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Dissertation - University Access Only
Doctor of Philosophy (PhD)
Agricultural and Biosystems Engineering
Considering the techno-economic feasibility of aquaculture production, feed cost is a primary concern. Currently, the goal is set to stop feeding the fish by fish. Plant-based proteins may make fish farming sustainable; however, utilization of them in aquafeed is somewhat challenging. Achieving the goal requires both appropriate pre-treatment of these protein sources and employing a proper production technology. The effect of three modified plant-based proteins (i.e. HP-DDG, SPC, and FSBM) and extrusion processing parameters on production of different aquaculture feeds was studied. To approach the goal, separate studies in pilot and lab scales have been conducted. In pilot scale study, nutritionally balanced ingredient blends containing FM, C-DDGS, HP-DDG, SPC, and FSBM, formulated for three different species, were extruded in a twin screw extruder. The physical properties of the extruded feeds gave insight about the processing functionality of these plant-based proteins which are important for developing a viable fish feed. Elevating levels of extruder water and conditioner steam increased density and water stability (WS), but reduced expansion ratio (ER) of Nile tilapia extrudates. It was determined that up to 40% HP-DDG inclusion, in contrast to C-DDGS, had no effect on bulk density (BD) of the rainbow trout diet. Increasing levels of HP-DDG did not change ER of these products. Inclusion of 20% FSBM-30%HP-DDG and 20% SPC-30%HP-DDG, substantially increased the ER of the yellow perch feeds. Thermal properties of the diet with SPC incorporation were considerably increased. It was determined that total FSBM inclusion could produce more expanded rainbow trout feeds compared to 40% HP-DDG inclusion. While FM elimination with FSBM inclusion in trout diets resulted in a significant reduction in BD, combination of 20% FSBM and 40% DDGS, could raise BD of the yellow perch feed. All extruded feeds had low aw and high PDI indicating that the products had long storage stability and high resistance against external mechanical forces. Producing of a solid quality feed requires understanding the effect of the ingredient and processing parameters on both nutritional and physical properties of the feed. In lab scale study, corn, cassava, and potato starches; FM, SBM, and DDGS proteins; FM, SPC, and FSBM-based feed blends were extruded in a single screw extruder. Based on the effect of extrusion processing severity on structural change and thermal stability of the starch extrudates, the starch robustness to survive the extrusion processing for this study can be ranked as Potato=Cassava> Corn. Functional and biochemical properties of the protein extrudates indicated that contributions of hydrophobic and ionic interactions were more significant than that of the disulfide bonds, particularly for FM and SBM extrudates. Despite the decrease in available lysine retention (RAL), the results for DDGS and SBM were comparable in quality to those of FM. It was found that SPC-based diet had the highest INVRPD. Optimal processing conditions for production of physically and nutritionally viable feeds were identified for each diet. It was determined that the best quality FSBM-based diet could be produced at higher T and MC compared with SPC-based diet. Using RSM, mathematical models were developed for feed properties, and required SME. In addition, this study compared the INVRPD of the extruded feeds with in vivo RPD of the pelleted feeds. This finding was in good agreement with in vivo RPD values.
Library of Congress Subject Headings
Fishes -- Feeding and feeds.
Fishes -- Nutrition.
Plant proteins as feed.
Distilling industries -- By products
Includes bibliographical references (pages 428-501)
Number of Pages
South Dakota State University
In Copyright - Educational Use Permitted
Fallahi, Parisa, "Understanding the Role of Plant-based Proteins and Extrusion Parameters in Different Fish Feeds" (2013). Theses and Dissertations. 1409.