Their ability to bring down temperatures in the fastest possible time makes blast chillers and freezers indispensible for maintaining food hygiene standards in commercial kitchens. Ross Bentley reports
Blast chillers are now standard apparatus in the vast majority of commercial kitchens, and new models are becoming ever more functional, making them important pieces of kit in helping caterers comply with food hygiene legislation.
According to David Clarke, designer of commercial kitchens at CDIS-KARM and member of the Foodservice Consultants Society International, 90% of the kitchens he plans today contain blast chillers. "Any kitchen where food is being cooled down to serve cold or is being refrigerated so it can be reconstituted later will need a blast chiller," he says. "It's the only way food can be cooled within specified guidelines."
At the Charted Institute of Environmental Health, policy officer Jenny Morris says blast chillers offer a scientific approach to compliance with HACCP legislation as users can preset the device to bring food down to a safe temperature within a set time.
Department of Health guidelines state that to safely blast-chill food its temperature must be reduced from 70°C to 3°C or below within 90 minutes. Many modern blast chillers now exceed this requirement and can safely blast-chill from a starting temperature of 90°C within the same time frame.
Keeping records of foods, their temperatures and the time it takes to chill or freeze them is an important part of HACCP - a process made easier using a blast chiller, according to manufacturers.
Foster Refrigerator's food service director, John Savage, says modern blast chillers have the facility to link their temperature probes directly to a PC. This means that as the temperature of the food is taken it can be automatically downloaded on to an Excel spreadsheet for record purposes.
It's also possible to link your blast chiller to a PC via a wireless connection, according to Scott Palmer, the director of business development at wireless communications specialist RAG (Remote Analysis Generation). Typically, RAG will set this up as part of a wider project to build remote temperature-monitoring devices into a range of units in a kitchen, such as refrigerators and freezers. A sensor and transmitter are attached to the chiller and data is sent to a laptop running dedicated software.
"You can set it up to transmit data at intervals of your choice, and it will give you a log of these recordings so you can look back and see that the chiller has been doing what it's meant to be doing," says Palmer.
Some chillers on the market, including those supplied by Gram and Enodis, come with a built-in printer on the control panel that gives a receipt-like print-out after each use. Angelo Po also offers the option of attaching a printer.
Despite all the technology available, some caterers, such as Mitie Catering Services' food and beverage director Laurent Brydniak, still prefer to use pen and paper to track temperature changes. "We use a probe to record the temperature before and after it goes into the chiller, and that is recorded manually on a form that we keep in a folder near by," he says.
Based at corporate events venue the Brewery in the heart of the City of London, Brydniak uses a WMBC90 blast chiller manufactured by Williams Refrigeration. With six rooms, the venue can accommodate up to 700 diners. "If 700 people get food poisoning, it is a threat not only to your reputation but your business as a whole," he says.
With so many diners to cater for, Brydniak says the WMBC90 suits his purpose because it is a large cabinet with the capacity for 90kg of food. An additional boon is that he can roll a trolley rack from the combi-oven into the chiller and then into a fridge. "This saves time and is more hygienic, because no one has to handle the food," he says.
Most manufacturers offer large cabinet chillers with the ability to accommodate trolley racks. Foster, for example, has designed its chillers so they can take trolleys of the same dimensions as Rational combi-ovens.
At the Jumeirah Carlton Tower hotel in Knightsbridge, London, executive chef Simon Young and his team use seven different blast chillers of varying sizes - from small under-counter models to large walk-in cabinets - most produced by Foster.
With a ballroom that seats 400 people and a catering operation that sometimes has to provide for 2,000 diners each day, Young emphasises how straightforward Foster chillers are to use. He says: "The manuals are easy to follow, and you soon get used to working them. There's also a timer alarm that goes off if you leave it too long."
Ensuring chillers are easy to use is a pet subject for Tim Smith, managing director of Williams Refrigeration. He says that many of the major blast chiller manufacturers have made great strides in ensuring the devices are easy to use, in response to the complex legislation that now exists around food hygiene.
"Over the past few years the control panels of blast chillers have become much easier to follow," he says. "Manufacturers have realised that if devices are too complicated, they won't get used."
Williams, for example, has incorporated what it calls a 1-2-3 Controller on its chillers. According to Smith, users only have to take three simple steps to initiate a blast chill or freeze cycle.
They select soft chill, hard chill or freeze cycle and then select whether they want to use a timed cycle of 90 (chill) or 240 (freeze) minutes or a food temperature probe-controlled cycle. The third step is to start the cycle.
While blast chillers have traditionally been aimed at the larger operators, manufacturers are now producing smaller cabinets for small or low-volume kitchens.
Foster, for example, has just launched its 10kg-capacity FXBC10 blast chiller, which, with a list price of £2,650, is 15% cheaper than its previous economy chiller.
At Gram UK, sales and marketing director Glenn Roberts says his blast chillers cost anything between £3,000 and £21,000, depending on requirements. He reports sales have increased by 30% in response to the HACCP legislation.
According to Roberts, advances in temperature probe design are helping to ensure that food quality levels are maintained. Both Gram and Angelo Po have developed an "intelligent food recognition probe", an instrument that takes the temperature of the food being cooled at three different points - at the core, just below the surface, and in the air circulating above.
The probe can be put into meat products and softer dishes such as lasagne and immersed in liquids. The detailed data picked up by the probe is fed back to controls within the chiller that will automatically adjust the temperature and humidity inside the unit as well as the speed of the fans and the air flow across the food. "This avoids users simply cranking the equipment up to ‘hard blast chill' every time, and helps caterers ensure the food keeps its look and taste," he says.
According to Nick Bates, research and development chef at Angelo Po, hard-chilling can ruin the look of food by freezing its surface. "If ice crystals form, then the food will deteriorate and not eat well," he warns.
Stephen Harrison, executive chef at events venue Magna in Rotherham, is keen to emphasise that, used properly, all sorts of delicate foods can be reconstituted after blast chilling without losing quality.
Arguably the largest banqueting venue in Yorkshire, Magna has a capacity of up to 1,000 seated diners and 3,000 standing for a buffet, so Harrison and his team have to use a plated regeneration system to cater for these large numbers.
Having cooked and chilled the food before the event - sometimes up to two days ahead - Harrison says his team can "bring back" 240 plates every eight minutes. That's 800 covers in half-an-hour.
Harrison's pride and joy is a roll-in Delfield Sadia T40 blast chiller, one of the largest models supplied by Enodis, which he describes as "a serious piece of kit".
"Foods like fondant potato mash can be ‘brought back' to be fluffy, while meats such as lamb can be sealed then chilled before being recooked to a rare or medium state," he says.
Key maintenance points
One of the most common service calls on a blast chiller or freezer is because it is not chilling the food quickly enough. This is usually due to the caterer overloading the unit, and the advice is: make sure blast chillers/freezers are loaded correctly, according to manufacturer's instructions, in terms of product depth and volume.
Take care not to jam the temperature probe in the door. Hang it back in its holder after use.
Temperature probes are not to be used for lifting products out of the chiller. They are sensitive devices and are key to maintaining good temperature control.
Keep a spare probe in the kitchen in case of damage.
Blast chillers must reduce core food temperature from 70°C to 3°C in 90 minutes. Blast freezers must reduced temperature to below -3°C in four hours. If it takes longer, something is wrong.
Many caterers plan a refrigeration maintenance visit just before the summer to ensure their refrigeration will cope with summer temperatures and heavy workload. But beware, last year the early hot weather caught caterers out. The hotter weather is coming earlier every year, so bring forward pre-summer refrigeration maintenance to, at the latest, April.
Regularly check door seals for damage and replace when split. Cold air is, literally, blasted into the chamber, and leakage will affect performance.
Cleaning door seals with a sharp knife wrapped in cloth will split them, and a split door seal will trap food soil.
Ensure that air vents, which are often at low level, are kept clear of obstructions and regularly cleaned. Also be aware that siting a blast chiller or freezer near a door next to a room with a carpet will make it clog more often as carpet fibres are dragged in by waiters, etc.
Blast chillers/freezers will usually defrost after each cycle. If you see a build-up of ice when starting a new cycle, call a service engineer to check over the machine before the ice causes damage.
Source: Serviceline (01438 363000)