Impact of heating and drying temperatures on the properties of konjac glucomannan/curdlan blend films

Effect of ultra-high pressure combined with heat-assisted treatment on the characterization, moisture absorption, and antioxidant activity properties of walnut peptide

In this study, ultra-high pressure (UHP) and heat-assisted technology (HT) were used to process walnut peptides (WP) and investigate their combined effects (UHP-HT) on the characterization, moisture absorption, and antioxidant activity of WP. The results indicated that UHP (300 Mpa, 10 min) combined with HT treatment (55 °C, 30 min) significantly increased the surface hydrophobicity and disulfide bonds of WP. UHP-HT-treated WP exhibited lower moisture absorption and more stable water molecule migration. Additionally, the moisture absorption capacity of the WP (48.78 %) was significantly decreased in WP-UHP, WP-HT and WP-UHP (45.37 %, 43.15 %, and 40.19 %, respectively) because of increasing the surface hydrophobicity. UHP-HT combined improved structural characteristics, including particle size, zeta potential, and functional group stability, and significantly enhanced the antioxidant activity of WP under high humidity conditions. Overall, these findings suggest that UHP-HT can effectively reduce the moisture absorption of WP, thus enhancing its storage stability and extending its shelf life.

Enhancing physical properties of konjac glucomannan/ethyl cellulose/zein blend films by optimizing molecular assembly with varying drying temperatures

Appropriate selection of the drying temperature is of great importance to achieve desirable film preparation. The present study investigated the impact of drying temperature (40-80 °C) on the physical properties and molecular assembly process of konjac glucomannan/ethyl cellulose/zein blend films through the casting method. Microstructural observations indicated that the drying temperature impacted the particle aggregation in the films, and at the drying temperature of 60 °C, a most even component distribution was suggested with the strongest hydrogen bond interaction according to the FTIR and micro-FTIR analysis. Moreover, at this drying temperature, the blend film reached optimum performance for most physical properties including mechanical properties, surface hydrophobicity, moisture barrier, and water resistance properties. To explain this phenomenon, the molecular assembly process during the KGM/EC/zein film formation was proposed. This contributed to a deepened understanding of the molecular assembly process of complex macromolecules under different drying conditions.

Improved konjac glucomannan/curdlan-based emulsion coating by mung bean protein addition for cherry tomato preservation

Biopolymer-based emulsion systems have been used for food preservation. In this study, mung bean protein (MBP) was added to konjac glucomannan (KGM)/curdlan-based camellia oil emulsion (KC-CO) to develop KCM-CO emulsion system. KCM-CO emulsions showed good compatibility and stability during storage. The confocal laser scanning microscopy, atomic force microscope, and infrared spectroscopy revealed that camellia oil was successfully emulsified by MBP, and the resulting droplets were evenly distributed in the polysaccharide network formed by KGM and curdlan micelles based on hydrogen bonds. The emulsions behaved as an elastic solid, and the KCM-CO emulsion films exhibited a compact microstructure, and the emulsification of MBP enhanced the compatibility, as K54C40M6-CO had the smoothest surface. The addition of MBP significantly improved the elongation at break (EAB), water contact angle (WCA), dissolution, and gas permeability of the emulsion films. K54C40M6-CO showed the largest EAB (37.6 %), strong hydrophobicity (WCA = 97.8°), and low water vapor and oxygen permeability. In the preservation experiments, K54C40M6-CO coating significantly delayed the weight loss (by 41.2 %) and firmness decline (by 54.5 %), and maintained the appearance, total solids, total acids, and ascorbic acid content of cherry tomatoes, and inhibited the respiratory intensity by 44.2 %. This coating showed great potential for fruit and vegetable preservation.

Effects of Different Plasticizers on the Structure, Physical Properties and Film Forming Performance of Curdlan Edible Films

This study successfully developed edible films with excellent mechanical strength and notable water resistance, utilizing curdlan (CL) as the primary matrix and incorporating various plasticizers, including glycerol (GLY), ethylene glycol (EG), propylene glycol (PRO), xylitol (XY), sorbitol (SOR), and polyethylene glycol (PEG). A comprehensive suite of analytical techniques, including Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), and tensile testing, were employed to evaluate the films' structural and mechanical properties. After incorporating PEG, the water sensitivity increased slightly, with a contact angle (CA) of 97.6°, and a water solubility (WS) of 18.75%. The inclusion of plasticizers altered the crystalline structure of the CL matrix, smoothing and flattening the film surface while reducing hydrogen-bonding interactions. These structural changes led to a more uniform distribution of amorphous chain segments and a decrease in glass transition temperatures. Among the tested plasticizers, GLY exhibited the highest compatibility with CL, resulting in the smoothest surface morphology and delivering the most effective plasticizing effect. The CL-GLY film showed a dramatic improvement in flexibility, with an elongation at break that was 5.2 times higher than that of the unplasticized film (increasing from 5.39% to 33.14%), indicating significant enhancement in extensibility. Overall, these findings highlight the potential of CL-GLY films as sustainable and effective materials for food packaging applications.

Bio-based composite film from konjac flour and dialdehyde starch: Development, properties and structural features

The development of environmental-friendly composite products from renewable resources has been considered as an excellent approach to address the negative impact of petroleum-based plastics on environment. Konjac flour (KF), as an excellent polysaccharide material, has a broad application in food field. It shows a promising future in the film field due to its excellent film-forming properties. In this work, KF was selected as primary film-forming matrix, and dialdehyde starch (DAS) as the reinforcing component. A series of KF/DAS composite films were prepared by adjusting the addition ratio of DAS component. Then, their physical and mechanical properties were characterized and analyzed. The results showed that KF/DAS composite film with 25 % DAS content exhibited the optimal mechanical properties, including tensile strength (TS) of 13.1 MPa and elongation at break (EAB) of 93.7 %, indicating that an excellent cross-linked system formed among KF and DAS utilizing the method described in this study. Furthermore, much evidences from the fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) confirmed that a strong chemical cross-linkages between DAS and KF via Schiff base and esterification reactions. Based on the thermogravimetry (TG) and scanning electron microscopy (SEM) results, KF/DAS composite films also had excellent thermal stability and a dense microstructure, although there are also changes with the DAS usage.

Improvement of mechanical, barrier properties, and water resistance of konjac glucomannan/curdlan film by zein addition and the coating for cherry tomato preservation

The mechanical, barrier properties, and water resistance of packaging materials are crucial for the preservation of fruits and vegetables. In this study, zein was incorporated as a hydrophobic substance into the konjac glucomannan (KGM)/curdlan (KC) system. The KC/zein (KCZ) showed good compatibility with the zein aggregates uniformly distributed in the network formed by an entanglement of KGM and curdlan micelles based on hydrogen bonds. The presence of zein inhibited the extension of the KC entangled structure and enhanced the solid-like behavior. The high content of zein (>6 %) increased zein aggregation and negatively affected the structure and properties of KCZ. The zein addition significantly improved the water vapor permeability, tensile strength, and elongation at break. The hydrophobicity of the KCZ films was significantly enhanced, accompanied by the water contact angle increasing from 81° to 112°, and the moisture content, swelling, and soluble solid loss ratio decreasing apparently. The K56C40Z4 coating exhibited an excellent preservation effect to inhibit the respiration of cherry tomatoes, significantly reducing the water loss and firmness decline and maintaining the appearance, total solid, total acid, and ascorbic acid content. This work provided a strategy to fabricate hydrophobic packaging for the preservation of fruits and vegetables.

Improving Structural, Physical, and Sensitive Properties of Sodium Alginate-Purple Sweet Potato Peel Extracts Indicator Films by Varying Drying Temperature

Sodium alginate (SA)-purple sweet potato peel extracts (PPE) from industrial waste indicator films were developed at different drying temperatures (25, 30, 35, 40, 45, 50, and 55 °C). The effects of drying temperatures on the film's structural, physical, and sensitive properties were investigated. On the structural properties, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction indicated that compactness, intermolecular interactions, and crystallinity of indicator films were improved at a lower drying temperature. On the physical properties, with the drying temperature increasing, elongation at the break increased significantly (p < 0.05); ΔE and water-vapor permeability decreased significantly (p < 0.05); and thickness and tensile strength initially increased significantly (90.46 → 98.46, 62.99 → 95.73) and subsequently decreased significantly (98.46 → 71.93, 95.73 → 55.44) (p < 0.05), with the maximum values obtained at 30 °C. On sensitivity, the corresponding colors of the films became lighter as the drying temperature increased, and the films exhibited relatively excellent pH and NH3 sensitivity, with easily discernible color changes at lower temperatures. The results of this paper revealed that the overall film characteristics are improved at lower drying temperatures, which will provide valuable references for selecting the drying temperature for preparing indicator films as a guide for industrialized production.

Tailoring hydroxypropyl starch films with curdlan for enhanced properties for edible packaging

Hydroxypropyl starch-based composite system has high potential for many applications such as food packaging and biomedical fields. Here, how the incorporation of curdlan, a thermo-irreversible heating-set gel, tailors the processability, structure, and film performance of hydroxypropyl starch, a cooling-set gel, has been systematically investigated, aiming to achieve enhanced material properties favorable for edible packaging applications. Curdlan incorporation increased the shear-thinning behavior and viscosity of hydroxypropyl starch solution, which was also strongly affected by temperature. The miscibility and comparability between the two polymers with distinct gelation behaviors is a practical and interesting scientific topic. Scanning electron microscopy, dynamic mechanical analysis, and thermogravimetric analysis all indicated good compatibility between hydroxypropyl starch and curdlan. There was no observable phase boundary between the two materials, and all composite films showed only a single relaxation peak and only one polymer thermal decomposition peak. This resulted in improved structural density and overall performance. Compared with pure HPS film, the 7:3 HPS/CD film showed increases in tensile strength by 66.12 % and thermal decomposition temperature by 3 °C, and a reduction in water solubility by 11.72 %. This knowledge gained here may facilitate the development of edible films based on hydroxypropyl starch with satisfying film performance and processability.

Advances of blend films based on natural food soft matter: Multi-scale structural analysis

The blend films made of food soft matter are of growing interest to the food packaging industries as a pro-environment packaging option. The blend films have become a novel pattern to replace traditional plastics gradually due to their characteristics of biodegradability, sustainability, and environmental friendliness. This review discussed the whole process of the manufacturing of food soft matter blend films from the raw material to the application due to multi-scale structural analysis. There are 3 stages and 12 critical analysis points of the entire process. The raw material, molecular self-assembly, film-forming mechanism and performance test of blend films are investigated. In addition, 11 kinds of blend films with different functional properties by casting are also preliminarily described. The industrialization progress of blend films can be extended or facilitated by analysis of the 12 critical analysis points and classification of the food soft matter blend films which has a great potential in protecting environment by developing sustainable packaging solutions.

Properties of konjac glucomannan/curdlan-based emulsion films incorporating camellia oil and the preservation effect as coatings on 'Kyoho' grapes

The strategy of emulsion coating was used for grape preservation. Camellia oil (CO) was incorporated with KGM/curdlan (KC) to fabricate KC-CO emulsion systems. KC-CO emulsions were analyzed by droplet size distribution and confocal laser scanning microscopy (CLSM), and KC-CO films were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mechanical properties, dissolution, gas permeability, water contact angle (WCA). KC-CO coating was used for preservation of 'Kyoho' grapes. The results indicated that the addition of CO had a positive effect on KC system. CO could form a uniform emulsion with KC, and the droplets were evenly dispersed in the KC matrix. KC-CO films displayed a continuous microstructure, and elongation at break (EAB) was improved, while tensile strength decreased. The dissolution, water vapor permeability (WVP), and WCA were significantly enhanced, while the permeability of oxygen and carbon dioxide exhibited no advantage compared with KC film. KC-CO-10 possessed optimal properties and was selected as an emulsion coating for preservation. The results suggested that KC-CO-10 significantly maintained the appearance, total solid and acid content of 'Kyoho' grapes, and delayed the weight loss and firmness decrease. This study contributed to the understanding of polysaccharide-lipid emulsion system and the applications.

Formation and characterization of konjac glucomannan/ethyl cellulose films by using ethanol and water as the solvents

Hydrophilic konjac glucomannan (KGM)/hydrophobic ethyl cellulose (EC) film was prepared in the ethanol/water environment. The film-forming solution and film properties were both characterized to analyze the molecular interaction changes. Although higher ethanol usage enhanced the stability of the film-forming solution, it did not benefit the film property improvement. The SEM images showed some fibrous structure on the air surface of the films, consistent with the XRD results. The changing trend of mechanical properties and the FTIR results suggested that both ethanol content and ethanol evaporation impacted the molecular interaction during the film formation. The surface hydrophobicity results indicated that the ethanol content could cause significant EC aggregation changes on the film surface only with high EC contents. The water vapor permeability results suggested that higher ethanol usage decreased the compactness of the films. Considering all results, the 20 % ethanol content and the weight ratio of KGM: EC = 7:3 were suggested for the film preparation due to the superior properties in most properties. This study contributed to the understanding of polysaccharide interaction in the ethanol/water environment and offered an alternative biodegradable packaging film.

Characterizations of konjac glucomannan/curdlan edible coatings and the preservation effect on cherry tomatoes

In this study, konjac glucomannan (KGM) and curdlan were used to fabricate composite coating (KC). The coating solutions were investigated using a rheological method, and the coatings were characterized by water solubility tests, water vapor permeability (WVP), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The preservation effect of KC coating on cherry tomatoes stored at room temperature was determined. Results indicated that the curdlan addition can adjust the hydrophilicity/hydrophobicity of KGM coatings. Curdlan addition enhanced intermolecular entanglement and film-forming property. Increasing curdlan content in KC coatings significantly decreased the moisture content, dissolution and swelling ratio, and WVP. The KGM-curdlan composites behaved as high-performance coatings with good compatibility and uniformity. The K₃C₂ coating showed the best uniformity, water barrier, and thermal stability. The application of K₃C₂ coating significantly reduced the weight loss, decay loss, and delayed the decreases of firmness, soluble solids, total acid, and VC contents of cherry tomatoes. The KGM/curdlan edible coatings have promising potential for prolonging the shelf life of cherry tomatoes and applications in fruits preservation in the future.

Characterization and evaluation of Bletilla striata polysaccharide/konjac glucomannan blend hydrogel for wound healing

Bletilla striata polysaccharide (BSP) is effective for wound healing and has important applications in health care. A series of blend hydrogels was designed with BSP and konjac glucomannan (KGM) in this study to overcome the deficient mechanical performance caused by the excessive dissolution of BSP without affecting its physiological activity. The interplay between them, as well as the effects of KGM concentration on the physical properties and microstructures of hydrogels, were also explored. It was proved that the frame of the hydrogel was primarily formed by KGM. BSP was dispersed uniformly and linked to KGM through hydrogen bonding, which effectively improved the physical properties, such as increasing the water-holding capacity, improving the swelling degree, and enhancing the mechanical properties. Blend hydrogel BK2-2 (containing 1.0% BSP and 1.0% KGM, w/v) was found to be the optimal formulation based on the thermal stability and microstructure, which was used for further research. In vitro experiments revealed the L929 cell proliferative effects of the blend hydrogel, and no difference was found with BSP sponge extract after 72 h of exposure. In vivo animal studies indicated that the BK2-2 accelerated wound healing compared with the control group; however, no difference was found with dressings only made of BSP. These results demonstrated that KGM improved the physical properties of BSP-based material without negatively affecting its physiological properties. Also, the BSP/KGM blend hydrogel had good comprehensive properties and is expected to be used as a wound healing material in the future.