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.

Improving the microbial and physicochemical shelf life of yufka paste using Lactobacillus plantarum and calcium propionate.

Considering the importance of reducing the use of chemical preservatives in food and the increasing attention of consumers to consume food products with minimal additives, the main goal of this research was to study the effect of use of chemical (calcium propionate) and biological (Lactobacillus plantarum) preservatives on increasing shelf life of yufka paste considering its physicochemical and microbial characteristics. For this purpose, three samples of yufka paste were prepared by adding concentrations of 103, 105, and 107 cfu/mL of L. plantarum individually and three samples of paste were prepared by adding the same amount of bacteria in combination with 0.3% calcium propionate and these samples were compared with the control sample (without preservative) and the sample only containing 0.3% calcium propionate. The obtained results showed that different treatments and time had a significant effect on physicochemical properties including pH, moisture, and protein of yufka paste (p < .05). The results of the survival of L. plantarum showed that with increasing time, the survival rate of bacteria increased (p < .05). The pH of the samples showed that the L. plantarum has a significant effect on controlling the chemical quality of yufka during storage. The count of mold and yeast in the combined use of L. plantarum and 0.3% propionate was lower than the single use of propionate chemical preservative, which indicated the very good effect of the green preservative in controlling the moldy spoilage of yufka. Low concentrations of bacteria showed better antimold results than treatments containing bacteria and propionate in a combined form, propionate or control treatment.

Biodegradable film of carboxymethyl cellulose modified with red onion peel powder waste and boron nitride nanoparticles: Investigation of physicochemical properties and release of active substances.

The aim of this study was to modify carboxymethyl cellulose (CMC) films with onion peel extract (OPE) (0-2 g), onion peel powder (OPP) (0-2 g) and boron nitride nanoparticles (BN) (0-100 mg). 17 different CMC/OPE/OPP/BN films were provided and the physicochemical properties of films were studied. The release of active compounds of the composite film was investigated over time. The obtained results showed that OPE, OPP and BN increased the physical resistance and flexibility of the films. The percentage of moisture and solubility of the films decreased with the increase of OPE, OPP and BN. By adding BN, OPE and OPP, the structure of the film became stronger and the permeability to water vapor decreased. Addition of OPE and OPP significantly increased the antioxidant property of the film. In general, it can be said that the antioxidant substances of the onion peel are protected inside the film by preparing a CMC/OPE/OPP/BN film, which, in addition to stabilizing the antioxidants, can play an effective role in the controlled release of these antioxidant substances.

Biodegradable film based on barley sprout powder/pectin modified with quercetin and V2O5 nanoparticles: Investigation of physicochemical and structural properties.

In this study, barley sprout powder/pectin (BS/Pec) composite film was prepared. Quercetin (Qu) and vanadium oxide (V2O5) nanoparticles were used to improve the physicochemical and structural characteristics of the film. The structural, physicochemical and thermal properties of the films were investigated by various techniques such as TGA, SEM, XRD, FTIR, texture analysis, etc. The thickness and tensile strength of the films increased from 120 µm to 2.4 MPa to 220 µm and 6 MPa respectively with the increase of V2O5 nanoparticles and quercetin pigment. Nanoparticles of V2O5 and quercetin decreased the moisture content of the film from 50% to 20%. Quercetin had little effect in reducing water vapor permeability (WVP), but V2O5 nanoparticles had a significant effect in reducing WVP. The pure BS/Pec film had almost 30% antioxidant properties, which increased to 81% with the increase of quercetin. Adding quercetin and V2O5 nanoparticles to the film increased the antimicrobial properties of the film against both Escherichia coli and Staphylococcus aureus bacteria. The SEM images showed the inhomogeneous surface of the BS/Pec film caused by BS powder fibers. The interactions between the components of the films (electrostatic type) was confirmed by FTIR results. The degradation temperature of the overall structure of the film in the presence of nanoparticles indicated the positive effect of nanoparticles in increasing the thermal resistance of the film. Investigating the crystal structure of the film showed that the BS/Pec film has an amorphous/crystalline or semi-crystalline structure. Considering that the prepared film has good mechanical properties and as well as antioxidant/antimicrobial properties, this film as an active composite can be used in food products packaging.

Investigation of physicochemical and sensory characteristics of low calorie sponge cake made from flaxseed mucilage and flaxseed flour.

This research aimed to extract flaxseed mucilage (FM) and investigate its rheological properties (static and dynamic tests) compared with animal oil. In the next stage, the D-optimal design was applied to investigate the effect of FM (0-60%) and FF (0-30%) replacements with animal oil and cake flour, respectively on the sponge cake's physicochemical, textural, and sensory properties. According to the flow behavior test, FM showed Newtonian behavior while animal oil had pseudoplastic behavior. The results of the dynamic test showed with an increase in frequency, the loss modulus (G×´) and storage modulus (G') of samples increased. However, G' was higher than G×´ in all samples. By replacement of FM and FF, the moisture content, water activity, antioxidant capacity, crumb hardness, and cohesiveness of the samples increased while springiness, crust hardness, and specific volume decreased (P < 0.05). Lightness of samples with replacement of FF decreased (P < 0.05). The overall acceptance score was enhanced with an increase in FM substitution while it was decreased with the replacement of FF (P < 0.05). The amounts of fat, calories, and peroxide values were decreased in sponge cake with the incorporation of FF and FM (P < 0.05). In general, the substitution of FM (60%) and FF (28%) in the cake formulation as an optimized sample to make new products with low-calorie content is possible without significant decreases in product quality.

Development of a colorimetric sensor based on nanofiber cellulose film modified with ninhydrin to measure the formalin index of fruit juice.

In this research, a color sensor based on nanofiber cellulose film modified with ninhydrin was designed to measure amino acids and formalin index in fruit juice. For this purpose, three types of cellulose films with porosity of 5, 30 and 125 µm were used. These films were treated with standard solution of ninhydrin. The characteristics of modified films were investigated using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and X-ray Diffraction (XRD) tests. The color factors of the sensors (a and b) changed in the presence of amino acids and juice with different levels of formalin index. Therefore, the modified films with ninhydrin as a colorimetric sensor were calibrated using 7 types of amino acids and based on the formalin index of 4 types of juice. Then the sensors were used to measure the formalin index in 4 types of juice. The results showed that the sensors have relative selectivity towards methionine amino acid. The formalin index values calculated in the juices by the sensor were compared with the titration method as a reference method. All three types of sensors were able to detect formalin index. The results of the sensor performance verification showed that the sensors can measure formalin index in different juices with 95-98 % accuracy. These sensors showed fast sensitivity and selectivity to the amino acids in juice, also these sensors are safe and the measurement method is fast and simple.

Photochromic biodegradable film based on polyvinyl alcohol modified with silver chloride nanoparticles and spirulina; investigation of physicochemical, antimicrobial and optical properties.

In this study, biodegradable film was prepared from polyvinyl alcohol (PVA), Silver chloride (AgCl) and spirulina (Sp). Surface morphology, mechanical properties, antioxidant, antimicrobial, optical properties, etc. were investigated. The FTIR results confirmed the effect of AgCl and Sp on PVA structure. Sp increased the moisture content and solubility in water. The XRD results showed the semi-crystalline structure of PVA. AgCl nanoparticles activated the antibacterial property of the film against Escherichia coli and Staphylococcus aureus bacteria and Sp caused a strong increase in the antioxidant property of the film. Examining the light transmittance of films containing AgCl nanoparticles showed that the transmittance of films containing nanoparticles decreased with exposure to sunlight and ultraviolet light with increasing treatment time, which indicates the activation of the photochromic property of films containing AgCl in the presence of light. The results showed the suitable photochromic property of the PVA/AgCl films.

Biodegradable film based on cress seed mucilage, modified with lutein, maltodextrin and alumina nanoparticles: Physicochemical properties and lutein controlled release.

In this study, maltodextrin (MDex), lutein pigment (Lut) and alumina (Al) were used to modify biodegradable film based on cress seed mucilage (Muc/MDex/Lut/Al). Central composite design (CCD) was used to study the effects of MDex, Lut and Al on the physical and chemical properties of the mucilage based film. The physicochemical, mechanical, antimicrobial and structural properties of the films were studied by various techniques such as FTIR, SEM, and XRD and TGA. The release of lutein from the film was investigated at 25 °C for 15 days. The results showed that lutein, alumina and maltodextrin increased the film thickness and lutein decreased the solubility and moisture content of the film. Maltodextrin improved the mechanical properties of the film and lutein reduced the film's flexibility. Lutein greatly increased its antioxidant properties, but alumina slightly increased its antioxidant properties. Lutein, alumina and maltodextrin improved the antibacterial properties of the film. Muc/MDex/Lut/Al film showed 26 ± 0.5 and 23 ± 0.8 mm non-growth halo against to Staphylococcus aureus and Escherichia coli, respectively. Maltodextrin filled the surface cracks, but lutein increased the surface cracks of mucilage film. The amorphous structure of the pure cress seed mucilage film was confirmed by XRD, which the alumina and lutein gave crystalline properties in the film. Maltodextrin and alumina increased the thermal stability of the film. The release results showed that the release rate of lutein depends on the structure of the film and by changing the structure of the film, the release rate can be purposefully controlled according to the required release rate.

Hydrocolloids: Structure, preparation method, and application in food industry.

Hydrocolloids are a group of polysaccharides that act as thickeners, gelling agents, emulsion stabilizers, inhibitors of the growth and expansion of ice crystals in frozen materials, and inhibitors of the growth of sugar crystals in different industries. Hydrocolloids are used both to improve the rheological and textural properties of food products and also as fat substitutes. Also hydrocolloids are used in the production of low-calorie foods and also their beneficial nutritional properties causes their extensive application in the food industry. Food hydrocolloids or gums are high molecular weight hydrophilic biopolymers that are used as functional compounds in the food industry. Hydrocolloids are obtained from plants, animals, microorganisms, and modified biopolymers. The purpose of this article is to review hydrocolloids and their application in food, pharmaceutical and agricultural industries. Therefore, this article discusses the structure, origin, preparation methods, extraction and the applications of hydrocoloids in various industries.

Synthesis and characterization of novel Spirulina protein isolate (SPI)-based hydrogels through dual-crosslinking with genipin/Zn2.

Spirulina protein isolate (SPI) is a bio-polymer that can be used in the design and synthesis of hydrogels due to its biodegradability and non-toxicity. Herein, dual-crosslinked hydrogels were synthesized based on spirulina protein isolate through covalent crosslinking with genipin and metal coordination with Zn2+, and used as delivery systems. From the analysis of colorimetric indices, a high correlation between color changes and the reaction of cross-linkers with amine group structure was observed. By increasing genipin concentration in the range of 5-15 mM, the degree of cross-linking increased up to 83 %. Cross-linked hydrogels, depending on the type and concentration of cross-linkers, had a smooth to rough and dense structure with low porosity. In the FTIR spectra, significant shifts were observed in amide bonds, which are related to the formation of secondary amides after genipin crosslinking. The maximum water absorption capacity (381 %) was obtained at pH 7.4, which was significantly reduced by increasing the concentration of cross-linkers or decreasing the pH of the environment. The release rate of vitamin B6 (model) at pH 2 (45 %) was much lower than at pH 7.4 (65 %) which makes hydrogels suitable for intestinal delivery. Vitamin B6 release data indicated the best fit to the Peppas-Sahlin model in all the cases (98-99 %) and showed that the release process occurs through quasi-Fickian diffusion. The finding reveals that spirulina protein-based hydrogels can potentially be used in the design of practical carriers for the targeted delivery of bioactive compounds.

Phenolic compounds of sugar beet (Beta vulgaris L.): Separation method, chemical characterization, and biological properties.

Sugar beet (Beta vulgaris L.) is a good source of bioactive compounds. However, information on the biological properties of sugar beet root is limited and its beneficial effects have not been completely understood. In this work, 10 phenolic compounds have been separated and identified in various parts of sugar beet for the first time, including the most abundant epicatechin (31.16 ± 1.89 mg/100 g), gallic acid (30.57 ± 2.69 mg/100 g), and quercetin-3-O-rutinoside (30.14 ± 3.63 mg/100 g). The biological activity tests indicated that sugar beet peel potently scavenged the nitric oxide and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radicals with IC50 values of 88.17 ± 05.14 and 28.77 ± 0.62 µg/ml, respectively. In addition, sugar beet peel exhibited the highest reducing power, IC50 values of 11.98 ± 1.20 µg/ml, and the highest ion-chelating activity, IC50 values of 48.52% and 55.21% for cupric and ferrous ions at 250 µg/ml, respectively. Compared to synthetic antioxidants, sugar beet showed promising biological activities, which could be considered further in future studies.

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.

Innovative smart and biodegradable packaging for margarine based on a nano composite polylactic acid/lycopene film.

In this study, polylactic acid (PLA)/titanium dioxide/lycopene (PLA/TiO2/Lyc) nano-composite film was prepared. The morphology and mechanical properties of the film were studied by SEM and texture analyser. Results showed that lycopene and TiO2 nanoparticles were distributed in the film matrix uniformly, TiO2 and lycopene increased the mechanical properties of PLA film. The PLA/TiO2/Lyc film was used to package margarine. The effect of PLA/TiO2/Lyc film, time and temperature of storage on the qualitative features of margarine were studied. Also the colour properties of PLA/TiO2/Lyc film were studied during storage period. Oxidative features (antioxidant activity, acidity number, peroxide value and thiobarbituric acid value) of margarine showed that the quality features of margarine decreased during storage, but the PLA/TiO2/Lyc film controled the oxidative factors and increased the margarine shelf life significantly (P < .05). Results also showed that the PLA/TiO2/Lyc film colour changed from red to light yellow during storage. With increasing margarine storage time, the film colour index a decreased (red colour diminished) while b increased (yellow colour increased). There were good relations between colour changes of film and oxidative parameters of margarine and storage time and storage temperature. Thus PLA/TiO2/Lyc film can be used as a visual indicator of the oxidation variations during storage of packaged margarine.

Specific Removal of Nitrite from Lake Urmia Sediments by Biohydrogel Based on Isolated Soy Protein/Tragacanth/Mesoporous Silica Nanoparticles/Lycopene.

In this study, a biodegradable biohydrogel based on isolated soy protein/tragacanth containing mesoporous silica nanoparticles and lycopene pigment (ISP/TG/MPS/Lyc) is prepared. The physicochemical characteristics and structure of the biohydrogel are investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, and thermal gravimetry analysis (TGA) techniques. Mechanical properties (tensile strength and elongation at break point), antioxidant activity, water solubility, water absorption capacity (WAC), and the humidity content of the biohydrogels are studied. Five optimal biohydrogels including pure ISP, ISP/TG, ISP/MPS, ISP/Lyc, and ISP/TG/MPS/Lyc are used for chemical treatment of Lake Urmia sediments. For this purpose, biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrate, and nitrite of sediments are examined before and after treatment with biohydrogels. According to the FTIR results, there is only physical interaction between lycopene and isolated soy protein. According to the TGA results, adding silica mesoporous to biohydrogel increases its thermal stability. Tragacanth gum and lycopene pigment reduce water solubility and increase the WAC of biohydrogel. The biohydrogel significantly reduces the BOD and COD of the sediments. The biohydrogel reduces nitrite content up to 90%, while reducing nitrate content by almost 30%. The results show that the biohydrogel containing lycopene selectively purifies nitrite from the sediment solution of Lake Urmia.

Bacterial and oxidative control of local butter with smart/active film based on pectin/nanoclay/Carum copticum essential oils/ß-carotene.

In this study, Pectin/Nanoclay (montmorillonite)/Carum copticum Essential oils/ß-Carotene (Pec/Clay/CCE/ßC) composite film was prepared. The effect of ß-Carotene (ßC) and Carum copticum Essential oils (CCE) concentration on the antioxidant activity and color/mechanical properties of Pec/Clay/CCE/ßC film was studied. The morphology and antibacterial activity of film were studied. The films containing maximum essential oil and ß-carotene showed the best antibacterial activity, antioxidant activity, flexibility and firmness. So the Pec/Clay/CCE0.5%/BC0.03% film as the optimum film was used for packaging of local butter. Oxidative stability, microbial count, and color properties (L*, a* and b*) of butter packaged with active film (Pec/Clay/CCE/ßC) were investigated. Results showed that Pec/Clay/CCE/ßC film was effective against Bacillus cereus (B. cereus) more than Escherichia coli (E. coli). According to the results active packaged butter had the highest oxidative stability, lowest microbial load, and the least color change during storage. In the packaging process, Pec/Clay/CCE/ßC film color was changed from orange to light yellow and this color change was used as a smart color indicator to detect the oxidation of butter and expiration time of butter.

Biodegradable film based on pectin/Nano-clay/methylene blue: Structural and physical properties and sensing ability for measurement of vitamin C.

In this study, biodegradable film based on pectin modified with Nanoclay and methylene blue was prepared. The Physicomechanical properties of the prepared film, including: thickness, water solubility, water vapor permeability (WVP), antioxidant activity and color properties were investigated. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Differential scanning calorimetry (DSC) and texture analysis techniques were used to investigate the physical and mechanical properties of the films. The optimum Pec/Clay/MB film was used as a colorimeter sensor to detect and measure vitamin C. The results showed that the addition of Nanoclay to the film increased the thickness and decreased the solubility of water and reduced the WVP. The addition of methylene blue had no significant effect on the thickness, but increased water solubility and increased antioxidant activity. The addition of Nanoclay increased the tensile strength (TS) of the film, but decreased its elongation at break (EB). The addition of Nanoclay increased the melting temperature of the film and decreased its crystallization temperature. In the SEM images, the clay particles at 50-100 nm in the film structure were characterized. Nanoclay and methylene blue reduced the surface cleavage of the film. Pec/Clay/MB film color was changed from blue to colorless in the presence of vitamin C. The linear range of vitamin C measurement was 10 to 500 and the detection limit was 10. By detecting the color changes of the film in the presence of vitamin C, the amount of this vitamin was measured in orange, kiwi and tangerine juice. The accuracy of the data was evaluated by the titration method. The sensor accuracy was obtained over 90%.

Molecular imprinted polymers for the controlled uptake of sinapic acid from aqueous media.

Several unique molecularly imprinted polymers (MIPs) were synthesized via a precipitation polymerization technique using 4-vinylpyridine as a functional monomer and ethylene glycol dimethacrylate as a cross-linker for selective separation of sinapic acid from aqueous solution. Three sets of MIPs with different functional monomer : cross-linker molar ratios at 4 : 20; 8 : 20 and 8 : 32 were prepared along with the corresponding non-templated polymers (NIPs). The MIPs and NIPs were characterized by scanning electron microscopy, dynamic light scattering, N2 adsorption analysis, thermogravimetry, and FT-IR/solids 13C NMR spectroscopy. Batch rebinding and selectivity experiments were carried out to evaluate their adsorption performance, where the MIP prepared with a 4 : 20 monomer : cross-linker mole ratio had significantly higher affinity toward sinapic acid. Notably, all MIPs displayed greater molecular recognition with sinapic acid relative to the NIPs. Therefore, MIPs prepared by this approach represent promising advanced materials for the pre-concentration, isolation and enrichment of sinapic acid from complex food matrices or controlled removal from agricultural waste streams.

Smart film based on chitosan/Melissa officinalis essences/ pomegranate peel extract to detect cream cheeses spoilage.

Antibacterial/biodegradable film based on Chitosan (CS)/pomegranate peel extract (PPE) and Melissa officinalis Essences (MOE) was prepared. To study the effects of PPE and MOE on the film characteristics, a central composite design (CCD) was used. The physicochemical characteristics of the film, including moisture, water vapour permeability (WVP), antioxidant activity, microbial properties, FT-IR/SEM/XRED spectrum, etc. were studied. The results showed that the addition of PPE significantly reduced the amount of moisture loss. The WVP increased with the addition of MOE and decreased with the addition of PPE. MOE and PPE increased the antioxidant activity of the films. In terms of microbial properties, the antimicrobial effect of MOE on B. cereus was greater than on E. coli. The results of SEM showed that the PPE particles were uniformly distributed in the film matrix and the MOE slightly reduced the surface compression of the film. The CS/PPE/MOE film was used for smart packaging of cream cheese and detection of cheese spoilage. It was observed that with increasing storage time and storage temperature, with regard to the change in the pH of the cream cheese, samples become acidic. The PPE contains anthocyanin pigments that are sensitive to pH changes so the film colour was changed (from blue to red) during storage. The colour change of the film was visible with the naked eye and can be used to estimate the expiry date of the cheese.

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.