Good agricultural and good hygiene practices

In general, good practice means quality assurance activities which ensure that food products and food related processes are consistent and controlled and assure quality procedures in food systems (Raspor & Jevšnik 2008), or simply defined as Doing things well and guaranteeing it has been done so (FAO 2006). GAP is the selection of methods which can best achieve the objectives of agronomic and environmental sustainability in primary food production. GHP consists of practical procedures and processes that return the production or processing environment to its original condition (cleaning programme); ensure that buildings and equipment operate efficiently (maintenance programme); and control for cross-contamination (usually related to people, surfaces, and the segregation of raw and processed products) (Raspor & Jevšnik 2008). GAP and GHP should be adopted to reduce as far as possible any source of contamination (Figure 2).

Figure 2: Contamination sources of food products addressed by GAP and GHP

Location, design and layout

Aquaponics requires a greenhouse in most climates. When deciding on the location of the aquaponic unit, the owner should consider certain factors such as the proximity to industrial plants, or to locations susceptible to airborne pollution or the proliferation of pests (e.g. incineration plants, plants releasing heavy metals, roads with heavy motor traffic, open air rubbish tips, etc.) (Copa – Cogeca 2018). The aquaponic producer should also consider the potential risk of natural disasters (flooding, heatwaves, etc.). Air and dust can act as a vehicle for hazards, which can be prevented with controlled ventilation. Additional wind protection for Deep Water Culture (DWC) systems is recommended since wind causes rafts to bounce, thereby splashing water through the holes and causing contact between the water and the leaves (Aquaponics Association 2015). If there is vegetation surrounding the aquaponic unit, it should be kept mown/strimmed, in order to reduce the risk of rodents and pest insects from getting into the greenhouse. There are some food safety concerns about liver flukes and other parasites carried by snails in aquaponic systems. However, snails are only one step in the liver fluke life cycle, which requires cattle to complete it. If there are no cattle or other ruminants in the immediate surroundings of the aquaponic unit, the risk is minimised or even eliminated since snails are unlikely to carry liver flukes (Aquaponics Association 2015).

Use of construction materials that may be a potential source of contamination (e.g. lead-based paint) should be avoided. Since pests can be very small (e.g. whiteflies and thrips), very fine mesh screens can prevent their entry into the unit. In Europe, screens are generally characterized by the number of spaces per centimetre in each direction (e.g. a 10x20 screen has 10 spaces per centimetre in one direction and 20 in the other direction). The reduction of natural ventilation caused by the use of fine mesh screens can be mitigated by increasing the screen area (e.g. by using concertina- shaped screens).

There should be washrooms available to workers at all times when they are on site. These should be connected to an effective drainage system. Handwashing stations (whether attached to the toilet facility or located near it), should be equipped with:

• a basin

• running potable water

• liquid soap

• disposable paper towels

• a covered waste container (see an example in Figure 3)

Facilities for washing produce after harvesting must be separate from the hand-washing facility. There should be a clean, safe place off the ground for employees to store personal items. This area can be small and simple, such as a shelf (Aquaponics Association 2015).

Figure 3: An example of handwashing station at ZHAW, Institute of Natural Resource Sciences (covered waste container is not visible on this photo) (Photo: Andrej Ovca)

Equipment

Produce will have physical contact with many surfaces during harvest and processing. These may include harvest equipment and containers, transport bins, knives and other utensils, sorting and packaging tables, and storage areas. Equipment with which food comes into contact should be:

• made of materials such as stainless steel, food-grade plastic, aluminium, ceramics, or tinned copper, and be kept in good condition in order to minimise any risk of contamination

• where relevant, fitted with control devices (e.g. a thermometer in the refrigerator)

• effectively cleaned

Whenever possible, dedicated equipment (Figure 4) should be used. Fish equipment and contact materials must be clean and uncontaminated (scoops and nets, transport containers, fish killing machine). Harvesting equipment should not be placed on the ground (Figure 4a). All weighing and dispensing equipment should be regularly calibrated. Storage equipment should be fitted with devices that enable constant monitoring of the temperature and an even distribution of the temperature conditions in order to maintain the cold chain (Copa – Cogeca 2018).

Figure 4: Colour coding system preventing cross-contamination through equipment at ZHAW, Institute of Natural Resource Sciences (Photo: Andrej Ovca)

Worker hygiene

Anybody working in the aquaponic unit should follow a simple rule: always be healthy and clean. It is also recommended to wear dedicated working clothes. Most diseases that affect humans can be introduced into the system by the workers or by visitors. One of the biggest risks to fresh produce safety is people and their hands, which are in continual contact with the environment. Sick workers, and those with open wounds or cuts, should not handle produce, fish, or equipment (Lee et al. 2015), or if they have yellow skin or eyes, a sore throat with fever, are vomiting or have diarrhoea, until the symptoms have stopped for at least 48 hours.

Smoking, chewing gum, or eating around the production areas should be prohibited. Hands should be washed every time after using the bathroom, eating, shaking hands with someone, handling fish, putting hands into the system’s water, touching one’s mouth, nose, ears, hair and, of course, before harvesting the plants. When washing hands liquid soap should be used at all times. The recommended hand washing technique (Figure 5) should be used. Hands should be rinsed with potable water and dried with single-use paper towels.

Figure 5: Handwashing technique (Source: WHO / http://www.who.int/gpsc/clean_hands_protection/en/)

The number of personal items carried while working should be minimized. This includes cell phones, jewellery, nail polish, hair extensions, etc., which can fall into the produce. If an injury occurs while handling fish or working in the system water, the area should be immediately washed with clean water and disinfected. If someone needs to wear a band-aid, it has to be of a non-food colour (e.g. blue), properly secured, and covered with a glove.

Walking into the greenhouse from outside is an important route of entry for food safety hazards. The risk can be reduced by hygienic barriers such as footbaths and a handwashing station at the entrance to the greenhouse or, if this is not possible, hand disinfection (Figure 6). As an alternative to footbaths, workers can use ‘in-greenhouse’ shoes or boots, or disposable paper booties. The latter is also an alternative for visitors (Aquaponics Association 2015). Footbaths should always be wet and have an active disinfectant solution in the mat. If the footbath mat is dry, it is not effective. Care should be taken to rinse out the footbaths on a regular basis to ensure that they do not get clogged up. The chemical solution should be changed on a regular basis depending on the product used.

Figure 6: Disinfection point for sanitising workers’ boots and hands at the greenhouse entrance at ZHAW, Institute of Natural Resource Sciences (Photo: Andrej Ovca)

Preventing cross-contamination

The concept of cross-contamination is usually used in terms of cross-contamination by microorganisms and lately also in terms of allergens.

Cross-contamination from produce to produce is less likely to occur in aquaponics. Cross- contamination through equipment can be (besides efficient cleaning) effectively managed by colour coding (Figure 4). Different types of tasks should be done separately. For example, a worker who is cutting lettuce heads or arranging lettuce heads in boxes should only be handling plants, not moving rafts, pulling net pots, or any other jobs where their hands come into contact with the system water. Similarly, a worker doing tasks where their hands are in contact with the water should not be handling plants without first washing their hands and/or changing their gloves (Aquaponics Association 2015). Preferably the fish, plants or media should not be handled with bare hands, but with disposable gloves. However, hands should also be washed before putting the gloves on. It is a good idea to get one-use, latex-free nitrile gloves, and dispose of them after each use. Dermatological zoonotic diseases including those caused by bacterial species such as, for example, Mycobacterium, Streptococcus (iniae), and Vibrio spp. have been discussed by Gauthier (2015). Although most humans have a strong natural immunity to wounds infected by bacteria such as Mycobacterium, more serious infections are often associated with immune-compromised individuals, deep puncture wounds, and highly virulent strains of bacteria. These topical infections usually occur as the result of injuries from the spines of fish or through contamination of open wounds.

It is important to prevent the system water from coming into contact with the produce during the harvest. Food and drinks should stay outside the aquaponic unit. In addition to unwanted bacteria, external food and beverages may bring allergens into your system that could pose risks to your consumers.

Training

Aquaponic workers must have the appropriate skills and information which match the complexity of the operations for which they are responsible (training in animal/plant management, health risks and safety practices in the workplace, operation of equipment, use of chemicals, etc.). The owner of the farm should ensure that all workers have been trained in the relevant health and safety and hygiene practices.

Visitors

Another method of introducing new pests and diseases into the aquaponic system is by visitors, and therefore it should be always assumed that visitors are ‘contaminated’. Visitors have to follow protocols such as washing or disinfecting hands before touching the system, using footbaths, and storing personal items in a designated location. Generally, visitors should be accompanied by someone so that these practices can be demonstrated (Aquaponics Association 2015).

Water supply

From the perspective of food safety, the source of water used in aquaponic systems has the potential to have a significant bearing on the quality of the final products, whether they are fish or plants (Chalmers 2004).

• Municipal (potable) water usually has the best quality because of previous testing and safety requirements. Potable water from a clean source is always preferred for a recirculating aquaponic system

• Ground or well water will have fewer pathogens than surface water (such as ponds, streams, or rivers) because there is less chance of contamination

• Surface water can be contaminated with animal manure and parasites

• It is important not to use rainwater collected from roofs as it may be contaminated by bird faeces. If using rainwater, it has to be ensured that birds are not roosting on the collection area. Otherwise treating the water before adding it to the system should be considered.

Fish feed

After water, fish food is the primary input into aquaponic systems. Feed should be purchased from a reputable source and should be always stored in a dry and secure area where birds, rodents and other pests will not be able to contaminate or eat it. Contaminated feed is an important route by which dangerous bacteria like Salmonella could be introduced in the system (Lee et al. 2015). Fish feed and other incoming materials should be checked for:

• pests

• expiry date

• intact/undamaged packaging

Additionally, fish feed should be routinely checked before feeding the fish to be sure that there is no condensed water or visible mould.

Harvesting and processing

Produce can become contaminated or cross-contaminated during harvesting and processing. If possible the ‘all-in-all-out’ production system (in which all of the fish and plants are introduced at the same time and harvested at the same time) is recommended to minimise the possibility of contamination. Processing means changing plants or animals into what we recognize as food. For produce, processing can be as simple as washing and sorting, or it can involve trimming and/or slicing. For fish, the first step of processing is slaughter. If processing of produce and/or fish on the site is planned, a special area/room is needed which is separated from the rest of the greenhouse and dedicated only to these kinds of activities.

Plants

It is crucial to prevent the aquaponic water from coming into contact with the leaves of the plants. If possible, the system should be designed in the way that physically prevents water from contacting the edible parts of the crops, rather than simply counting on workers to be careful (Aquaponics Association 2015). This prevents many plant diseases as well as potential contamination of produce by the fish water, especially if the produce is to be eaten raw. Vegetables (produced in an aquaponic system or otherwise) must always be washed before consumption (FAO 2014). Diseased plants and compost piles should be kept far from the system in order to prevent contamination.

For Nutrient Film Technique (NFT) and DWC beds where harvesters can reach the whole bed from the aisles, bench harvesting (cutting plants directly out of the raft while the rafts are still in the bed) minimizes splashing. Removing rafts from DWC beds before harvest poses a food safety hazard because of splashing and dripping, and in the case of small beds often adds more work than it saves (Aquaponics Association 2015).

The producer should look very carefully for small snails and slugs that might be stuck deep down in the plant. Produce that has pest damage should not be harvested, because it main contain pathogens. Any product that has snails, slugs or their slime on it should be thrown away (collected as waste). Produce should be pulled apart as appropriate and rinsed in clean, cool, potable water (never in aquaponic system water) (Hollyer et al. 2009).

Fish

Sick or injured fish should be identified and separated from the healthy ones to avoid cross- contamination. After slaughter, the fish should be immediately chilled. The temperature of the fish should reach 4⁰C or less as fast as possible, and this temperature should thereafter be maintained throughout storage and distribution. Ice used for chilling aquaculture products should be made from potable water. Processing fish involves certain risks beyond what usually occurs with plant production. If fish slaughter and processing is foreseen on-site, the legal and ethical requirements of the competent food safety authorities should be followed.

Storage of vegetables and fish

If harvesting is done a long time before selling, cold storage should be used. If the harvested fish is stored, the storage should be in a dedicated facility that meets minimum standards of hygienic design and construction for fish storage and processing facilities. Produce needs to be kept cool after harvest. The safe temperature is 4°C or below. 4°C is also the maximum storage temperature for fresh fish. Storage of fresh fish between -1°C and 2°C will maintain better quality and more than double the shelf life. -18°C is the minimum required storage temperature for frozen fish. Storage at - 27°C or lower maintains quality for 1-2 years (CDC 2014). The temperature for preservation has to be maintained at all times. Different types of produce will require different storage regimes. After the fish or plants have been harvested, the produce should be kept at the appropriate temperature in order to slow or stop the growth of harmful bacteria. The ‘cold chain’ starts at harvest and ends with the consumer (Lee et al. 2015). One should store food packaging materials separately from chemicals and cleaning, disinfecting, and plant protecting products.

Traceability

Good record-keeping allows the possibility of tracing (both forwards and backwards) any possible source of contamination, or of finding the origin and cause of problems in the food chain. Therefore the aquaponic producer should ensure that record-keeping systems are in place so that traceability can be guaranteed (Copa – Cogeca 2018).

³ Withdrawal period refers to the minimum period of time from administering the last dose of medication and the production of animal-derived products for food

The produce containers have to be labelled if the produce is sold to mass caterers and/or to final consumers. Where foods are offered for sale to the final consumer or to mass caterers without pre- packaging, but prepared for direct sale at the aquaponic unit, the following information is mandatory:

• The name of the food (for fish both the commercial and scientific names must be displayed)

• Any allergens present (any ingredient or processing aid listed in Annex II of Regulation 1169/2011 causing allergies or intolerances used in the manufacture or preparation and still present in the finished product). Note: Not required when the food name clearly refers to allergen(s) e.g. fish

• ‘Best before’ or the ‘use by’ dates should be displayed on all non-prepacked products

• Date of catch/harvest (voluntary information). The date of catch / harvest can be considered as a lot or batch. ‘Lot’ or ‘batch’ are useful for traceability in case of a necessary product recall

• A statement advising consumers to ‘rinse before eating or serving’ is recommended for plant produce (voluntary information)

Mandatory information for farmed fish (aquaculture) is also:

• Production method

• Country of production

How to label your produce?

• On the product. If possible, the information should be presented in a label either on the packaging, attached to the packaging, or visible through the packaging

• On a notice. The information can be presented on a notice in close proximity to the produce or on the shelf edge

• Verbally. In the case of allergen information only, you can give the customer the information verbally. You must place a notice in close proximity to the produce (or on the produce itself) inviting customers to ask a member of staff for allergen information – for example, ‘Please ask us about allergens in our food’

Commission Regulation (EC) No 710/2009 (Organic Aquaculture Regulation) lays down detailed rules governing practices in the production of aquaculture products which can be labelled as organic.

Food contact materials

Food contact materials (FCM) are either intended to be brought into contact with food, are already in contact with food, or can reasonably be brought into contact with food or transfer their constituents to the food under normal or foreseeable use. Examples include:

• containers for transporting food

• machinery to process food

• packaging materials

• kitchenware and tableware

The safety of FCM is tested by the business operators placing them on the market, and by the competent authorities during official controls. Any material or article intended to come into contact with food should be sufficiently inert to preclude substances being transferred to food in quantities large enough to endanger human health or to bring about an unacceptable change in the composition or a deterioration in the organoleptic properties of the food. There is a wide range of FCM types, the most common being:

• Ceramics

• Cork

• Glass

• Metal and alloys

• Paper and cardboard

• Regenerated cellulose

• Rubber

• Silicone

• Wood

The international symbol for material appropriate for contact with food (Figure 7) generally assures that the material surface is free of any toxic contaminants from the manufacturing process and that the material will not potentially become a source of toxic contamination through usage.

Figure 7: international symbol for material appropriate for contact with food(Source: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2004:338:0004:0017:DE:PDF)

Cleaning and sanitation

Cleanliness is a key requirement applying to personnel, the facility, and equipment. For the latter two, good conditions must continually be maintained. Harvest tools, cutting utensils, and produce contact surfaces have to be kept clean.

Chemicals used for cleaning and sanitising must be used according to their instructions and always stored away from areas where food or feed is produced, stored or handled. Chemicals in their original packaging and those transferred to smaller units should always be labelled (readable, unmistakeable, waterproof) with at least the following information: name, date, concentration.

The aquaponic producer has to make sure that tools are cleaned before and after each use, and ensure that any cleaning supplies such as brooms and mops are specifically designated to the aquaponic unit. If there are multiple systems the cleaning equipment (brushes, sponges, cloths, water sampling pots, etc.) should be separated for each system, with colour-coded labelling (Figure 8a).

Figure 8: Cleaning tools separated for each line with colour coding system (a) and stored away from the aquaponic unit with cleaning agents in the closed closet (b) at ZHAW, Institute of Natural Resource Sciences (Photo: Andrej Ovca)

Cleaning process

The surfaces cleaned should include hydroponic channels, fish tanks, sides of greenhouses, pathways, etc. It is recommended to prepare the cleaning schedule where the following information is defined:

• What is to be cleaned?

• How?

• When/how?

• Who is cleaning?

What to clean?

Surfaces can be divided into different zones (Bihn et al. 2014), for example:

• Zone 1: Direct food contact surfaces (sorting tables, racks, utensils, harvest/storage bins)

• Zone 2: Non-food contact surfaces that are in close proximity to the produce (internal and external parts of washing or processing equipment, housing, framework)

• Zone 3: Areas inside the aquaponic unit such as trash cans, floors, drains, restrooms, forklifts)

• Zone 4: Areas outside of the aquaponic unit

How to clean?

One should always begin the cleaning process in zone 1 and finish in zone 4. Additionally, the cleaning should always start at the top and continue downwards, sweeping and mopping the floors at the end.

• Step 1: The surface should be rinsed so any obvious dirt and debris are removed. All biological matter (plants, algae, etc.) should be removed before further cleaning procedures

• Step 2: Detergent/cleaning agent should be applied and the surface scrubbed

• Step 3: The surface should be rinsed with potable water

• Step 4: An appropriate disinfection agent should be applied if needed. If the disinfection agent requires a final rinse, this will require an extra step

• Step 5: The surface should be left to air dry

After the fish have been removed from the system, it should be drained and the tanks cleaned properly using a high-pressure hose. Using a high-pressure hot water unit with detergent is a good way to clean and sanitise surfaces too. All the equipment (nets, buckets, etc.) coming into contact with the system water must be disinfected. Note: After harvest the rafts should be cleaned but not disinfected, and left to dry so as to avoid killing the nitrifying bacteria on the submerged surface of the raft. Cutting boards and knives should be washed with soap in hot water before cutting produce. All soap should be rinsed under running water and dried as necessary with a single-use paper towel. Cutters may also be routinely cleaned using a disinfecting solution such as bleach, alcohol, or other commercial product.

How to disinfect?

Aquaponics producers should always follow the labelling on a product and wear the proper protective gear. Different agents can be used for disinfection. Chlorine bleach, mixed to a 10 percent solution and allowed to stand for five minutes, is very effective at killing disease pathogens (Moran 2013). Other types of products are those containing quaternary ammonium, which are less volatile and more stable than bleach, and are mostly recommended for metal surfaces. Chlorine dioxide is a gas, so it can penetrate and infiltrate greenhouse nooks and crannies far better than liquid products. Vinegar is another disinfectant (Godfrey 2015). Concentrated peroxyacetic acid (max. 15 ml per 3 m³ of fish tank water) can be used for disinfecting drum filters and also for removing any limestone which has formed on the mesh. Care must be taken that the acid does not get into the biofilter and the fish tank all at once. Important: Disinfection should only ever be done by properly trained personnel.

How often to clean?

• Debris and standing water should be removed daily for worker safety as well as to minimize the risk of attracting pests. The removal of all plant debris, including the roots, at the end of each harvest helps to reduce the incidence of pests and diseases

• The floor of the system should be cleaned once a week (spider webs, fish feed, etc.) with a broom and, if necessary, with the wet cloth

• Pumps and drum filters should be cleaned at least once every 2 months

• Once or twice a year the fish tanks should be scrubbed to remove algae and biofilm from the walls.

Animal and pest control

Pest control was already addressed in Chapter 8 (Integrated Pest Management), so only the key points will be addressed here. Pests and wild animals such as birds, vermin and insects, and domestic animals (dogs, cats, etc.) can be a source of food contamination and can also act as a vector for infectious diseases. The aquaponic producer should take steps to prevent pests from contaminating produce directly, and any equipment and other materials coming into contact with produce. Wildlife/pest exclusion is also needed to prevent fish and vegetables from being predated by wildlife (Aquaponics Association 2015). Vermin, wildlife, and pets should be excluded or minimised in the general area where the greenhouse is located. Birds can be prevented from contaminating the system by using netting and deterrents.

The greenhouse doors should be kept closed most of the time, and waste removed from the facility surroundings. Visual inspection of pest presence should be in place, and any corrective measures taken if signs of pests are detected. The improper or illegal use of chemicals to control pests can result in hazards to human health. The best practice is to net all production systems. Netted systems severely restrict any warm-blooded animal access. To prevent rodents in the greenhouse, mousetraps should be used and checked 3-4 times per week, especially in autumn and winter when the chances of them appearing are higher. If produce is sold to consumers and/or food business operators, the mousetraps should be installed by a registered and competent authority which should also take care of any animals captured. Insect lamps should be checked and cleaned.

Waste and hazardous substances

Veterinary products and chemicals (plant protection products, biocides, cleaning agents, etc.) should be stored according to the guidance provided by the manufacturer and away from any areas where food production, storage and handling is carried out.

Table 3: Measures to prevent risk from veterinary products, chemicals, waste and waste water (Copa – Cogeca 2018)

Copyright © Partners of the Aqu@teach Project. Aqu@teach is an Erasmus+ Strategic Partnership in Higher Education (2017-2020) led by the University of Greenwich, in collaboration with the Zurich University of Applied Sciences (Switzerland), the Technical University of Madrid (Spain), the University of Ljubljana and the Biotechnical Centre Naklo (Slovenia).