Quality and Shelf Life of Cold and Frozen Rainbow Trout (Oncorhynchus mykiss) Fillets: Effects of Fish Protein-Based Biodegradable Coatings

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.

No evidence for a relationship between farm or transformation process locations and antibiotic resistance patterns of Pseudomonas population associated with rainbow trout (Oncorhynchus mykiss)

AIMS

Study the relationship between antibiotic resistance patterns of Pseudomonas isolated from farmed rainbow trout fillets and farm or transformation process locations.

METHODS AND RESULTS

Pseudomonas strains were isolated from rainbow trout sampled in two differently located farms and filleted in laboratory or in a processing factory. One hundred and twenty-five isolates were confirmed as belonging to Pseudomonas using CFC selective media, Gram staining, oxidase test and quantitative polymerase chain reaction methods. Fifty-one isolates from separate fish fillets were further identified using MALDI-TOF mass spectrometry, and the minimal inhibitory concentrations (MIC) of 11 antibiotics were also determined by microdilution method. Most of the isolates belonged to the Pseudomonas fluorescens group (94.1%), and no relationship was established between antibiotic resistance patterns and sampling locations (farms or filleting areas). Multiple resistance isolates with high MIC values (from 64 µg ml^-1 to more than 1024 µg ml^-1 ) were identified.

CONCLUSIONS

Antibiotic resistance patterns found in Pseudomonas isolates were not influenced by farms or transformation process locations. Seven isolates were found highly resistant to four different antibiotic classes.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study does not provide evidence of a relationship between farm or transformation process locations on antibiotic resistance patterns of Pseudomonas population.

Hyperspectral Imaging (HSI) Technology for the Non-Destructive Freshness Assessment of Pearl Gentian Grouper under Different Storage Conditions

This study used visible/near-infrared hyperspectral imaging (HSI) technology combined with chemometric methods to assess the freshness of pearl gentian grouper. The partial least square discrimination analysis (PLS-DA) and competitive adaptive reweighted sampling-PLS-DA (CARS-PLS-DA) models were used to classify fresh, refrigerated, and frozen–thawed fish. The PLS-DA model achieved better classification of fresh, refrigerated, and frozen–thawed fish with the accuracy of 100%, 96.43%, and 96.43%, respectively. Further, the PLS regression (PLSR) and CARS-PLS regression (CARS-PLSR) models were used to predict the storage time of fish under different storage conditions, and the prediction accuracy was assessed using the prediction correlation coefficients (R_p²), root mean squared error of prediction (RMSEP), and residual predictive deviation (RPD). For the prediction of storage time, the CARS-PLS model presented the better result of room temperature (R_p² = 0.948, RMSEP = 0.255, RPD = 4.380) and refrigeration (R_p² = 0.9319, RMSEP = 1.188, RPD = 3.857), while the better prediction of freeze was by obtained by the PLSR model (R_p² = 0.9250, RMSEP = 2.910, RPD = 3.469). Finally, the visualization of storage time based on the PLSR model under different storage conditions were realized. This study confirmed the potential of HSI as a rapid and non-invasive technique to identify fish freshness.

Effect of anchovy by-product protein coating incorporated with thyme essential oil on the shelf life of anchovy (Engraulis encrasicolus L.) fillets

The effects of anchovy by-product protein coatings incorporated with thyme essential oil (TEO) on the shelf life of anchovy (Engraulis encrasicolus L.) fillets stored at 4 ± 1 °C were investigated. We grouped fillets in three categories: untreated fillets, fillets treated in coating solution alone, and fillets treated in coating solution containing 1.5% TEO and analyzed on 0, 3, 6, and 9 days of storage. It was observed that the total volatile basic nitrogen (TVB-N) and pH of all the fillet groups increased under cold storage conditions; however, this increase was much slow in both the coated anchovy fillets. Both coating applications slowed down the lipid oxidation but the coating containing TEO exhibited better effect than coating alone. The coating application alone or with essential oil had limited effect on microbial growth but positively affected the sensory quality. These results revealed that anchovy by-product protein coating mixed with TEO may prolong anchovy fillets' shelf life stored under cold condition.

Processing and characteristics of canola protein-based biodegradable packaging: A review

Interest increased recently in manufacturing food packaging, such as films and coatings, from protein-based biopolymers. Among various protein sources, canola protein is a novel source for manufacturing polymer films. It can be concentrated or isolated by aqueous extraction technology followed by protein precipitation. Using this procedure, it was claimed that more than 99% of protein was extracted from the defatted canola meal, and protein recovery was 87.5%. Canola protein exhibits thermoplastic properties when plasticizers are present, including water, glycerol, polyethylene glycol, and sorbitol. Addition of these plasticizers allows the canola protein to undergo glass transition and facilitates deformation and processability. Normally, canola protein-based bioplastics showed low mechanical properties, which had tensile strength (TS) of 1.19 to 4.31 MPa. So, various factors were explored to improve it, including blending with synthetic polymers, modifying protein functionality through controlled denaturation, and adding cross-linking agents. Canola protein-based bioplastics were reported to have glass transition temperature, T_g, below -50°C but it highly depends on the plasticizer content. Canola protein-based bioplastics have demonstrated comparable mechanical and moisture barrier properties compared with other plant protein-based bioplastics. They have great potential in food packaging applications, including their use as wraps, sacks, sachets, or pouches.