Protein Extraction From Alkaline Feedstock Using CO2 Precipitation
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Solution Overview
Problem
Existing methods for extracting proteins from brewer's spent grains using alkaline solutions require significant amounts of mineral or organic acids, leading to impurities, taste issues, and increased washing efforts due to the pH adjustment to the isoelectric point.
Innovation Solution
The method involves using carbon dioxide-containing gas to lower the pH during protein precipitation, optionally supplemented by inorganic and/or organic acids, sourced from biogenic fermentation, to reduce chemical usage and impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If mineral acids (hydrochloric acid, phosphoric acid, or sulfuric acid) are used to lower pH for protein precipitation, then the pH can be effectively reduced to the isoelectric point, but impurities (chlorine, phosphorus, or sulfur) are introduced that affect the properties, color, and taste of the precipitated protein concentrate
Solution Approach 1:
Carbon dioxide serves as an intermediary substance to lower the pH from alkaline conditions to the isoelectric point of proteins. When CO2 is introduced to the alkaline protein extract, it reacts with water to form carbonic acid, which gradually reduces the pH without introducing harmful mineral acid impurities. This intermediary approach achieves the desired pH reduction while maintaining product quality.
Solution Approach 2:
Carbon dioxide is used as a temporary, consumable reagent that achieves pH reduction and then dissolves or decomposes without leaving persistent harmful residues. The CO2 is either absorbed into the solution or can be removed by heating, leaving no harmful mineral acid impurities behind, unlike mineral acids that leave lasting salt residues.
2Quantity of substance
If mineral acids are used for pH adjustment, then the protein precipitation is effective, but subsequent washing steps are necessary to remove resulting salts and acid residues
Solution Approach 1:
Carbon dioxide acts as a clean intermediary that reacts temporarily to adjust pH and then disappears or becomes innocuous. The reaction products (carbonic acid, bicarbonate, carbonate) are either soluble and easily removed or can be decomposed by heating, eliminating the need for extensive washing steps required when using mineral acids that leave insoluble salt residues.
Solution Approach 2:
The carbon dioxide is effectively 'discarded' after serving its pH-adjustment function, either by dissolving into the solution, being removed during subsequent processing, or decomposed by heating. This eliminates the need to recover and remove harmful mineral acid residues through multiple washing steps.
3Quantity of substance
If organic acids (such as citric acid) are used to lower pH, then the pH reduction is achieved, but they are expensive, often come from non-biogenic sources and also influence the taste of the final concentrate
Solution Approach 1:
Carbon dioxide is a inexpensive, readily available gas that serves its pH-adjustment function and then dissolves or decomposes without leaving taste-affecting residues. Unlike organic acids that impart their characteristic flavors to the final product, CO2 leaves no persistent taste influence, making it ideal for food applications.
Solution Approach 2:
Carbon dioxide can be sourced from biogenic fermentation processes, making the system self-sufficient and sustainable. The CO2 produced during fermentation is reused for pH adjustment, eliminating the need to purchase expensive organic acids and reducing the overall chemical input requirements of the process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces the need for acids, minimizes the generation of harmful salts, improves taste, and decreases washing requirements while maintaining protein extraction efficiency.
Implementation Method 1
a carbon dioxide-containing gas is used to lower the pH value in the protein-rich liquid phase
Implementation Method 2
lowering the pH to the isoelectric point. This causes the proteins to flocculate, allowing them to be separated
Data Source
Figure 1
AI summary
The invention relates to a method for extracting proteins from a protein-rich raw material, comprising the steps of - treating the raw material (F1) with an alkaline solution (L1, L2), whereby a mixture (M1, M2) is obtained which comprises a solid phase (R1, R2) and a protein-rich liquid phase (EXT 1, EXT2) containing the proteins, - separating the protein-rich liquid phase (EXT 1, EXT2) from the solid phase (R1, R2), - lowering the pH in the protein-rich liquid phase (EXT 1, EXT 2, M3), whereby the proteins are precipitated and a further mixture (M4, M5) is obtained which comprises a further liquid phase and a protein-rich solid phase, - separating the precipitated proteins from the mixture (M4, M5) to obtain a protein extract (R4).The process according to the invention is characterized in that a carbon dioxide-containing gas (G3) is used to lower the pH value in the protein-rich liquid phase (EXT 1, EXT 2, M3).