Tailoring Multi-Level Structural and Practical Features of Gelatin Films by Varying Konjac Glucomannan Content and Drying Temperature

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.

Effect of Drying Temperature on Physical, Chemical, and Antioxidant Properties of Ginger Oil Loaded Gelatin-Sodium Alginate Edible Films

The drying temperature is one of the crucial parameters that impacts the physical, chemical, and biological properties of edible films (EFs). This parameter determines the degree of crystallinity, which can further impact the film's mechanical, barrier, and optical properties. The present work is designed to investigate the effect of different drying temperature conditions (25 °C and 45 °C) on ginger essential oil (GEO) loaded Gelatin-sodium alginate composite films over their physical, chemical, and antioxidant properties. Results indicated that drying of films at 25 °C had a positive effect on certain properties of the EFs, such as the moisture content (MC), water solubility (S), swelling degree (SD), water vapor permeability (WVP), and mechanical and optical properties. SEM analysis showed that films dried at 25 °C presented more uniform surface properties with fewer cracks and pores compared to films dried at 45 °C. TGA analysis demonstrated the higher thermal stability of the films when dried at 25 °C. Findings obtained from X-ray diffraction (XRD) and fourier-transform infrared spectroscopy (FTIR) showed film crystallinity and electrostatic interactions between GE, SA, and GEO. Results obtained from antioxidant assays revealed that films dried at 25 °C showed comparable antioxidant capacity to that of butylated hydroxytoluene (BHT). Furthermore, it was found that the addition of SA and GEO to the blank GE films improved their physical, chemical, and antioxidant properties. The present work suggests that GEO loaded GE-SA based films showed better physical, chemical, and antioxidant potential when dried at a lower temperature. These novel materials can be utilized as potential packaging materials in the food industry.

Increasing agar content improves the sol-gel and mechanical features of starch/agar binary system

Starch/agar systems are highly potential for versatile applications such as packaging and biomedical materials. Here, how combined factors affect the features of a starch/agar binary system were explored. An increase of starch amylose/amylopectin ratio from 0/100 to 50/50 increased the sol-gel transition temperature and gel hardness of the aqueous starch/agar mixture. An increased agar content (mainly from 30% to 70%) allowed increases in both the tensile strength (reaching 50-60 MPa) and elongation at break of the starch/agar binary films. This phenomenon should be related to the strengthened crystalline structure and the weakened hydrogen bonding between starch chains (reflected by infrared spectroscopy). Furthermore, a higher relative humidity (from 30% to 70%) allowed enhanced chain interactions and probably nanoscale molecular order but weakened the crystalline structure, leading to reduced tensile strength and increased elongation at break. This work could facilitate the design of starch/agar binary systems with improved sol-gel and mechanical performance.