Table 3.

Studies showing the possibility of microgreen contamination.

No.	Reference	Investigation Context	Results
1	Xiao et al., 2015 [66]	Escherichia coli O157:H7 were able to survive and proliferate significantly on radish microgreens in both soil-substitute and hydroponic production systems, with higher populations reported in the hydroponic production system.	The results showed that contaminated seeds led to systematic contamination of whole plants, including both edible and inedible parts, and seed coats remained the focal point of Escherichia coli O157:H7 survival and growth throughout the period of microgreen production.
2	Wang et al., 2015 [67]	Examined the survival and proliferation of seed-borne Listeria monocytogenes and other members of the seeds microbiota on microgreen plants grown in soil substitute and hydroponic production systems.	During microgreen growth for 10 days, Listeria monocytogenes counts on the seed coats increased by 0.7 and 1.3 log, respectively, for soil and hydroponic systems. Similar increases were observed on the edible portion of the microgreens. Seed coats, roots, and cotyledons were most heavily.
3	Di Gioia et al., 2016 [52]	Reported lower microbial populations in recycled fiber mats and on microgreens growing on them than in peat-based mixes and microgreens grown in pure peat.	They suggested that recycled fiber mats may be safer growth media than peat. Recycled textile-fiber and jute-kenaf-fiber may be valid alternatives to peatbecause both ensured a competitive yield, low nitrate content and a similar or higher microbiological quality.
4	Wang and Kniel 2016 [64]	Evaluated the capability of the human norovirus surrogate, murine norovirus (MNV), to internalize from roots to edible tissues of kale and mustard microgreens, as well as virus survival in recirculated water without disinfection.	They found constant high levels of viral RNA in edible tissues. MNV remained infectious in previously contaminated hydroponic systems for up to 12 days and was translocated in edible tissues via roots. Examination of the spatial distribution of bacterial cells on different parts of microgreen plants showed that contaminated seeds led to systematic contamination of whole plants, including both aerial parts and roots.
5	Reed et al., 2018 [68]	Reported that the type of growth medium played an important role in serovar-dependant Salmonella survival and growth on microgreens irrigated with contaminated water.	Of the different growth media tested, hydroponic pads resulted in the highest percentage of Salmonella-positive samples and the highest Salmonella population level on microgreens.