"Some people think a horizontal or a barrel mixer is better because it's stronger and more rigid,” Robbins says. “But, that being said, I'm a firm believer in spiral mixers. We have three Sancassianos. We actually tried about six different types of spiral mixers several years ago, but these mixers we chose are, I believe, the best we've seen. They have a cylindrical breaker bar in the middle, as opposed to some of the spiral mixers that have an L-like bar. The L-like breaker bar sort of slides the dry ingredients, as opposed to the cylindrical breaker bar that incorporates ingredients much quicker. It's very good for the dough and adds life to it.”

At the Robbins' bakery, once the dough is mixed, it goes through a divider; conical rounder; intermediate/overhead proofer where it rests for 12 minutes; through a final moulder, where it is degassed; then formed and placed on pans that are set onto racks and then blast frozen. The whole process takes 18 minutes. “Even though we've tried to automate and expedite our process, it still is more natural,” Robbins says. “The dough is allowed to rest for 12 minutes after it's rounded, and then it goes through a moulder. The main attribute to having the yeast remain dormant throughout the resting process is having that lower dough temperature.”

Robbins strives for a mixing temperature of 63°F (17°C) for his frozen dough versus the temperature range of 75°F to 80°F (24°C to 27°C) used for proof-and-bake bread production.

Formulation constraints
Yeast used in frozen dough has to survive frozen storage for three to six months. Typically, bakers use the same strain of yeast for proof-and-bake bread production and frozen dough, although the yeast, which is preferably the cream type, should be as fresh as possible, van Eijk notes.

The presence of trehalose, a natural disaccharide sugar with good water retention properties, is a cryoprotective compound that has been associated with yeast. Yeast with higher levels of trehalose tend have lower gassing power; therefore, the yeast tends to stay dormant longer in frozen dough, and activates more slowly, according to Lallemand.

Yeast strains specially engineered to be more cryoresistant also are available in compressed/crumbled and liquid/cream forms, Bohm notes.

Dough conditioning systems are particularly important for protecting the dough throughout freezing. “Generally, the conditioning systems are higher in oxidation, lower in reducing agents and contain high amounts of dough strengtheners and/or enzymes and hydrocolloids,” Bohm says.

High levels of antioxidants are recommended of at least 60 ppm; however, 90 ppm to 120 ppm of ascorbic acid is preferred for optimum oxidation, according to Lallemand. When reducing agents are used to reduce mixing time and speed up dough development, more oxidation is required.

Dough conditioners are very important in frozen dough. Robbins uses all natural vitamin C in all of his make-and-bake and par-baked products. Reportedly, no all-natural dough conditioners exist that work in frozen dough. The emulsifier DATEM (di-acetyl tartaric acid esters of monoglyceride) works very well in frozen dough. “Our product has a lot of tolerance, a nice shelf life and will hold up for the end user,” Robbins adds.