Refrigeration

A good fridge is a vital piece of kitchen equipment. A commercial kitchen without refrigeration is dangerous, and environmental health officers would almost certainly close it down.

While refrigeration equipment might look simple - little more than a cabinet with a compressor and some dials - commercial specification refrigeration equipment is much more hi-tech than the domestic variety. A professional kitchen should never be tempted to use domestic refrigeration; the looks are similar, but that's where it ends.

When the door on an upright fridge is opened, the cold air falls out and is replaced by warm air from the kitchen. This causes the fridge's internal temperature to rise, which in turn alerts the thermostat, triggering the compressor pump to circulate the cooling refrigerant, and pulling down the internal temperature.

With a domestic fridge, the power of the compressor is designed around the few times the fridge door is opened during the day. Hence, a cheaper compressor with quite modest power can keep the food cool and safe.

With a commercial specification fridge in a busy working kitchen, the door is going to be opened regularly and the fridge will probably be exposed to a far hotter kitchen than in the home. The compressor needs to be powerful enough to pull down the internal fridge temperature rapidly to replace heat loss. The compressor in a domestic fridge is not powerful enough to maintain a safe food temperature in a commercial environment.

Most commercial fridges also incorporate fans, which evenly spread the cool air through the cabinet, a feature not available on domestic fridges. Commercial fridges are better insulated - again, to combat the kitchen heat problem and run with more energy efficiency - and they will be designed for easy cleaning. Some are able to record temperatures electronically, a feature that can be used as proof of due diligence in food safety procedures should a food poisoning claim be made.

Other useful features can include lockable doors to ensure there is no unauthorised access by staff when the kitchen is unmanned, gastronorm-compatible internal dimensions, and self-closing doors. Further food-safety elements can include an illuminated temperature display, temperature rise alarm and wheels for moving the fridge out for better cleaning.

As well as freestanding fridges, there are walk-in fridges, which can be bought off-the-shelf or built from assembly panels to fit a specific kitchen or storage area. Many commercial kitchens could use more refrigeration, and they usually have some part of the kitchen area that is under-utilised. Bespoke walk-in coldrooms provide a solution to both problems.

Freezers

Commercial freezers share all the high specification features of commercial fridges and should always be used for the same reasons of performance, food safety and cost efficiency. There is a temptation on cost grounds to buy commercial specification for fridges but use domestic chest freezers. Frozen food, where the temperature has been allowed to rise through constant opening of the door, is as dangerous as chilled food where the temperature has risen.

Blast chillers and freezers

These refrigeration cabinets use fiercely driven cold air to pull down rapidly the temperature of hot food so that it can be safely stored in chilled or frozen form for future reheating. Letting foods cool without refrigeration is very dangerous, as harmful bacteria can develop during the long cooling process. Bacteria growth is greatest between 68¼C and 3¼C.

Department of Health guidelines say that, to minimise food safety risk, food should be reduced from 70¼C to 3¼C in 90 minutes. Many blast chillers do it more quickly than that and from a higher starting temperature.

Cooling hot foods in a fridge already containing chilled food is also dangerous as it will raise the temperature of all the food in the fridge. Any kitchen that needs to have precooked, chilled food as a major part of its operation must have blast refrigeration.

Blast freezers work in the same way, but EU guidelines recommend that the temperature should drop from 70¼C to -18¼C in not more than four hours.

Tempering fridges

Allowing frozen food to defrost before regeneration is now a widespread practice. With dense foods or complete meals, defrosting ensures that the meal is heated throughout and bacteria are killed - a common problem when cooking frozen food in underperforming microwave ovens.

Defrosting should never be done at room temperature or left overnight. Bacterial infection is a very high risk and cooking may not kill any bugs that have developed. Putting the food in a fridge to thaw is far safer, as none of the cooked food will rise above the default temperature setting of the fridge.

If lots of frozen ready-cooked food is being thawed before reheating, the best method is to use a dedicated tempering fridge. Instead of maintaining a constant temperature during a thawing cycle, the tempering fridge allows a slight raising of cabinet temperature in the first part of the cycle to kick-start the thawing process. The fridge then automatically lowers to a holding temperature for the completion of the thawing.

Refrigerated preparation tables

These are mainly used for food assembly, such as in made-to-order sandwiches, salads or pizzas, but can be very useful for production of desserts in a restaurant.

The tables are made up of a large stainless-steel work surface, a bank of refrigerated open-top containers at the rear of the work surface and refrigerated space underneath. Their purpose is convenience and speed. In the case of a made-to-order pizza, a customer has a delivery expectation of not much more than 15 minutes. For the kitchen team this means rolling out the fermented dough ball, putting the toppings on and getting the pizza into the cooking oven. Most of the time between ordering and delivery will be the cooking, not the putting together of the toppings.

While in a high-volume pizza operation there are many topping ingredients that do not require chilling for food safety reasons, the benefit of a refrigerated preparation table comes in being able to pick the topping ingredients quickly. Food safety also plays an important role in the value of refrigerated preparation units for pizza. The cooking area - either front of house or back of house - is going to be hot, so protein and dairy products need to be kept chilled as well as accessible.

Salad and sandwich bars are expected to be fast on delivery as well as high on freshness. Being able to prepare the bread and pick instantly the fast-moving ingredients of a sandwich or salad satisfies the customer in a hurry and fulfils the guidelines for food safety.

There are several permutations of this refrigerated preparation area system, from refrigerated storage units and no-preparation or under-counter storage systems to units with a chilled work surface, which can be useful for creating desserts.

Ice-makers

Ice cubes are mainly needed for adding to cold drinks in the bar area, but since the ice-maker is refrigeration equipment, it may often fall to the kitchen manager to buy, even though there may be no regular use for it in the kitchen. However, the kitchen team does need cubed ice for rapid chilling or keeping ingredients cool while they are being whisked.

A growing number of restaurants that feature fresh fish on the menu also want to have a glass-fronted refrigerated cabinet front of house to show the catch of the day before it is cooked. Having the fish laid out on glistening ice is far more attractive and safer than just displaying it on trays. The kitchen, not the restaurant staff, will have responsibility for this display unit.

Ice-cubers and ice-flakers are the two types of equipment available. A dedicated flaker will be needed if a large quantity of flaked ice is required, but for small amounts of flake, such as in cocktails or "slush"-type soft drinks, cubes can be crushed in a commercial specification food processor or blender.

The simplest type of ice-maker works by automatically depositing water in moulds and then ejecting the ice cubes when frozen into a storage hopper. This gives ice cubes with the familiar cloudy appearance of ice made in a domestic freezer.

If a clearer ice cube is required, such as in a hotel cocktail bar or fine-dining restaurant, then an upward-spraying ice maker will be needed. The upward spraying of water - into little cup-like moulds to be rapidly frozen - makes very pure ice because many of the impurities present in tap water drop out before they can be frozen in the cube.

A water filter will usually need to be fitted to prevent the internal pipework of the ice-maker becoming furred up through limescale deposits from dissolved salts in mains tap water. This will also assist in delivering clearer ice cubes.

Where there is a heavy and constant demand for ice, it makes sense to split production between two ice-makers. This will ensure cover during servicing or in the event of a breakdown.

Ice is legally considered food and is subject to similarly strict hygiene legislation. Cleanliness of the machine is very important and manufacturers' cleaning routines should always be followed. Good hygiene practice by staff handling ice is essential: staff should never touch ice with hands, and only proper ice scoops should be used to fill ice buckets from the storage bin. Using glasses to fill ice buckets is very dangerous due to the risk of glass chips getting into the ice. Ice tongs should be present in every ice bucket.

Bottle coolers

While the obvious function of bottle coolers is to chill down the can or bottle so it is served at the best temperature, they are also merchandising units, with glass-fronted doors displaying the offer to the customer.

The chill-down time from a cellar may be several hours, so it is important to train staff to rotate the stock within the bottle cooler to avoid pulling warm bottles from a cold cabinet.

Busy bars will often work a tandem system. The bottle cooler is the merchandiser, but staff take the requested drink from another refrigerated unit under the counter. This gives a drink of the right temperature, avoids the bottle cooler door being continually opened and means that the merchandising display always looks full.