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

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.

Effect of Dual-Modified Tapioca Starch/Chitosan/SiO2 Coating Loaded with Clove Essential Oil Nanoemulsion on Postharvest Quality of Green Grapes

As consumer awareness regarding health and nutrition continues to increase, there is a growing demand for fresh, nutritious fruits such as green grapes. However, the short storage life and susceptibility of these fruits to spoilage lead to significant commercial losses. Currently, the plastic wrap method is commonly used to keep green grapes fresh, but this packaging effect is limited and not environmentally friendly. Therefore, there is an urgent need to explore sustainable and effective preservation methods. In this study, a high-pressure microfluidization technique was employed to prepare an essential oil nanoemulsion with a ratio of Tween 80 to clove essential oil of 1:1, and a biopolymer-based film solution was prepared using dual-modified tapioca starch and chitosan loaded with clove essential oil nanoemulsion. The dual-modified tapioca starch/chitosan/SiO2/1.25 wt % clove essential oil (DM/Ceo-1.25) solution coating was successfully applied for the packaging and preservation of fresh green grapes. Compared with the CK and polyethylene wrap (PE) groups, the DM/Ceo-1.25 coating significantly improved the quality of the green grapes, increasing the storage period of the green grapes from 4 to 8 days at room temperature. On the 10th day of storage, the coated grapes retained significantly better quality, with a hardness of 4.01 N, a titratable acidity of 1.625%, an anthocyanin content of 1.013 mg/kg, and a polyphenol content of 21.32 μg/mL. These results indicate that the DM/Ceo-1.25 solution coating developed in this study can be used as a new active material for fruit preservation and provides ideas for the development of safer and more sustainable food packaging.

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.

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.

Moisture loss inhibition with biopolymer films for preservation of fruits and vegetables: A review

In cold storage, fruits and vegetables still keep a low respiratory rate. Although cold storage is beneficial to maintain the quality of some fruits and vegetables, several factors (temperature and humidity fluctuations, heat inflow, air velocity, light, etc.) will accelerate moisture loss. Biopolymer films have attracted great attention for fruits and vegetables preservation because of their biodegradable and barrier properties. However, there is still a certain amount of water transfer occurring between storage environment/biopolymer films/fruits and vegetables (EFF). The effect of biopolymer films to inhibit moisture loss of fruits and vegetables and the water transfer mechanism in EFF system need to be studied systematically. Therefore, the moisture loss of fruits and vegetables, crucial properties, major components, fabrication methods, and formation mechanisms of biopolymer films were reviewed. Further, this study highlights the EFF system, responses of fruits and vegetables, and water transfer in EFF. This work aims to clarify the characteristics of EFF members, their influence on each other, and water transfer, which is conducive to improving the preservation efficiency of fruits and vegetables purposefully in future studies. In addition, the prospects of studies in EFF systems are shown.

Application of Plant Oils as Functional Additives in Edible Films and Coatings for Food Packaging: A Review

Increasing environmental concerns over using petroleum-based packaging materials in the food industry have encouraged researchers to produce edible food packaging materials from renewable sources. Biopolymer-based edible films and coatings can be implemented as bio-based packaging materials for prolonging the shelf life of food products. However, poor mechanical characteristics and high permeability for water vapor limit their practical applications. In this regard, plant oils (POs) as natural additives have a high potential to overcome certain shortcomings related to the functionality of edible packaging materials. In this paper, a summary of the effects of Pos as natural additives on different properties of edible films and coatings is presented. Moreover, the application of edible films and coatings containing POs for the preservation of different food products is also discussed. It has been found that incorporation of POs could result in improvements in packaging's barrier, antioxidant, and antimicrobial properties. Furthermore, the incorporation of POs could significantly improve the performance of edible packaging materials in preserving the quality attributes of various food products. Overall, the current review highlights the potential of POs as natural additives for application in edible food packaging materials.

Effect of Adding Red Propolis to Edible Biodegradable Protein Films for Coating Grapes: Shelf Life and Sensory Analysis

Red propolis is an active ingredient of great nutritional interest which offers numerous benefits as an antioxidant and antimicrobial agent. Thus, the objective of this research was to evaluate the application of an edible and antimicrobial gelatine coating containing red propolis to increase the shelf life of grapes. Gelatine films with an addition of 5, 10, 15, 20 and 25% of red propolis extract were produced to evaluate their antimicrobial activity using the disk diffusion test in solid media. The films with 25% red propolis extract showed antimicrobial activity against the bacteria Staphylococcus aureus and Pseudomonas aeruginosa. The grapes were coated with pure gelatine, without a plasticizer and with gelatine with 25% red propolis and then stored for 1, 4, 10, 19 and 25 days at temperatures of 25 °C and 5 °C. The results showed that the gelatine coating with propolis reduced the mass loss of grapes stored at 25 °C for 19 days by 7.82% and by 21.20% for those kept at 5 °C for 25 days. The pH, total titratable acidity, soluble solids and color of the grapes increased due to the ripening process. Furthermore, the sensory acceptability indexes of the refrigerated grapes with coatings were superior (>78%) to those of the control samples (38%), proving the effectiveness of the coatings in maintaining the quality of grapes during storage.