From grain to feed – process development concerning production of high protein fractions from grain and legum products to be used in extruded fish feed pellets

The Danish project “Organic Aquaculture” the link between sustainable production and superior products” is examining the availability of relevant organically produced crops with a high protein content to be used as raw materials for fish feed. Fish meal is the main source of protein for fish feed. On a global scale the production of fish meal will not increase. There is a demand for developing sustainable protein sources as a substitution for fish meal. Protein from crops and legumes is an obvious solution, however, the crops and legumes need to be processed into fractions with a higher protein content in order to compete with fish meal. The process development was carried out at The Danish Technological Institute’s pilot plant located in Sdr. Stenderup, Denmark. Sweet lupine seeds were processed among other grains and legumes. A dehulling process was developed based on three process steps: knife mill grinding, vibration sifting and zig zag air classifying. The protein content was concentrated from 34 % to 43 % protein on dry matter and fat free basis. 90,5 % of the hull was removed. The dehulled lupines were grinded so that 84 % of the fraction was below 250 µm. The grinding was carried out using a hammer mill with a 2.0 mm and a 1.0 mm sieve at 2950 rpm and finally using an Alpine 160 Z pine mill at 18.900 rpm. The grinded product was air classified by using a MP 400 Alpine Air Classifier. A protein fraction of 62 % protein on dry matter and fat free basis was reached. The relation between the particle size of the protein product and the protein content in the fraction was investigated. A linear relation was found and demonstrated; when the protein content in the product was increased the amount of particles in the fraction below 70 µm also increased linearly. The lupine protein was incorporated into a recipe for fish feed and extruded into pellets on a Werner Pfleider Continua 37 Twin Screwed Extruder

TOLERANCE OF CEREALS TO POST- EMERGENCE WEED HARROWING

This study defines crop tolerance to post-emergence weed harrowing as the combined effect of crop resistance and crop recovery. Crop resistance is the ability of the crop to resist soil covering and recovery is the ability to recover in terms of yield. In two experiments, resistance, recovery and tolerance were quantified in barley, oat, wheat and triticale by a new method based on digital image analysis. Important differences in resistance, recovery and tolerance among species were seen and resistance was not linked to recovery. Oat showed higher resistance than wheat, and barley. Triticale showed the lowest resistance. Oat and barley showed both lower ability to recover from soil covering than wheat, and triticale showed complete recovery. Triticale was the most tolerant species followed by wheat, oat and barley. Differences in tolerance caused species dependent crop yield losses in weed-free environments in the range of 0 to 10% for a practical relevant aggressiveness of weed harrowing

A general extrudate bulk density model for both twin-screw and single-screw extruder extrusion cooking processes

Effects of extrusion parameters and raw materials on extrudate expansion are respectively investigated in a twin-screw extruder and a single-screw extruder extrusion cooking experiments for fish feed, wheat, and oat & wheat mixture processing. A new phenomenological model is proposed to correlated extrudate bulk density, extrusion parameters and raw material changes based on the experimental results. The average absolute deviation (AAD) of the correlation is 2.2% for fish feed extrusion in the twin-screw extrusion process. For the single-screw extrusion process, the correlation AAD is respectively 3.03%, 5.14% for wheat and oat & wheat mixture extrusion; and the correlation AAD is 6.6% for raw material change effects. The correlation results demonstrate that the proposed equation can be used to calculate extrudate bulk density for both the twin-screw extruder and the single-screw extruder extrusion cooking processes