Investigation of solid-state fermentation to enhance the nutritional value of cold-pressed and hexane-extracted canola meals, and the functional properties of extracted canola protein.

Abstract

Canola meal is the byproduct of the canola oil extraction process and is rich in protein (30%-45%), total dietary fibre (~33%), B-vitamins and essential minerals. However, its utilization in animal feed and food industry is limited by the presence of anti-nutritional factors especially phytic acid and total phenolic content. The overall goal of this thesis was to apply solid-state fermentation (SSF) using Aspergillus niger NRRL 334 and Aspergillus oryzae NRRL 5590 to hexane-extracted (HE) and cold-pressed (CP) canola meal to study the effect on the reduction of antinutrients and functionalities of extracted canola protein products. In study 1, a significant reduction of phytic acid (~80%) was found after SSF, whereas a decrease in TPC from 2.7-3.1 to ~1.0 mg (gallic acid equivalent)/ g dry meal (~65% to 81% reduction) was reported. Oil content of CP meal decreased from ~12% to 9%. An increase in crude protein level was observed upon SSF with both strains (from ~36% to ~40%) while minor changes were found for ash content. In study 2, functionality of protein products extracted from fermented meals using salt-extraction (SE) and alkaline extraction-isoelectric precipitation (AE-IP) were tested. Protein products obtained using SE showed high protein content (~95%), while products extracted using AE-IP showed much lower protein content (56.5% to 85%). After SSF, solubility of protein products decreased at pH 3 but increased at pH 7. Increases were found in water and oil holding capacities of protein products after SSF. All protein products displayed emulsifying activity index values ranging from 5.6 to 21.1 m2/g and emulsion stability index values from 1.1 to 4.5 min. All canola protein products showed a foaming capacity ranging from 154.4% to 480.0% with foaming stability ranging from 68.0% to 89.0%. Overall, SSF using Aspergillus niger NRRL 334 and A. oryzae NRRL 5590 has showed the potential to improve the nutritional value of both CP and HE meals by increasing the protein content while reducing the levels of phytic acid and total phenolic compounds. After 72-hour SSF, both beneficial and adverse impacts were found on functionality of protein products extracted from fermented meals.