Experts have identified and evaluated ways to reduce foodborne illness associated with sprouts.

They reviewed studies as well as guidelines from authorities and industry associations with findings published by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO).

In 2019, the Codex Alimentarius Commission approved new work to develop guidelines on Shiga toxin-producing E. coli (STEC) in leafy vegetables and sprouts.

In September 2021, scientists on the Joint FAO/WHO Expert Meetings on Microbiological Risk Assessment (JEMRA) panel reviewed measures for the control of microbial hazards from primary production to point-of-sale in fresh, ready-to-eat (RTE) and minimally processed fruits and vegetables.

An expert meeting in November looked at relevant ways to control such hazards in sprouts, from the production of seed for sprouting, to the harvesting and packing of sprouts and to point-of-sale, record-keeping and traceability.

Conditions under which sprouts are produced are ideal for foodborne pathogen growth. Outbreak investigations have shown pathogens are most likely to originate from the seed, but contamination could also be attributed to the production environment.

Primary processing issues
Sprouts are also frequently eaten raw or only slightly cooked, so there is no kill step prior to consumption. Pathogens of concern are E. coli, Salmonella and Listeria monocytogenes, which may survive for long periods of time during seed storage and grow quickly during production.

Potential sources of contamination in the field include water, improperly managed animal manure, contact with wild animals and inadequate worker hygiene. Growing equipment, growing water and spent water are of great concern also.

Good agricultural practices (GAPs) should be applied at all stages for seeds destined for sprout production, including planting, growing, harvesting, cleaning, storage and transportation. Equipment used to grow, harvest and transport seed should be designed for effective cleaning and sanitation, which should be done regularly. Different solutions may be needed depending on the type of sprout – such as alfalfa or mung bean.

Treatments are one approach to reducing microbial contamination but there is currently none available that can guarantee pathogen-free seed. Effectiveness of chemical and physical treatments is varied between studies and has rarely been validated under industrial conditions, plus it can be costly. They can be challenging because of low water activity of the seed and the need to preserve viability of the seed and its ability to germinate, found the report.

Testing can enable early detection of contaminated production batches and is a verification that seed used for sprouting and the production process does not contribute to sprout contamination. However, the likelihood of detecting pathogens in seed is extremely low. Spent sprout irrigation water has been identified as an appropriate target to test.

From production and onwards
Poor hygienic practices and an unsanitary production environment could also lead to sprout contamination. Environmental monitoring is important to identify sources of contamination. One critical factor for sprout contamination is stagnant water.

It is anticipated that climate change will play an increasing role in outbreaks linked to contaminated seed because of more extreme weather events, such as flooding, and higher temperatures.

Producers and suppliers should have a system to identify seed lots, trace the associated production sites and agricultural inputs and allow for the retrieval of seed in the event of a suspected hazard. This is especially important as seed used for sprouting is often imported.

Mitigation strategies at point-of-sale include training of operators and retailers, use of clean, enclosed, refrigerated transport vehicles, a sanitary environment, and fit-for-purpose water for cleaning, sanitizing and cooling.

Experts said as interventions can be technical, training should be developed for the sprout supply chain covering seed sourcing and storage, treatment, sampling and microbial testing, cleaning and sanitizing and record-keeping.