Increased shelf life of Oncorhynchus mykiss (Rainbow trout) through Cu-Clay nanocomposites

Microbial growth is widely responsible for shortened shelf life of cold water-living fish products. So, it seems that current chemical-based food packaging has no acceptable efficacy, and food industrialists tend to the usage of more novel approaches like active food packaging. Among them, there is a great research interest in nanotechnology-emerging approaches. This study aimed to investigate the anti-microbial efficacies of Polyethylene/CuNP/nanoclay nanocomposites to enhance the shelf life and physiochemical features of rainbow trout. Three main nanocomposites with various concentrations of Cu and clay nanoparticles were examined. SEM, XRD, and EDX (as physiochemical analysis), disk diffusion (as antimicrobial assays), total volatile nitrogen (TVB-N), and peroxide value (PV) (as biochemical parameters) were measured. Based on the results, nanocomposites could reduce the microorganism growth rate by reducing the number of colonies (33.3%), inhibitory activities against both gram-positive (8 mm) and gram-negative bacteria (10 mm), maintenance of TVB-N (42% reduction), and PV (44% reduction) below the standard range. To sum up, these new nanocomposites can be a good candidate to enhance the shelf life of Rainbow Trout.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01031-0.

The Toxicity Testing of Cyanobacterial Toxins In Vivo and In Vitro by Mouse Bioassay: A Review

Different biological methods based on bioactivity are available to detect cyanotoxins, including neurotoxicity, immunological interactions, hepatotoxicity, cytotoxicity, and enzymatic activity. The mouse bioassay is the first test employed in laboratory cultures, cell extracts, and water bloom materials to detect toxins. It is also used as a traditional method to estimate the LD50. Concerning the ease of access and low cost, it is the most common method for this purpose. In this method, a sample is injected intraperitoneally into adult mice, and accordingly, they are assayed and monitored for about 24 hours for toxic symptoms. The toxin can be detected using this method from minutes to a few hours; its type, e.g., hepatotoxin, neurotoxin, etc., can also be determined. However, this method is nonspecific, fails to detect low amounts, and cannot distinguish between homologues. Although the mouse bioassay is gradually replaced with new chemical and immunological methods, it is still the main technique to detect the bioactivity and efficacy of cyanotoxins using LD50 determined based on the survival time of animals exposed to the toxin. In addition, some countries oppose animal use in toxicity studies. However, high cost, ethical considerations, low-sensitivity, non-specificity, and prolonged processes persuade researchers to employ chemical and functional analysis techniques. The qualitative and quantitative analyses, as well as high specificity and sensitivity, are among the advantages of cytotoxicity tests to investigate cyanotoxins. The present study aimed at reviewing the results obtained from in-vitro and in-vivo investigations of the mouse bioassay to detect cyanotoxins, including microcystins, cylindrospermopsin, saxitoxins, etc.

Antimicrobial Properties of Food Nanopackaging: A New Focus on Foodborne Pathogens

Food products contaminated by foodborne pathogens (bacteria, parasites, and viruses) cause foodborne diseases. Today, great efforts are being allocated to the development of novel and effective agents against food pathogenic microorganisms. These efforts even might have a possible future effect in coronavirus disease 2019 (COVID-19) pandemic. Nanotechnology introduces a novel food packaging technology that creates and uses nanomaterials with novel physiochemical and antimicrobial properties. It could utilize preservatives and antimicrobials to extend the food shelf life within the package. Utilizing the antimicrobial nanomaterials into food packaging compounds typically involves incorporation of antimicrobial inorganic nanoparticles such as metals [Silver (Ag), Copper (Cu), Gold (Au)], and metal oxides [Titanium dioxide (TiO2), Silicon oxide (SiO2), Zinc oxide (ZnO)]. Alternatively, intelligent food packaging has been explored for recognition of spoilage and pathogenic microorganisms. This review paper focused on antimicrobial aspects of nanopackaging and presented an overview of antibacterial properties of inorganic nanoparticles. This article also provides information on food safety during COVID-19 pandemic.

Effect of Carum copticum nano-essence against Saprolegnia and Fusarium, and the Use of Multiplex PCR Assay for the Detection of These Organisms in Rainbow trout Oncorhynchus mykiss

This study aimed to investigate the fungal species isolation and confirmation by the Multiplex PCR method in aquatic fish. Evaluation of the inhibitory effect of nano-essential oils of Carum copticum on isolated fungal species was also conducted in this study. The PCR results showed that 3 out of 5 samples were diagnosed with Fusarium solani, and two of them were positive for Saprolegnia. Moreover, in 0.1% of the females' nanoparticles, one peak appeared that showed a particle with an average diameter of 360 nm, and two nanoparticles showed a peak with a mean diameter of 242 nm. The results of minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC) showed that 0.01% nano essential oil had 0.08 and 0.07 mg/ml MIC values against Fusarium solani and Saprolegnia, respectively. Gram/ml was on the growth of Fusarium solani species. The essential oils of female plants had an MIC of 0.07 in 0.1% essential oil and 0.03 mg/ml in 0.01% essential oil in Saprolegnia. Furthermore, in the case of 0.1% nano essential oil, the results showed the MIC values of 0.04 and 0.03 mg/ml against Fusarium solani and Saprolegnia, respectively. The MFC values of 0.1% nano essential oil were 0.1 and 0.07 mg/ml against Fusarium solani and Saprolegnia, respectively. It was not found on Fusarium and Saprolegnia. Overall, the results of this study using PCR for direct detection showed that 70% and 50% of the samples were Fusarium solani and Saprolegnia positive, respectively; therefore, the PCR was an efficient method for the detection of fungi. According to the results of nano-essential oil (0.1%) of females, this nano-essence had a strong inhibitory effect on Fusarium solani and Saprolegnia.

Study the antimicrobial effects of chitosan-based edible film containing the Trachyspermum ammi essential oil on shelf-life of chicken meat

Packaging using chitosan-based edible films incorporated with natural essential oils is a safe and economic way to increase the shelf-life and acceptability of food products and especially chicken meat. Trachyspermum ammi is a natural medicinal plant with high antimicrobial effects cultivated in Iran. The present research was done to study the antimicrobial effects of chitosan-based edible film containing T. ammi essential oil on shelf-life of chicken meat. T. ammi fruits were collected and dried. Essential oil was extracted from plants using the Clevenger’s apparatus. High molecular weight chitosan with 1% and 2% concentrations of T. ammi essential oil were used for coating of chicken fillets. Treatments were stored at 4°C for 12 days. Count of the total aerobic, total psychrophilic and coliform bacteria had ranges of 3.8±0.25 to 8.32±0.26, 4±0.23 to 8.65±0.28 and 1.8±0.09 to 5.62±0.16 CFU/g during the storage period. Antimicrobial effects were significantly increased with the incorporation of T. ammi essential oil (P<0.05). Antimicrobial effects were also depended on the concentration of T. ammi essential oil (P<0.05). Chitosan film incorporated with 2% T. ammi essential oil had the highest inhibitory effects on total aerobic, total psychrophilic and coliform bacteria (P<0.05). Our results pointed out that the incorporation of T. ammi essential oil at 2% concentration has potential for using the developed chitosan edible film as an active packaging of chicken meat.