From modern loss in weight control to spicy crisps

In modern food processing most products require a specifically designed manufacturing process.

This not only relates to the treatment of raw materials or the formulation, but also to the way, all components are put together. You will not meet success if you simply mix all ingredients. Imagine the seasoning of potato crisps: If you simply mix potato crisps and the seasoning in a vessel you will end up with a fine powder and be able to eat the acrisps' with a spoon.

But there are solutions to such problems. One of them is the principle of controlled material flow. In general there are two different ways to determine and control the amount of material fed into a process.

In volumetric systems a defined volume is fed with a known velocity. From this a flow rate can be calculated. The accuracy and reproducibility of this procedure depends on the density and flow characteristics of the material. After a calibration fluids can be batched with high accuracy but if those parameters change a new calibration would be required.

Gravimetric systems automatically react to changing material characteristics because the flow rate is directly determined and controlled in kg/min. In a typical gravimetric system a vessel is mounted on a scale. Subsequently the gain or loss in weight of the material is registered, irrespective of density or flow characteristics.

Taken the example of potato crisps the seasoning is done by feeding a controlled amount of spices onto a running conveyer with crisps. Feed rate of the spices is again controlled by the feed rate of the conveyer to arrive at the exact ratio and homogeneity without the need for excessive mixing.

In general a trend in favour of gravimetric methods can be noticed in the market. This trend is driven by applications that require high standards of accuracy, traceability and comprehensive documentation (GAMP, HACCP, EHDG).

To support loss-in-weight applications nowadays dedicated instruments and controllers are available. So-called system controllers provide the accurate control of the complete production process including modern fieldbus interfaces and connection to PC systems. The controllers can work stand-alone or as part of a more complex system. Loss-in-weight controllers allow a highly accurate feed rate control including the provision of infinitive material flow. The controller directly control the process via integrated PI-controller. The total amount of material in the vessel is checked too and the refill is initialised automatically.

enquiry no 62A

GWT Global Weighing Technologies GmbH is based in Hamburg, Germany. www.global-weighing.com

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