Investigating the effect of acoustic waves on spoilage fungal growth and shelf life of strawberry fruit.

The effects of acoustic waves on growth inhibition of food spoilage fungi (Aspergillus niger, Aspergillus flavus, Aspergillus parasiticus and Botrytis cinerea) on the medium and strawberry surfaces were investigated. Firstly, single-frequency sound waves (250, 500, 1000, 2000, 4000, 8000, 12,000 and 16,000 Hz) were induced on inoculated medium with fungi spores for 24 h and growth diameter of each mold was evaluated during the incubation period. In the second stage, the sound waves with two frequencies of 250 Hz and 16,000 Hz were induced on inoculated strawberries with fungi spores at 5 °C for different times (2, 4, 6, 8 and 10 days). The results from the first stage indicated that the sound waves inhibited the growth of A. niger (20.02%) at 250 Hz and B. cinerea (4/64%) at 4000 Hz on potato dextrose agar (PDA) surface. Also, comparison of the growth diameter of some species of Aspergillus revealed various responses in presence of 250 Hz frequency. In the second stage, applying a frequency of 250 Hz over a period of 10 days proved to be more effective in inhibiting the growth of A. niger and B. cinerea on strawberries inoculated with fungal spores. Consequently, the shelf lives of the strawberries significantly increased to 26 days and 18 days, respectively, under this treatment. Based on the findings, it is concluded that sounding with acoustic waves can be used as a green and cheap technology along with other technologies to improve food safety.

Fabrication of green colorimetric smart packaging based on basil seed gum/chitosan/red cabbage anthocyanin for real-time monitoring of fish freshness.

Novel green intelligent films based on basil seed gum (BSG)/chitosan containing red cabbage extract (RCA) (0, 2.5, 5, and 10, % (v/v)) as a colorimetric indicator for food freshness detection were fabricated by casting method. The physicochemical, barrier, mechanical, and antioxidant characteristics, as well as sensitivity to pH and ammonia gas of smart edible packaging films, were investigated. The interaction of anthocyanin extract as a natural dye with biopolymers in films characterized by FTIR spectroscopy and SEM images revealed their suitable compatibility. The film with maximum anthocyanin content (10% (v/v)) appeared robust color changes against various pH and ammonia gas levels. The color of indicator films when exposed to alkaline, neutral and acidic buffers are indicated with green, blue, and red colors, respectively. The DPPH radical scavenging activity of smart BSG/chitosan films improved from 23% to 90.32% with increasing RCA content from 2.5 to 10% (v/v). Generally, the incorporation of RCA in film structure enhanced their solubility, WVP, ΔE, turbidity, and flexibility, and reduced tensile strength. The observations successfully confirmed the efficacy of pH-sensitive indicator smart film based on BSG/chitosan for evaluation of fish spoilage during storage.

Edible Packaging as a Functional Carrier of Prebiotics, Probiotics, and Postbiotics to Boost Food Safety, Quality, and Shelf Life.

The safety limitations of chemical preservatives led to an increasing trend among industries and customers toward preservative-free foods; hence, the necessity has arisen for developing innovative, safe antimicrobial elements to prolong the shelf life. Beneficial microorganisms that are described as probiotics and also their metabolites are increasingly being considered as bioprotective agents. These microorganisms could be beneficial for extending food shelf-life and boosting human health. During distribution and storage (25 °C or 4 °C), they could contribute to suppressing unwanted microbes and then improving food safety and quality. Also, by tolerating the harsh conditions of gastrointestinal tract (low pH (~3), presence of bile salts, digestive enzymes, competition with other microbes, etc.), probiotics could exert several biological effects at the host. Besides inclusion in foods and supplements, probiotics and their functional metabolites could be delivered via edible packaging (EP). Recent studies have demonstrated the strong potential of pre/pro/post-biotic EP in food biopreservation. These packaging systems may show different potency of food biopreservation. Among others, postbiotics, as metabolic by-products of probiotics, have gained tremendous attention among researchers due to their unique properties like presenting a variety of antimicrobial activities, convenience in use in different industrial stages and commercialization, extended shelf life, and stability in a wide range of pH and temperature. In addition to antimicrobial activities, various bio-EP could differently influence physical or sensorial attributes of food commodities, impacting their acceptance by consumers. Hence, this study is aimed at presenting a comprehensive review of the application of bio-EP, not only by providing a protective barrier against physical damage but also by creating a controlled atmosphere to improve the health and shelf life of food.

Novel antimicrobial/antioxidant Eremurus luteus root gum coating containing rosemary essential oil nanoemulsions for extension of chicken meat shelf life.

Herein, the effect of incorporation of rosemary essential oil (REO) nanoemulsions with the smallest (98.14 nm) and largest (148.04 nm) droplets' sizes at different concentrations (0%, 2%, and 4% v/v) in Eremurus luteus root gum (ELRG) coating solution on microbial, chemical, and sensory qualities of chicken fillets during cold storage was investigated. The results demonstrated a significant reduction in pH and TBA value and total viable microbial count (TVC) of chicken meat samples after using an active ELRG coating compared with the uncoated sample. Moreover, the properties of active ELRG coatings were more affected by the concentration of REO nanoemulsions than the size of their droplets. More antimicrobial and antioxidant activities were observed in coated samples containing 4% (v/v) REO nanoemulsions (L-4 and S-4). The highest and lowest pHs at the end of storage belonged to uncoated (6.89) and S-4 coated (6.41) samples, respectively. Unlike the control sample (8th day), the microbial population in the active coated samples (>12th day) reached the threshold level (7 log CFU/g) later. The TBA value in the control and coated samples was 0.56 and 0.4-0.47 mg/kg after 12 days of cold storage, respectively. Increasing the REO nanoemulsion content from 2% to 4% (v/v) in the coating solution enhanced the score of sensory parameters such as odor, color, and total acceptance of the chicken meat, especially on the last day of cold storage. The obtained results suggested ELRG-REO coatings as an effective strategy to delay the chemical and microbial deterioration of chicken meat fillets.

Fabrication and characterization of biodegradable active films with modified morphology based on polycaprolactone-polylactic acid-green tea extract.

This research focused on developing an eco-friendly packaging for food products through blending polycaprolactone (PCL) and polylactic acid (PLA) as two biodegradable polymers, and green tea extract (GTE) as a natural antioxidant pushing the films toward active packaging; thereby, the morphological, mechanical, thermal, barrier, antioxidant, and biodegradation features of the composite films were analyzed. The films containing 30% PLA exhibited a reduction of 14.96%, 38.89%, 8.75%, and 35.55% in the hydrophilicity, water-solubility, water vapor permeability (WVP), and oxygen transition rate (OTR), respectively. Furthermore, GTE incorporation led to antioxidant behavior as well as better barrier properties (up to 6.25% decrease in WVP and 55.78% in OTR), mechanical properties (an increase of 14.96%, 38.89%, and 8.75% in elastic modulus, tensile strength, and elongation at break, respectively) and biodegradable rate (124.13%). Indeed, the presence of polyphenol compounds in green tea improved molecular interaction between the polymers and launched a co-continuous structure and an unparalleled level of compatibility, which was also approved by the changes in FTIR spectra of the PCL/PLA films. These results demonstrate the benefits of blending PLA with PCL and GTE integration in terms of operational enhancement and film activating, respectively, to provide reliable food packaging.

Reducing cytotoxicity of poly (lactic acid)-based/zinc oxide nanocomposites while boosting their antibacterial activities by thymol for biomedical applications.

In the present study, ternary blends based on poly (lactic acid)/poly (ε-caprolactone)/thermoplastic starch were prepared at different concentrations of synthesized zinc oxide nanoparticles (ZnO-NPs) and thymol. The sizes of ZnO-NPs with an average diameter of about 30-50 nm were detected by FE-SEM analysis. Moreover, the effect of ZnO-NPs and thymol on morphological, FT-IR spectrum, UV absorption, thermal stability, cytotoxicity, and antibacterial properties of neat blend was investigated. TGA analysis showed that the addition of ZnO-NPs and/or thymol diminished thermal stability of the system. Incorporating ZnO-NPs improved antibacterial activities of the neat blend, but MTT-assay and AO fluorescent staining test results depicted a decrease in cell viability to less than 20% by the addition of 5 wt% ZnO-NPs. In such a condition, the addition of thymol to the nanocomposites exhibited a dose-dependent increase in cell survival mostly due to thymol antioxidant properties. Interestingly, the antibacterial performance of compounds was also improved by the presence of thymol. Therefore, the obtained nanocomposites have potential to extend applications of innovative biomedical devices for future research in which both high cell viability and superior antibacterial properties are needed such as an antibacterial wound healing film.

Investigating the best strategy to diminish the toxicity and enhance the antibacterial activity of graphene oxide by chitosan addition.

The main objective of this work was to find a way to increase the bio-applicability of graphene oxide (GO) nanoparticles. In this way, various kinds of graphene oxide-chitosan (GO-CS) nano-hybrids were synthesized through attachment of different kinds of chitosan (CS) structures with GO. Subsequently, they were assessed in terms of structural characterization, antibacterial activity and cytotoxicity to obtain a hybrid structure representing the highest bactericidal and biocompatibility performance. Our results revealed that the single-layer GO and also three different kinds of GO-CS nano-hybrid structures (pristine powder, spherical and nano-fibrilar network structures) were successfully synthesized. Antibacterial activity results indicated superior antibacterial activity of nano-hybrids compared to the pure GO. In addition, it was observed that the attachment of CS to GO interestingly reduced the cytotoxicity effect of GO and even caused cell proliferation in some samples. Furthermore, the antibacterial and bio-safety properties of different hybrids were compared and suggestive mechanisms for their particular performances were proposed.

Bioactive compounds, antioxidant and antimicrobial activities of Arum maculatum leaves extracts as affected by various solvents and extraction methods.

The different species of Arum maculatum plant can be found in all over the world, and a wide range of medicinal applications has been mentioned for them. Thus, it can also be valued as a source of natural compounds with antioxidant and antimicrobial activities. In this study, the effect of solvents (water, ethanol, ethanol:water (50:50)) and extraction methods (maceration and ultrasound) on the extraction yields and bioactive properties of extracts were analyzed. The antioxidant capacity of Arum maculatum leaves extracts was investigated, and the concentrations of total phenolics, tocopherols, tannins and flavonoids were determined. 1,1-diphenyl 2-picrylhydrazyl free radical (DPPH), ß-Carotene bleaching, and oxidative stability index (OSI) were used to determine antioxidant activity. The ability to scavenge radicals was measured in these experiments by the discoloration of the solution. Also, the antimicrobial activity of different extracts against Gram-positive (Staphylococcus aureus and Listeria monocytogenes) and Gram-negative bacteria (Escherichia coli, Salmonella enteritidis, and Pseudomonas aeruginosa) was evaluated by using of microdilution and agar diffusion assays. The results demonstrated that ultrasonic extracts (especially ethanol:water (50:50) solvent) had the higher extraction yield and antioxidant potential than maceration extracts. All extracts were effective against all tested bacteria, and Listeria monocytogenes was the most sensitive bacterium with lowest MIC value (12.5 mg/ml) and biggest diameter of growth inhibition zone (13.77 mm). Generally, this Arum maculatum leaves extracts can be suggested as an economical source of antioxidant and antimicrobial agents and can be a suitable substitute for artificial and chemical food preservatives.

Facile and rapid in-situ synthesis of chitosan-ZnO nano-hybrids applicable in medical purposes; a novel combination of biomineralization, ultrasound, and bio-safe morphology-conducting agent.

In this study, zinc oxide nanoparticle (ZnO-NPs) and also chitosan­zinc oxide (CS-ZnO-NPs) nano-hybrid were synthesized by a rapid ultrasound assisted co-precipitation method. The morphology, chemical bonding, crystal structure, UV absorption, toxicity and antibacterial properties of the CS-ZnO-NPs and ZnO-NPs were characterized. The FE-SEM (field emission scanning electron microscopy) micrographs and XRD (X-ray diffraction) analysis revealed that the used technique led to the preparation of homogeneous, ultra-thin (thickness of 20-30 nm) and highly pure ZnO sheets for the both kinds of nanoparticles. The obtained results also demonstrated a superior performance of CS-ZnO-NPs hybrid rather than ZnO-NPs in terms of antibacterial activity, cell viability and UV absorption. It was deduced that the designed biomineralization technique was a very fast and successful strategy to provide a ZnO hybrid with elevated bacterial growth inhibition and bio-safety. Furthermore, the experimental data of antibacterial analyses were compared with the curves obtained from modified Gompertz model and good accordance was observed.

Application of F⁺RNA Coliphages as Source Tracking Enteric Viruses on Parsley and Leek Using RT-PCR.

The objective of this study was to identify sources of fecal contamination in leek and parsley, by using four different F(+)RNA coliphage genogroups (IV, I indicate animal fecal contamination and II, III indicate human fecal contamination). Three different concentrations (10(2), 10(4), 10(6) pfu/ml) of MS2 coliphage were inoculated on the surface of parsley and leek samples for detection of phage recovery efficiency among two methods of elution concentration (PEG-precipitation and Ultracentrifugation) by performing double agar layer (DAL) assay in three replications. Highest recovery of MS2 was observed in PEG method and in 10(6) inoculation concentration. Accordingly, the PEG method was used for washing and isolation of potentially contaminated phages of 30 collected samples (15 samples from the market and 15 samples from the farm). The final solutions of PEG method were tested for the enumeration of plaques by DAL assay. Total RNA was then extracted from recovered phages, and RT-PCR was performed by using four primer sets I, II, III, and IV. Incidence of F(+)RNA coliphages was observed in 12/15 (80 %) and 10/15 (66/6 %) of samples were obtained from farm and market, respectively, using both DAL and RT-PCR test methods. Different genotypes (I, II, and IV) of F(+)RNA coliphages were found in farm samples, while only genotype I was detected in market samples by using the primer sets. Due to the higher frequency of genotype I and IV, the absence of genotype III, and also the low frequency of genotype II, it is concluded that the contamination of vegetable (parsley and leek) in Neyshabour, Iran is most likely originated from animal sources.