Measuring moisture and density in fish food

When fish food is introduced into water, it should act in accordance with the fish's feeding behaviour; staying afloat or sinking. These properties largely depend on the density of the fish food, which in turn determines the type of fish food:

- Feed that floats on the water surface

- Feed that sinks slowly

- Feed that sinks and is water-resistant

- Feed that sinks and is extremely water-resistant

The density of fish flakes, pellets or chips is an important aspect of product quality. So is the moisture content in the feed. Both too high and too low moisture content causes loss of quality and can make further processing of the fish feed difficult or even impossible. An ideal moisture content leads to a longer shelf life and prevents rotting.

Producing high-quality fish feed

Regular checks of moisture content and density are therefore necessary to produce high-quality fish feed. The general method for quality control is laboratory measurement. Operators in the fish feed process manually take samples from production and to analyse the moisture and density content in a laboratory. This produces the moisture and density values, which can take between five minutes and several hours, depending on the method. Sampling is both time-consuming and labour-intensive, and the measured values are generally available too late to adequately control the production process.

Controlling the process with continuous (in-line) moisture measurements

TEWS has developed a measurement technology that allows the moisture content and density of fish feed to be measured continuously during the production process.Using bypass sensors integrated into the process, the values are reliably and accurately measured and visualised in seconds.Rapid and targeted intervention in the production process is thus possible.Improved control of production processes leads to energy savings and less waste and better quality fish feed.In short, moisture and density measurements during the process increase the efficiency of the entire production chain.

Find more information on the inline moisture measurement of TEWS here.

Microwave resonance technology for real-time control of the fish feed production process

The patented measurement method is based on microwave resonance technology. Once the material passes through the field of the microwave sensor, its resonance properties change depending on the water content. A single configuration of the systems is all that is needed to operate continuously and reliably. The particular uniqueness of this technology is its independence from colour, density, grain size or surface influences of the product being measured. Unlike the so-called NIR method, which measures the moisture content only on the surface, the microwave measurement equipment also determines the core moisture inside the product.

Functioning of the microwave resonance method

Water molecules are among the smallest molecules that are positively and negatively charged.

The moisture sensor generates a low-energy electromagnetic field, which reacts with the water molecules in the product sample.As the microwave field penetrates several centimetres into the sample, water is measured not only on the surface but also in the core of the product.

The product sample reduces the propagation speed of the microwave field and the water molecules in the sample are continuously aligned with the electromagnetic field, depriving it of energy.The moisture meter continuously measures these two effects, which is also called the dual parameter method.

A moisture value is then calculated based on the resonance parameters. When commissioned, the moisture meter is calibrated using a laboratory method (e.g. the LOD method or Karl Fischer titration) so that the moisture content of the product can be displayed, stored or processed as a percentage.

The microwave resonance working method can also be used to measure bulk density.

Webinar: Measuring moisture in feeds

For more information on measuring moisture and density measurement in fish feed, watch the webinar on measuring moisture in feed here.

Contact Inventech today

Measuring moisture and density in fish food

Inventech is the specialist in moisture measurements; also for fish food.