Use of gamma irradiation technology for modification of bacterial cellulose nanocrystals/chitosan nanocomposite film.

The objective of this work was to investigate the influence of different gamma ray dosages (5, 10, and 10 kGy) on the structural, mechanical, surface and barrier properties of chitosan (Ch) based nanocomposite film. The results showed gamma irradiation caused an increase in the surface hydrophobicity, water vapor permeability and sensitivity of films to water and also, yellowness and opacity of films increased, simultaneously. By increasing the irradiation doses up to 10 kGy, the mechanical properties of Ch/BCNC film was significantly enhanced. As observed by FTIR spectra, no change occurred in the chemical functional groups of the films during irradiation. XRD studies confirmed that crystallinity of films was increased after irradiation. The nanocomposite film irradiated by 10 kGy had the highest thermal stability. In conclusion, gamma radiation can be considered as a safe method for sterilization of foods and modification of Ch/BCNC film properties.

The effects of gelatin-CMC films incorporated with chitin nanofiber and Trachyspermum ammi essential oil on the shelf life characteristics of refrigerated raw beef.

The effects of gelatin-carboxymethyl cellulose (Gel-CMC) based films containing chitin nano fiber (CHNF) and Trachyspermum ammi essential oil (Ajowan), on the shelf life extension of the raw beef at refrigerated temperature (4 °C) over a 12-day period were evaluated. Ajowan essential oil (AJEO) and CHNF were added to the films at 0.24, 0.64 and 1% v/v; and 2 and 4 wt%, respectively. The microbiological (total viable count, psychrotrophic count, Pseudomonas spp., Staphylococcus aureus, lactic acid bacteria, molds and yeasts), the chemical (pH, thiobarbituric acid and total volatile basic nitrogen), color and sensory properties of the packaged samples were evaluated periodically. Bacteria grew the most quickly in the control samples, followed by those wrapped with the Gel-CMC films; The lowest microbial counts, the least change in the chemical properties and the highest sensory scores after 12 days of storage were obtained for the samples wrapped in the films incorporated with 1% AJEO and 4 wt% CHNF.

The optimization of gelatin-CMC based active films containing chitin nanofiber and Trachyspermum ammi essential oil by response surface methodology.

The effects of carboxymethyl cellulose (CMC: 4-16 wt%), chitin nanofiber concentrations (CHNF: 2-5 wt%) and Trachyspermum ammi (Ajowan) essential oil (AJEO: 0.26-1 v/v%) on the physical and antimicrobial characteristics of the gelatin-based nanocomposite films were studied by response surface methodology (RSM). The optimization was based on maximizing contact angle, ultimate tensile strength (UTS), strain at break (SAB), lightness (L), antibacterial activity, while minimizing water vapour permeability)WVP(, solubility, swelling, yellowness index (YI), and total color difference (ΔE) values. An increase in the CMC/gelatin ratio in the film formulations caused a decrease in WVP, SAB, ΔE, and YI. In addition, the incorporation of CHNF improved their mechanical strength and barrier properties. Furthermore, the addition of AJEO clearly improved the antimicrobial activity against Staphylococcus aureus and Escherichia coli, while reducing the mechanical and light barrier properties. The optimal values of CMC, CHNF and AJEO for composition of the gelatin film were 15.83 (wt%), 3 (wt%) and 0.74 (v/v%), respectively.

Physico-mechanical and antimicrobial properties of tragacanth/hydroxypropyl methylcellulose/beeswax edible films reinforced with silver nanoparticles.

The novel trinary bio-composite film based on Tragacanth/Hydroxypropyl methylcellulose/Beeswax reinforced silver nanoparticles (AgNPs) was developed. This study investigated the effect of AgNPs (2, 4 and 8%) on some physico-mechanical and antimicrobial properties of bio-composite film. It was discovered that AgNPs reduced the composite tensile strength from 33.64 to 16.12 MPa. However, water vapor permeability was improved by addition of the nanoparticles (4.57-2.16 × 10-13 g m/m2 s Pa). The use of AgNPs influenced the apparent color of bio-composite film. The microscopic surface structure and topography of the films were also examined by scanning electron microscopy and Fourier transform infrared, respectively. Dynamic mechanical thermal analysis results showed that the thermal stability of film was slightly decreased through incorporation with AgNPs. Finally, nano-composite films demonstrated strong antibacterial activity against tested pathogen bacteria in the contact surface zone. The antimicrobial results suggest that new nanocomposite film may be used as food active packaging.

Exopolysaccharides production by Lactobacillus acidophilus LA5 and Bifidobacterium animalis subsp. lactis BB12: Optimization of fermentation variables and characterization of structure and bioactivities.

In this study, the most important variables (incubation temperature, fermentation time and yeast extract concentration) responsible for the exopolysaccharides (EPSs) production by Lactobacillus acidophilus LA5 and Bifidobacterium animalis subsp. lactis BB12 were screened. The EPSs synthesize by LA5, BB12, and their co-culture were successfully optimized and were 349.82 ±â€¯5.39, 146.83 ±â€¯3.99 and 187.02 ±â€¯1.54 mg/L, respectively. GC-MS analysis indicated that the purified EPSs are heteropolysaccharide and consisted of glucose, galactose, glucuronic acid, and xylose. The FT-IR analysis was used to investigate functional groups of purified EPSs and NMR analysis was used to study the structure of them. The DSC, TGA and DTG analysis of the extracted EPSs showed that they had high thermal stability and degradation temperature. The results of bioactivity analysis indicated that maximum DPPH and hydroxyl radicals scavenging activity were 59.30 ±â€¯1.95, 56.76 ±â€¯0.79, 62.33 ±â€¯1.02% and 59.94 ±â€¯1.68, 46.40 ±â€¯0.73, 53.54 ±â€¯0.76%, respectively for the EPSs of LA5, BB12, and their co-culture. Additionally, reducing power of the produced EPSs by LA5, BB12, and their co-culture were 1.047 ±â€¯0.001, 1.270 ±â€¯0.045 and 1.139 ±â€¯0.018, respectively. Consequently, all these results showed that the EPSs produced by LA5, BB12, and their co-culture had a high potential as natural antioxidants or bioactive additive in the food industry.