Food Technology
Parisa Dianat; Mahdi Haji Abdolrasouli; Morteza Yousefzadi
Abstract
Introduction Consumer demand for healthy food free of chemical preservatives and environmental concerns with plastic packaging environments are analyzed, which can be replaced by aquatic environments that can be contaminated, for the development of bio-based packaging materials. Natural polymers ...
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Introduction Consumer demand for healthy food free of chemical preservatives and environmental concerns with plastic packaging environments are analyzed, which can be replaced by aquatic environments that can be contaminated, for the development of bio-based packaging materials. Natural polymers have the ability to be biodegradable due to the presence of oxygen or nitrogen atoms in their main polymer chain compared to the dominant carbon-carbon bonds in fossil-based polymers. Among the various biopolymers used to prepare multilayer films, polysaccharides are considered as the main components of the film due to their abundance and non-toxicity. These films generally have good mechanical strength, moderate physical properties, and most importantly, are edible and easily degradable. However, they are very brittle and hydrophilic, and these properties are undesirable in food packaging applications. Among polysaccharides, agar, commercially extracted from seaweed, is one of the most common and widely studied base materials. Agar is insoluble in cold water, but soluble in water at 90-100°C. When making an agar film, the solution and casting surface must be kept above the agarose gel setting temperature to avoid premature gelation. Compared to other biopolymers, agar is more stable at low pH and high temperature. This thermoplastic and biocompatible polysaccharide creates films with high mechanical strength, transparency and moderate barrier properties to carbon dioxide and oxygen, and most importantly, it is edible and easily biodegradable. Mixing agar with other polymers such as polyvinyl alcohol (PVA) and polyethylene improves the mechanical, thermal and biodegradability properties of bio composites. The main goal of this study is to make biofilms for use in packaging industries with agar polymer extracted from macroalgae species Acanthophora sp. Agar was extracted by sodium hydroxide/heating method and the film was prepared in combination with industrial polymer PVA and glycerol. Materials and Methods To make biofilms based on agar polymer, firstly, optimization of agar polymer extraction from macroalgae species Acanthophora sp. was done by sodium hydroxide/heating method, and in the next step, total phenolic compounds and the amount of soluble protein in extracted agar were measured. In the next step, glycerol with 30% by weight was used as a softener and PVA polymer with a weight ratio of 25% to the dry weight of agar powder was used to make bio composite by solvent casting method, in order to strengthen the mechanical and physical properties of bio composites. Characterization tests of the prepared composites included: XRD, FTIR and Tensile test. Laboratory tests include; The percentage of solubility in water and degree of swelling for all bio-composites were evaluated to determine the optimal physical properties of bio-films. Results and Discussion:he results showed that; 15% extraction efficiency was obtained for sodium hydroxide/heating pretreatment method. The results of measuring the amount of total phenolic compounds in agar solution extracted by sodium hydroxide/heating method showed that the number of phenolic compounds in agar solution was 0.077 ± 0.004 in terms of mg of gallic acid/g of agar. The results of measuring the amount of protein in extracted agar determined by Bradford method showed that the agar solution contains 0.040 ± 0.019 mg/ml of protein. A decrease in the swelling rate and an increase in the water solubility of the agar bio composite occurred with the addition of glycerol and PVA polymer. The results of the tensile test showed that the addition of glycerol, a small hydrophilic molecule, to the agar bio composite leads to a decrease in the elastic modulus and an increase in flexibility. Adding PVA to agar/glycerol biofilm caused a decrease in the amount of elastic modulus and percentage of flexibility, which is the main factor of this phenomenon, the low values of elastic modulus and flexibility of PVA. Finally, the results confirm the use of these coatings for packing fruits and vegetables in tropical regions by increasing their shelf life for at least 5 days at 25°C.
Hesam Omrani Fard; Mohammad Hossein Abaspour fard; Mehdi Khojastehpour; Ali Dashti
Abstract
Introduction: One of the new methods for improving the mechanical properties of bioplastics is the production of blending based bioplastics. Recent studies show that proteins, in combination with starch, form a strong network of hydrogen bonds and intermolecular interactions that resulted stable 3-D ...
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Introduction: One of the new methods for improving the mechanical properties of bioplastics is the production of blending based bioplastics. Recent studies show that proteins, in combination with starch, form a strong network of hydrogen bonds and intermolecular interactions that resulted stable 3-D materials. The big problem in the commercialization of blending based bioplastics is the lack of industrial machinery for the continuous production of bioplastics with the direct use of biopolymers. Industrial production of bioplastics is accompanied by increasing heat along with applying the pressure. It is necessary to know the kinetics of thermal degradation of bioplastics to study thermal behavior at different temperatures in order to design bioplastics processing devices and molding machines, software modeling of processes, mass and energy equilibrium, and optimizing energy consumption in the production process along with improving the thermal properties of the bioplastics.
Materials and methods: In this study, the dynamics thermal decomposition of bioplastics prepared from a mixture of potato whole flour-gelatin and glycerol with a control sample consisting of potato whole flour and glycerol was investigated and compared. The gelatin was extracted from chicken feet using chemical methods. In this research, two isoconversional models including Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models were considered. Using each of these models, thermal decomposition kinetic parameters were calculated for bioplastic samples.
Result and discussion: The results showed that the maximum activation energy of the mixed bioplastics determined 162 and 150 kJ/mol by FWO method at the conversion ratio of 0.9 and 0.5 respectively, while it was 217 kJ/mol at the ratio of 0.6 for control bioplastics. The amounts of kinetic parameters calculated in this study, were able to determine the thermal behavior at different temperatures and the thermal decomposition process. Also, it can help to redesign and optimize the methods of molding and shaping of potato-gelatin based bioplastics by the use of existing machinery in the industry.
