Structuring canola oil with canola proteins
Date
2021-04-13
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
Oleogelation is an approach to structure liquid oil without using saturated or trans-fat for improved health benefits. With the official ban of the partially hydrogenated oil in the United States and Canada in 2018, this alternative oil structuring approach have gained increased interest over the years. The overall goal of the research work was to develop emulsion-templated oleogel from canola protein-stabilized concentrated oil-in-water (O/W) emulsions. Canola protein isolate (CPI) (1-4 wt%), extracted from cold-pressed canola meal, was used to stabilize 50 wt% O/W emulsions using high-pressure homogenization, and the effect of different environmental factors on the emulsions stability and rheology was studied. The emulsions were stable to coalescence with the addition of 1 wt% salt, 10 wt% vinegar, both salt and vinegar and heat treatment (80 °C for 30 min). All emulsions exhibited higher storage (G′) than loss moduli (G″) before crossover in the strain-dependent oscillatory rheological analysis, suggesting gel-like behaviour. In the presence of salt or vinegar, gel strength decreased due to the salt-soluble nature of CPI and higher droplet charge in the presence of vinegar. With the addition of both salt and vinegar, the droplets aggregated and formed a strong gel due to the charge screening effect from salt and increased surface hydrophobicity in acidic pH. The heated emulsions exhibited about ten times higher in gel strength than the unheated emulsions, which was attributed to the protein denaturation leading to extensive droplets and protein aggregation.
Subsequently, 1 and 4 wt% CPI-stabilized emulsions (unheated and heated) were vacuum dried and sheared to form oleogels. In general, the heated emulsion (HE) oleogel showed a higher gel strength and oil binding capacity than the unheated emulsions (UE) oleogel. Among all, the 4 wt% CPI HE oleogels showed the highest gel strength, firmness, stickiness and oil binding capacity, indicating better retained structure. Hence, the 4 wt% CPI oleogels was selected as shortening replacer in cake baking. Oleogel cakes were softer, and their specific volume was also significantly higher than the shortening cake. It was proposed that the protein-stabilized continuous air channels, observed in the HE oleogel cakes, contributed to its higher cake volume leading to lower hardness than the shortening cake. Overall, this research showed that canola protein isolates from cold-pressed meal can be used as a highly efficient stabilizer of concentrated O/W emulsion, which can be used in both liquid and gelled food applications. It also successfully demonstrated the application of canola protein isolate in oil structuring by forming emulsion-templated oleogels as a successful replacer of conventional highly saturated fat in cake baking.
Description
Keywords
canola proteins, emulsions, oleogel
Citation
Degree
Master of Science (M.Sc.)
Department
Food and Bioproduct Sciences
Program
Food Science