Large Blanchers & Leaching
VOL. 21 NO.3
Since all of the examples cited below occurred fifteen or more years ago, information concerning specific processors has been industry wide knowledge for a long time. Large belt blanchers have always been part of Gem Equipment's product line. During the thirty-three years this company has been in business, large blanchers have become much bigger. The six foot wide, forty foot long blancher this company manufactured in the early 1970's was large. Gem's first big belt blancher for french fry potatoes was manufactured in 1975. Over forty feet long with a ten foot wide belt, this unit was considered huge. By the mid 1990's, french fry blanchers, over one hundred feet long with twelve foot wide belts, were being put into service. Blanching french fry potatoes serves four functions: Sterilization and killing enzymes are the same process as with most other vegetables. In addition, blanching french fry potatoes controls the texture and leaches out excess sugar. Using high sugar potatoes, without leaching, produces a fried product with too dark a color.
Leaching, which is washing sugar and starch out of the potato strips, has been the driving force behind the increase in blancher size. Overhead sprays, usually furnishing eight to ten gallons of water per square foot of blanching area, provide the washing action. The original reason for distribution of the hot water with overhead sprays was to have water flowing down through the belt to assure product moved at the same speed as the belt. On the first blancher, the ten degree delta T specification determined water flow which worked out to about two and one half gallows per minute per square foot. Gem's first two large belt french fry blanchers went to two different processors. Both blanchers were started up by the same production manager. His experience with the first blancher probably influenced temperature specifications for the second unit. Five degree delta T was specified, resulting in about five gpm per square foot, high enough to do some leaching. By using temperature specifications, this production manager got water flow rates high enough to leach without alerting the rest of the industry.
Several years later, Gem's first high volume deluge blancher went into service. These units out perform auger blanchers. This was illustrated to your writer during a trip as a guest on the customer's corporate aircraft. The only other passengers were Quality Control Managers from three plants. This was during the time of year with high sugars in the raw product. The two Quality Control Managers from plants still using auger blanchers spent considerable time discussing how much trouble they were having keeping their finished product in grade. Finally, the Quality Control Manager with the belt blancher spoke up. "Since we installed the deluge blancher, all of those troubles are behind us." This was verified a few years later in another company's plant. Again, during a period with high sugar in the raw product, this plant switched on the fly from their existing auger blanchers to their new deluge blancher. The "A"/"D" comparison put big smiles on the Quality Control and Production Managers' faces. While in many growing areas, auger blanchers are satisfactory much of the time, eventually high sugar potatoes will have to be processed. A deluge blancher is insurance for those times.