The warm side of freezing
Oct. 1, 2013
by Charlotte Atchley
Freezing preserves product quality. Properly freezing baked goods prevents microbial growth and locks in moisture that contributes to the texture and taste people expect from their bread and rolls. “The amount of moisture in the product directly impacts its texture, quality and freshness,” said Peter White, president, IJ White Systems, Farmingdale, NY. Bakers can only reap the rewards of locking in moisture with freezing, however, if it’s done properly.
Whether bakers freeze bread and rolls before or after the oven, the products face a number of risks: diminished quality, premature staling, compromised crust integrity, sticking, loss of toppings and active yeast killed off. All these concerns and more can be avoided with speed adjustments, indirect or direct freezing or even airflow and product positioning.
It’s critical that when choosing a method of freezing or chilling, bakers are up front with suppliers about their needs and expectations. Testing products on a variety of equipment with different conditions, whether it’s a cryogenic or mechanical freezer, fast or slow, linear or spiral, can help bakers discover just the right freezing or chilling methods their products need to meet expectations.
Preserving yeast life
Freezing or chilling raw bread and roll dough comes with the unique challenge of maintaining the life of the active yeast contained in that dough. Overfreezing, or going beyond 0°F, will kill yeast cells. Without them, the bread and rolls won’t proof properly once the dough is thawed.
“When you’re dealing with anything that’s yeast-based, it’s a challenge because you have to slow down the process of the bread rising, but you can’t kill it,” said Brendon Somerfield, freezer applications engineer, JBT FoodTech, Sandusky, OH. He said the key is balancing the temperatures and speed of the freezing process, thus JBT FoodTech usually recommends higher discharge temperatures and a gentler approach.
“If you’re talking about raw dough, most bakers would prefer to freeze quickly, although they will not freeze it to a core temp that we would typically freeze other products,” said Daniel Plante, JBT FoodTech’s director of sales and marketing for North America. “Most bakers would prefer to leave the core temp a little warmer than that because they don’t want to overfreeze the product. They want to let it equilibrate over time.”
Mr. White also understands the importance of temperature when it comes to keeping yeast alive. IJ White’s blast freezers are designed to maintain and control temperature, allowing bakers the ability to protect a dough’s yeast cells.
Cryogenic freezing can also be used to freeze raw dough, if applied properly. Cryogenic gases can be applied using either direct or indirect spray. While direct spray is a fast way to freeze product, it is too harsh for the active yeast. Ed Cordiano, program manager, Bakery & Prepared Foods for Linde North America, Inc., Murray Hill, NJ, suggested indirect spray of the cryogenic gases to protect rising capabilities.
Saving the crust
On the other side of the oven, bakers can freeze or chill par-baked or fully baked bread and rolls. When freezing proofed products, bakers no longer need to consider the life of the yeast; however, they need to consider the heat transfer rate of each product and their goals to determine which freezing rate and system is right for them. Whether a baker wants to preserve crust integrity or lock in moisture will determine how the products will be frozen or chilled.
Locking in moisture preserves product quality. “The faster you freeze something, in general, the more water molecules you lock in, and in doing that, you preserve the product taste and texture profile so you create a higher value, better-tasting product,” Mr. Cordiano said. Bakers want to freeze products as fast as possible for the freshest taste but without causing damage to the bread or roll.
“Bread and rolls are more sensitive to the freezing process due to lack of fat, and they have air pockets that slow down freezing rates,” said Frank Martin, marketing manager, food refrigeration, Praxair, Danbury, CT.
Finished baked goods often act as an insulator to themselves, trapping in heat. Freeze too fast and that heat will expand and try to escape. “Baked bread and par-baked bread are susceptible to cracking if you shock them too quickly,” Mr. Plante said. “For the most part, a lot of people use a prechilling or precooling stage with a fully baked bread before freezing.”
With slower freezing rates, the heat dissipates from the product completely preventing any damage to the crust.
Keeping air flowing
While sealing in moisture by freezing preserves finished product quality, airflow in a freezing or chilling system can dry out dough, nullifying this benefit of the process.
“By drying it out, you’re promoting staling the bread,” Mr. White said. “So by controlling the airflow, air temperature and the humidity, you’re able to improve the quality of the product.” Improper airflow, temperature and humidity will shorten the product’s shelf life.
IJ White’s Variable Airflow (VAF) technology can reduce the chance of this happening. The VAF system provides control of the airflow across the product zone to inhibit staling.
Improper airflow within a freezing or chilling system can also cause logistical challenges such as product blowing off the belt or losing toppings or egg washes. If units sit too close to each other on the belt within a freezer, the lack of airflow between them can cause them to freeze together.
Airflow can also be the difference between efficient and inefficient freezing. With JBT FoodTech’s GYRoCOMPACT product line, the freezers employ vertical down airflow to ensure fast and uniform freezing throughout the system.
Linde also pursued even and efficient airflow with the development of its new Cryoline Crossflow Spiral Freezer. “You’re getting an even airflow across the entire belt within a spiral, which is an extremely difficult thing to do,” Mr. Cordiano said.
Alit, Marsongo, Italy, designed its spiral freezers to give the baker full control of the air’s direction. The open design of the spiral optimizes the air handling including speed.
At the end of the day, to get a proper freeze or chill on either raw, par-baked or fully baked bread and rolls, bakers need to communicate their needs to their equipment suppliers. Mr. Cordiano said it’s important that suppliers understand each product and the baker’s expectations and needs.