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August 2009
SPECIAL REPORT

Blast Chilling, Your Way

Newer midsize blast chillers cool food quickly and easily to save time, enhance product quality and improve food safety. Here's how to spec reach-in or roll-in models with capacities of 100 lbs. to 200 lbs.

To see a variety of blast chillers, click here for the Blast Chiller Gallery.

By Mike Sherer

Cook-chill systems became emblematic of big institutional foodservice kitchens 30 years ago. Steam-jacketed kettles and tilting braising pans coupled with monstrous roll-in blast chillers enabled volume feeders to cook in large batches, which saved them time and food costs while preserving product quality.

When smaller blast chillers first hit the market, they seemed like an expensive way to cool down product. But when paired with fast-cooking combi ovens, they offered many of the same benefits of cook-chill systems on a smaller scale. Hotels and banquet facilities saw the advantages of consolidating production with fast-cooking, fast-cooling equipment that allowed them to bank meals in advance with very little loss in product quality.

The rest of the industry has been slower to adopt the use of blast chillers, but that's changing with the advent of smarter boxes that are easier to operate and full of features. If what you need is a 100- to 200-lb.-capacity reach-in or roll-in model, you've got plenty of options.

All The Reasons Why
Most operations still primarily use blast chillers to consolidate production. You may cook most items to order but still have a few things that you could cook in bulk once a week instead of daily, saving time, labor and food cost.

The time savings of batch cooking and quick-chilling foods can be as much as 30% compared to producing smaller quantities more often. Making something like a special sauce or roasting meats once a week instead of daily means your chefs and cooks don't need to supervise onsite as often, which saves labor. And blast chillers typically prevent up to 7% weight loss through evaporation as products cool. That means better quality product, lower food cost, less waste and more profit.

Another equally valuable reason to use blast chillers is their contribution to food safety. Chillers are designed to bring core temperature of food from around 160°F or more down to 41°F or less in about 90 minutes. Most units will freeze food in four hours or less. The FDA Model Food Code (on which most state and local codes are now based) says you have two hours to bring cooked product temps down to 70°F and another four hours to get it down to 41°F or less. Obviously, cutting the time of that process by 75% is a great benefit to any HACCP plan. And cooling leftovers faster means employees go home sooner at shift's end.

If production consolidation and enhanced food safety aren't good enough reasons to invest in blast chiller technology, consider what a lot of users have learned after buying one: Like other equipment, once you have it, your staff will find more uses for it than you intended or even imagined.

As mentioned earlier, blast chillers bring food temps down so quickly they prevent loss of moisture in food through evaporation. They also prevent the bacterial buildup that can occur in the temperature “danger zone" between 140°F and 40°F which both degrades food quality and makes it potentially hazardous. In essence, chillers help maximize both the shelf life and quality of the food you produce. And advanced electronics have given blast chillers greater flexibility, letting you do more things with them.

A couple of manufacturers, for example, have added a special blast freeze cycle to their units that enables them to freeze ice cream with less ice crystal buildup, resulting in a smoother, creamier product. Or consider the recent trend of high-end restaurants serving out of mobile vending trucks. A blast chiller would make it easier to prepare products the day before and rethermalize them to order onboard the truck with little loss in quality.

Even something as simple as offering prepared sandwiches from a to-go case can be enhanced with a blast chiller. Chilling sandwiches faster with less moisture loss than a walk-in means longer shelf life in a merchandising case, with crisper lettuce, juicier tomatoes …you get the point.

Power And Performance
Blast chillers are essentially convection ovens in reverse—the polar opposite, if you will. Instead of heating air and pumping it into a cavity to transfer it to a food product like in a convection oven, blast chillers move cold air through a box to transfer heat out of the product. The key to pumping that heat out quickly is a powerful compressor and a way to circulate high volumes of air.

You'll typically see compressors in the 2-hp range for medium-sized blast chillers, though some are as small as 1½ hp and as large as 3 hp or 4 hp. One manufacturer uses two compressors in some of its units; its 100-lb. reach-in has both 1¼-hp and ½-hp compressors that operate simultaneously to blast chill or freeze product. When product reaches its target temp, the larger compressor shuts off, and the smaller compressor holds the product at the proper temp until it's removed.

Where the rubber meets the road is how cooling power and airflow work together to remove heat from cooked product. All blast chiller makers claim their equipment will bring product temperature down to a safe 41°F or less in about 90 minutes. Pay close attention, though, when setting specs. Some units' claims are based on a starting temperature of 140°F, the minimum hot holding temperature in most health jurisdictions. But what if you want to cool banana cream pies fresh out of the oven with a core temp of around 200°F? Or stuffed turkeys that many food codes say must be cooked to an internal temp of 185°F?

All blast chillers will still bring product temps down within HACCP (and FDA Food Code) guidelines, but depending on the model, it may take an extra 30 to 60 minutes or more if your food is hot out of the oven. If your production cycle depends on faster cool-down times, you'll need a more powerful unit.

Go With The Flow
Airflow is important in other ways, too. While cooling product faster minimizes moisture loss, paradoxically, moving lots of air over the product can cause it to dry out. Some manufacturers, in fact, suggest covering pans of food in the blast chiller to prevent this. However, manufacturers have come up with their own designs to maximize airflow through the cabinet to facilitate cooling while minimizing the drying effect it has on food.

Units may have one or more fans to move air through the cavity. Many blow cold air into the cavity, either from back to front or side to side. A couple of manufacturers draw air out of the cavity, the idea being to pull heat from the product and allow cold air to be drawn across the product, claiming it's a more effective way to transfer heat.

One manufacturer's units have louvers that direct air in a laminar flow over and under each food pan, which it says is more efficient and less drying and requires no lids on pans. Yet another claims its “turbo" air circulation moves air in a more effective circular motion. And one says its fan, with more blades than any competitor, is designed by an airplane propeller manufacturer to make it efficient.

Need Soft Chill, Or Hard Chill?
Ultimately, what makes this equipment effective is how useful it is to you, meaning how well it does what you want it to within the parameters of your operation. The good news is that manufacturers continue to make blast chillers more flexible and capable of more specialized tasks.

Even the most basic units typically have three operating modes: soft chill, hard chill and blast freeze. In soft chill mode, the units constantly circulate 39°F air to cool product. It's an ideal way to quickly chill delicate or thin items—fish, seafood, rice, vegetables, thin cuts of meat or poultry—without danger of freezing them. In hard chill mode, the units circulate sub-freezing air (usually around 0°F) to cool thicker food items—roasts, pans of potatoes or beans, etc. In blast or shock freeze mode, chillers operate at temps as low as -32°F to quickly freeze products at 0°F or below, often in four hours or less.

While older models required employees to keep track of how long products had been chilling, even basic models now usually give you the option of choosing a cycle based on time or temperature. You either set a time and the unit automatically shuts off when the timer runs down, or you insert a temperature probe in the product and the unit shuts down when the desired core temp is reached.

Keeping Your Options Open
A lot of features are out now that may sway your purchase decision when you're shopping for chillers. For example, several makers offer additional probes as an option, but in some cases the probes offer more than redundancy in case one breaks. Some models operate in a multi-probe mode that offers even greater automatic control over the cooling process. Up to three probes provide input, giving the unit more data on which to base the proper cooling cycle.

Some manufacturers also provide special probes for the freezing mode on their units. In one case, the probe can be heated at the end of the cycle for easier removal from the frozen product. Another maker designs freezer probes that are conical in shape so they pop out of frozen products more easily.

One supplier even offers a probe that comes with special self-sealing tape to use with sous vide packaging.

Most manufacturers offer snap-on magnetic door gaskets that can be easily removed for cleaning or replaced when worn. In some cases you can get heated gaskets that prevent condensation.

And speaking of condensation, several models are available with a defrost cycle that can be operated manually or automatically. Often, however, these models need to be positioned near a floor drain to accommodate the buildup of condensation during the defrost cycle.

A couple of makers, though, offer models with automatic hot gas defrost that eliminates the need for a condensate line. Some operate on an automatic timed cycle, but newer models incorporate sensors on the evaporator coil that kick on the defrost cycle when they detect freezing temps in the evaporator.

Some models have the option of a remote condensing unit, possibly saving energy costs and taking some heat out of the kitchen. Since most units are self-contained, look for models that provide easy access to the condensing coil so you can keep it clean and help your unit run efficiently.

Finally, a couple of models now offer you the option of interior UV sanitizing lamps. While the stainless finish and coved interior corners of most models make them easy to keep clean and sanitary, UV lights add another layer of protection to your food safety plan.

Some Final Notes
Since blast chillers are designed to cool product quickly, they're not as energy-efficient as refrigerators, which are designed to hold products at cold temps. But most models are solidly built and use adequate insulation to achieve an NSF listing. Since chillers aren't an Energy Star category yet, there's no easy way to compare efficiency of one to another. You can, however, ask manufacturers about how many Btus their units move per hour and at what amperage. Units that move more Btus with the same amount of energy usually are more efficient.

Cleaning and maintenance are simple. Stainless interiors and exteriors are easy to wipe down after each shift. Make sure employees also keep the condenser coil and air vents clean to keep the unit running efficiently.

Finally, compare after-sales service networks and availability of parts in areas where you have stores to make sure the manufacturer you select can give you the level of support you need. Many manufacturers also throw in training sessions as part of their purchase and/or service agreements. Check to see what else a maker might offer, such as free accessories, seminars on additional product uses or international service networks.

Trying It On For Size
Harkening back to the days of bulk food production and cook-chill systems, blast chillers still often delineate their size by capacity in terms of pounds of food. The medium-sized units we're covering here range from 100 lbs. to 200 lbs. in capacity.

A better determinate of what size unit you need is how many pans of food a chiller holds. Most manufacturers measure this by how many 12" x 20" x 2½" hotel pans a unit holds. In this size range, most models hold from 10 to 20 pans. Figure out how much food you need to chill in what timeframe and you'll have a pretty good idea of what size blast chiller you need in one kitchen.

Keep in mind a couple of things, though, when shopping for models. First, you may want to have the flexibility of putting sheet pans in your unit, not just steam table pans. Several, but not all, models accommodate 18" x 26" sheet pans. Check before you buy.

Second, make sure the tray or pan slides in the unit give you the flexibility you need for the types of food and combination of pans your staff will put in it at any given time. Usually, the more positions the slides offer the better. Some units have adjustable slides; on others they're fixed, so choose carefully. In all cases, they should be removable so the interior of the unit can be cleaned easily.

Finally, don't forget to consider footprint when sizing a unit for your stores. Blast chillers with the same capacity may come in a range of physical shapes and sizes. One manufacturer, for example, makes two versions of a 10-pan chiller: one that stacks pans vertically in a 36" x 34" footprint and another that is configured horizontally to fit under a worktable.

Chillers Get Smart
If you're looking for the most advanced chilling possible, these are good times. Several manufacturers have introduced models recently that automatically control the chilling cycle based on the product inside. All you have to do is insert probes in the product and the unit determines the best and fastest way to cool it. Using the same sort of algorithms combi ovens use to cook product without browning the surface too quickly, these chillers will constantly adjust the air temp (and how hard the compressor runs) based on internal product temp so they cool quickly without freezing the product surface.

Several of these models give you the option of setting cycles based on time, temperature or product type, and some let you program in your own parameters for particular menu items so all employees have to do is push one button for a particular product.

Electronic controls with LED displays make operation simple on both base and more advanced models. Most units feature timer countdowns showing time left in a cycle, and you'll find both visual and audible alerts for things like unit malfunctions or HACCP issues.

As far as HACCP compatibility goes, several models have onboard printers that print the results of each cooling or freezing cycle so you have documentation for your files. Some units also have electronic memory and data ports that allow you to hook up the chiller to a PC to track and record HACCP data.

To see a variety of blast chillers, click here for the Blast Chiller Gallery.

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