Issues in Extrusion of Aquafeeds


April 11, 2016 Facebook Twitter LinkedIn Google+ Aquaculture News,News-Global



Introduction

Extrusion technology provides a number of major benefits over the more traditional pellet milling processes commonly used for aquaculture feeds. In particular extrusion can provide a much higher degree of control over the “cook” achieved, as well as better control of the product density (therefore controlling the floating/sinking characteristics).

But extrusion is a very complex process – and we only have “indirect” control over that process. We never have just one parameter change during extrusion – if ingredients vary, it doesn’t just change the final product composition – it changes the rheology of the mix and therefore changes how the melt moves through the extruder and the die, which in turn affects the residence time and temperature developed in the melt, which changes degree of cook and expansion – and therefore affects digestibility and floating/sinking characteristics. Within this complex relationship, we need to achieve consistency – of nutrition, of digestibility, of physical characteristics. It is the cumulative effect of these parameters which ultimately determine the feed conversion ratio (FCR) for the product.

So to use extrusion effectively – and take full advantage of the opportunities offered by the technology – the extrusion process needs to be properly understood. This paper discusses just a couple of the issues relating to successful extrusion of aquafeeds.

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