Effect of film constituents and different processing conditions on the properties of starch based thermoplastic films

Preparation and properties of thermoplastic starch under the synergism of ultrasonic and elongational rheology

Thermoplastic starch, as an eco-friendly alternative to petroleum-based plastics, possesses numerous advantages, including cost-effectiveness, complete biodegradability, and renewable sourcing. Nevertheless, the plasticizer dispersion and starch plasticization efficiency are poor via the processing method dominate by shear deformation. Thus, the aim of this study is proposing a new approach combining ultrasonic treatment and elongational rheology to prepare thermoplastic starch and evaluate its properties. This innovative approach facilitated the production of thermoplastic starch with glycerol as the plasticizer at varying rotor speeds. Furthermore, this study was carried out by using a self-developed ultrasonic-assisted vane mixer (UVM) based on elongational flow. The samples were analyzed using FTIR, WAXD, polarized optical microscope, dynamic rheometer, universal testing machine and thermogravimetric analysis. FTIR and dynamic rheological analysis showed that elongational rheology and ultrasonics stimulate hydrogen bond formation between starch and glycerol, elevating starch thermoplasticity. Tensile tests and thermogravimetric analysis highlighted that high-intensity elongational field improved the mechanical properties and thermal stability of the thermoplastic starch. Additionally, the incorporation of ultrasonic treatment yielded further improvements, yielding remarkable tensile strength (6.09 MPa) and elongation at break (139.3 %). This synergistic interplay between ultrasonics and elongational rheology holds immense potential for advancing thermoplastic starch manufacturing.

Fabrication of double layer nanoparticle infused starch-based thermoplastic food packaging system for meat preservation

The current work aims to produce nanoparticle-infused starch-based bioactive thermoplastic packaging films. The FeO and ZnO nanoparticles were examined to be potential active ingredients for the production of nanoparticle-infused bioactive thermoplastic packaging films. The bio-thermoplastic films infused with FeO and ZnO nanoparticles showed high oxygen scavenging and antimicrobial activity, respectively. Consecutively, both films were combined to form a double-layer Nano-Biothermoplastic packaging system for food preservation. The distribution and diffusion of nanoparticles in starch-based films were examined to be influenced by the amorphous character of starch and the swelling index of the film, respectively. The amorphous property of starch molecules showed a masking effect on the crystalline characteristics of nanoparticles in Nano-Biothermoplastic films. The diffusion of nanoparticles from the Nano-Biothermoplastic packaging system was found to influence the microbial, chemical, and color characteristics of mutton and chicken meat stored at 4 °C.

Facile fabrication and characterization of novel antimicrobial and antioxidant poly (3-hydroxybutyrate)/essential oil composites for potential use in active food packaging applications

Poly (3-hydroxybutyrate) (PHB) is a bio-based biodegradable biopolymer with excellent potential to substitute petrochemical-based food packaging materials. Nevertheless, low elongation at break is one of the limiting factors for its commercial-scale application in the packaging field. Microbial contamination and lipid oxidation are the two main causes of food spoilage and pose huge challenges to the food industry. In this regard, essential oils are bioactive compounds that, in addition to providing antimicrobial and antioxidant properties, can improve the flexibility of biopolymers. Therefore, to overcome the aforementioned challenges, the current study aimed to fabricate novel PHB composite films loaded with essential oils, viz. grapeseed oil (GS), bergamot oil (BG), and ginger oil (GG), by a simple solution casting technique. To evaluate the potential of prepared PHB/essential oil composites for food packaging applications, extensive characterizations of their mechanical, structural, barrier, optical, and thermal properties were carried out. Interestingly, PHB/essential oil composites demonstrated good UV-blocking properties without affecting its transparency. PHB films loaded with 5 wt% GS showed a 30-fold enhancement in flexibility compared to pristine PHB. The DPPH radical scavenging activities of PHB/5GS, PHB/5BG, and PHB/5GG films are 53.17 ± 4.76, 50.70 ± 3.92 and 86.38 ± 2.73 %, respectively. The antibacterial activities of PHB/5GS, PHB/5BG, and PHB/5GG films against the model bacterium E. coli are 19.72 ± 0.97, 12.62 ± 2.23 and 29.98 ± 2.15 %, respectively, whereas, for S. aureus, the values are 61.56 ± 3.39, 30.28 ± 0.92 and 70.97 ± 0.26 %, respectively. Moreover, the overall migration values of the composite films in simulants representing hydrophilic, acidic, and lipophilic foods did not exceed the prescribed overall migration limit (10 mg/dm2).

Irradiation effects on characteristics and ethanol fermentation of maize starch

Maize starch was irradiated by a Co60 irradiator with different doses. The morphology and physicochemical properties of native and irradiated starches were investigated. Scanning electron microscopy showed that the shape and size of starch granules did not change after irradiation. However, the irradiated starch granules were easily destroyed by dissolution. Irradiation also caused the change of starch color, the decrease in the pH value, light transmittance, stability index, degree of polymerization, total sugar content, and the increase in the swelling index and the reducing sugar content. In this study, irradiated maize starch was also used as material for ethanol fermentation to investigate its potential as a pretreatment method. Results showed that the ethanol yield of cooked and raw starch fermentation using irradiated starch increased by 20.41 % and 5.18 %, respectively, and the ethanol concentration increased by 3 % and 2 %. This finding indicated that irradiation effectively improved the utilization rate of maize starch, making it an effective pretreatment method for ethanol fermentation.

Ultrasonication effects on physicochemical properties of biopolymer-based films: A comprehensive review

Biopolymeric films manufactured from materials such as starch, cellulose, protein, chitosan, gelatin, and polyvinyl alcohol are widely applied due to their complete biodegradability. While biopolymer-based films exhibit good gas barriers and optical properties when used in packaging, poor moisture resistance and mechanical properties limit their further application. Ultrasonication is a promising, effective technology for resolving these shortcomings, with its high efficiency, environmentally friendly nature, and safety. This review briefly introduces basic ultrasonication principles and their main effects on mechanical properties, transparency, color, microstructure, water vapor permeability, and oxygen resistance. We also describe the thermal performance of biopolymeric films. While ultrasonication has many positive effects on the physicochemical properties of biopolymeric films, many factors influence their behavior during film preparation, including power density, amplitude, treatment time, frequency, and the inherent properties of the source materials. This review focuses on biopolymers as film-forming materials and comprehensively discusses the promotional effects of ultrasonication on their physicochemical properties.

Rheological, Thermal, Superficial, and Morphological Properties of Thermoplastic Achira Starch Modified with Lactic Acid and Oleic Acid

The modification of achira starch a thermoplastic biopolymer is shown. Glycerol and sorbitol, common plasticizers, were used in the molten state with organic acids such as oleic acid and lactic acid obtaining thermodynamically more stable products. The proportion of starch:plasticizer was 70:30, and the acid agent was added in portions from 3%, 6%, and 9% by weight. These mixtures were obtained in a torque rheometer for 10 min at 130 °C. The lactic acid managed to efficiently promote the gelatinization process by increasing the available polar sites towards the surface of the material; as a result, there were lower values in the contact angle, these results were corroborated with the analysis performed by differential scanning calorimetry and X-ray diffraction. The results derived from oscillatory rheological analysis had a viscous behavior in the thermoplastic starch samples and with the presence of acids; this behavior favors the transitions from viscous to elastic. The mixture of sorbitol or glycerol with lactic acid promoted lower values of the loss module, the storage module, and the complex viscosity, which means lower residual energy in the transition of the viscous state to the elastic state; this allows the compounds to be scaled to conventional polymer transformation processes.

Mechanical properties and antibacterial activities of novel starch-based composite films incorporated with salicylic acid

To control food contamination and meet the growing demand for high quality food, a novel and excellent starch composite film as packing material with optimized physical, mechanical properties and antimicrobial activity was produced in this paper. Starch-based composite films incorporated with salicylic acid (SA) and waxy maize starch nanoparticles/κ-carrageenan (WMSNs/KC) were used to achieve antimicrobial activity and improve the mechanical properties. WMSNs were fabricated through enzymolysis and recrystallisation method, followed by individually adding KC to form WMSNs/KC by self-assembly, and used as a nanofiller and stabilizer to be incorporated into hydroxypropyl tapioca starch-based films at a concentration of 0-9%. Characterization of macromorphology and scanning electron microscope indicated the starch composite films with WMSNs/KC were smooth, uniform, and transparent. X-ray diffraction pattern and Thermogravimetric analysis also showed strong interactions such as hydrogen bond formation among films, WMSNs/KC and SA. Compared with the pure starch-based films, the composite films reinforced by the addition of WMSNs/KC significantly increased the tensile strength, water vapor barrier and thermal stability, while the transparency and elongation at break decreased slightly. Moreover, the starch composite films showed excellent antimicrobial activity for three typical undesired microorganisms in foods, Escherichia coli, Staphylococcus aureus, and Bacillus subtilis.