CASE STUDIES IN INNOVATION: Rheometer for Continuous In-line Measurement Overcomes Challenges at Yogurt Manufacturing Facility

Nov. 12, 2012

In the food processing industry, viscosity indicates whether the product is lumpy or smooth, watery, or too thick. A company may test a product and then adjust it to build the texture it wants. But, if not handled properly in the processing line—for example, if the product is sheared too much—it will take much more energy and expensive raw materials to achieve the final desired texture. In reality, controlling texture is difficult and there are frequent fluctuations. Especially, for non-Newtonian products, it is a real challenge to effectively measure viscosity in-line.

Amy Richardson

A yogurt factory sought to continuously monitor viscosity during a batch transfer, after its cooling process, on a main production line. So, the plant installed a VISCOLINE CVL030S, manufactured by KROHNE Inc. (Photo courtesy of KROHNE)

Editor’s Note: In the October 2012 issue of Flow Control, 11 case studies/application stories featured the winners of our 2012 Innovation Awards program. In the following weeks, each winner will be featured on the FlowStream blog. The following post focuses on KROHNE Inc.’s VISCOLINE CVL030S.

Take the example of a large yogurt factory that uses batch processing to mature its product. Quality control personnel found that the quality of the white mass yogurt was not as stable as for what they expected, particularly after the maturation and cooling processes. Viscosity measures were determined by sampling several production batches, and the results showed a variability of +/-25 percent for the same product manufactured within one month. QC personnel did not expect such a wide variation, and it then became a serious concern.

The off-line measurement method used involved sampling and laboratory analyses. However, the very act of taking a sample out of the line affects the product. The product goes through the line in a pressure condition, so when passing through the sampling valve, the product is submitted to a shear rate that affects its texture. In addition, the time needed to get the product to the laboratory and conduct an analysis has an impact on the results.

In this context, the QC group at the yogurt plant was seeking more information and measurements to understand the factors generating defects and inconsistencies so they could avoid them. Rather than the off-line measurement process, they sought to continuously monitor viscosity during a batch transfer, after its cooling process, on a main production line. So, they installed a VISCOLINE CVL030S, manufactured by KROHNE Inc. The VISCOLINE is constructed from stainless steel, no moving parts, and no in-situ calibration required. It features continuous measurement with analog or digital outputs. The unit is reliable, with a repeatability of 0.2 percent, resolution to 0.1 CP, while meeting government policy on metrological traceability.

With the VISCOLINE installed in the mainline, the smoothing valve can be opened or closed in an automated fashion to achieve constant viscosity in real time. Leveling the texture fluctuations, the recipe can be adjusted upfront to get closer to the required minimal specifications. This reduces the consumption of expensive ingredients like proteins and results in a consistent, stable, uniform product that costs less money.

In addition, with the VISCOLINE installed right after the cooler, operators observed that 10 percent of the product was out of specification for texture after the transfer. This was happening at every start and stop during a batch transfer, due to a lack of heat exchanger control during these transient operations. Prior to using the VISCOLINE, there had been no way to measure the effect of these transitions.

Related Link:
www.krohne.com