Improving the safety and quality of raw tuna fillets by x-ray irradiation

Authors: MAHMOUD, B.S - Mississippi State University; NANNAPANENI, R - Mississippi State University; CHANG, S.K - Mississippi State University; WU, Y - Mississippi State University

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2015
Publication Date: 1/1/2016
Citation: Mahmoud, B.M., Nannapaneni, R., Chang, S.C., Wu, Y. 2016. Improving the safety and quality of raw tuna fillets by x-ray irradiation. Food Control. 60:569-574.

Interpretive Summary: In recent years, consumers are eating more raw fish products such as sushi and sashimi. However, raw fish products can serve as vehicles for many foodborne pathogenic microorganisms. The fish products can be contaminated from the environment and/or through processing steps. In recent years, consumers are eating more raw fish products such as sushi and sashimi. However, raw fish products can serve as vehicles for many foodborne pathogenic microorganisms. The fish products can be contaminated from the environment and/or through processing steps.

Technical Abstract: In this study, raw tuna fillet (25 g) samples were inoculated by immersing in 0.1% peptone water that contained 108-9 CFU ml-1 of a three-strain mixture of Salmonella enterica for 1 min. The samples were then air dried at 22 oC for 30 min and were packaged separately in sterilized bags prior to X-ray treatments (0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 kGy). The surviving Salmonella populations on raw tuna fillets samples were evaluated using a nonselective medium (tryptic soy agar) for 6 h with xylose lysine desoxycholate (XLD) selective medium overlay. The plates were then incubated for an additional 18 h at 37 oC. Finally, the colonies were counted and the results were expressed as log CFU g-1. Furthermore, un-inoculated tuna samples (25 g) were packaged separately in sterilized bags and exposed to the lowest and highest X-ray doses (0.0 and 6.0 kGy), then stored at 5 oC, 10 oC or 25 oC for 25, 15 or 5 days, respectively. On the testing-dates, samples were withdrawn and microflora (psychrotrophic and mesophilic) counts, quality [color (using Hunter colorimeter) and texture (using Instron machine)] were evaluated. The results indicated that more than a 6 log CFU reduction of Salmonella population being achieved with 0.6 kGy X-ray treatment. Furthermore, treatment with X-ray significantly reduced the initial inherent microbiota on raw tuna fillets and inherent levels were significantly (p < 0.05) lower than the control samples throughout the shelf-life storage at 5, 10 or 25 oC for 25, 15 or 5 days, respectively. There was a significant effect of X-ray treatment on tuna color after treatment (day 0). However, no significant differences (p > 0.05) in color or texture of control and treated samples were observed after (day 0). These results indicated that X-ray is a good preservative technology for seafood products intended to be consumed raw.