissues, for the development of novel, functional food matrices. For that reason, this article includes a bibliometric analysis characterizing research trends in food protein-polysaccharide hydrogels (over the last ten years). Additionally, it characterizes the most recent developments in hydrogel induction methods and the most recent application progress of hydrogels as food matrices as carriers for the targeted delivery of bioactive compounds. Finally, this article provides a future perspective on the need to evaluate the feasibility of using plant-based proteins and polysaccharides to develop food matrices that protect nutrients, including bioactive substances, throughout processing, storage, and digestion until they reach the specific targeted area of the digestive system.

Different nitrogen fertilizer application in the field affects the morphology and structure of protein and starch in rice during cooking

Nitrogen fertilization is one of the most important cultivation practices that affects the eating quality of rice. During the cooking process, nitrogen fertilizer application in the field changed the structure of protein and starch during cooking, which eventually reduced the rice eating quality. However, the morphology and structure of rice during cooking under high nitrogen fertilizer application in the field have not been explored. The relationship between the morphological and structural changes of rice protein and starch during cooking and the rice eating quality has not been studied. In this study, we conducted field trials at two nitrogen fertilizer levels (0 N and 350 N), and the rice was cooked after harvest. Our results showed that the peak viscosity of rice flour was 3326 cp and 2453 cp at 0 N and 350 N, respectively, and the peak viscosity of rice starch was 3424 cp and 3378 cp, respectively. Rice proteins played an important role in the starch gelatinization properties and thermodynamic properties. High nitrogen fertilizer application increased the protein content of rice from 5.97 % to 11.32 %, and more protein bodies adhered to the surface of amyloplasts eventually inhibiting starch gelatinization. The rice proteins could bind to amylose-lipid complexes during cooking, promoting the formation of V-type diffraction peaks. What is more, under high nitrogen fertilizer, rice protein had more β-sheets, which slowed the entry of water into the interior of starch molecules and prevented the destruction of the short-range ordered structure of starch. Our study provides the possibility to further improve the eating quality of rice under nitrogen fertilizer treatment.

Effect of Ethanol on Preparation of Konjac Emulgel-Based Fat Analogue by Freeze-Thaw Treatment

In the current study, a method using ethanol to modulate the texture properties of konjac gel during freeze-thaw process was used to prepare konjac emulgel-based fat analogue. A certain amount of ethanol was added to konjac emulsion, heated to form a konjac emulgel, then frozen at −18 °C for 24 h, and finally thawed to obtain konjac emulgel-based fat analogue. The effects of different ethanol contents on the properties of frozen konjac emulgel were explored, and data was analyzed by one-way analysis of variance (ANOVA). The emulgels were compared with pork backfat in terms of hardness, chewiness, tenderness, gel strength, pH, and color. The results showed that the konjac emulgel with 6% ethanol had similar mechanical and physicochemical properties to pork backfat after freeze-thaw treatment. The results of syneresis rate and SEM showed that adding 6% ethanol could not only reduce the syneresis rate, but also effectively weaken the damage to the network structure caused by freeze-thaw treatment. The pH value of konjac emulgel-based fat analogue was between 8.35–8.76, and the L* value was similar to that of pork backfat. The addition of ethanol provided a new idea for the preparation of fat analogues.

Effects of Konjac Glucomannan on Retrogradation of Amylose

The effect of konjac glucomannan (KGM) on the retrogradation of amylose was explored during storage. The color, rheological properties, texture, water-holding capacity (WHC), low-field nuclear magnetic resonance (LF-NMR), and X-ray diffraction (XRD) were investigated. Results of color and rheological measurements showed that with the increasing amount of KGM, the L value of the system decreased, but the elastic modulus, viscous modulus, and tangent value of loss angle increased. The textural result presented that KGM obviously inhibited the growth rate of gel strength of amylose. Results from WHC and XRD suggested after 14 days of storage, when the concentration of KGM increased from zero to 0.3% in the mixture, the WHC grew from 80% to 95% and the crystallinity degree declined from 35.3% to 25.6%. The LF-NMR result revealed that KGM limited the conversion of free water to bound water in the system. In general, a small amount of KGM in a mixed system could inhibit the short-term and long-term retrogradation of amylose. This research could provide a theoretical reference for the influence of hydrophilic colloids on the retrogradation of starch, and it could also provide support for the processing and production of starch-based food.

Casein-hempseed protein complex via cross-link catalyzed by transglutaminase for improving structural, rheological, emulsifying and gelation properties

In present study, microbial transglutaminase (MTGase) was applied to strengthen the interaction between casein and hempseed protein (HPI) through crosslinking. The structural and functional characteristics of this heteropolymers were investigated. Both homologous and heterologous crosslinking were achieved by adding MTGase in casein-HPI system, and thus enhanced zeta potential, surface hydrophobicity, viscosity, emulsifying and gelation properties of the complex. However, HPI hindered the crosslinking due to unbalanced Lys/Gln ratios. Emulsifying and gelling properties were significantly correlated with the secondary structures. When MTGase activity was < 30 U/g or treatment time was < 2 h, the α-helix content decreased by 9% while the β-sheet content increased by 12%, respectively, with MTGase activity and treatment time increase. The structural alterations resulted in the better emulsifying activity, gel networks and water holding capacity of the complex. This work represents a novel interaction mode between casein and HPI via MTGase to elevate functional properties of complex.

Influence of ultrasound and enzymatic cross-linking on freeze-thaw stability and release properties of whey protein isolate hydrogel

This study investigated the effect of ultrasound and enzymatic cross-linking on the freeze-thaw (FT) stability and release properties of whey protein isolate hydrogels. We evaluated the FT stability by the changes in the microstructure, riboflavin retention, syneresis, water holding capacity (WHC), and texture of gels subjected to 3 FT cycles. High-intensity ultrasound (HUS) and transglutaminase (TGase)-mediated cross-linking improved the FT stability of whey protein isolate hydrogels loaded with riboflavin (WPISAR), as demonstrated by a more uniform and denser porous structure, significantly higher riboflavin retention, WHC, and textural properties, and lower syneresis after 3 FT cycles than those of untreated hydrogels. Furthermore, HUS- and TGase-mediated cross-linking decreased protein erosion and swelling ratio of WPISAR in simulated gastrointestinal fluids (SGIF) and reduced the riboflavin release rate in SGIF both with and without the addition of digestive enzymes. After 3 FT cycles, faster riboflavin release occurred due to a more porous structure induced by ice crystal formation compared with their unfrozen counterparts as detected by confocal laser scanning microscopy. High-intensity ultrasound- and TGase-mediated cross-linking alleviated the FT-induced faster riboflavin release rate in SGIF. High-intensity ultrasound- and TGase-treated gel samples showed that both diffusion and network erosion were responsible for riboflavin release regardless of FT. These results suggest that HUS- and TGase-mediated cross-linking improved the FT stability of WPISAR with a high riboflavin retention, and might be a good candidate as a controlled-release vehicle for riboflavin delivery to overcome undesired FT processing.

Synthesis and properties of maleic anhydride-modified agar with reversibly controlled gel strength

Agar is modified by chemical methods to improve its functional properties and meet the increasing demand of the market. Some of the functional properties of agar are improved after chemical modification, while other properties are reduced, especially gel strength. This study aimed to comprehensively improve the functional properties of agar through acylation and crosslinking by reacting with maleic anhydride. ¹³C NMR indicated the maleylation reaction was preferred at the C2 hydroxyl group of D-galactose, and the crosslinking reactions occurred at the C2 and C6 hydroxyl groups of D-galactose in different agar chains. Interestingly, the maleylated agar monoester had higher gel transparency (1.5%, w/v) of up to 76% than the native agar (58%). However, it showed a significant decrease in gel strength from 783 g/cm² to 403 g/cm², while crosslinking endowed agar with higher gel strength (845 g/cm²) and gel transparency (78.4%). The high transparency of the modified agar plate made colony observation and colony counting easy. Maleylation of agar further enhanced the freeze-thaw stability of agar gel (24.8%, 7th freeze-thaw cycles). Overall, the maleylated agar possessed superior functional properties, and it could be used as food, bacteriological, and biotechnological agar.

Properties of soybean protein isolate/curdlan based emulsion gel for fat analogue: Comparison with pork backfat

To obtain an analogue of pork backfat (PBF), we combined emulsion and gel to fabricate emulsion gel, which was prepared by using soybean protein isolate (SPI) and curdlan (CL) through a facile heat-treatment method in this paper. The microstructures, rheology properties, water holding capacity and freeze-thawing stability of the emulsion gel were investigated. The results suggested that the SPI/CL-stabilized emulsion gel was thermal-irreversible, and SPI was the emulsifying agent of the emulsion gel. Oil contents significantly affect the water holding capacity and freeze-thawing stability of emulsion gel. Subsequently, the TPA, gel strength and color of emulsion gels with different oil contents were compared with PBF. The hardness, chewiness, springiness, and gel strength of emulsion gel with 10 wt% oil contents were no significant differences from that of PBF (P > 0.05). Hence, this SPI/CL based emulsion gel can be used as an analogue to PBF, providing an alternative ingredient for the development of plant-based low-fat meat products.

Fabrication and Characterization of Gel Beads of Whey Isolate Protein-Pectin Complex for Loading Quercetin and Their Digestion Release

In this study, emulsion gel beads for loading quercetin were prepared through an emulsification/gelation process using whey protein isolate (WPI) and pectin. Emulsion gel beads’ properties were investigated by different pectin content. Additionally, the physicochemical properties, morphology and quercetin release properties from beads were explored. Firstly, electrical characteristics and the rheology of bead-forming solutions were measured, revealing that all systems had strong negative charge and exhibited shear-thinning behavior. The textural results demonstrated that the properties of emulsion gel beads were improved with increasing the content of pectin. It was also confirmed that crosslinking was formed between WPI emulsion and pectin by Fourier Transform Infrared (FTIR) analysis and thermogravimetric analysis (TGA). In addition, the shape of the beads was spherical or ellipses with smooth surfaces and they had a tight gel network of internal structures, which was visualized by using electron microscopy (SEM). Finally, the amount of quercetin released in vitro was gradually decreased with increasing pectin content; it was as low as 0.59%. These results revealed that WPI emulsion–pectin gel beads might be an effective delivery system for quercetin as a colon target and are worth exploring further.