Effectiveness of UV-C irradiation on growth of post-inoculated Listeria monocytogenes on fresh-cut broccoli
G.R. Gamage, J. Wargent, J. Palmer, J.A. Heyes
Abstracts of 7th International Postharvest Symposium 2012 (IPS2012). 25-29 June, 2012. Putra World Trade Centre (PWTC), Kuala Lumpur, Malaysia. 238 pages.
2012
บทคัดย่อ
Ultraviolet (UV) light irradiation has demonstrated positive effects as a postharvest treatment in prolonging the storage life of fresh produce and as a non thermal method of inactivation of pathogenic microorganisms. The objective of this research is to study the effectiveness of UV-C light irradiation as a postharvest treatment on the subsequent attachment and growth of human pathogens on fresh produce. Fresh-cut broccoli is highly perishable and susceptible to deterioration and contamination by pathogenic microorganisms after harvest. Fresh-cut broccoli branchlets were treated with UV-C doses of 2.5 and 5 kJ/m2 and inoculated with Listeria monocytogenes at various times (0 h, 6 hand 24 h) after treatment. Growth of the bacteria on UV -C treated surfaces of broccoli branchlets was evaluated by extracting and enumerating the microorganisms on day 3,4, 6, and 8 after treatment. Results of the study show UV-C irradiation at a dose of 5 kJ/m2 was able to restrict the growth of L. monocytogenes in the samples inoculated 24 h post treatment, with no significant differences in colour and weight loss of the broccoli compared to the control treatments. These results imply UV -C treatment may be effective not just in controlling pre-existing pathogens but also reducing the risk of postharvest contamination. Previous studies have suggested that mild stress produced by UV -C light irradiation stimulates the synthesis of defence related phytochemicals in broccoli (such as glucosinolates) which also offer a variety of health benefits. It is not yet clear whether this mechanism is also responsible for the restriction of 1. monocytogenes attachment and growth after UV -C irradiation.