Influence Of Alcohol Washing On The Flavour Profiles And Functionality Of Oilseed Proteins
Date
2025-03-20
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
Oilseed meals are obtained after pressing and extracting oil from the seed, the remaining meal is predominantly used as animal feed. Oilseed meals are rich in proteins, vitamins, minerals, fibres and have a well-balanced amino acid profile. Due to the increasing demand for protein-rich food, a sustainable and reliable source of protein is essential. Though oilseed meals are an ideal source, the presence of phenols, glucosinolates and phytates impart bitter, off-flavours and dark pigments into the meal. Besides these compounds, oilseed meals also contain antinutritional compounds and have poor functional properties which limit the usage of oilseed meal in the human food industry. The overall goal of this research is to examine the effect of alcohol washing on oilseed meals (canola and sunflower) using two alcohols: ethanol and isopropanol at different concentrations of 35, 65, and 95%. It was hypothesized that this treatment would reduce the off-flavour and dark pigments from the oilseed meals since the flavour and colour-imparting compounds are alcohol-soluble in nature, thus making them acceptable for future use in the food industry.
The combined treatment with the change of alcohol concentrations and type increased the protein concentration for both canola and sunflower. For canola, untreated meals had 86% protein, and the highest increase in protein content was observed in 65% ethanol wash (91%). For sunflower, protein content increased the most at 35% isopropanol treatment and increased from 87% to 93%. Lipid content was seen to increase for canola meal at 35% ethanol wash (6%) from untreated canola meal (1%). A similar trend was observed for sunflower protein, where the highest lipid content was observed at 35% ethanol wash (7%) from untreated sunflower protein (1%). At 35% ethanol wash, canola and sunflower meal had considerably lightened for canola and sunflower protein.
Functional properties such as water and oil holding properties were improved at 35% ethanol wash (⁓2 g/g) from the untreated canola protein which had around 1.5 g/g water holding capacity and 0.9 g/g oil holding capacity. Water holding capacity was seen to improve the most at 35% isopropanol wash (2.3 g/g) from 1.9 g/g for untreated sunflower protein. Oil holding capacity was seen to improve at 35% ethanol wash (2.0 g/g) from 1% for untreated sunflower protein. Foaming capacity was seen to improve from 140% to 196% at 65% ethanol wash for canola protein and for sunflower protein, the foaming capacity improved from 118% to 147% at 95% ethanol wash. Foaming stability had improved overall after the isopropanol wash in the case of canola protein and for sunflower protein, the foaming stability had not improved significantly. For canola protein, emulsion stability was seen to improve at 65% isopropanol wash from 36% to 47% and for sunflower protein, no improvement was observed after alcohol washing. Protein solubility had significantly increased at 95% isopropanol wash for canola protein. For sunflower protein, the protein solubility had not improved.
Aldehydes were the major volatile flavour compounds that were removed after alcohol washing. Around 95% of aldehydes were removed from canola protein. 2- Butenal, 2-Methyl butenal, and 3-Methyl butanal were the aldehyde groups that were predominantly removed from canola protein. The aldehyde compounds such as 2- Butenal contributes a pungent- fruity flavour, 2-Methyl butenal contributes a greenish fruit flavour and 3- Methyl butanal adds a malt flavour to the protein concentrate. For sunflower, hexanal was the aldehyde group predominantly removed after alcohol washing, which contributes towards the grassy flavour of the sunflower protein concentrate. Roughly 90% was removed after ethanol washing and 70% was removed after isopropanol washing. Sinapine is the non-volatile compound that adds bitterness to canola meal protein and chlorogenic acid is the non-volatile compound that adds astringency and bitterness to sunflower protein. The total amount of sinapine was reduced by 20% after 35% ethanol washing which was the highest reduction. In the case of sunflower, the highest amount of chlorogenic acid was reduced by 26% after 65% ethanol washing. Amino acid scores for the oilseed protein concentrate revealed that the only limiting amino acid was lysine. Even though lysine was the limiting amino acid before washing the protein, alcohol washing has improved the amino acid scores for lysine. After calculating IVPD scores, it was seen that there was significant improvement at 35% ethanol (85.9%) wash for canola protein in comparison to untreated canola protein (83.1%). For sunflower protein, there was no negative effect after washing with alcohol. IV-PDCAAS values showed a slightly different trend where the highest value was observed at 95% isopropanol wash (69.2%) from the untreated canola protein (63.8%). While no significant improvement was observed in the IV-PDCAAS values for sunflower protein.
Overall ethanol was slightly more effective in comparison to isopropanol treatment. Protein functionalities had improved or had no effect for canola protein, while for sunflower protein, protein functionalities had either improved or had a negative effect (emulsion stability). The flavour compounds were removed effectively after alcohol washing. The overall colour of the sample was also altered based on the alcohol concentrations, it had either lightened or darkened. To attain a clean-tasting product which is widely accepted by consumers and to use oilseed meal as a protein source in the plant-based food industry, the flavour profiles and colour play a crucial role. The data collected from this study will be beneficial to understand the effects of alcohol washing on oilseed meal protein and to thereby increase the utilization of plant-based protein.
Description
Keywords
Oilseed proteins, Alcohol washing.
Citation
Degree
Master of Science (M.Sc.)
Department
Food and Bioproduct Sciences
Program
Food Science