Effect of drying temperature on structural and thermomechanical properties of konjac glucomannan-zein blend films

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.

Investigation of physicochemical and biological properties of bacterial cellulose & zein-reinforced edible nanocomposites based on flaxseed mucilage containing Origanum vulgare L. essential oil

In the present study, the effect of zein and different amounts of bacterial cellulose (BC; 1, 2 and 3 wt%) on the physical, mechanical and barrier properties of flaxseed mucilage/carboxymethyl cellulose (FM/CMC) composite was investigated. The appearance of the absorption band at 1320cm-1 in the ATR-FTIR spectra of nanocomposites indicated the successful introduction of zein into their structure. The characteristic peak at 2θ of 9° belonging to zein disappeared in XRD patterns of the prepared composites suggesting the successful coating of zein via hydrogen bonding interactions. SEM images proved the formation of semi-spherical zein microparticles in the FM/CMC matrix. TGA plots ascertained the addition of zein and nanocellulose caused a significant increase in the thermal stability of FM/CMC film, although zein showed a greater effect. The presence of zein and nanocellulose increased the mechanical strength of nanocomposites. The WVP of FM/CMC decreased after the incorporation of zein and nanocellulose, which created a tortuous path for the diffusion of water molecules. The zein particles exhibited a greater influence on improving the mechanical and barrier properties compared to nanocellulose. FM/CMC-Z film exhibited the highest mechanical strength (49.07 ± 5.89 MPa) and the lowest WVP (1.179 ± 0.076). The composites containing oregano essential oil (EO) showed higher than 60 % antibacterial properties. The bactericidal efficiency of FM/CMC/Z-EO and FM/CMC/Z-EO/BC1 nanocomposites decreased about 10% compared to FM/CMC/EO and FM/CMC-Z/BC1. This evidenced the successful encapsulation of EO molecules in zein particles. According to the in vitro release study, entrapment of EO into zein particles could delay the release and provide the extended antimicrobial effect.

Recent progress in using zein nanoparticles-loaded nanocomposites for food packaging applications

Biopolymers are important due to their exceptional functional and barrier properties and also their non-toxicity and eco-friendly nature for various food, biomedical, and pharmaceutical applications. However, biopolymers usually need reinforcement strategies to address their poor mechanical, thermal, and physical properties as well as processability aspects. Several natural nanoparticles have been proposed as reinforcing agents for biopolymeric food packaging materials. Among them, zein nanoparticles (ZNPs) have attracted a lot of interest, being an environmentally friendly material. The purpose of the present review paper is to provide a comprehensive overview of the ZNPs-loaded nanocomposites for food packaging applications, starting from the synthesis, characteristics and properties of ZNPs, to the physicochemical properties of the ZNPs-loaded nanocomposites, in terms of morphology, permeability, solubility, optical features, hydrophobic/hydrophilic behavior, structural characteristics, thermal features, and mechanical attributes. Finally, at the end of this review, some considerations about the safety issues and gastrointestinal fate of ZNPs, as well as the use of ZNPs-based nanocomposites as food packaging, are reported, taking into account that, despite the enormous benefits, nanotechnology also presents some risks associated to the use of nanometric materials.

Topography and physical properties of carboxymethyl cellulose films assembled with calcium and gelatin at different temperature and humidity

Effects of the environmental temperature and relative humidity of drying conditions on the surface ultrastructure of carboxymethyl cellulose (CMC) films were investigated by atomic force microscopy. The mechanical and water vapor barrier properties of the films were also evaluated. The results showed that CMC molecules self-assembled into a uniform network at the solution of 5% calcium chloride. And continuous structure was formed of composite mixture with the CMC/gelatin ratio in 1:1. The CMC/Gel film forming solution was respectively dried at 2-8 °C, 23 °C, 50 °C and 23 °C with ventilation to obtain films. The size and numbers of holes on the films surface were affected by the temperature and relative humidity. Correspondingly, the mechanical properties and water vapor permeability were altered with the films structure. Moreover, the surface structure of the composite films was changed by the infiltration and delivery of water vapor when films were stored at 2-8 °C and -20 °C for days.

Optimization of oil-in-water emulsion capacity and stability of octenyl succinic anhydride-modified porang glucomannan (Amorphophallus muelleri Blume)

Surfactants are used to reduce surface and interfacial tension to form emulsions. Polysaccharides such as Porang Glucomannan (PG) with high viscosity can be used as surfactants. This research aimed to optimize the concentration of sodium carbonate (Na₂CO₃) and octenyl succinic anhydride (OSA) in modifying PG using a microwave. The optimization process is carried out using response surface methodology (RSM) with a two-factor central composite design (CCD), namely concentration of Na₂CO₃ (0.17–5.834%) and OSA (2.17–7.83%). The result showed that the concentration of Na₂CO₃ and OSA strongly influences emulsion capacity and stability. The optimum conditions that resulted in the highest emulsion capacity and stability were obtained at concentrations of Na₂CO₃ and OSA which were 2.25% and 6.19%, respectively. Degree of Substitution (DS), FTIR analysis, contact angle, and increased viscosity confirmed that OSA substitution occurred in PG. The characteristics of OSA-modified porang glucomannan (PGOS) such as: emulsion capacity and stability, Degree of Substitution (DS), contact angle, and viscosity increased to 34.6% and 32.5%, 1.02%, 92^o, 5720 cP, respectively. FT-IR analysis confirmed the presence of OSA substitution at 1734 cm⁻¹. PGOS can be used as a surfactant or gelator in oleogel production.

Characterization and application of porous polylactic acid films prepared by nonsolvent-induced phase separation method

Nonsolvent-induced phase separation (NIPS) method was employed to prepare polylactic acid (PLA) films using N-methyl-2-pyrrolidone (NMP) as a nonsolvent. The morphology and structure of PLA films were characterized, and the application of the films in pork preservation was investigated. When 10 wt% NMP was added, film with uniform porous structures was obtained. The crystalline and Fourier-transform infrared spectra analyses indicated that the addition of NMP during the preparation of PLA films caused their crystalline properties to change, but had no effect on their composition. However, the 10 wt% NMP/PLA film had improved thermal stability, water vapor transmission and oxygen permeability. The results on the changes in pH, total volatile basic nitrogen content and total viable counts of pork during refrigerated storage indicated that the 10 wt% NMP/PLA film could more effectively extend the shelf life of pork than polyethylene film. This work demonstrates the potential of the porous PLA film in pork packaging.

Deacetylation enhances the properties of konjac glucomannan/agar composites

From a microstructural point of view, this work concerns how deacetylation improves the practical characteristics of deacetylated-konjac glucomannan/agar (DK/A) composite films. As disclosed by infrared spectroscopy and X-ray diffraction, the deacetylation of konjac glucomannan (KGM) enhanced the chain interactions in DK/A composites and suppressed the realignment of agar molecules into crystallites. The enhanced associations between acetyl-free regions of KGM and agar reduced the exposure of OH groups and thus increased the hydrophobicity of the composites. Besides, the partial removal of acetyl groups allowed shortened distances between chains; consequently, denser composite matrices emerged with lower water vapor permeability and higher tensile strength. Also, the KGM deacetylation increased the matrix flexibility and elongation at break for DK/A composites, associated with the hindered rearrangement of agar chains. Thus, altering the deacetylation degree of KGM may be an effective way to design KGM-based composites with improved hydrophobicity and mechanical performance.

Drying Behavior and Kinetics of Drying Process of Plant-Based Enteric Hard Capsules

The drying process is a significant step in the manufacturing process of enteric hard capsules, which affects the physical and chemical properties of the capsules. Thus, the drying characteristics of plant-based enteric hard capsules were investigated at a constant air velocity of 2 m/s in a bench scale hot-air dryer under a temperature range of 25 to 45 °C and relative humidity of 40 to 80%. Results indicate that the drying process of the capsules mainly occur in a falling-rate period, implying that moisture transfer in the capsules is governed by internal moisture diffusion rate. High temperature and low relative humidity reduce drying time but increase the drying rate of the capsules. Investigation results of the mechanical properties and storage stability of the capsules, however, reveal that a fast drying rate leads to plant-based enteric hard capsules of low quality. Scanning electron microscopy further demonstrates that more layered cracks appear in capsules produced under a faster drying rate. The Page model yielded the best fit for describing thin-layer drying of the capsules based on the coefficient of determination and reduced chi-square. Moreover, it was established that the effective moisture diffusivity of the capsules increases with an increase in drying temperature or reduction in relative humidity.

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

The impact of preparation conditions including heating temperature (from 60 °C to 90 °C) and drying temperatures (from 25 °C to 90 °C) on the properties of pure curdlan film and konjac glucomannan (KGM) and curdlan blend films were analyzed. Microstructure analysis indicated the KGM addition could significantly improve the relatively poor film-forming property of curdlan. FTIR and X-ray analysis showed that at high heating temperature 90 °C, molecular interaction might be enhanced in the films due to the stretched structure of curdlan and dissociation of curdlan bundles or triple-helix structure. This was supported by the changes in the mechanical property, surface hydrophobicity, moisture barrier, and moisture tolerance property. The impacts of drying temperature were some different for the curdlan film and KGM/curdlan blend film, and were explained from the molecular hydrophilicity-hydrophobicity, compactness of the films, curdlan conformation, and molecular interaction. This work guided biodegradable film production especially with curdlan added.

Changes in microstructure and rheological properties of konjac glucomannan/zein blend film-forming solution during drying

During film formation at 60 °C, the microstructure and rheological properties of konjac glucomannan (KGM) film-forming solution and KGM/zein blend film-forming solution were investigated. The drying process of film-forming solutions was divided into two stages according to the drying curves. Scanning electron microscopy showed that KGM chains in the blend solution aggregated into thicker chains and formed a molecular network with larger pores. Zein particles grew larger but were homogeneously distributed during drying as observed by confocal laser scanning microscopy. The addition of zein improved the thermal stability of the film-forming solution. As the drying proceeded (up to 8 h), KGM solution exhibited a typical concentrated solution behavior due to molecular entanglement; whereas the blend solution gradually formed a weak gel after 2 h. Complex viscosity data for the film-forming solutions were well-fitted by the power-law model. The information obtained from the study is important for understanding the film-forming mechanism.

Preparation and characterization of Konjac glucomannan and pullulan composite films for strawberry preservation

The present study aims to develop the new composite films by blending Konjac glucomannan (KGM) and pullulan with different ratios and concentrations. The structural, physical, barrier properties and morphology of the films were investigated and the practical use on strawberry preservation at 4 ± 1 °C, 85 %±5% relative humidity (RH) and 25 ± 1 °C, 55 %±5% RH was evaluated. Fourier transform infrared and scanning electron microscopy indicated the well-dispersion of film matrix was due to the good compatibility of the components. The mechanical and barrier properties of blend films were markedly enhanced although the light transmittance of which were decreased slightly. It was a further proof that 1% (w/v) KGM/pullulan (with the mass ratio of 2:1) blend film could decrease the weight loss significantly and maintain the titratable acidity, soluble solids and skin color on the strawberry preservation, thus improving the qualities of strawberries during storage time and offering a potential alternative to synthetic materials.