Investigating the physicochemical, antimicrobial and antioxidant properties of chitosan film containing zero-valent iron nanoparticles and oregano essence.

The problems caused by the pollution of the environment by petroleum polymers in recent years have caused researchers to think of replacing petroleum polymers with biodegradable and natural polymers. The aim of this research was to produce composite film of chitosan (Chit)/zero-valent iron (Fe) nanoparticles/oregano essence (Ess) (Chit/Fe/Ess). Central composite design was used to study physical, morphological, antioxidant and antimicrobial properties of films. The results showed that with the increase of iron nanoparticles and oregano essence, the thickness of the film increased. The moisture, solubility and water vapor permeability of the film decreased with the increase of iron nanoparticles and oregano essence. The results of the mechanical test showed that with the increase of iron nanoparticles and oregano essence, the tensile strength and elongation at break point decreased. Iron nanoparticles and oregano essence increased significantly the antioxidant activity of the film. The results of the antimicrobial activity of the prepared films show that the addition of iron nanoparticles and oregano essence enhanced the antimicrobial activity of the film against Escherichia coli and Staphylococcus aureus. X-ray diffraction analysis showed that iron nanoparticles were physically combined with chitosan polymer. Fourier transform infrared (FTIR) results confirmed the physical presence of iron nanoparticles and oregano essence in the polymer matrix. The results of scanning electron microscopy (SEM) showed that the surface of nanocomposite films is more heterogeneous than chitosan. Iron nanoparticles and oregano essence could delay the thermal decomposition of chitosan and increase the thermal stability of chitosan film.

Application of cellulose plate modified with encapsulated Cinnamomum zelanicum essential oil in active packaging of walnut kernel.

In this study, Cinnamomum zelanicum essential oil was encapsulated with ß-cyclodextrin and sodium caseinate (EO/BCD/Ca) and nanoemulsion was optained. In order to encapsulation of essential oil, different formulations of nanoemulsions containing essential oil were produced by ultrasound method and the effect of different polymers on the particle size and turbidity of the nanoemulsion was investigated. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) techniques were used to study the structure and morphology of the produced nanoemulsions. Cinnamomum zelanicum essential oil encapsulated with ß-cyclodextrin and sodium caseinate was used to modify porous cellulose plates (Cel/EO/BCD/Ca). Cellulose/encapsulated essential oil plates were used to package the walnut kernel to control oxidative changes during storage. The effect of packaging type (under vacuum and ordinal), plate type and storage time on quality control of walnut kernel and oil extracted from walnut kernel was investigated. The results showed that the particle size of essential oil, essential oil/ß-cyclodextrin and essential oil/ß-cyclodextrin/sodium caseinate were in the range of 84-85, 713-713 and 237-234 (nm), respectively. The encapsulation efficiency of both formulations was above 70%. Zeta potential was negative for essential oil/ß-cyclodextrin/sodium caseinate samples and free essential oil samples. The effect of different polymers on the turbidity of emulsions was significant. The results of sensory evaluation of walnut kernel showed that the use of encapsulated essential oil compared to free essential oil caused the protection of color, taste and other quality characteristics during storage. Also, the essential oil encapsulated with ß-cyclodextrin/sodium caseinate had a greater effect on quality control of walnut kernel and its oil than the essential oil encapsulated with ß-cyclodextrin. Also, the quality characteristics of walnut kernels and walnut kernel oil packed in vacuum conditions were better than walnut kernels and walnut kernel oil packed in non-vacuum conditions during storage.

Nanocomposite base on carboxymethylcellulose hydrogel: Simultaneous absorbent of ethylene and humidity to increase the shelf life of banana fruit.

The main purpose of this study was to increase shelf life of banana using active hydrogel. For this purpose, carboxymethylcellulose/nanofiber cellulose/potassium permanganate (CMC/NFC/KMnO4) hydrogel film was prepared. The morphology and physicochemical properties of CMC hydrogels was investigated. The prepared films were used as humidity/ethylene absorbent in banana packaging for 30 days at 0 and 25 °C. The physical, mechanical and sensory properties of bananas were studied during storage. SEM images confirmed the presence of nanofibers in the hydrogel structure. NFC and KMnO4 increased the tensile strength of the film and decreased its elongation. On the 15th day of storage, bananas packaged with optimal active hydrogel (CMC/NFC/KMnO4) at 25 °C had a flavor of 3 and a general acceptance of 3.5, while control bananas had a flavor of 0.5 and a general acceptance of less than 1. On the 30th day of storage, bananas packaged with optimal active hydrogel at 25 °C had a toughness of 4 (N·s) and a firmness of 20 (N), while control bananas had a toughness of about 1 (N·s) and a firmness of about 8 (N). On the 30th day of storage, the humidity inside the package of bananas packed with the optimum active hydrogel at 25 °C was 59.5%, while the humidity in the control packages was 85%, indicating that the hydrogel was able to absorb the moisture inside the package. Totally it can be said that CMC/NFC/KmnO4 hydrogel can increase shelf life of a banana by simultaneously controlling ethylene and humidity in food packaging.

Use of bacterial cellulose film modified by polypyrrole/TiO2-Ag nanocomposite for detecting and measuring the growth of pathogenic bacteria.

The aim of this study was to use of bacterial cellulose/polypyrrole/TiO2-Ag (BC/PPy/TiO2-Ag) nanocomposite film to detect and measure the growth of 5 pathogenic bacteria. For this purpose, at first, 13 BC/PPy/TiO2-Ag films were fabricated, then bacterial suspensions were prepared according to McFarland standard. The results showed that by increasing the bacterial concentration, the electrical resistance of sensors was decreased and there was a relation between bacterial concentration and bacterial type with electrical resistance change of sensors. The obtained data showed that the sensitivity of the sensors was increased with increasing the concentration of polypyrrole and TiO2-Ag. FT-IR and SEM tests were performed to investigate the interaction between nanoparticles and determine the size of nanoparticles. The BC/PPy/TiO2-Ag biosensors are portable and the response time of these sensors is very short for target analysis. Therefore, these sensors have the potential to improve biological safety as diagnostic tools.

Intelligent and active packaging of chicken thigh meat by conducting nano structure cellulose-polypyrrole-ZnO film.

In this work intelligent and active films based on bacterial cellulose (BC) modified by polypyrrole-Zinc oxide nanocomposite (BC-PPy-ZnO) were provided. Chemical polymerization in the atmospheric condition was used for providing BC-PPy-ZnO film. Scanning electron microscopy (SEM) was used for studying BC-PPy-ZnO film morphology. The nanosized PPy-ZnO (50-150 nm) composites covered the BC surface. The BC-PPy-ZnO film was used for packaging of chicken thigh. The effects of storage time and storage temperature on the chicken thigh characteristics were studied based on a central composite design (CCD). The effects of BC-PPy-ZnO film on the chicken thigh characteristics, including pH, microbial property (Mesophilic and psychrophilic bacteria), color property, antioxidant and rheological properties were studied. The results showed that the BC-PPy-ZnO film could decrease the growth of microbial load in chicken thigh and could control the pH increasing. The BC-PPy-ZnO film could increase the shelf life and stabilize rheological properties of chicken thigh by increasing of antioxidant and antimicrobial activity as active packaging. According to the results there are good relations between film electrical resistance change and storage time-storage/temperature that this could help us to estimate the storage time and storage temperature of chicken thigh as intelligent packaging.

Design of a portable gas chromatography with a conducting polymer nanocomposite detector device and a method to analyze a gas mixture.

A portable chromatography device and a method were developed to analyze a gas mixture. The device comprises a chromatographic column for separating components of a sample of the gas mixture. It has an air pump coupled to the inlet of a chromatographic column for pumping air and an injector coupled to the inlet of chromatographic column for feeding the sample using the air as a carrier gas. A detector is arranged downstream from and coupled to the outlet of the chromatographic column. The detector is a nanostructure semiconductive microfiber. The device further comprises an evaluation unit arranged and configured to evaluate each detected component to determine the concentration. The designed portable system was used for simultaneous detection of amines. The possibility of applying dispersive liquid-liquid microextraction for the determination of analytes in trace levels is demonstrated. The reproducibility of this method is acceptable, and good standard deviations were obtained. The relative standard deviation value is less than 6% for all analytes. Finally, the method was successfully applied to the extraction and determination of analytes in water samples.

Rapid determination of pyridine derivatives by dispersive liquid-liquid microextraction coupled with gas chromatography/gas sensor based on nanostructured conducting polypyrrole.

Polypyrrole (PPy) gas sensor has been prepared by polymerization of pyrrole on surfaces of commercial polymer fibers in the presence of an oxidizing agent. The sensing behavior of PPy gas sensor was investigated in the presence of pyridine derivatives. The resistive responses of the PPy gas sensor to pyridine derivatives were in the order of quinoline>pyridine>4-methyl pyridine and 2-methyl pyridine. The PPy gas sensor was used as gas chromatography (GC) detector and exhibited linear responses to pyridine derivatives in the ranges 40-4,000 ng. Dispersive liquid-liquid microextraction (DLLME) combined with GC/PPy gas sensor has been developed for simultaneous determination of pyridine derivatives and quinoline. The purposed method was used for determination of pyridine derivatives from cigarette smoke. The GC runs were completed in 4 min. The reproducibility of this method is suitable and good standard deviations were obtained. RSD value is less than 10% for all analytes.