Blast Chillers

Dan Bendall

Food safety is an important reason to buy a blast chiller but not the only reason, as many foodservice directors are finding. Blast chillers are not just a complicated oversized refrigerator in the corner of the kitchen that is used to comply with someone’s HACCP plan. Many of the newer models are quite user-friendly. With just a little training, they can be an asset in any kitchen.

Operators also find there is more to be gained from a blast chiller than just easier compliance with food safety requirements. Food cost savings, improved food quality and reduced labor are some of the added benefits to having a blast chiller.

Blast chillers have been available for many years, although until recently they were found mostly in larger institutional facilities like hospitals, schools or prisons.

Cost Benefits

Operators commonly ask how food cost can be improved by using a blast chiller. Blast chillers allow for strict portion control, which reduces waste. Also, cooked product yield is generally greater than with other forms of cooling because more moisture is retained in the blast chilling process. Another cost saver is being able to safely cool, reheat, and reuse food.

Products from a steamtable, for example, can often be recycled the next day because they can be chilled quickly and safely and not lose too much quality in the process.

Food quality also is improved because of the rapid chilling process itself. Rapid chilling stops some of the deterioration that begins immediately at the end of the cooking process when food quality reaches its peak. Such deterioration includes loss of moisture, color, texture, vitamins and flavor, especially in vegetables.

Frozen food quality can also be enhanced when you are blast-freezing foods. Products that are flash frozen with a blast chiller are usually of much better quality than those foods frozen in an ordinary freezer. Blast freezing does not allow large ice crystals that damage tissues and change food textures to form. Rethermalized product that was blast frozen is generally very much like fresh food, with less sogginess and crisper vegetables.

Large batch cooking and chilling can save labor over traditional smaller batch cooking. Larger batches can be made if you have a blast chiller because rapid cooling allows a longer safe shelf life of product. Also, some items can be par-cooked in bulk, chilled, and stored. The items can then be reheated and finished as needed quicker and using less labor than if prepared fully in one step.

Even with all these other reasons to have a blast chiller, though, food safety is still the primary consideration. Without safe food, food and labor cost and product quality are meaningless. The concern for food safety is real and has driven the market for blast chillers for a number of years. Ensuring safety in the kitchen and in the food prepared there requires both equipment and procedures to carry out the standards necessary. By themselves hygienic procedures and food handling techniques are not enough without the proper equipment to provide the necessary control.

Procedures and the right equipment must go together. There are numerous equipment items that aid in prevention of food borne illness, but the blast chiller is leading the way. Blast chillers are an important equipment item for every facility to easily help promote safe food.

Food sanitation standards, though now probably at their safest levels in history, remain a critical issue for today's foodservice operations. Millions of people in the United States alone contract some sort of food illness and several thousand die from those illnesses each year.

While serious wide-spread food-borne illnesses are rare, they are well publicized in the media and can take their toll on the involved food operations. Not surprisingly, improper cooling of food products is the number one cause of food-borne illness.

The Food and Drug Administration Food Code, a model code recommending nationwide standards, requires that food be cooled from 140°F to 41°F within six hours. This guideline has gained wide acceptance and is now the standard most recognize. Some areas have even more stringent requirements to cool product in four hours.

Conventional reach-in and walk-in refrigerators cannot meet this standard. They are only designed to maintain already cold temperatures. They are not designed to chill product within a specified time period. The only real solution for most situations is a blast chiller.

The renewed interest in supporting rapid refrigeration and proper holding temperatures has sparked more manufacturers to develop blast chillers and build them to suit operations varying in size from an average school or corporate cafeteria on up to central kitchen operations. Let’s look at what a blast chiller does.

Custom Engineering

The object in chilling product is to bring the core temperature of food items down through the danger zone (140°-41°F) quickly so rapid bacterial growth is not an issue. Blast chillers, through the use of well engineered air flow designs and powerful refrigeration systems, are able to continuously strip away heat from the outside of product and lower its core temperature quickly.

A normal refrigerator has little air movement, allowing hot product almost to insulate itself with its own internal heat. Blast chillers are outfitted with very powerful refrigeration equipment capable of blowing high velocity chilled air in the refrigerator cavity for maximum cooling even when there is a large quantity of product to be chilled. There needs to be a lot of precisely engineered air movement in the cavity through and around pans of food to make use of the high horsepower refrigeration systems and create the air flow necessary to chill product.

A comparison of refrigeration systems in a similar sized refrigerator and blast chiller illustrates the difference in equipment. The typical 10- to 12-pan blast chiller uses a 1- to 2-horsepower or larger refrigeration system, essentially the same size system needed to cool a 240- square-foot standard walk-in refrigerator.

Because blast chillers are precisely engineered, there are some particulars to be aware of when using them. The equipment is typically set up to hold shallow, two- and one-half inch deep steamtable pans. In smaller reach-in chillers the units have fixed pan slides appropriately spaced for the shallow pans. Larger blast chillers have mobile racks with pan slides that can be rolled into the units and then into a holding refrigerator for easy handling of the product.

It is essential to use the shallow pans since, to achieve rapid cooling, the food generally needs to be no more than two inches deep. Most manufacturers base their units’ capacities on between eight and 11 pounds or about one gallon in each steamtable pan.

It is important to remember that food products have different densities and therefore different cool down times. Generally dryer foods also chill slower than products containing more water.

Especially if there are a lot of different products to be chilled, you may want to consider a chiller model with temperature sensing probes, a common feature. The temperatures sensed by the probe will control the refrigeration system and let the operator know when the proper cool-down temperature has been reached. The probes are also essential if using a temperature recording device, something very useful for documenting proper product handling. Some equipment has an alarm that signals the completion of a chill cycle to let you know when it is safe to remove product and put in a new batch.

Optional Features

Many blast chillers have a few additional features that may be beneficial for your particular needs. Most have a holding mode that allow a unit to be operated as a holding refrigerator at normal temperatures once the blast chill mode is complete. When using temperature probes, the unit switches itself into the holding mode automatically once the preset safe temperature is reached.

Some blast chillers offer a delicate product or soft chill mode for light loads or low density products. This mode typically uses reduced air flow to accommodate products like leafy greens that may freeze in the full blast chill mode.

Many blast chillers can also be used in a flash freezing mode when a quality frozen product is desired. In flash freezing, the rapidly penetrating cold prevents the formation of large ice crystals. Consequently, the food does not loose its original consistency or integrity the way conventionally frozen product does.

If you have decided a blast chiller is right for your operation, there are many models in different sizes and price tags to consider. The high cost of the units in general is still a drawback to many operators. Expect to pay $10,000 for even the smallest of operations, and usually several times more for larger operations.

Many institutions will spend $100,000 or more on blast- chilling equipment. Be sure once you have decided to make the purchase to have enough space available because the overall unit is quite large in comparison to the actual refrigerated cavity size. Other considerations are the heat generated by the units if the refrigeration is self-contained. Most larger units and some smaller ones can have remote or air-cooled refrigeration systems, thereby removing the heat generation issue.

Instead of looking at the blast chiller as a necessary evil, consider some of the benefits you can receive from your unit and it may become one of your most valued kitchen equipment items. Also, be sure your staff is well trained in using the chiller so they will actually use the unit as intended.

Remember, the equipment alone is not enough to make a food safety program work. Time for training staff on procedures must be invested along with the equipment investment to ensure the outcome intended. The full benefits of blast chillers are new to many foodservice directors, but every operator needs to be asking, "Are we getting our full money’s worth?"