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Oat protein structure-function properties and value-added application
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- Author / Creator
- Nieto Nieto, Talina V
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The global protein market is growing with focus on plant-based proteins. Oat protein is a good source of plant protein, and is regarded as a by-product of the β-glucan extraction process; therefore oat protein is waiting research to develop its full potential. Globular proteins in oat closely resemble the proteins in soy, which have demonstrated good gelling properties. Thus, this research aims to develop a new oat protein based gelling ingredient for food and non-food applications. For this, it was necessary to complete a systematic study of the thermal gelation of oat protein under different environmental conditions. Mechanical and rheological properties of oat protein gels were determined and their microstructures were observed. We attempted to better understand gelling mechanisms of oat protein based systems by correlating protein structure changes during heating to gel microstructures and bulk properties. Special emphasis was placed on enzymatic hydrolysis and protein-polysaccharide blending, as two important strategies to improve oat protein gelling properties due to their mild reaction conditions and in consequence higher consumer acceptability. In the first part of this work, the effect of enzymatic hydrolysis on the structure and gelling properties of oat proteins was investigated. Flavourzyme and trypsin hydrolysates could form gels with similar mechanical strength and water-holding capacity comparable to animal protein. The acidic polypeptide of the 12S fraction exerted great influence over the gelling ability of oat protein. Partial hydrolysis with the appropriate enzyme altered the charges on the protein molecular chains, allowing a balance between attractive and repulsive forces at pH 8 and 9 to establish strong three-dimensional gel networks when heated at 110 and 120˚C. Additionally it was suggested that the partial hydrolysis also led to increased exposure of hydrophobic groups that remained in the peptide chains, which allowed development of gel with improved strength via hydrophobic interactions. Both oat protein and its hydrolysates gels exhibited excellent water holding capacity at neutral or mildly alkaline conditions. In the second part of this work, the impact of polysaccharide addition on oat protein gelling properties was investigated. Four different types of polysaccharide were tested including inulin, dextrin, carrageenan and chitosan. A synergistic effect was observed when gels were prepared under conditions that favored segregative phase separation. In contrast an antagonistic effect was observed when gels were prepared under conditions that promoted attractive interactions. This was especially evident for oat protein gels prepared with carrageenan at neutral pH, as a two-fold increase in mechanical strength was observed. Moreover, it has been suggested that strong repulsive forces caused by carrageenan addition resulted in a highly order network structure which permitted the development of hydrogen and hydrophobic interactions to further strengthen the protein networks. The findings from this work may encourage oat producers to promote the utilization of oat protein as an ingredient for human consumption, which could add economic value to their operations, and also motivate food producers to apply oat protein as a gelling agent in response to the increasing demand for plant-based proteins, which could increase the profit generated by producers and processors.
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- Subjects / Keywords
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- Graduation date
- Fall 2015
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.