Significance and Impact of the Study: Generally, nuts have lower water activity which precludes the growth of food-borne pathogens. But, food-borne outbreaks due to pathogen-contaminated nuts have been reported in the last few decades. Pistachios are one of the most popular nuts and have many health beneficial effects. However, many pasteurization interventions have been used to reduce pathogens on pistachios, but most of them are not effective. This study confirms the effectiveness of gamma irradiation on pasteurization of pistachios. This may be helpful in nut processing industries to ensure the microbial safety of nuts. AbstractThis study evaluated the efficacy of gamma irradiation to inactivate food-borne pathogens on pistachios (Pistacia vera L.). Pistachios inoculated with Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes were subjected to gamma irradiation in the range of 0, 0Á5, 1, 3 and 5 kGy, and colour change was evaluated after treatment and during storage at room temperature. Pathogen populations decreased with increasing treatment doses. A gamma irradiation dose of 5 kGy decreased the three pathogens on pistachios to under the detection limit (1Á0 log CFU per g) without effecting colour change. During storage following treatment, pathogens were reduced due to the postirradiation effect. D-values of pathogens on pistachios showed that L. monocytogenes was more resistant to gamma irradiation than was E. coli O157:H7 or S. Typhimurium. During gamma irradiation treatment, L, a and b values of pistachios did not significantly change but these values changed during storage. These results show that gamma irradiation has potential as a nonthermal process for inactivating food-borne pathogens in pistachios without inducing colour changes.

Weizmannia coagulans (formerly Bacillus coagulans ) is Gram-positive, and spore-forming bacteria causing food spoilage, especially in acidic canned food products. To control W. coagulans , we isolated a bacteriophage Youna2 from a sewage sludge sample. Morphological analysis revealed that phage Youna2 belongs to the Siphoviridae family with a non-contractile and flexible tail. Youna2 has 52,903 bp double-stranded DNA containing 61 open reading frames. There are no lysogeny-related genes, suggesting that Youna2 is a virulent phage. plyYouna2 , a putative endolysin gene was identified in the genome of Youna2 and predicted to be composed of a N -acetylmuramoyl-L-alanine amidase domain (PF01520) at the N-terminus and unknown function DUF5776 domain (PF19087) at the C-terminus. While phage Youna2 has a narrow host range, infecting only certain strains of W. coagulans , PlyYouna2 exhibited a broad antimicrobial spectrum beyond the Bacillus genus. Interestingly, PlyYouna2 can lyse Gram-negative bacteria such as Escherichia coli , Yersinia enterocolitica , Pseudomonas putida and Cronobacter sakazakii without other additives to destabilize bacterial outer membrane. To the best of our knowledge, Youna2 is the first W. coagulans -infecting phage and we speculate its endolysin PlyYouna2 can provide the basis for the development of a novel biocontrol agent against various foodborne pathogens.

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