PREDICTING AQUACULTURE FEED INGREDIENTS SOLUBILITY AND QUALITY THROUGH PROCESS CONDITIONS OF A TWIN SCREW EXTRUDER

Ingredients used for aquaculture feed have a large impact on the quality of the feed from both a nutritional standpoint and a quality standpoint.  One key aspect of feed quality is its solubility in water as it can impact both which type of  marine species it is suitable for and how long it remains in the water. This can be due to  both the protein and starch-based components in the feed.

During the manufacturing of  feed pellets in the extrusion process, the starch and protein  components can undergo a variety of chemical changes as it is subjected to the extreme pressure, shear, and heat. The chemical changes that occur can lead to a vast difference in product quality through means of solubility . While a majority of  prior  research has explored final product chemical solubilities and starting material solubilities, it is also important to understand the changes occurring within the extruder as the process variables change.

In order to understand the changes for starch-based components of an aquatic feed , flour was extruded in a co-rotating twin screw extruder and brought to a dead stop under different extrusion conditions. By quickly opening the extruder, samples of starch were retrieved from the feed, transition, and cooking zones of the barrel.  The ingredients were then analyzed for amount of chemical degradation as represented through intrinsic viscosity. It was found that the chemical degradation of the feed ingredients correlated strongly to the amount of mechanical energy produced in the extruder (Figure 1) and also correlated strongly with the water solubility of the final feed product (Figure 2).

By using instant measurement in the process for extruder mechanical energy, the end solubility of the feed product can be correlated and predicted accurately to design higher quality feed products that are better targeted towards different marine species.