Advanced Materials Research Vol. 380

Abstract: An analytical method was developed to measure the migration of residual solvent from composite packaging film to food medium. By using gas chromatography / mass spectrometry, migration levels of toluene and ethyl acetate, the main residual solvents in composite packaging film were measured in food so that the migration characteristic of toluene and ethyl acetate in different simulations was studied. The results show that all the linear correlation coefficient were greater than 0.999 and the detection limit was lower than 0.005μg/ml. This method is of high sensitivity, accurate analysis of quantity and can meet the practical demands.

Abstract: With the improvement of living standards, the requirement of food quality, nutrition, and freshness have been higher and higher. As the characteristics of highly effective, non-toxic, low cost, easy operation and significantly preservation effect, chitosan has been used widely as a new type of natural antistaling agent. Chitosan fresh-keeping mechanism and application in food preservatives are discussed in this study. From the three aspects of chitosan coating, composite coating, and chitosan modification, this work provides an overview of some researches about chitosan fresh food technology in abroad and domestic. And further development is discussed: the effect of the sole use of chitosan is not very good. Composite coating of chitosan will be more and more attractive with the merits about effectively preventing moisture loss, reducing weightlessness rate and so on. Storage stability about liquid chitosan can be solved by modified chitosan, which will also have a more attractive effect. This paper has theoretical significance to develop chitosan applications in food fresh-keeping technology.

Abstract: This article describes different types of antimicrobial agents added into plastic, such as inorganic antibacterial agents, organic antibacterial agents and natural antimicrobials. And summarize new environmental protection antibacterial technology in the application of plastic packaging, from the aspects about molecular self-assembly technology, nanotechnology, natural antimicrobials and composite antimicrobials technique. Finally, this article briefly introduces the development prospect of antibacterial plastic packaging. We developed plastic products prepared by different antibacterial such as the molecular assembly antibacterial, nanoscale antibacterial agent, natural antimicrobials and composite antimicrobials, at the same time considering its mould proof and insect-resistant.

Abstract: Currently, single factor experiments are used in most of the traditional materials preparation without considering the interaction of the various process factors. Plackett-Burman (PB) design and central composite design (CCD) were applied to optimize eight factors for the silica (SiO_x) films deposited by RF magnetron sputtering. The results show that the three key factors, RF power density, work pressure and target sample distance are significant to prepare (SiO_x) films using PB design, in which the deposition rate is regarded as the target response. By CCD design and response surface analysis, the optimal deposition conditions are 3.72W/cm², work pressure 0.7Pa, target substrate distance 6cm, and deposition rate is 3.5nm/min.

Abstract: Polyvinyl alcohol (PVA) is a kind of biodegradable film material, and its degradation process is mainly done through PVA-degrading enzymes, but the film biodegradation cycle is longer, so it needs other polymers with favorable biodegradability to improve the degradation rate in the nature environment. In this paper the biodegradation mechanism of PVA films and the influence of structural feature on biodegradability were described. The research development of starch-based biodegradable PVA films by blending starch to reduce the biodegradation cycle was emphasized and the biodegradable films modified by chitosan to improve film properties was briefly described.

Abstract: The SiO_x thin films for food packaging were deposited by RF magnetron sputtering physical vapor technology on the substrates of 20μm polyethylene terephthalate (PET) by using a pure SiO₂ target. The molecular structure of thin film surface composition were detected and analyzed by Fourier transform infrared spectroscopy (FTIR); and the barrier properties of the films were examined by MOCON water vapor permeability testing instrument, also，the relationship maps between permeability and process parameters were drew and the process parameters were optimized; The mechanical properties of thin films were tested by electronic tensile testing machine, and the curves of the relationship between the mechanical properties and process parameters depicted. The SiOx/PET thin films of the lowest water vapor permeability were prepared under the pressure of 7.5×10^-3 Pa, the sputtering pressure of 0.23 Pa, the deposition time of 30min and the sputtering power of 1500W. The yield strength increased 4 times and elastic modulus increased 3 times when the water vapor permeability of the SiO_x/PET thin films rose about 10 times of the blank.

Abstract: Poly-3-hydroxybutyrate (PHB) has already become the hot spot research in food packaging area because of its excellent biocompatibility and biodegradability as a kind of new plastic substitute. The Methane-Utilizing mixed Culture HD6T is able to synthesize PHB with methane in an open system. In order to obtain microbial species of high production PHB low carbon cost in an open system, the ability of accumulating PHB was studied. Through inspecting the culture medium component, the results indicated that: Cultivation was performed in two stages: a continuous growth phase and a PHB accumulation phase under different concentration of essential nutrient (ammonium, nitrate, magnesium or copper) in batch culture. The highest density of cultivated cells was 0.72g dry wtL-1, and PHB content of biomass was as high as 31%.A bacterial mixed culture being used for the biotechnological production of PHB is an important step towards the development of a viable large-scale process for the production of PHB using cheap substrates like methane.content of biomass was as high as 31%.A bacterial mixed culture being used for the biotechnological production of PHB is an important step towards the development of a viable large-scale process for the production of PHB using cheap substrates like methane.

Abstract: Physical and chemical quality including vitamin C, TSS, browning index and pH and sensory quality indexes including appearance, color and odor of orange juice were studied during the storage under ambient temperature, take oxygen scavenging films (OSF) as the packaging materials, and high barrier packaging and normal food packaging as the control group. Experimental results showed vitamin C, total soluble solid and pH value of orange juice packed in oxygen scavenging packaging were higher than that in control group, browning index was significantly lower than that in control group, and the sensory quality evaluation was better than that in control group after storage for 5 weeks. This indicated that oxygen scavenging packaging can remove oxygen in package headspace, prevent oxygen from penetrating into package from outside, and form a lower oxygen concentration environment in package. And it can obviously retard the degradation of vitamin C and sugar, delay the browning, delay the decline of orange juice quality, and prolong the shelf life of orange juice.

Abstract: Using starch as the stabilizing agent, glucose as reducing agent, nano-size silver particles colloidal sols have been synthesized via ultrasonic irritation in aqueous solution. The nanoparticles size distribution in typical colloidal sol is from 15 to 45 nm. The silver nanoparticles-PE blend film with silver content of 86 ppm was prepared by mixing silver nanoparticles colloids sol with the PE master batch and then by film blowing. The silver nanoparticles-PE blend film and the prepared nano-silver sol show effective antibacteial activity to the Staphylococcus aureus and Escherichia coli. The pear fruit package application of the silver nanoparticles-PE blend film has demonstrated that the film has effective fresh preservation ability for the packaged fruits and vegetables.

Abstract: The blow-extruded tube-like regeneration cellulose films in different blow-up ratios were prepared by NMMO technology. It was studied the effect of different blow-up ratio on the mechanical and obstructing properties as well as the morphology cross-section of cellulose blown films. It is found that the tensile strength and obstructing performance except elongation at break of films are improved when blow-up ratios increasing. The tensile strength of 1.3, 1.7 blow-up ratio cellulose blown films in longitudinal and transverse is 36.4MPa and 39.9MPa, 13.8MPa and 29.04MPa, respectively. The elongation at a break of 1.3, 1.7 blow-up ratio cellulose blown films in longitudinal and transverse is 105.4% and 72.01%, 42.4% and 25.79%, respectively. The OPF and WVP value of 1.3, 1.7 blow-up ratio cellulose blown films are 13.34×10^-15cm³•cm/(cm²•s•Pa) and 1.36×10^-15cm³•cm/(cm²•s•Pa) , 4.18×10^-13g•cm/cm²•s•Pa and 1.87×10^-13g•cm/cm²•s•Pa, respectively. The SEM picture of cross-section of 1.7 blow-up ratio films displays denser and lower porosity than 1.3 blow-up ratio films. According to the results of study, the films prepared by using NMMO technology would be used in food packaging or other fields as a kind of green packaging material.