Monitoring & metering alginate casing


Alginate is found in the cell walls of brown algae which is a large group of multicellular algae, including many seaweeds located in colder Nor thern Hemisphere waters. An impor tant feature of alginate is its ability to hold many times its own weight in water, making it a naturally gelling substance. As a film-forming natural polymer,


alginate can be used as a casing for sausages through its gel formation with calcium ions. During the production process, meat mixture is extruded to form the sausage, and a layer of sodium alginate is simultaneously applied (co- extruded) to the outer surface, before a calcium chloride brine solution is used to for dehydration and to induce gel formation. This creates a layer of calcium alginate film on the sausage, which provides the strength and flexibility required in a sausage casing. The salt content in the brine solution is


very important and needs to be closely monitored because it affects the colour, texture and overall quality of the sausage.


The main advantages of co- extrusion over natural casings:


Lower purchase cost Ideal for automation Low labour requirement Product consistency


Flexibility – can be used for many different types and size of sausages


Stored as alginate powder, so no refrigerated storage necessary


Speed and throughput


Suitable for vegetarian, vegan and Halal (if alginate)


Monitoring alginate brine with in-line refractoMeters


The brine solution is stored in a brine tank, and spent brine is recycled to this same tank. Consequently, the brine is constantly diluted by the moisture that is removed from the casing gel. It is therefore necessary to monitor the salt solution so that the correct amounts of salt can be added to the brine solution. This function is performed by the Vaisala refractometer which monitors the salt content in real-time. There are two possible locations


for the refractometers; directly in the brine tank itself, and a second refractometer can be installed in the salt supply tank. The Vaisala refractometer measures the


refractive index (RI) of the liquid, which correlates directly with the salt concentration of the brine solution. In-line RI monitoring with automatic feedback control enables process operators to ensure consistent and reliable operations; thereby protecting product quality and reducing downtime. In contrast with many other liquid concentration methods, the Vaisala refractometer is extremely accurate and reliable and needs no regular maintenance. Impor tantly, these refractometers are not affected by par ticles, bubbles, crystals or colour, so they can be employed in a wide variety of solutions for measuring liquid concentration. The Vaisala K-PATENTS refractometers are also 3-A Sanitary Standards and EHEDG cer tified, which is essential for food processing equipment. The refractometers produce mA and


Ethernet output signals that allow automatic operation of the process. Moreover, the refractometers can be calibrated to read the concentration of NaOH in g/L, wt-% or any other engineering unit preferred by the factory.


Continued on page 36...


Instrumentation Monthly August 2022 35


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