Inactivation of Escherichia Coli On Alfalfa Seeds by Ultraviolet

Inactivation of Escherichia coli on alfalfa seeds by ultraviolet (UV-C) irradiation.

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana

Session 54F, Nonthermal Processing: General I

D. Gonzalez-Dector1, F. SAN MARTIN2, E. Palou, and A. López-Malo. (1) Universidad de las Americas Puebla, Ex-Hacienda Santa Catarina Martir S/N, San Andres Cholula, Pue., 72820, Mexico, (2) Dept. de Ingeniería Química y Alimentos, Univ. de las Américas, Puebla, Sta. Catarina Martir, Cholula, Puebla, 72820, Mexico

Short-wave ultraviolet irradiation is effective for decontamination of water and surfaces. Reports about the effectiveness of UV-C irradiation for decontamination of seeds for sprouting are scarce. Some countries, including the U. S., have reported Escherichia coli and Salmonella outbreaks associated to the consumption of sprouts. The objective of this work was to evaluate the effectiveness of UV-C irradiation of alfalfa seeds for inactivation of Escherichia coli inoculated into seed surface. Alfalfa seeds (200g) were soaked in an 18h culture of Escherichia coli and mixed with a sterile spatula. After 1min, seeds were decanted and spread over cheesecloth and allowed to dry under a laminar flow hood for 24h. Seeds were transferred to a sterile bag and stored at 5o C until needed. UV-C irradiation was done using a collimated beam UV-lamp (30 W, 254 nm). Seeds (2.5g) were weighed and spread over a 10cm diameter sterile petri dish. Exposure times ranged from 1 to 8min. After treatment, samples were serially diluted and plated in VRB and nutrient agar. Germination rate was evaluated by placing 100 seeds in a moist filter paper. Germinated seeds were counted after 72h. Results show that surface treatment of alfalfa seeds increased with exposure time but after treatment for 8min no further reduction was observed. At 4min and 8min one log reduction was observed for selective and general media. In order to improve the effectiveness of the treatment, seeds were exposed to half of treatment time, shaken for 20s and treated for the remaining half time. Treatment after 8min showed 1.8 log reduction as compared to 1.0 log-cycle for 4min treatment. UV-C irradiation is a technology with potential to be used as a hurdle during disinfection of seeds for sprouting. Our results encourage the study of treatment combination with traditional and nontraditional sanitizers.