New cryogenic impingement freezer for baking industry
According to Michael Newman, manager of equipment development for BOC's Process Gas Solutions, Food Group, the new cryogenic freezer differs from earlier impingement freezers in its ability to combine high-velocity airflow with atomized liquid nitrogen to produce "a continuous, consistent uniform freezing not found in mechanical impingement freezers."
Newman said that when the system was tested on a variety of bakery products, including cookie dough, pizza dough and pastry dough, dehydration loss was routinely well below the loss rate usually found in a conventional tunnel freezer. "And because the impingement freezer runs at a much colder temperature than a mechanical freezer, you can achieve higher production rates in a smaller floor space."
The impingement freezer produces extremely high convective heat transfer along with efficient use of cryogen to produce a continuous, consistent uniform baking across and along the belt from both top and bottom surfaces. Upon entering the freezer, the surface of the food product is instantly crust-frozen with a liquid nitrogen spray and high-velocity nitrogen gas, thereby trapping product moisture and resulting in a higher yield.
As the product continues along the belt, it is impinged from above and below with high-velocity nitrogen gas. Maximum process efficiency is achieved by moving and warming the nitrogen gas as it travels with product flow down the length of the freezer.