Integrated moisture management at a food manufacturer

In-pipe microwave moisture meter on feed to extruder
In-pipe microwave moisture meter on feed to extruder

Online moisture control from Callidan Instruments has boosted productivity and product quality in extruded food manufacture.

Moisture management specialist Callidan Instruments has developed a suite of online moisture metres specifically for the food manufacturing sector. Using expertise gained in the minerals industry, Callidan has taken its successful microwave moisture measurement equipment and re-engineered it to meet the strict standards and challenging applications of the food industry.
After several years of R&D and proof of concept trials, Callidan Instruments has commercially available moisture meters specifically designed to measure moisture in a wide range of materials across various applications. Models exist to measure moisture on conveyor belts and rollers, in chutes and hoppers, in pipes and in mixers and dryers.

A major international snack food manufacturer recently implemented an integrated moisture management system as part of a yield maximisation program being implemented by the company. The batch process starts by taking raw material and adding moisture. The wet mix is then fed to a hopper where more water can be added. From the hopper the mixture is fed through a hydrator which is the final point in the process where moisture is added. Finally the mixture passes through the in-pipe moisture analyser before being extruded.

Online microwave moisture analysers are installed at four critical monitoring points in the process. Two analysers monitor the moisture in raw feeds. Combining this data with weigh scale data the total dry mass feed to the mixer is calculated, and output via a 4-20mA signal, to very precisely control the addition of water to the mixer (the customer also uses that data as a cross check to ascertain whether its raw material supply is within specification with respect to maximum moisture percentage).

Mixing occurs in batch mode. Once the batch achieves the desired mix consistency, it is transported to a storage hopper. A third moisture analyser is situated at the exit to the hopper feeding a hydrator. Again, this analyser, in combination with a weigh scale, calculates dry mass feed to the hydrator. The final moisture analyser is situated in a pipe exiting the hydrator and feeding the extruder. Hence the inlet moisture and outlet moisture to the hydrator is known and from this information the temperature of the hydrator and the addition of moisture to the hydrator is automatically controlled.

The result is a hydrated mixture of precise moisture content. If the water content of the feed mix to the extruder is too high theextruder produces “skinny” snacks which are rejected. Similarly, ifthe moisture content is too low the extruder “clogs” and the operation stops.