Ultra-Niche Crops Series: Basil Postharvest Handling and Food Safety

Ultra-Niche Crops are defined as exceptionally high-value crops that can provide a significant source of income to the farmer while using minimal land area.

The visual appearance of basil is critical to its marketability. Careful handling from harvest to distribution is necessary to maintain a desirable appearance. Direct market sales can reduce the time between harvest and sale, increasing both freshness and shelf life for the customer. Basil is often consumed fresh/raw/uncooked, requiring careful consideration of food safety risks within the production operation.

Postharvest Quality and Handling

Should workers be trained on how to harvest basil?

Farm workers who harvest the herb play a key role in its overall quality. Basil may be harvested as individual leaves, stems with leaves, or by the entire plant. Employees must be trained on how to properly select, handle, grade, and pack the basil. These tasks can vary depending on the production methods, harvest preference, sales method, and environmental conditions.

How often should the basil be harvested?

Basil can be harvested at multiple stages of maturity, but always prior to bloom. The goal is to harvest fresh looking tender leaves. When harvesting single leaves only, the plant should not be reduced to less than four sets of leaves, allowing for additional plant growth. Whole stems can be harvested with multiple leaves and bagged or bunches, or another option is to dig or grow to sell the whole basil plant, including washed roots. Basil leaves should be cool and dry when harvested. Early morning harvests can be cooler in temperature, but these conditions often produce dew that wets the leaf surfaces. When possible, a late afternoon harvest can provide the cooler temperatures in addition to dry leaves.

How should fresh-market basil be prepared for sale?

Fresh-market basil should be evaluated to determine if washing is needed. Washing may be required if there is soil present on the leaves. Leaves not needing washing should be inspected for debris and other unwanted plant material. Leaves needing washing should be washed with clean water (see details below) and dried prior to storage to prevent decay. If basil is harvested in bunches, the leaves must be dry, and bunches should be loosely arranged to allow for airflow. Portable coolers may be used to store harvested basil at market locations. Basil stored in coolers alone will tend to warm. Utilizing ice packs or ice blankets is one way to lower the temperature. Since basil is susceptible to chilling injury, care must be taken to keep the basil directly off the ice packs. In addition to fresh-market sales, growers may create dried basil products that may extend their market season. For a dried basil product, lay out leaves on a clean surface to dry out of direct sunlight for several days. Circulated air will help the leaves dry more quickly and can help retain their green color.

At what temperature should basil be stored?

Basil is susceptible to chilling injury. Symptoms include blackening of leaves, stem discoloration, and loss of aroma. The optimal storage temperature for basil is 55° F. University of California Davis research found the visual quality of basil stored between 50° F and 68° F after 10 days was markedly better than basil stored at 32° F for 10 days (Kader, 2002). Consider how basil will be stored and transported from the field to the packing, storage, or display area.

At what relative humidity should basil be held in the cooler?

The ideal relative humidity is between 90 to 95%. If harvesting basil stems or selling basil in bunches, stems placed in water can reduce water loss and increase the relative humidity in the air. Covering the basil with a non-sealed covering is another method of increasing humidity around the plants. Reduction of temperatures in the storage area will help reduce moisture loss from the leaves.

Food Safety Considerations

Do I have to worry about food safety issues with basil?

Basil is commonly consumed without cooking. Consideration should be given to the risk for contamination of basil within your production system and postharvest handling. Each farm operation is unique, and the food safety considerations must be specific to the location, employees, field operations, and postharvest operations of a farm.

Are there water quality standards specific to irrigation for basil?

Contaminated irrigation water that comes in contact with basil has the potential to transfer pathogens onto the edible leaves. Contaminated overhead irrigation water can spread both plant and human diseases throughout a crop. Water used for overhead irrigation is likely to come in contact with the basil leaves and should be tested to better understand its quality. This is particularly true for surface irrigation water, such as ponds and streams. Ideally, for both plant disease and human disease, irrigation of basil should be done through drip tape. Irrigation water should be tested for generic E. coli to determine its quality. Well water should be tested annually at the beginning of the growing season. Surface water sources, including ponds, streams, and harvested rainwater, should be tested three times a year at minimum. Water testing labs should be certified, and results should be given to you in number form, not presence/absence. Water that is used for washing harvested basil should be from a source that has been tested for generic E. coli with results showing non-detectable levels.

Can I use compost with animal manures in basil production?

Animal manures can serve as an important nutrient source for crops and can improve the overall quality of soil. Considerations must be taken on how the manure is being used on the farm and the human pathogen risks resulting from that use. Animal manures can carry human disease such as E. coli, Listeria monocytogenes and Salmonella. Using scientifically validated methods when composting is critical. Currently the National Organic Program Standards are accepted by USDA and the FDA as acceptable practices. When adding raw manure to production areas, it should be applied at least 120 days prior to the harvest of the crop.

What should I do if I find that wildlife has entered the basil production area?

Developing an action plan to be used when fecal material or wildlife feeding on crops occurs is important. It is recommended that fields are scouted for animal activity prior to harvesting and that any areas where fecal material or feeding is found are marked so that harvesting does not take place there. A five foot buffer around fecal material is recommended. Once this plan is developed, all workers should be aware of it so that proper action is taken when they see a potential contaminant from wildlife.

Can farm workers contaminate basil?

Basil is commonly harvested by hand in small scale production, and the health of the harvester is critical. Workers coming in contact with produce and its growing area should receive annual training on human health and hygiene specific to fresh produce safety. This annual training should focus on human diseases communicable to others, the routes of contamination, proper handwashing, proper restroom use, and food safety policies specific to the farm. More information on this type of training can be found in the Rutgers “Worker Health and Hygiene” Fact Sheet FS1230.

Do I need to worry about using storage and sales containers more than once?

Packing materials can serve as a source of contamination if they are not handled and stored properly. Re-using containers is possible, if you know that they have been handled and stored in a sanitary way. Appropriate storage areas for containers are areas that have a rodent control program, are free from other wildlife and pets, and free of physical contaminants. Cleanable reusable containers are ideal. It is up to the farmer to determine at what point the containers need to be cleaned and sanitized and to establish instructions and procedures for how the containers are to be cleaned.

Critical Considerations

1. Temperature management is the most critical aspect of prolonging postharvest quality for basil. Harvested basil should be cooled, dried, and removed from direct sunlight as quickly as possible.
2. Attend an on-farm food safety training to better understand food safety risks and modes of contamination.
3. Conduct risk assessments for your operation focusing on: land use history, water system and movement, animal activity (wildlife and domestic), soil amendments used and made, packing house area and activities, and produce distribution methods.
4. Develop written instructions, known as standard operating procedures (SOPs), for activities deemed high risk, such as procedures for washing and sanitizing product contact surfaces. These SOPs will streamline processes at the farm and ultimately reduce the risk of product contamination.
5. Train workers annually on worker personal health and hygiene and the identified risks on the farm.
6. Sample irrigation and postharvest water as deemed necessary.

Resources

• Specialty and Minor Crops Handbook, University of California. 1998, pp.17-19
• Kader, A. Postharvest Technology of Horticultural Crops, University of California. 2002, pp.327-331.

Project sponsored by the USDA-NIFA Beginner Farmer and Rancher Development Program.

April 2018