Optimization of Protein Recovery Process from Rapeseed Cake

Abstract

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.

Popular Abstract

Improving rapeseed protein isolation by ethanolic pre-washing and leaching time optimization.
A large and so far, underutilized, source of high-quality protein is the press cake obtained as byproduct during rapeseed oil production. Rapeseed, a plant well known in Scandinavia and Canada for its high oil quality especially with regards to the rich mono and poly unsaturated fatty acid profile. The press cake, produced as a byproduct of the oil extraction has a potential to supply 1.12 million tons of high-quality vegetable protein per a year. The protein recovery process is initiated by an extraction step at a high pH of 10.5, followed by precipitating the extracted proteins at the isoelectric point of pH3.5. The problem is when it comes to the purity of this protein after recovery. Antinutrients in rapeseed include glucosinolates and phenolics, the latter of which is the focus of the thesis. Phenolics can get oxidized at high pH and react with the protein to cause a dark color and bitter taste of the concentrated protein obtained.
Proteins are indispensable in day to day nutrition, but due to the exploitation of the earth’s resources at an exaggerated rate, there needs to be a call for sustainability. The use of alternates to commonly known protein sources are one way to combat this exploitation, and this is done in the form of the development of products from plant-based sources of protein.
After optimizing the time of the process down to an hour, a step was introduced where the press cake was washed with ethanol, in order to extract the phenolics, thereby improving the color and flavor of the recovered protein. Different concentrations of ethanol were used and it was at 30% (v/v) where the highest yield of protein was obtained along with a relatively high amount of phenolics removed. The last step, was to study the effect of lowering the pH during the leaching step, and the purity and color obtained from the resulting concentrate was better than at the original pH 10.5. But in spite of this, the yield was very low and therefore, the experiment needs further work, by modulating the ionic strength using a salt like NaCl.
By reducing the time, further research can be done in a shorter time. There also is some data to prove that ethanol washing results in the removal of phenolics and results in a better isolate.
There were days where you had to worry about getting the “complete nutritional package” from your products, but now with the advancements in science and technology, antinutrients are slowly becoming a thing of the past. Rapeseed protein has the potential to overtake major plant-based protein sources like soybean and peanut, with its diverse amino acid profile and its non-allergenicity as compared to its competitors. For rapeseed protein to be successfully integrated into market foods, the problem with the antinutrients first needs to be solved, but huge strides are being made and it is only a matter of time before rapeseed protein products become a mainstay in the market for years to come.

• author: Pillai, Manav
• supervisor: Johan Thuvander
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM01 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Agriculture and Food Sciences; Technology and Engineering
• keywords: Rapeseed, Food, Protein, Leaching, Recovery, Precipitation, Food engineering, Livsmedelsteknik
• language: English
• id: 9023536
• date added to LUP: 2020-09-11 11:35:45
• date last changed: 2020-09-11 11:35:45