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

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

Replacement of fish meal with a matrix of organic plant proteins in organic trout (Oncorhynchus mykiss) feed, and the effects on nutrient utilization and fish performance

This study examined the effects on nutrient utilization and fish performance when replacing 16, 31, and 47% of fish meal protein (corresponding to replacing 15, 29 and 44%, respectively, of total dietary protein) with a fixed matrix of organic pea, horsebean and rapeseed plant protein concentrates (PPC) in a ratio of 1.07:1.00:0.66. Four iso-energetic and iso-nitrogenous diets were produced to include 0, 136, 274 or 410 g kg-1 of the organic PPC matrix, respectively. The organic protein ingredients were chosen based on their high protein content, and the matrix was established to mirror the amino acid composition of fish meal. The plant ingredients were dried, dehulled, grinded and air classified in accordance with the European Union Commission Regulation on organic aquaculture production, increasing the protein concentrations up to 577 g kg-1 dry matter. Two experiments were carried out using juvenile rainbow trout (Oncorhynchus mykiss): 1) a digestibility study to examine the apparent digestibility of protein, lipid, nitrogen-free extract (NFE), total phosphorus and phytate-phosphorus, followed by a water sampling period to determine the output of nitrogen and phosphorus and enabling the setup of nitrogen and phosphorus mass-balances; and 2) a 57 days growth study including 3 growth periods each of 19 days and using pit-tagged fish. Substituting fish meal with organic PPC significantly increased the apparent digestibility coefficient (ADC) of protein and lipid (P<0.008) at the highest PPC inclusion level, while there was a significant (P<0.044) decrease in the ADC of NFE with increasing PPC inclusion level. The apparent digestibility coefficient of phytate-phosphorus was significantly lower (P<0.005) at the highest PPC inclusion level compared to the fish meal control diet. The mass-balances revealed a significant increase in the excretion of ammonium-nitrogen (NH4N, P< 0.017) at the two highest PPC inclusion levels and a decrease in phosphorus (P<0.009) excretion at the highest organic PPC inclusion level. There was no overall effect on the specific growth rates (SGRs) or feed conversion ratios (FCRs). The study thus demonstrated that it is possible to replace fish meal by 47% organic PPC without compromising rainbow trout performance. However, the results also indicated that it will be difficult to replace much more than this as long as supplementation with synthetic amino acids and exogenous phytase is not allowed in organic feed