We have all heard about the several deadly E. coli O157:H7 outbreaks linked to romaine lettuce that sickened hundreds of people last year in the United States. That contamination apparently occurred while the greens were growing in the field. But can leafy greens such as spinach be contaminated with pathogens during germination?
Unfortunately, leafy greens are a main source of foodborne illness, because they are easily contaminated in the field and typically aren’t cooked before serving. But that contamination was on the surface of the plant, not internalized into the leaves themselves.
Now researchers have looks at the possibility that spinach can be contaminated at germination. Even worse, this contamination can be internalized in the leaf, which means that no amount of cleaning or rinsing will remove the pathogen.
This is already a problem with raw sprouts. That food is inherently risky, especially to people who are at high risk for serious complications from foodborne illness, because the seed itself is often contaminated. Then, the moist and warm growing environment is perfect for bacterial growth as well as germination.
Scientists at the University of Arizona studied the contamination of spinach at germination with Salmonella bacteria. The study was published in the International Journal of Food Microbiology. The researchers contaminated the seeds by either immersing them in a suspension of Salmonella and then sprouting them, or sprouting them in Salmonella contaminated water.
After five days, germinated sprouts were analyzed for Salmonella Newport population and internalization. Germinated sprouts were then potted in soil and grown for four weeks. The researchers then sampled the leads, stems, and roots for Salmonella.
They found that sprouts germinated using contaminated water or seeds had Salmonella Newport populations that were “significantly higher than other spinach tissues.” And the scientists found internalization in plants developing from contaminated seeds and in sprouts germinated using contaminated water.
That means that contamination of spinach during germination can result in “persistence, internalization and environmental reintroduction of Salmonella.”
Kumar, G. D., Patel, J., & Ravishankar, S. (2020). Contamination of spinach at germination: A route to persistence and environmental reintroduction by Salmonella. International Journal of Food Microbiology, 326, [108646]. https://doi.org/10.1016/j.ijfoodmicro.2020.108646
