The only specialised marine publication in Oceania that focuses on the maritime industry, from super yachts to small craft to large commercial ships, including coastal shipping, tugs, tow boats, barges, ferries, tourist, sport-fishing craft
Issue link: https://viewer.e-digitaleditions.com/i/79766
Peter Hutchinson with the kiwi product The extruder at EN Hutchinson Ltd Auckland Twin Screw. Up until now extrusion had been well defi ned in terms of what ingredients could be used and at what percentages. The Thermal Twin changed everything. Starting with a completely redesigned and improved High Intensity Preconditioner which allows for increased addition of meat slurries, increased levels of process steam, higher gelatinisation levels, and greater retention time. The key for tuna feed production is the ability to use high levels of wet aquatic meats and/or terrestrial waste material, at inclusion rates of 50 percent to 60 percent or higher by weight. This preconditioner's design allows for the mixing of dry and liquid raw material whilst yielding a free fl owing friable product into the extruder barrel. The new extruder barrel design, unlike standard twin screw extruders, allows for four to fi ve times the steam injection with specially designed injectors into a reengineered screw profi le, allowing complete inclusion and utilisation of the steam. Up to 12 percent steam injection by weight provides a thermal energy to mechanical energy ratio of 14 to 1. This is a critical process advantage given that it is virtually impossible to cook with mechanical energy when the moisture levels are approaching 40 to 50 THE TUNA HAD NO HESITATION IN SLAMMING THE PELLETS… percent. The addition of mid barrel fl ow restrictors as well as the proven back pressure valve, increase this machine's ability to produce these unique and challenging products that have never before been possible. Trials were conducted at the Tech Centre in Sabetha, Kansas, in Nov 2010, where wet fi sh inclusion was pushed in excess of 50 percent, while still producing beautiful pellets. These pellets were not dried, but were cooled with the inclusion of water loving ingredients, acids and mould inhibitors allowing the resulting high moisture pellets to remain shelf stable. Unfortunately, due to border biosecurity restrictions it was not possible to bring any volume of product produced in the US to Australia for trials. Over the last two years ENH Ltd and Wenger Manufacturing have worked towards a common goal of establishing large scale sea trials. This has also involved some work with the development of hatchery feeds for juvenile tuna, based on the same extrusion technology, as it became apparent that the soluble protein available from inclusion of wet fi sh appeared to be a requirement for tuna nutrition. It is worth noting that in Australia and elsewhere, the impact The Wenger feed plant in Kansas of large numbers of hatchery reared tuna becoming available will have an enormous impact on aquaculture nationwide, not just locally. Australian tuna farming is currently restricted to the area surrounding Port Lincoln due to the supply of wild migrating tuna through this area in late spring. The colder temperatures which prevail in this region are a limiting factor for growth. Availability of hatchery reared fi sh will open up the ability to farm east, west, and in warmer more northerly waters, and could see large scale growth in the industry in a very short space of time. As of June 2012 the fi rst tonne of extruded semi-moist tuna feed has been delivered to South Australia for extensive palatability trials, with the fi rst commercial volumes for grow out trials due to be manufactured in Australia later this year. Following closely behind is feed destined for Europe, and the newly formed TRANSDOTT programme with its sea cage feed trials planned for next season. Not a moment to soon, with great expectations that juveniles will fl ow swiftly from the land based hatchery currently under construction! SEPTEMBER/OCTOBER 2012 ■ NZ AQUACULTURE ■ 7 An example of our local product