Advancing freezing technology protects baked foods
Nov. 1, 2012
by Shane Whitaker
While mixing, makeup and baking play major roles in the final quality of baked foods, so does freezing. If frozen too quickly, at improper temperatures or in unsanitary environments, a product’s quality will be adversely affected.
Bakeries freeze raw, par-baked and fully baked foods to extend shelf life, retain moisture and flavor, and increase distribution capabilities. While cold storage holding areas can freeze pallets of packaged baked foods, often processors opt for continuous automated systems because of the advantages that they offer in handling during packaging or for subsequent processing such as icing of cakes.
“The challenge for industrial bakers has always been to find ways to freeze their product as fast as possible while maintaining the product’s taste, texture and appearance,” said Ed Cordiano, program manager, bakery and prepared foods, Linde North America, Murray Hill, NJ.
Peter White, president of IJ White Systems, Farmingdale, NY, said bakeries need continuous freezing systems that allow extended production runs without requiring downtime for defrosting. Today, its Ultra Series Freezing Systems use direct drive technology, eliminating drive chains, sprockets and frequent oiling inside the freezer. Companies also seek equipment that can be sanitized using less time and man-hours, he added.
Bakeries must select a freezing system that’s right for their products and facilities. They need to deliberate space concerns, startup and operational costs, future product expansions and throughput.
Bakers often mistakenly believe that fast freezing by spiral or tunnel systems vs. a cold storage area will negatively change the color, water activity, moisture content, taste or appearance of the product, according to Andrew Knowles, freezer sales support manager, JBT FoodTech, Sandusky, OH.
“In my experience, if the product is properly precooled and/or packaged prior to entering a spiral or tunnel freezer, generally the intrinsic properties of the food are maintained and can be verified by using sensory testing, baking color meter and moisture analyzer,” he said.
IJ White improved the designs and components of its blast freezing systems so that bakeries can increase production runs and better control operating costs, Mr. White said.
The company’s Extended Prod-uction System (EPS) features Auto-matic Pressurization Systems (APS) at infeed and outfeed openings to prevent outside warm moist air infiltrating the freezer and causing frost to build up on coils. “We are retrofitting this new technology onto existing blast freezers, and our customers’ blasts freezers are able to now maintain freezing temperatures longer and reduce the frequency of defrost.”
Also, EPS-equipped freezers use a patented Thermal Pak finned coil design to provide greater efficiency. The coil’s elliptical tube design includes closer tube spacing for a greater surface area than the typical round tube designs. “Because of its lower resistance to airflow, the Thermal Pak coil permits greater water loading, making it the most effective design available,” Mr. White observed. “Thermal Pak coils also require less horsepower to operate, feature a more compact design and increase capacity.”
In addition, IJ White’s blast freezers use completely enclosed, fan-cooled, high-efficiency motors on the direct-driven fans to provide high-velocity multipath airflow and baffling for uniform freezing, he said.
The Continuous Production System (CPS) from IJ White takes extended manufacturing runs in its blast freezers a step further. CPS includes sequential defrost coils that can be independently isolated and defrosted. “Traditional systems require extensive horizontal baffling and structure to accomplish this,” Mr. White said. “Our new coil Isolation Technology (CIT) eliminates the labyrinth of internal structure and horizontal decking that is very difficult to clean.”
CIT improves efficiency and elevates total system hygiene. “As the coils build up with snow and ice, the PLC-controlled CPS performs a sequential defrosting of the coils, one at a time,” Mr. White explained. “With this system, bakers can run their freezers for a week, two weeks or even longer without ever stopping for defrost.”
However, CPS requires the refrigeration system to handle the heat load for the extra coil being defrosted, according to Mr. White. “The energy you use to defrost coils sequentially is tremendous, so EPS is generally the choice bakeries will make unless they need to run continuously for more than a week.”
Because many bakeries run six days a week or longer before defrosting and cleaning the freezer, Mr. Knowles said, freezers need to be equipped with an effective air-balance system, sufficiently large coils and measures to continuously keep the coils relatively free of thick frost and ice accumulation to achieve the desired runtime.
To increase uptime on its GyroCompact spiral freezers, JBT FoodTech optimized the design of its fan-driven air-balance tunnel to minimize the amount of moisture entering the spiral through the infeed and outfeed openings, he said.
In addition, the equipment manufacturer introduced a sequential defrost system for its GyroCompact that can be operated based on timing or triggered by monitoring the pressure differential across the coil to maximize the length of time between defrosts. “This system uses hot gas to defrost coil banks and allows a full redundant coil and fan so that capacity and/or outfeed temperatures are maintained during periods of sequential defrosting,” he added.
Anthony Salsone, senior associate, G&F Systems, Roosevelt, NY, cited limited plant space and continuous maintenance requirements as top challenges for bakeries’ freezing systems. G&F’s Spiral Evolve addresses both space and maintenance issues related to a traditional spiral freezer, he said.
Traditionally, spiral freezers include refrigeration units around or above the spiral conveyor, but the Spiral Evolve does not have a rotating center drive drum. That allows the company to place refrigeration units inside the spiral, saving bakeries valuable floor space, Mr. Salsone noted.
“Also, where ceiling height limitations do not allow overhead hung refrigeration units, we can now design a spiral freezer system for a bakery that has very low ceilings,” he said.
Freezing with gases
Bakeries also rely on cryogenic systems that use liquefied gases, generally nitrogen or carbon dioxide, for automated continuous freezing of baked foods in either spirals or tunnels. Manufacturers of these systems claim that one of their primary advantages over mechanical systems is the upfront costs; however, cryogenic systems also have higher operating costs because plants have to replenish cryogen gas supplies.
Praxair, Inc., Danbury, CT, recently improved its ColdFront-branded cryogenic freezing systems to include an ultra-performance tunnel freezer that reduces tunnel lengths by at least 30% while providing improved sanitation, according to Frank Martin, business development manager, food market.
The company offers three types of tunnel freezers and builds them using a modular design so bakeries can expand them as they grow. Praxair has installed systems as short as 9 ft to as long as 81 ft based on product freezing rates, heat removal and desired production rates, he said. Available in three sizes, the company’s cryogenic spiral freezers can be prefabricated and shipped over-the-road or built in place at the bakery.
A common misconception about cryogenic freezing is that it diminishes baked foods’ quality and taste performance. “Cryogenic freezing quickly locks in flavor and quality to minimize any loss from the freshly baked taste,” Mr. Martin noted.
Additionally, a small cryogenic system can quickly set up coatings or frosting on finished goods to preserve the appearance through the packaging process, he added.
Another concern bakers have, according to Mr. Martin, is that a cryogenic system requires a tremendous amount of capital and space and would mandate significant downtime to install. “Praxair cryogenic freezers have low capital requirements, take up less valuable plant space and can be installed in a few days,” he said.
Linde also provides a range of cryogenic technologies that can freeze, crust-freeze or chill a variety of baked foods quickly and efficiently, Mr. Cordiano said. Its technologies includes entry-level box spirals, its patented Cryoline XF cross-flow spiral freezers and high-efficiency Cryoline tunnel freezers with modular designs so that sections can be added as a bakery grows.
The company’s engineers design and test systems according to exact product needs, Mr. Cordiano noted. “Our food team listens to the specific issues a baker is facing, and we perform an engineering assessment of the existing chilling or freezing process,” he said. “We look at a host of variables and make a recommendation on cryogenic technology at that location. We provide a before-and-after on the overall cost to freeze, and we also examine operational efficiencies.”
Bakeries must consider many variables when selecting a freezing system that is right for their products and operations. But freezing products properly should not have adverse effects on baked foods and can increase distribution so bakers can expand geographically.