Introduction

What is a disinfectant or sanitizer?

EPA further defines disinfectants as products that are used on hard inanimate surfaces and objects to destroy or irreversibly inactivate fungi and bacteria but not necessarily their spores. Disinfectant products are divided into two major types: hospital and general use. Hospital type disinfectants are the most critical to infection control and are used on medical instruments, floors, walls, bed linens and other surfaces. General disinfectants are the major source of products used in households, swimming pools and water purifiers.

Sanitize is to make sanitary, as by cleaning or disinfecting and to be sanitary is to be free from elements such as filth or pathogens that endanger (mushroom) health. Sanitizers are used to reduce, but not necessarily eliminate, microorganisms from the inanimate environment to levels considered safe as determined by public health codes or regulations. Sanitizers include food contact and nonfood contact products. Sanitizing rinses for surfaces such as dishes and cooking utensils, as well as equipment and utensils found in dairies, food-processing plants and eating and drinking establishments comprise the food contact sanitizers. These products are important because they are used on sites where consumable food products are placed and stored. Nonfood contact surface sanitizers include air-handling equipment, spawning and casing equipment, bedboards, trays, floors, walls and breezeways.

Antiseptics and Germicides are used to prevent infection and decay by inhibiting the growth of microorganisms. Because these products are used in or on living humans or animals, they are considered drugs and are thus approved and regulated by the Food and Drug Administration (FDA). Germicidal products are generally more closely regulated and are not commonly used around mushroom farms.

Disinfectants and sanitizers will be used interchangeably in this article.

Food safety and tolerance for disinfectants or sanitizers

Often we take for granted the use of certain chemicals as common practice around a mushroom farm. Certainly we are well educated on the registration, use and safety of pesticides on a farm, however, disinfectants and sanitizers are often used without much consideration to food or worker safety. Growers need to remember that all chemicals (including disinfectants and sanitizers) have an EPA registration number and require growers to follow the details of the product’s label. Some of these disinfectants and sanitizers are registered for Food Contact Surfaces (FCS) and can be used around the crop at their allowable concentrations. However, some are only registered for General Sanitation (GS) and cannot be used in anyway if the chemical can contact the mushrooms, compost or casing. Contact that is unintentional is not allowable. Inadvertent movement of these products can potentially create minute amounts of residues on the mushrooms.

The objective of disinfecting is to kill both spores and mycelium of mushroom pathogens, like Trichoderma and Verticillium, as well as human pathogens that are a potential food safety issue. In addition, the disinfecting of the farm after and between crops is to kill mushroom spores and mycelial fragments for control of virus disease, not often found on the white button mushrooms, but a potentially serious problem for Portabella and Phase III tunnel farms. It is known that mushroom viruses can be carried back into the process via surviving mushroom spores and mycelium. Some products (chlorine or some oxidizing chemical), approved for direct application because there is zero residue, are used to reduce bacterial populations on the mushrooms.

What disinfectants should I use?

Cost is an important factor and the grower must think of not just the cost per gallon, but cost per working solution. If it takes twice as much chemical to achieve the effective concentration for the working solution, the concentrate should not cost twice as much as another chemical that requires less quantity to achieve the effective working solution.

Effectiveness is always the grower’s main concern. Data for the relative effectiveness of all the disinfectants is not readily available. Results reported are often from tests in a petri dish, not under cropping conditions. Most growers and scientist realize that what works in a petri dish does not always work in real life. Part of that difference is that all disinfectants lose their effectiveness as the organic matter load increases. That is why effectiveness is related to cleanliness.

Corrosiveness of the chemical is also a consideration when sanitizing equipment. Several disinfectants are very effective, but continuous use will cause damage to metal or moving parts. A thorough rinsing of the equipment is necessary and of course that extra step is an additional cost. The cleaning and disinfecting of HVAC equipment is often dependent on how corrosive disinfectants are and whether they leave a residual that could possibly dry and then be dissipated into a room. Therefore, to be safe and avoid any possible migration of chemicals into the room, it is best to use a FCS chemical or soap and water that would not be a food safety concern.

Water quality is generally not a concern, except for some of the chlorine products. Chlorine is only effective at a pH of less than 7.0. Therefore, to achieve an effective disinfecting with chlorine, the pH of the water has to be adjusted, adding an additional cost to the use of these products.

Where can I use what disinfectants?

Mechanical harvesting equipment, conveyors, sorting or packing lines or other food processing or handling equipment, e.g., slicers, mushroom washing and blanching equipment are other examples of FCS, that must be cleaned with the proper disinfectants or thoroughly rinsed with potable water after use with non-FCS chemicals.

All disinfectants/sanitizers are inactivated by dirt load or organic matter loads. Therefore, for the most effective disinfecting, remove all dirt and debris before sanitizing by thoroughly brushing and cleaning all surfaces with soap or detergent and then rinsing with generous amounts of water. Disinfectants are commonly used in breezeway foot baths and the rapid increase of dirt load in these baths has to be considered to insure an effective concentration is maintained. Another concern is worker safety. Only a few chemicals available can be used where nonimpervious shoes or boots are worn.

Dip tanks and foot baths are often filled with some type of disinfectant. The rapid accumulation of dirt and organic matter in these containers will make the disinfectants quickly inactive. Therefore, cleaning or rinsing equipment before dipping is recommended. Any harvesting equipment must be rinsed unless an approved FCS disinfectant is used. Footbaths also raise an issue with worker safety, since only some products are registered to use ONLY with impervious (impermeable) footwear. A general rule is to ensure the proper Personal Protective Equipment (PPE) is used for each chemical.

Spawn/casing crews should use high-pressure hot water to clean their spawning equipment because some chemicals may deteriorate on the bearings or other moving parts. The casing equipment, buckets, cart, track, around the doors, the wharf area and the truck can be sprayed with phenols, quats or idodiphors, however all equipment that comes in contact with compost or casing layer must be thoroughly well rinsed with potable water. Chlorine and several types of oxidizing agents can be used, but rinsing will prolong the life of the equipment. Some people feel that good old soap and water will work just as well.

Make sure that other indirect or inadvertent contact does not occur with either the crop or food contact surfaces. Examples of this would be drift or splashing, use of an aerosol or fogging agent, intake through air ducts, etc.

The most common use for disinfectants may be the sanitation of breezeways (walls, floors and doors) or picking halls. However, it is critical that all picking boxes, trays, and tills must be removed until the area is dry and all volatiles have dissipated. Potential drift may migrate to harvesting containers causing unwanted residues and product damage.

Aerosol application of disinfectants is allowed, however, air handling equipment must be turned off until the product dries and volatiles have dissipated. When using FCS sanitizers, air handlers may be left on to sanitize the internal coils.

HVAC equipment is often a concern for carry over of disease from crop to crop. It may be a common practice on farms to clean and disinfect the coils and ducts of the air handling equipment. Although this equipment is not considered FCS, the potential for a chemical used to clean this equipment to be dissipated throughout a cropping room is a concern.

Unintentional contact with mushroom compost or casing material is a concern because of the resulting inadvertent residues (possibly in only the ppb levels) that could remain on the mushroom tissue. This inadvertent contact may occur when equipment is washed and sanitized prior to daily usage. Several fruits and vegetables have some type of residual tolerance for different types of disinfectants. Unfortunately, at this time, residues for some of the disinfectants used in the mushroom industry have no tolerance established for mushrooms. Efforts by Penn State, IR4 and AMI are under way to pursue some type of "inadvertent tolerance" label for the important disinfectants used in the industry.

What disinfectants are available for mushroom farms?

FCS = food contact surfaces; GS = general sanitation; OM = organic matter

What do labels tell us?

Growers should read the disinfectants and sanitizer labels to know the percent active ingredient. Different brands of the same generic compound may have various percent active ingredients. Often, the percent active ingredient or ppm for final, terminal sanitation is much lower for FCS compared to that for general sanitation of walls, floors and equipment. The higher acceptable ppm is with non-FCS disinfectants.

EPA regulation of disinfectants and sanitizers

Recently, some concern has emerged regarding whether public health products used to kill microorganisms pathogenic to man on inanimate surfaces and objects in hospitals, schools, restaurants, and homes work as claimed on the label. The private and public sector communities, including competitor registrants, have made the Agency aware of disinfectants which may be ineffective. EPA has responded to this situation by developing a comprehensive strategy to improve the regulation of antimicrobial pesticides. EPA is attempting to improve communications with the public, all levels of government, academia, user communities, industry, health professionals, trade organizations and independent testing groups. Also, EPA has committed funds to ensure that the tests used to demonstrate the efficacy of antimicrobial products are reliable and reproducible; is in the process of developing a complaint system to handle concerns regarding ineffective products; amplified internal controls to ensure the integrity of data submitted by registrants; and is currently publishing a quarterly newsletter designed to educate the general public about the status and direction of the regulation of disinfectants and sanitizers.

References and Suggested Reading

Wuest, P. J. 1990. Sanitation and hygiene at a mushroom farm.
Mushroom News: April 1990. pp 23-25.

Proper Uses/Recommendations Web sites:
http://mushgrowinfo.cas.psu.edu