Potential of nanochitosan coating combined with walnut green husk to improve the preservation of rainbow trout (Oncorhynchus mykiss) during refrigerated storage.

The present study evaluated the potential of nanochitosan coating enriched with ethanol-water extract of the walnut green husk (WGHE) on spoilage and rancidity of rainbow trout (Oncorhynchus mykiss) during six-day refrigerated storage. Hence, we have considered fresh trout fillets without any treatment as control (C), immersed in 2% solution of chitosan nanoparticles (CN), combination with 1.5% and 3% WGHE with nanochitosan coating (CN + WGHE 1.5 and CN + WGHE3), for physicochemical, microbial and sensorial assays. The highest levels and total volatile nitrogen were observed after day 6 in C, while the lowest was found in CN + WGHE3 groups. Thiobarbituric acid reactive substance (TBARS) and peroxide value of untreated fillets on day 6 of the study were significantly higher than NC + WGHE3 with 0.08 mg/g and 3.27 mEq/kg, respectively. The total microbial population was: C ˃ CN ˃ CN + WGHE 1.5 > CN + WGHE3, which expresses the effect of the extract on the total microbial population. Overall, the combination of WGHE with CN increased the extract's efficiency in reducing peroxide value, TBARS, and total volatile nitrogen and delayed the pH increase, improving the overall acceptability of rainbow trout fillets stored in refrigerated conditions.

Isolation and characterization of E. coli O157: H7 novel bacteriophage for controlling this food-borne pathogen.

E. coli O157: H7 is known as a high-risk food-born pathogen, and its removal is vital for maintaining food safety. The increasing trend of food-borne diseases caused by this bacterium and other pathogens indicates the low efficiency of the methods to remove pathogens from foodstuffs. One of the new and effective methods is to use of a bio-control agent called bacteriophage, which has shown good function in eliminating and reducing pathogens. In this study, a novel bacteriophage was isolated and identified from the slaughterhouse wastewater to control E. coli O157: H7. This bacteriophage belonged to the Myoviridae family. Two bacterial genera including E. coli and Salmonella, were allocated to determine the bacteriophage host range; the result showed that the anti- Salmonella effect of phage was low. The phage was stable at high temperature (80 °C) and caused an acceptable reduction in the E. coli O157: H7 (4.18 log CFU / mL for 10 h). The isolated bacteriophage was corroborated to be completely safe based on the whole genome sequencing and lack of any virulence factor from the host bacteria. Considering the characteristics of this phage and its function in vitro, this bacteriophage may be used as an effective bio-control agent in foods with the possible E. coli O157: H7 -induced contamination.