Hybrid organic-inorganic coating with enhanced oxygen- and UV-barrier performance: Polyelectrolyte complex based on sodium alginate, poly (vinyl alcohol), and reconstructed layered double hydroxide.

Organic-inorganic hybrid materials with high oxygen- and UV-barrier properties were developed using a polyelectrolyte complex comprising sodium alginate (SA), poly (vinyl alcohol) (PVA), and reconstructed layered double hydroxide (RLDH). These materials were applied to poly (ethylene terephthalate) (PET) as a barrier coating layer at a harsh drying temperature of 120 °C, similar to environments for the industrial coating process. The RLDH nanoplatelets within the coating matrix restricted the polymer chain mobility, elevating the glass transition temperature to 105.222-159.114 °C. Below RLDH 0.2 %, the apparent coating density significantly increased to 0.93-0.94 g/cm3. The embedded RLDH gave a tortuosity within the matrix, as evidenced by an intensified (003) diffraction peak in the XRD analysis. These structural alterations contributed to high oxygen- and UV-barrier performance. Notably, the PET/SA1.0PVA0.5RLDH0.2 film exhibited an extremely low oxygen transmission rate of <0.005 cm3/m2·day, with effectively blocking UV-A (62.41 %), -B (92.45 %), and -C light (100 %). Moreover, the susceptibility of the coated film to water vapor was mitigated by laminating cast polypropylene, achieving a water vapor transmission rate of 1.17 g/m2·day. Overall, the packaging materials with advanced oxygen-, water vapor-, and UV-barrier properties show great potential for practical applications in various sectors, including food packaging and medical/electrical devices.

Comparative study on physicochemical properties of starch films prepared from five sweet potato (Ipomoea batatas) cultivars.

Five different sweet potato (Ipomoea batatas) cultivars (Daeyumi, Gogeonmi, Sincheonmi [SCM], Singeonmi, and Sinyulmi [SYM]) were used to extract sweet potato starch (SPS) for developing starch-based films. After the chemical composition and amylose contents of all SPSs were evaluated, the morphological, moisture, mechanical, and barrier properties of the SPS-based films were investigated. As one of the film characteristics, the X-ray diffractograms revealed that the SCM-based film with the highest amylose content (26.34%) had the highest relative crystallinity (24.31%). The SCM-based film also showed higher tensile strength (3.05-fold) and elastic modulus (2.38-fold) than the SYM-based film with the lowest amylose content (21.84%). The water vapor and oxygen permeabilities of the SPS-based films were negatively correlated with the amylose content. Thus, the SCM-based film was less permeable for water vapor (3.16-fold) and oxygen (1.81-fold) than the SYM-based film. These results demonstrated that the sweet potato cultivar, especially the amylose content, plays a significant role in determining the physicochemical properties of the SPS-based films.

Effects of mung bean starch/guar gum-based edible emulsion coatings on the staling and safety of rice cakes.

Antimicrobial starch/gum-based edible emulsion coatings were developed to improve the storage stability of rice cakes by retarding starch retrogradation and inhibiting microbial growth. Rice cakes were coated with mung bean starch (MBS) and guar gum (GG) containing various concentrations of sunflower seed oil (SO). Among these, the (2 g MBS +0.75 g GG +1.5 g SO) / 100 g (optimum) decreased the hardness of rice cakes by 29 % and the crystallization rate (k) by 24 % compared with those of uncoated samples. The moisture loss in uncoated samples was markedly higher than that in the optimum blend-coated samples. Crystallinity analysis revealed the retarding effect of the developed coatings in starch retrogradation. Furthermore, adding 0.8 % (w/w) grapefruit seed extract to the optimum blend led to a distinct antimicrobial activity. Therefore, the newly developed edible coating was effective in maintaining the quality and safety of rice cakes.

Development of Protein-Based High-Oxygen Barrier Films Using an Industrial Manufacturing Facility.

In this study, protein-based high-oxygen barrier multilayer films were manufactured at a pilot plant scale by a roll-to-roll coating process and an adhesive lamination process. Also, their characteristics were examined to evaluate their industrial feasibility. Oxygen transmission rates (OTRs) of the protein-based films (polyethylene terephthalate [PET]/pea protein isolate [PPI]/nylon/cast polypropylene [CPP], PET/whey protein isolate [WPI]/CPP, PET/WPI/nylon/CPP, and PET/PPI/nylon/low-density polyethylene [LDPE]) were significantly lower than OTR of the PET/nylon/CPP film without a protein-coating layer and that of the commercial high-barrier multilayer film copolymer (PET/aluminum/CPP). In addition, water vapor transmission rates of the films containing protein layer were significantly lower than that of the commercial high-barrier film containing ethylene vinyl alcohol [nylon/nylon/EVOH/easy peel layer [EPL]). Among the tested polymers, the PET/WPI/nylon/LDPE film showed the highest heat-sealing ability, tensile strength, and elastic modulus. Moreover, transparency and haze of the PET/WPI/nylon/CPP film were similar to the film without WPI coating. Taken together, our results indicate that the protein-based coating films showing high-oxygen and high-water barrier properties can be manufactured using industrial facilities and could replace commercial multilayer films based on synthetic materials. PRACTICAL APPLICATION: Oxygen barrier property is an important feature in food packaging materials. Therefore, protein-coated high-oxygen barrier multilayer films were manufactured at a pilot scale to verify the possibility of their mass production. Specifically, high-oxygen and high-moisture barrier coating was produced by pea and whey proteins. Finally, the protein-based multilayer films made by an industrial facility were confirmed to be able to replace current commercial films containing synthetic barrier materials.

Ascorbic Acid-Based Oxygen Scavenger in Active Food Packaging System for Raw Meatloaf.

A nonferrous oxygen scavenger (NFOS) comprising activated carbon and sodium l-ascorbate was developed to enhance the preservative efficacy of raw meatloaves. To determine the optimum formulation of activated carbon and sodium l-ascorbate, NFOSs with varying ratios of components (1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, and 1:2, w/w) were prepared and their oxygen-scavenging volumes were measured over 4 d at 25 °C. Assays of oxygen-scavenging capacities indicated that the optimum NFOS formulation of activated carbon and sodium l-ascorbate was achieved at a ratio of 1:1.6 (w/w). Finally, the optimal NFOS sachet was applied to packaging of raw meatloaves and its oxygen-scavenging capacity was periodically analyzed. Moreover, microbiological changes (including total aerobic bacteria, lactic acid bacteria, and yeasts and molds) and an effect on lipid oxidation during the storage were examined at 4 °C for 4 d. The meatloaves packaged with NFOS sachet had lower thiobarbituric acid reactive substances and microbiological changes than control meatloaves, indicating the practical utility in the food packaging industry. PRACTICAL APPLICATION: Oxygen-scavenging sachets containing iron powder have been generally used although those have several problems. Therefore, to solve them, an ascorbic acid-based oxygen scavenger composed of activated carbon and sodium l-ascorbate was newly developed. It did not only inhibit lipid oxidation but also reduce microbial growth in meatloaves. It could be used as a promising packaging material to protect meat products from lipid oxidation and microbial contamination.