The milling of cheese to a fine particle size is critical to the operations of parmesan cheese maker Isanti Foods, but, until recently, it has also been a source of problems for the Dalbo, Minn.-based processor.

To manufacture its fine-grated product, Isanti typically combines cheese from a variety of sources, mills it to a fine particle size and then dries it to a specified moisture content. However, problems with unacceptable particle size variations recently prompted the processor to retool its milling operations.

The original processing line employed a two-step process to mill the cheese. First, a conveyor deposited the product into a pre-breaker, which would break down blocks of cheese before discharging it by gravity into a Fitzpatrick FitzMill Comminutor, which would then fine-grind the cheese.

Isanti found that the FitzMill worked best when receiving a consistent feed of material. But since the pre-breaker was capable of processing considerably more material than the mill, the control of the feed to the FitzMill was based on the operator's rate of feeding product to the conveyor, as well as the size of the cheese blocks and wheels. These controls proved inadequate and caused material to surge to the FitzMill, resulting in both particle size variations and the occasional overloading of the mill motor. Further, the size of some cheese blocks was so large that material would occasionally bridge in the pre-breaker feed throat, requiring the milling line to be shut down until the material could be cleaned from the pre-breaker.

As a result, the pre-breaker was replaced by a newly developed machine called the Triver -- a three-roll pre-break capable of processing up to 55 gallon cylinders or 640 pound blocks of material without bridging in the feed throat. In addition, the Triver can accept all sizes and shapes of material in a flood feed condition and pre-break it to a smaller size than the original pre-breaker.

A blender was added between the pre-breaker and the FitzMill to combine the material and act as a metering device. The blender "stores" feed surges and meters material at the desired rate to the FitzMill. A newly installed dumper delivers batches of product to the feed of the Triver. Typical batches weigh approximately 500 lbs. and include wheels and blocks of various sizes and shapes.

Prior to installing the new Triver, capacities at Isanti varied by 1500 lbs./hr, with fluctuations in particle size and moisture content. Mill motor current draw was likewise inconsistent, resulting in large spikes. By eliminating surging to the FitzMill, the entire process operates more consistently, and fluctuations in particle size and moisture content have been eliminated.

Providing uniform material feeds made it possible to configure the FitzMill equipment to achieve smaller particle sizes, making drying easier in the subsequent fluid bed dryer. Additionally, the finer processed cheese is whiter and has better mouth feel.

Finally, the ability to flood feed the Triver allows for more efficient use of operator time. The operator fills the dumper for five minutes and then has five minutes available to clean the work areas or take care of other business.

The Fitzpatrick Company, 832 Industrial Drive, Elmhurst, IL 60126. Tel. 630-530-3333; Fax: 630-530-0832; e-mail: info@
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