Investigation of Microbial Contamination Sources during Production of Radish Sprout

Introduction:  In recent years, raw sprouts have been involved in a number of cases of foodborne illness. Processing stages, such as seed soaking, germination, sprouting and packing provide many opportunities for bacterial contamination.

Purpose:  The purpose of this study was to investigate what source most contributes to contaminating radish sprout by assessing microbial loads on sprout and agricultural inputs that came into contact with the sprout.

Methods:  To estimate microbial loads, fecal indicators (coliform and Escherichia coli) as well as foodborne pathogens (E. coli O157:H7, Salmonella spp., and Listeria monocytogenes) were enumerated. A total of 180 samples including seeds, sprouts, hydroponic nutrient solution, irrigation water, and tools from three different radish sprout farms were tested.

Results: Coliform contamination observed from sprout cutting knife and germinating seeds for all farms. For E. coli contamination, 14.4% (26 of 180) of the samples were positive, of which mostly sprouts and irrigation water collected from one particular farm. This implies that irrigation water could have served in transmitting E. coliwithin the production environment to the sprout being grown in the same premises. No foodborne pathogen was detected from the sample tested.

Significance:  This study suggests more cautions should be taken if water source for sprout production is contaminated with potential fecal matters or foodborne pathogens.