Optimization of Protein Recovery Process from Rapeseed Cake

Sammanfattning: The need for sustainable sources of food is brought about by the never-ending exploitation of natural resource that our planet has provided. The heavy dependence on animal-based foods for protein has led to major depletion of the earth’s resources. The search for a sustainable protein source has led to the increase in utilization of the rapeseed cake which is a byproduct of rapeseed oil production. What would be used as animal feed is now considered as a sustainable product for the future due to its high protein and fiber content. Rapeseed cake is rich in cysteine and methionine which are essential amino acids usually lacking in most plant foods. The proteins in the cake however are not utilized to their full potential due to the presence of antinutrients in the form of phytic acid, phenolics etc. The main goal of this project therefore was to reduce the level of phenolics and attempt to reduce the total time for the process by testing different alkaline leaching times. After all, a protein concentrate for the customers must be rich in the essential amino acids and well balanced nutritionally, has a light color and does not have a bitter taste. Previous work done on this field, shows potential in obtaining high yields of protein via alkaline assisted leaching followed by isoelectric precipitation to obtain a protein concentrate. By building on this platform, the protein leaching process which originally was set to be as long as 4hours, was cut down to one hour, as the extraction yield stayed constant at around 61-65%, and the protein yield in the final concentrate at around 41-43%. A washing step was introduced where the rapeseed cake was allowed to soak in ethanol for one hour in order to leach out some of the phenolic. The results showed that soaking in ethanol in concentrations anywhere between 30% and 60% resulted in sufficient extraction of phenolics without too much of a drop in the protein yield. Additionally, the color of the protein concentrates was also of concern, and it showed that at washing at 30% resulted in the least loss in protein precipitate yield and extract as well as a comparably high loss of phenolic compounds. Due to the success of extracting phenols using ethanol, a combination of a lower pH and ethanol was attempted, but there was no improvement in the yield at a lower pH, although it did show a higher purity of around 80-82% than the purity at pH10.5 which was around 60-70%. The color of the protein concentrates also were lighter in color at a lower pH because it is likely that the phenolic oxidation occurs more at more alkaline pH. The use of rapeseed cake as an alternative to animal-based products for the requirement of protein seems like it still has a long way to go, but the following results show that there is a lot of potential in the quality and yield of protein obtained.