Effect from Combining Marine and Agricultural By-products during pH-shift Processing

Examensarbete för masterexamen

Please use this identifier to cite or link to this item: https://hdl.handle.net/20.500.12380/257138
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Type: Examensarbete för masterexamen
Master Thesis
Title: Effect from Combining Marine and Agricultural By-products during pH-shift Processing
Authors: Olofsson, Ellen
Abstract: Seafood is an important and nutritious part of our diet, for which a high demand calls for new approaches to sustain aquatic food resources. Residuals emerging in seafood production are very nutrient-rich and among other things containing high levels of protein. For extraction of proteins, a processing method has been developed, referred to as pH-shift processing, where proteins are solubilized at acid or alkaline pH followed by precipitation at the isoelectric point (pI). However, due to a high content of pro-oxidants and lipids in seafood by-products, the issue of lipid oxidation can remain during processing. The hypothesis behind this study, which is part of the Formas-funded CROSS-project, was that seaweed as well as residuals from processing of agricultural raw materials and shellfish, which comprise high levels of compounds with antioxidative, textural, pigmenting and other functional properties, could be added during pH-shift processing of fish by-products to improve the quality of the produced protein isolates. To investigate this hypothesis, herring and salmon filleting by-products were cross-processed with seaweed, shrimp peeling by-products and lingonberry press cake (referred to as “helpers”). Evaluations were made based on protein solubility, used volume of acid and base as well as protein yield in the pH-shift process. Total protein, moisture content, color and lipid oxidation products in the final protein isolate were also monitored. Results revealed that cross-processing of the helpers with fish by-products had remarkable effects on the pH-shift processing yield and quality of the final protein isolate, although the exact effects were highly dependent on type of helper and fish by-product, as well as the employed process conditions. As examples, addition of helpers to the fish by-products in the first step of the process reduced the protein solubility and thereby the total protein yield. However, there were indications that new textures were achieved, e.g. with seaweed, and that lipid oxidation was prevented, e.g. with lingonberry press cake. Trials with adding lingonberry press cake in the second step of the process revealed that this by-product could completely replace the use of hydrochloric acid to precipitate proteins, and also, when added in this step, did not give rise to reductions in protein yield.
Keywords: Biokemi och molekylärbiologi;Bioprocessteknik;Livsmedelsteknik;Livsvetenskaper;Biochemistry and Molecular Biology;Bioprocess Technology;Food Engineering;Life Science
Issue Date: 2019
Publisher: Chalmers tekniska högskola / Institutionen för biologi och bioteknik
Chalmers University of Technology / Department of Biology and Biological Engineering
URI: https://hdl.handle.net/20.500.12380/257138
Collection:Examensarbeten för masterexamen // Master Theses

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