Preventive controls for the hygienic production of sprouted seeds
On this page
- Seed production
- Control of sprouting production
- Sample collection and testing of the spent irrigation water and sprouts
This document provides information about good agricultural practices (GAP) and good hygienic practices for the production of sprouted seeds that may be consumed raw. It sets out specific recommendations for the production of sprouts and general recommendations for the growing of seeds destined for sprout production.
For the purpose of this document, the following definitions apply.
- Seed distributor:
- Any person responsible for the distribution of seeds (handling, storage and transportation) to sprout growers. Seed distributors may deal with single or multiple seed producers and can be producers themselves.
- Seed producer:
- Any person responsible for the management of activities associated with the primary production of seeds including post-harvest practices.
- Seed lot:
- A quantity of seeds produced and handled under uniform conditions with as little variation as possible (e.g., seeds grown under similar agricultural
- Spent irrigation water:
- Water that has flowed over and through the sprouts.
- Sprout lot:
- A quantity of sprouts produced and handled under uniform conditions with as little variation as possible and harvested on the same day (e.g., sprouts produced from a single seed lot, germinated, grown and harvested at the same time using the same disinfection and growing methods and type of equipment).
- Sprout grower:
- Any person responsible for the management of the activities associated with the production of sprouted seeds.
- Sprouted seed:
- Any seed that has been sprouted for human consumption. This includes seeds grown in soil.
Microbial and chemical contamination may occur during the cultivation and harvesting of seeds in fields or during storage and transportation. The safety of sprouts is highly influenced by the degree of preventive measures used on farm to avoid contamination of seeds. It is recommended that seeds used for sprout production be produced using good agricultural practices (GAP) at all stages during the planting, growing, harvesting, cleaning, storage and transportation. Sprout growers can recommend that seed producers adopt GAP and provide evidence that the product was grown according to specifications.
Composting and other treatments (including environmental conditions) may reduce but may not eliminate pathogens in manure, bio solids and other natural fertilizers. It is particularly important to prevent microbial contamination during the production of seeds because of the potential for pathogens to grow during the sprouting process.
Water used for irrigation and other agricultural uses is a potential source of microbial contamination.
- Evaluate the source of water used on farm (well, open canal, reservoir, reused irrigation water, municipality, rivers, lakes, ground water, etc.), monitor its safety and control potential sources of contamination.
- Avoid using water known or suspected to be contaminated with animal or human waste.
- Adjust harvesting equipment to minimize soil intake and clean from any debris or earth before harvesting.
- Clean and inspect handling equipment (augers, conveyors, etc.).
- Clean and sanitize transport trucks, wagons, etc. if used to haul manure and soil.
- Clean storage bins, totes, etc. and ensure they are bird and rodent proof or stored in a rodent controlled facility.
- Avoid using diseased or damaged seeds for sprout production, which could be susceptible to microbial contamination.
- Segregate seed lots intended for sprouting from product to be used as animal feed (e.g., for hay production).
Seeds for sprouting should be free to the extent possible from foreign matter including soil, insect fragments, bird and rodent droppings, metal and glass fragments. Conditioning utilizes a variety of equipment to remove soil, weed seeds and other debris from seeds. Conditioning should be carried out in a hygienic manner employing practices that minimize potential sources of contamination.
- Equipment is constructed to allow for easy cleaning and, when necessary, sanitizing.
- Equipment is protected from pests.
- All equipment is thoroughly dry cleaned (compressed air, brushes, etc.) between lots and sanitized if required.
- Seed conditioning facilities ensure that the equipment has not been used to handle animal products. If it has, it is thoroughly cleaned and sanitized before cleaning seeds.
Packaging of seeds for sprouting should be carried out in a hygienic manner.
- Equipment is constructed to allow for easy cleaning and, when necessary, sanitizing.
- Equipment is protected from pests.
- Use solid bags - open weave bags should not be used.
- Avoid using contaminated or recycled bags.
- Mark each package to identify source and lot. For any seed that has been treated, clearly state this on the label.
- Store packaged seeds in a clean and dry area and protected from vermin and pests.
Analyses, documentation and records
Seed distributors should analyse each lot for the presence of microbial pathogens of concern such as Salmonella spp. and E. coli O157:H7 using internationally accepted analytical methods. Microbial analysis of seeds may help identify highly contaminated lots. Seed producers and sprout growers should be aware that negative results do not guarantee pathogen free seeds because of analytical and sampling limitations. It is important to use random sampling techniques, sufficient sample sizes and sub sample numbers to represent the lot as best as possible.
- Avoid using lots of seeds for which positive results are obtained for sprout production. Other lots which were produced under similar conditions (e.g., on the same sites or with the same agricultural inputs) which present a similar hazard are also not used for sprouting. Hold these lots until they are disposed of properly.
Seed producers should keep all records on agricultural activities current, such as the site of production, suppliers' information on agricultural inputs, lot numbers of agricultural inputs, irrigation data, agricultural chemical and fertilizer usages, water quality data, cleaning schedules for premises, facilities, equipment and containers, and details of disposition of rejected lots.
Control of sprouting production
Prevention of cross-contamination
During sprout production, effective measures should be taken to prevent cross-contamination of seeds and sprouts. To prevent cross-contamination, sprout growers can consider the following.
- The traffic pattern of employees should prevent cross-contamination of sprouts. For example, the employees should avoid going back and forth to various stages of production. The employees should avoid going from a potentially contaminated area to the germination and/or packaging area unless they have washed their hands and changed to clean protective clothing. Boot sanitizing stations can be located at the entrance to germination and packaging areas.
- Protective clothing (e.g., coats, aprons, etc.) should stay in the germination or packaging areas when the employee leaves these areas (e.g., before breaks, etc.)
As a sprout grower:
- Recommend that seed producers adopt GAP.
- Obtain certificates of analysis for microbial pathogens of concern from seed producers or distributors for each incoming lot.
- Maintain a documented history of seed suppliers' adherence to specifications (e.g., analytical results, GAP records, etc.)
- Ensure each bag of seeds is labelled with the name of the seed producer or distributor, the lot number and the country of origin. That information should be available also for all components constituting seed blends.
- Keep records to facilitate trace-back and recall procedures.
Control of incoming seeds
Each bag should be examined at its arrival to minimize the potential for introducing obvious contaminants into the establishment. If certificates of analysis are not provided by seed producers or distributors, sprout growers should analyse the seed lots for the presence of microbial pathogens of concern as described in Analyses, documentation and records above.
- Examine each bag for physical damage (e.g., holes from rodents) and signs of contamination (e.g., stains, rodent, insects, feces, urine, foreign material, etc.) upon arrival. If found to be damaged, contaminated or potentially contaminated, its contents should not be used for sprout manufacture.
- If seed lots are analysed for the presence of microbial pathogens of concern, avoid using until results of analysis are available. Lots of seeds for which positive results are obtained should not be used for sprout production.
- Document results of analysis and disposition of contaminated seeds.
- Use statistically valid sampling methods.
The storage area for seeds should be clean, dry, and protected against pests and separate from the rest of the facility. It should not be used to store equipment, chemicals or personal items.
- Handle and store seeds in a manner that will prevent damage and contamination.
- Store seeds off the floor, away from walls and in proper storage conditions to prevent mould and bacterial growth and facilitate pest control inspection.
- Store open bags in closed containers or otherwise protected from contamination.
Specific steps in sprout production
All steps involved in antimicrobial treatment for seeds (e.g., initial rinse and disinfection) should be carried out in an area separate from the germination and packaging areas and designed to avoid contamination of sprouts by non-disinfected seeds or chemical disinfectants.
The seeds should be rinsed thoroughly before the antimicrobial treatment to remove dirt and increase the efficiency of the antimicrobial treatment.
- Rinse and agitate seeds in large volumes of potable water. Repeat the process with potable water until most of the dirt is removed and rinse water remains clear.
- Carry out the rinsing process in such a way to maximize surface contact with water (e.g., use large buckets of water and sieves).
Antimicrobial treatment for seeds
If seeds for sprouting have been grown under GAP and stored and transported in closed containers, the likelihood of being contaminated with pathogenic bacteria is minimized but not eliminated. Seeds should undergo an antimicrobial treatment to reduce the potential for pathogenic microorganisms. There is currently no treatment available that can guarantee pathogen free seeds. An antimicrobial treatment for seeds that can achieve a minimum 3 log reduction of the microbial pathogens of concern should be considered. Examples of such treatments are the use of 2,000 ppm of calcium hypochlorite or sodium hypochlorite for 15-20 minutes or 6-10% hydrogen peroxide for 10 minutes. Other antimicrobial treatments for seeds may be evaluated by the Food Directorate, Health Products and Food Branch, Health Canada, if enough data is provided.
During the antimicrobial treatment, sprout growers can consider the following.
- Use a fresh solution of disinfectant for each sprout lot.
- Ensure seeds are well agitated in large volumes of disinfectant solution to maximize surface contact. There should be at least five times the volume of disinfectant for the amount of seeds (e.g., for each 5 kg of seeds, at least 25 litres of disinfectant is used).
- Use disinfectants that are approved for use on foods.
- Accurately measure and record the duration of treatment and the concentration of disinfectant used.
- Put strict measures in place to prevent re-contamination of seeds after the antimicrobial treatment.
- Chemical disinfectants could be hazardous. For people handling chemicals, follow the label directions and take appropriate precautions.
- Ensure protective equipment is worn such as: waterproof gloves, chemical-resistant footwear and socks, protective clothing such as coveralls over long sleeve shirt and long pants, protective eye wear, and chemical-resistant headgear for overhead use.
Rinse after antimicrobial treatment
Rinse the seeds thoroughly with potable water after the antimicrobial treatment. Repeat rinsing sufficiently with potable water to eliminate disinfectant.
Soaking is often necessary to improve germination. When soaking, the sprout grower can consider the following.
- Sanitize all containers used for soaking prior to use.
- Soak seeds in water for a short period to minimize microbial growth.
- This step may also include an additional antimicrobial treatment.
- After soaking, rinse seeds thoroughly with potable water.
During germination, it is critical to keep the environment and equipment clean to avoid potential contamination. All equipment should be cleaned and sanitized before each new batch.
- Physically separate the germination, harvesting and packaging areas from the receiving.
- Protect storage and disinfecting areas from outside contaminants.
- Use only potable water. If recirculating water is used, put proper water treatments in place to maintain the potability of the water. Monitoring systems should be in place to ensure the adequacy of the treatment.
- When used, ensure soils are pathogen free.
- As a means to monitor the presence of pathogens in the finished product, it is recommended that the spent irrigation water be collected after 48 hours of germination and analysed for the presence of microbial pathogens.
All equipment should be cleaned and sanitized before each new batch. Harvesting should be done with cleaned and sanitized tools dedicated for this use.
Final rinse and cooling
A final water rinse will remove hulls and may reduce microbial contamination on sprouts. Cold water will lower sprout temperature and slow down potential microbial growth. When the final rinse is being carried out, the following can be considered.
- Rinse sprouts in cold potable water.
- Change water as needed (e.g., between lots or batches) to prevent cross-contamination.
- Where applicable, drain sprouts using a sanitized food grade centrifugal dryer.
- Place sprouts in a cool room to further lower the temperature.
- Place sprouts in small, shallow containers to allow for rapid cooling and to minimize the potential growth of pathogens.
Packaging design and materials should provide adequate protection for sprouts to minimize contamination, prevent damage, and accommodate proper labelling. Packaging materials should be clean, non-toxic and pose no threat to the safety and suitability of sprouts under the specified conditions of storage and use. There should be no unnecessary delays between harvesting and packaging.
Storage of finished product
The cold storage room used for sprouts should allow for adequate maintenance and cleaning; prevent pest access and harbourage; and consistently provide an environment which minimizes microbial growth (e.g., by temperature control and air circulation).
- Keep sprouts refrigerated during storage to minimize microbial growth.
- Install a thermometer and monitor the storage room temperature daily.
Analysis of spent irrigation water and finished product
Sprout growers should have a sampling plan to ensure the consistent collection of samples in an appropriate manner. Spent irrigation water is the water that has flowed over and through the sprouts and is a good indicator of the types of microorganisms in the sprouts themselves. It should be analysed for microbial pathogens of concern by collecting a representative sample from each production lot or batch. Finished product samples may also be collected and analysed.
Sample collection and testing of the spent irrigation water and sprouts
Microbial testing of spent irrigation water is considered to be one of the most practical and acceptable testing techniques currently available. Health Canada recommends that sprout growers regularly test the spent irrigation water, because water that has flowed over and through the sprouts is a good indicator of the types of microorganisms in the sprouts themselves, including pathogens of microbial concern (Salmonella spp., E. coli O157:H7). Sprouts should not be tested in place of spent irrigation water unless the production methods make it impossible to test the spent irrigation water. However, the recommendation to test spent irrigation water does not preclude additional testing of sprouts (either sprouts collected during production or finished product). Representative samples should be collected from each production lot and analysed for microbial pathogens of concern.
More guidance about general sampling techniques can be found in Sampling procedures guidance.
Sampling equipment and containers
Equipment and containers used to collect samples should be clean and sterile. They may be purchased pre-sterilized or, alternatively, they may be sterilized at 121°C (250°F) for 30 minutes in an autoclave, prior to use. Heat-resistant, dry materials may be sterilized in a dry-heat oven at 140°C (284°F) for 3 hours. Once sterilized, the sampling equipment and containers should be protected from contamination at all times before and during use. Ensure that the used sampling equipment, containers and the collected samples do not contaminate remaining sterile equipment and containers.
The type of sample containers to be used depends on whether spent irrigation water or sprout samples are being collected. Containers may include pre-sterilized plastic bags, bottles, tubes, cups and flasks. They should be dry, leak-proof, wide-mouthed, and of a size suitable for the samples. Containers should also seal properly to ensure the integrity of the sample. The containers should be properly labelled prior to collecting the sample.
When to sample
Samples of spent irrigation water can be collected as early as 48 hours after the start of sprouting. If the seeds are pre-soaked (e.g., soaked in water for a short time and then transferred to growing units for sprouting), include the pre-soak time. Early results will allow the sprout growers to take corrective actions sooner, thus minimizing the potential for one lot of sprouts to contaminate other lots.
Procedures for sample collection
Sample collection of spent irrigation water and sprouts should be done on site by trained personnel. Aseptic sampling procedures should be used to avoid contaminating the sample and the product being sampled.
Personnel should wear a clean lab coat, hair net and sterile gloves. Hands should be washed immediately prior to putting on sterile gloves. The sterile gloves should be put on in a manner that does not contaminate the outside of the glove. During sample collection, hands should be kept away from the mouth, nose, eyes and face. After sample collection, the gloves should be properly discarded.
The sterile sample container should be opened only sufficiently to allow for the sample to be collected. The sample should be placed directly in the container. Once the sample is collected, it should immediately be closed and sealed. If collecting samples in a container with a lid, the lid should not be completely removed. The lid should not be held separately or placed on a counter.
The sample container should be filled no more than ¾ full to prevent overflow. The air from the container should not be expelled when sealing, particularly for plastic bags
Once collected, the samples should be delivered to the laboratory promptly. The sample should be kept at an appropriate temperature, preferably between 0 and 4°C (32° to 40°F). To avoid cross-contamination from melting ice, sealed coolant packs should be used.
Pooling samples from different sprout lots may reduce the number of lab analyses to be performed, however if a presumptive positive is found, all sprouts lots represented by the pooled sample are suspect. The suspect sprout lots should either be discarded or each sprout lot should be analysed separately to determine which lot(s) is (are) contaminated.
The volumes given below for spent irrigation water and sprouts represent a sufficient sample size to test for the presence of the microbial pathogens of concern (i.e., Salmonella spp., and E.coli O157:H7).
A. Spent irrigation water
One (1) litre of water should be aseptically collected as the water leaves a drum or tray(s) during the irrigation cycle. Spent irrigation water samples should be collected directly into clean, sterile, pre-labelled containers.
One (1) litre of spent irrigation water may be collected from the drum.
Trays with common trough
One (1) litre of spent irrigation water may be collected at the common trough.
Trays with no common trough
If there is no common trough, spent irrigation water samples from individual trays should be collected and pooled. If the tray is large, spent irrigation water samples from different areas of the tray should be collected.
When Ten (10) or fewer trays make up a production lot, approximately equal volumes of spent irrigation water should be collected from each of the 10 trays to make a total sample volume of one (1) litre. For example:
- Ten (10) trays: Collect 100 ml of spent irrigation water samples from each tray to make up one (1) litre sample.
- Eight (8) trays: Collect 125 ml of spent irrigation water samples from each tray to make up one (1) litre sample.
When there are Ten (10) or more trays, collect ten (10) spent irrigation water samples throughout the entire production lot. For example: if there are 20 trays in a production lot, collect samples from every other tray in the rack, moving from top to bottom, side to side, and front to back.
Five (5) sample units of approximately 200 grams each should be aseptically collected from different locations in the drum or growing trays, to ensure the sample collected is representative of the lot. The sample units should be collected throughout the entire production lot (e.g., from top to bottom, side to side, and front to back of the drum or trays). Each 200 gram sample unit should be placed directly into individual clean, sterile, pre-labelled containers.
Microbial testing procedures
All microbial testing for pathogens should be conducted in an external, certified, independent laboratory, and consider the following criteria:
- The laboratory is physically separated from the food production facility to prevent cross-contamination.
- The laboratory is staffed by personnel with training and experience in analytical microbiology techniques to ensure that tests are performed correctly and that all appropriate safety precautions, including appropriate waste disposal, are followed.
- The laboratory has appropriate resources and be able to demonstrate that they follow a quality management system.
- If the microbial analysis is done by the sprout grower, the laboratory facilities, personnel, and quality management system meet the above mentioned criteria, to ensure that testing is reliable and does not create food safety hazards.
The testing procedures described below can be used to obtain results as simply and quickly as possible on the presence or absence of the microbial pathogens of concern (i.e., Salmonella spp. and Escherichia O157:H7). These methods are described in the Health Canada (HC) Compendium of Analytical Methods.
Please keep in mind that seasonal or regional differences in water quality, type of seed being sprouted, and variations in sampling and analytical conditions may all impact on the effectiveness of the screening tests.
Escherichia coli O157:H7:
- MFLP-87 VIP EHEC. Biocontrol Systems, Inc., Bellview, WA.
- MFLP-94/95 Reveal E. coli O157:H7, Neogen Corp., Lansing, MI.
- MFLP-91 Tecra UVA method for E. coli O157:H7.
- Any other methods listed in the Compendium for E. coli O157:H7.
- MFHPB-24 Vidas SLM method, Biomerieux, Montreal.
- MFLP-96 Reveal kit for Salmonella.
- MFLP-97 Alert kit for Salmonella.
- MFLP-35 Tecra VIA for Salmonella.
- Any other methods listed in the Compendium for Salmonella spp.
General laboratory instructions
Follow instructions in each method.
Dividing samples into sample units for analysis
Spent irrigation water
Total of one (1) L of spent irrigation water should be collected. Two (2) 100 ml sample units should be analysed for the presence of E. coli O157:H7. Two (2) 375 ml sample units should be analysed for the presence of Salmonella spp. Any unused portion of spent irrigation water should be stored under refrigeration pending completion of the analysis.
Total of five (5) sample units of 200 g of sprouts should be collected. For each sample unit, one 25 g sample unit should be analysed for the presence of E. coli O157:H7 and one 25 g sample unit should be analysed for the presence of Salmonella spp. Unused portions of the sprout sample units should be stored under refrigeration pending completion of the analysis.
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