Part I　Food Safety

Chapter 4

Cleaning, Disinfection, and Preventing Foreign Objects

Most food poisoning bacteria and viruses reach food through hands, cutting boards, and cleaning cloths. "Just pour boiling water on it" and "just spray some alcohol" do not work if you get the order or the strength wrong. They can even end up protecting the bacteria. This chapter covers what to do, in what order, and why.

In this chapter you will learn

• To explain the difference between cleaning and disinfection, and why you clean first and disinfect second
• To explain the correct handwashing steps, and when double handwashing is needed
• To choose between alcohol, sodium hypochlorite, and hot water, with the right strength, temperature, and precautions for each
• To keep cutting boards, cleaning cloths, and sponges clean, and to prevent cross-contamination and foreign objects
• To plan daily, weekly, and monthly cleaning, and to set up measures for garbage, drains, rodents, and insects (Grade 1)

4.1　Cleaning and Disinfection Are Separate Jobs

Cleaning means removing dirt with detergent, water, and scrubbing. Disinfection means killing the remaining bacteria with heat or chemicals, or reducing them to a harmless number. You cannot switch the order of these two jobs.

There are three reasons. First, dirt is a hiding place for bacteria. Neither alcohol nor chlorine reaches bacteria under a film of fish blood or fat. Second, dirt uses up the disinfectant. When a chlorine disinfectant meets protein, it reacts and is used up. It loses its power before it reaches the bacteria.

Third, heat sets protein. If you pour boiling water straight onto a plate with raw egg on it, the egg cooks and sticks. The same thing happens if you pour boiling water onto a cutting board with fish blood left on it. The hardened dirt wraps around the bacteria inside and protects them. Boiling water before washing only bakes the dirt on.

Always care for utensils in this order: wash with detergent, rinse with water, disinfect, and dry completely. The last step, drying, is essential too. Bacteria cannot multiply without water. If you leave things wet, the few bacteria left after disinfection start to multiply. Bacteria that divide once every 20 to 30 minutes can increase a millionfold overnight.

4.2　Handwashing

Soap "lifts and rinses away" bacteria

Bacteria hide in the oils of the skin, in wrinkles, in the grooves of fingerprints, under the nails, between the fingers, and on the wrists. Water alone does not remove bacteria protected by oil. Soap mixes with both oil and water. It wraps up the bacteria together with the oil and lifts them into the water. Soap does not kill bacteria; it lifts them and rinses them away. That is why you need both time spent scrubbing with lather and running water to rinse. Guidance from Japan's Ministry of Health, Labour and Welfare (MHLW) says to scrub for about 30 seconds and rinse for about 20 seconds.

1. Wet and lather　Wet your hands up to the wrists under running water, and work liquid soap into a good lather. Do not use bar soap, because bacteria stay on its surface.
2. Palms and backs of the hands　Rub your palms together. Rub the back of each hand with the other palm, as if stretching the skin.
3. Fingertips and under the nails　Press the fingertips of one hand into the other palm and scrub as if scratching, to clean under the nails. This is the place most often missed.
4. Between the fingers　Interlace the fingers of both hands and rub down to the base.
5. Thumbs and wrists　Grip each thumb with the other hand and wash it with a twisting motion. Wash the wrists the same way. Up to this point takes about 30 seconds.
6. Rinse　Rinse under running water for about 20 seconds, until the lather is gone.
7. Dry, then alcohol　Dry your hands with disposable paper towels. Rub alcohol into your dry hands, and keep rubbing until it dries. Do not keep a shared cloth towel; it becomes a place where bacteria pass from one person to the next.

Double handwashing

In some situations, your hands are likely to carry many bacteria or viruses. These include after using the toilet, after touching raw seafood or meat, after handling garbage or cleaning, and when entering the kitchen. In these situations, repeat steps 1 to 6 once more. This is called double handwashing.

The first wash removes heavy dirt such as skin oil, fish blood, and slime. The second wash lets the soap reach the bacteria deep in the wrinkles and under the nails. If dirt remains, the soap cannot reach that far. Alcohol does not work well against norovirus (Chapter 2), so this "rinse twice" approach is the best defense against it.

When to wash, and getting ready for work

First, wash your hands when you enter the kitchen. Next, wash them after touching raw seafood, meat, or eggs. Wash them after touching your face, hair, nose, or mask. Wash them after touching money, a mobile phone, garbage, cardboard, or the floor. Wash them after using the toilet. And wash them when your next task moves to a clean step (Section 4.6).

Cut your nails level with your fingertips, and do not wear nail polish or false nails. Remove rings, watches, and bracelets. The skin under a ring cannot be washed and is always damp, so it holds many bacteria.

Gloves are not hands

Chapter 6 deals with the problems of gloves. Bacteria on gloves do not die. Because the wearer does not feel dirty, people tend to move on to the next task without washing.

If you use gloves, wash your hands before putting them on. Always change to a new pair when the task changes, after touching raw food, after using the toilet, after touching your face, and when a glove tears. Take gloves off by turning them inside out without touching the outside, and wash your hands after taking them off too. "I'm wearing gloves, so I don't need to wash my hands" is the exact opposite of good hygiene.

Why double handwashing works better, and dirt that is easy to overlook

Washing twice for 30 seconds with a rinse in between removes dirt better than washing once for 1 minute. The dirt lifted by the first wash can be rinsed off and discarded. The soap in the first wash gets used up by skin oil, blood, and slime.

The dirty item most often overlooked is the mobile phone. It goes into the toilet with you and is held all day. Do not touch it while cooking. Remove wedding rings too. Make no exceptions. Nail polish and false nails are banned because they can peel off and become foreign objects, and because bacteria cling to their uneven surfaces.

4.3　Alcohol, Sodium Hypochlorite, and Hot Water

Alcohol works best at about 70%

Alcohol sanitizer (ethanol) kills bacteria by dissolving their membranes and destroying the proteins inside. Stronger alcohol is not always better. It works best at around 70%, or roughly 60 to 90%. That is because a little water is needed to destroy proteins. Alcohol close to 100% only draws water out of the bacteria, and it actually works less well.

There are rules for using it too. It does not work on wet hands or utensils. The water on the surface dilutes it below the strength that works. Always wipe off the moisture first, then spray, and rub it in until it dries. It does not work well against norovirus, and it does not work on spores either. A spore is a dormant form that some bacteria make, covered with a shell that resists heat and chemicals (Chapter 2). Also, alcohol catches fire easily, so do not spray it near the torch used for aburi (searing with a flame) or near a stove.

Sodium hypochlorite: strength, and "Danger: Do Not Mix"

Sodium hypochlorite is the main ingredient of chlorine bleach. It is powerful and destroys the bodies of bacteria and the proteins of viruses. It is one of the few disinfectants that reliably works against norovirus. It is cheap, and it can also be used to bleach cleaning cloths.

Its strength is shown in ppm. The letters are read "P-P-M," and the unit means parts per million. 1% equals 10,000 ppm. Dilute it to 200 ppm for utensils, work surfaces, and cleaning cloths, and 1,000 ppm for cleaning up vomit or stool. Many products sold in stores are 5 to 6% solutions. For 200 ppm, dilute about 250 times. For 1,000 ppm, dilute about 50 times. If the product is 5%, add 12 milliliters of it to 3 liters of water for 200 ppm, or 60 milliliters for 1,000 ppm (Table 4-1).

Sodium hypochlorite has weak points too. It rusts metal, so do not leave it on knives or stainless steel for long, and rinse well with drinkable water after use. Light and heat break it down, so use up any diluted solution the same day. It is too harsh for hands and fingers, so do not use it on them. And if it is mixed with anything acidic, it gives off toxic chlorine gas.

Hot water: 80°C or higher for 5 minutes or more

The standard for disinfecting utensils and cutting boards with hot water is water at 80°C or higher for 5 minutes or more. This condition comes from the MHLW's Hygiene Management Manual for Large-Scale Cooking Facilities. Quickly splashing boiling water over the surface is not enough. The surface temperature rises only for a moment. Cleaning cloths can also be boiled at 100°C for 5 minutes or more. However, spores do not die even at 100°C.

Above all, remove the dirt with detergent first, and then use hot water.

Comparing and choosing disinfection methods

When alcohol contains a little water, it dries more slowly. That keeps it in contact with the bacteria longer, which also helps it work. Another explanation is that strong alcohol sets the proteins on the surface of the bacteria first, forming a shell that keeps the alcohol from soaking in. Alcohol leaves nothing behind, so it suits surfaces that touch food and the final step for washed utensils.

Sodium hypochlorite does not reach the bacteria if you use it on things that are still dirty. Store the concentrate in a cool, dark place, away from light and heat. It can also be used to kill bacteria on vegetables and fruit. Dilute it to 100 to 200 ppm. Soak for 5 minutes at 200 ppm or for 10 minutes at 100 ppm, and rinse thoroughly under running water. The strength of the concentrate also varies by country. In the United States, many products are around 8%.

Table 4-2 compares five methods. Alcohol is fast but weak against norovirus. Chlorine works against norovirus but is weak against dirt, acid, and metal. Hot water backfires unless the dirt is removed first. Drying does not kill bacteria, but it stops them from multiplying.

4.4　Cutting Boards

Wooden cutting boards

Sushi chefs use wooden cutting boards, such as hinoki cypress or ginkgo, because of their soft blade contact. Blade contact is how the board feels when the knife edge strikes it. On wood, the edge chips less easily, and a freshly sharpened knife stays sharp longer.

But wood absorbs water and keeps knife marks. When fish blood and water get into the fine grooves of the knife marks, the inside stays wet even if you wipe the surface. Those spots become nests of bacteria. Protect a wooden cutting board with two habits: dry it completely every day, and resurface it from time to time.

1. Rinse with water　First rinse off blood and dirt with room-temperature water. Do not pour boiling water on it right away.
2. Detergent and a scrub brush　Scrub along the grain with a scrub brush to scrape the dirt out of the knife marks.
3. Rinse, then hot water　After rinsing off the detergent, disinfect the board with water at 80°C or higher for 5 minutes or more. Chlorine damages wood and leaves an odor, so hot water is the standard for wood.
4. Stand it up to dry　Stand the board on edge so that air reaches both sides, and let it dry completely overnight. If you lay it flat, the underside does not dry and turns dark; that darkness is mold. Long exposure to direct sunlight makes the board warp.
5. Resurface it　When the knife marks get deep, the board darkens, and it dries slowly, have it planed, either yourself or by a specialist. It depends on use, but about once every few months is a guideline.

Plastic cutting boards, and separating boards by use

Resin cutting boards, in other words plastic ones, do not absorb water. They can be bleached with sodium hypochlorite, and they are easy to color-code. But once they are covered with cuts, bacteria stay in the grooves, just as with wood. Replace them when the surface gets fuzzy and dirt no longer comes off.

Use at least five separate cutting boards. The board for scaling and gutting (mizu-arai) is for handling scales, gills, and internal organs. The others are for cutting saku (trimmed blocks of fillet) and kiritsuke (slicing the topping), for vegetables, for cooked foods, and for allergy orders. When you use a board beyond its purpose, put it through the reset described in Section 4.6.

Cutting board materials, and why blade contact matters

Wood gives good blade contact because the edge sinks very slightly into the wood fibers and does not slip. When you slice neta (topping) with a pulling cut, the feel of the cut also travels accurately to your hand. For the sake of flavor, nothing replaces wood. Some studies also show that bacteria have a hard time surviving on a thoroughly dried wooden surface.

Plastic cutting boards feel hard to the blade and dull the edge. Like wood, they keep bacteria in deep knife marks. A plastic board covered in cuts can even be less sanitary than a well-kept wooden one. Synthetic rubber cutting boards feel close to wood under the knife, do not absorb water, and withstand heat to some degree. For professional kitchens, they are a middle option between wood and plastic.

4.5　Cleaning Cloths, Sponges, and Knives

A damp cleaning cloth has food juices, water, and room temperature all together. It is one of the things in the kitchen where bacteria multiply most easily. If you wipe everything with it, you spread bacteria everywhere. There are three rules.

First, keep separate cloths for each use. Separate cloths for cutting boards and knives, work surfaces, tableware, and floors by color or pattern, and never use one cloth for two jobs. For drying hands, disposable paper towels are the sure choice. Second, after closing, wash the cloths by hand with detergent, and then soak them in 200 ppm sodium hypochlorite or boil them at 100°C for 5 minutes or more. Third, dry them completely. A cloth left damp and balled up will have more bacteria the next morning than it had before washing.

Sponges hold food scraps and water in their tiny holes. After closing, squeeze-wash them with detergent, kill the bacteria with hot water or sodium hypochlorite, wring them out tightly, and dry them. Replace them early once they lose their shape. With knives, dirt collects where the handle meets the blade. Wash and rinse a knife right after use, and wipe it with a dry, clean cloth. Steel knives rust with chlorine, so disinfect them with hot water or alcohol. Sharpening and storage are covered in Chapter 22.

Detailed rules for cleaning cloths, sponges, and knives

Bleaching cleaning cloths is not for looks. It is the act of killing bacteria itself. During service too, replace dirty cloths with clean ones, and put used cloths in a dedicated container.

Sponges are porous. This means they are full of countless holes, so rinsing the surface does not clean the inside. Utensils washed with them get coated with bacteria all over again. A worn-out sponge does not dry deep inside its holes, even after you kill the bacteria. So replace sponges with new ones often. Keep separate sponges for fish preparation and for washing tableware. Replace sponges used at sinks where raw seafood has been handled at especially short intervals.

On knives, dirt collects around the ferrule (kuchigane), the fitting where the handle meets the blade. Never take a deba (heavy filleting knife) that was used for scales and organs straight to cutting saku.

4.6　Stopping Cross-Contamination

Cross-contamination is the movement of bacteria from something dirty to something clean. Bacteria move through hands, utensils, cleaning cloths, water splashes, and storage places. Much food poisoning comes from this movement rather than from the food itself. Cases of Vibrio parahaemolyticus food poisoning from cucumbers cut on the same board used for fish have been reported again and again (Chapter 3).

Work has an "order of dirtiness"

If you line up the work of a sushi restaurant by how dirty it is, a clear order appears. The dirtiest are delivery boxes, the floor, and mizu-arai. Mizu-arai is the work of removing scales, taking out the gills and organs, and washing off the blood. Bacteria from the surface, gills, and organs of fish fly around with the water splashes.

Cutting saku and kiritsuke are clean steps that handle only filleted flesh. Flesh cut at this stage can no longer be washed. The last area is the tsukeba, the chef's work area behind the counter, where nigiri is shaped. It is the last stop before food goes into the guest's mouth, so it must be the cleanest place of all. The principle is this: work flows one way, in this order, and hands and utensils never go back to the dirtier side (Figure 4-1).

Separate or reset

There are only two measures. You either separate utensils and areas, or reset completely whenever the step changes. In a large kitchen, keep the mizu-arai area away from the table for cutting saku, and prepare a separate set of cutting board and knife for each.

If a small restaurant uses the same cutting board for both, reset it before moving from mizu-arai to cutting saku. Care for the cutting board, the knife, and the counter around them in this order: wash with detergent, rinse, hot water, then shake off the water and apply alcohol. Use double handwashing, and change to a clean cleaning cloth. "Just rinsing with water" or "just spraying alcohol" is not a reset. Alcohol on top of dirt does not work, and hot water poured on without washing hardens the dirt.

Raw and cooked, floor and work surface

Also keep separate utensils and storage places for raw seafood and for cooked foods. Cooked foods include simmered anago (conger eel), tamagoyaki (Japanese omelet), boiled shrimp, and vinegared rice. They will not be heated again, so bacteria transferred from raw fish go straight into the guest's mouth. You will learn how to arrange food in the refrigerator in Chapter 5. Do not put boxes or bowls that were on the floor onto the work surface. Wash your hands after picking up anything that fell on the floor.

A closer look at the paths dirt takes

Cross-contamination is not only about fish. A well-known example is Campylobacter moving from chicken to vegetables through the same utensils (Chapter 3).

The floor is the dirtiest surface in the kitchen. Shoe soles, drainage, rats, and insects all pass over it. If you crouch to take something from the bottom shelf of the refrigerator, stand up and wash your hands before your next task. You will learn more about handling delivery boxes and slatted racks in Chapter 5.

4.7　Keeping Foreign Objects Out

Foreign objects are not food poisoning. But they destroy a guest's trust in an instant, and metal or glass can cause injury.

• Hair　A person loses 50 to 100 hairs a day. Wear a cap or net that covers the bangs and the nape of the neck. Before entering the kitchen, use a lint roller to remove hair from your shoulders, back, and arms. Keep work clothes for the kitchen only, and do not enter in the clothes you commuted in.
• Insects　Put insect screens on windows and vents, and do not leave doors open. Cardboard boxes are homes for insects, so do not bring them into the kitchen (Chapter 5). Clean the drains every day.
• Metal and glass　Check knives for chips before and after use. If a knife is chipped, look for the missing piece. Steel wool sheds fine fibers that break off and get mixed in, so do not use it on utensils that touch food. If a glass breaks, throw away any uncovered food that was nearby.
• Bandages　Use blue bandages for cuts on the fingers. Natural foods are almost never blue, so if a bandage falls in, it is easy to spot.

Detailed measures against foreign objects

For hair, do not touch your hair or face while cooking. Cover or shave beards as well. For insects, install air curtains or automatic doors at entrances. For insects drawn to light, place insect traps outside the kitchen.

For metal and glass, also watch out for staples, the cut edges of cans, and peeler blades. Fit light fixtures with covers that do not scatter if they break. Throw away rubber bands and scraps of plastic wrap right where you used them. Some bandages contain metal so that a metal detector can find them. Count the bandages you are wearing at the start of work, check at the end that they are all still there, and wear gloves over them. To a guest, fish scales and small bones are also foreign objects.

4.8　Cleaning Plans, Garbage, Drains, and Pests

Cleaning is not something you do "when it gets dirty." Plan when, who, what, and how to clean, and record it on a checklist. The records also help you explain your practices to the public health center (hokenjo). Table 4-3 gives example frequencies. After closing, the focus is on killing bacteria on cutting boards and cleaning cloths and drying them. Every week, the focus is the inside of the refrigerator and the grease trap. Every month, it is defrosting and the drain pipes.

Garbage and drains

Food waste feeds bacteria, insects, and rats. Put it in containers with lids, tie the bags shut, and do not let them fill up, even during service. In summer, refrigerate food waste, or take it outside after every service. Keep the garbage area away from the kitchen, and build it with a floor and walls that can be washed.

Drains and the grease trap are sources of slime, bad odors, and insects. A grease trap is a tank that separates oil from wastewater and removes it. Scrub it with a brush every day, and take it apart and clean it once a week. If you leave the scraps that collect in the drain screen, small flies breed there.

Rats and cockroaches

Rats get in through gaps about 2 centimeters across. Small house mice can pass through even narrower gaps. Rats spread Salmonella and other bacteria through their droppings and urine, and they gnaw through bags and electrical wires. Cockroaches come in through drain pipes and cardboard boxes, and they walk over food with bacteria on their bodies.

1. Block the entrances　Seal the gaps around pipes, under doors, and at vents.
2. Cut off their food　Seal food in containers, take out food waste, and clean up spills on the floor.
3. Cut off their water　At night, dry the sinks and cleaning cloths.
4. Look for signs　Check for droppings, gnaw marks, and cockroach egg cases (oothecae), and check whether anyone has seen pests at night.

If you find signs, call a professional pest control company before you spray insecticide your own way and contaminate food. Store disinfectants and insecticides away from food, under lock and key. Never transfer them into food containers.