Effect of gamma-irradiation on the survival of Listeria monocytogenes and allergenicity of cherry tomatoes

Gamma irradiation delays tomato (Solanum lycopersicum) ripening by inducing transcriptional changes

BACKGROUND

Tomato (Solanum lycopersicum) has a relatively short shelf life as a result of rapid ripening, limiting its transportability and marketability. Recently, gamma irradiation has emerged as a viable method for delaying tomato fruit ripening. Although few studies have shown that gamma irradiation delays the ripening of tomatoes, the underlying mechanism remains unknown. Therefore, the present study aimed to examine the effects of gamma irradiation on tomato fruit ripening and the underlying mechanisms using transcriptomics.

RESULTS

Following gamma irradiation, the total microbial count, weight loss, and decay rate of tomatoes significantly reduced during storage. Furthermore, the redness (a*), color change (∆E), and lycopene content of gamma-irradiated tomatoes decreased in a dose-dependent manner during storage. Moreover, gamma irradiation significantly upregulated the expression levels of genes associated with DNA, chloroplast, and oxidative damage repairs, whereas those of ethylene and auxin signaling-, ripening-, and cell wall metabolism-related, as well as carotenoid genes, were downregulated.

CONCLUSION

Gamma irradiation effectively delayed ripening by downregulating the expression of ripening-related genes and inhibiting microbial growth, which prevented decay and prolonged the shelf life of tomatoes. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of phytosanitary irradiation and methyl bromide fumigation on the physical, sensory, and microbiological quality of blueberries and sweet cherries

BACKGROUND

The objective of this study was to determine whether irradiation could serve as a suitable phytosanitary treatment alternative to methyl bromide (MB) fumigation for blueberries and sweet cherry and also to determine the effect of phytosanitary irradiation treatment on survival of Salmonella spp. and Listeria monocytogenes on these fruit. 'Bluecrop' blueberries (Vaccinium corymbosum) and 'Sweetheart' cherries (Prunus avium) were irradiated at 0.4 kGy or fumigated with methyl bromide and evaluated for quality attributes during storage.

RESULTS

Irradiation caused an immediate decrease in firmness of both fruit without further significant change during storage. Fumigated fruit, in contrast, softened by 11-14% during storage. Irradiation did not adversely affect blueberry and cherry shelf-life. MB fumigation did not impact blueberry and cherry quality attributes initially; however, fumigated fruit exhibited greater damage and mold growth than the control and irradiated samples during storage. Irradiation at 400 Gy resulted in a ∼1 log CFU g(-1) reduction in Salmonella spp. and Listeria monocytogenes counts, indicating that this treatment cannot significantly enhance safety.

CONCLUSION

This study indicates that irradiation at a target dose of 0.4 kGy for phytosanitary treatment does not negatively impact blueberry and cherry quality and can serve as an alternative to methyl bromide fumigation. © 2016 Society of Chemical Industry.

Influence of refrigerated storage time on efficacy of irradiation to reduce Salmonella on sliced Roma tomatoes

Contamination of tomatoes with Salmonella is a recurring food safety concern. Irradiation is a nonthermal intervention that can inactivate pathogens on fresh and minimally processed produce. However, the influence of tomato processing protocols, including time in refrigerated storage and time between slicing and irradiation, has not been determined. Roma tomatoes were sliced and inoculated with a cocktail of Salmonella outbreak strains. The inoculated tomatoes were held in refrigerated storage for various times after inoculation to simulate the potential time delay between packaging and irradiation. Tomatoes were irradiated immediately (0 h) or after 24, 48, or 72 h in storage. The surviving populations were recovered and enumerated. Irradiation effectively reduced Salmonella at all times. The D(10)-values (the dose necessary for a 1-log reduction of the pathogen) were not significantly different at each storage time and ranged from 0.382 to 0.473 kGy. These results suggest that the time required for holding of processed Roma tomatoes or shipment to an off-site irradiation service provider will not alter the efficacy of irradiation in a commercial environment.