Extracting plant proteins at industrial scale presents significant challenges in yield and purity. Current methods typically achieve protein yields between 40-75%, with conventional isoelectric precipitation processes struggling to maintain protein functionality while removing unwanted components like phenolics, pigments, and anti-nutritional factors. These processes must balance pH-dependent solubility, temperature effects, and ionic strength across multiple unit operations.

The fundamental challenge lies in selectively isolating target proteins while preserving their native structure and functionality through the extraction and precipitation steps.

This page brings together solutions from recent research—including two-step isoelectric solubilization processes, controlled pH gradient techniques, enzymatic modifications, and selective precipitant strategies. These and other approaches focus on improving protein yield and purity while maintaining the functional properties needed for food applications.

1. Two-Step Isoelectric Solubilization and Flocculation Process for Protein Recovery from Plant By-Products

TEAGASC - THE AGRICULTURE AND FOOD DEVELOPMENT AUTHORITY, 2024

Protein recovery from plant by-products like rapeseed press cake using a two-step isoelectric solubilization process synergistically combined with flocculation. The method involves treating the plant material at low pH to solubilize the proteins, then flocculating and separating the protein fraction. This is followed by optionally hydrolyzing polysaccharides and repeating the solubilization at higher pH. The resulting protein product has high protein yield, low fiber, fat, and phytochemical content compared to conventional methods.

2. Process for Extracting Soybean Protein Isolate Using Controlled pH and Temperature with Selective Alkali Solubilization and Acid Precipitation

NANTONG SUN-GREEN BIO-TECH CO LTD, 2023

A process for extracting soybean protein isolate through a more efficient and controlled method compared to traditional methods. The process involves selectively extracting alkali-soluble proteins from soybean meal using a controlled pH and temperature environment, followed by precise acidification to precipitate the protein. The process achieves higher purity and protein recovery compared to conventional methods, while minimizing water consumption and environmental impact.

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3. Protein Extraction Process Using Biomass Lysis, Centrifugation, Filtration, and Activated Carbon Adsorption for Impurity Removal

INST SUPERIOR AGRONOMIA, 2023

Improved process for extracting proteins like RuBisCO from plant sources like leaves, seeds, algae, and bacteria in a way that produces pure, clean, and tasteless protein powders. The process involves steps like lysing the biomass, centrifugation, filtration, and activated carbon adsorption to selectively remove impurities like chlorophylls, pigments, and metabolites while isolating the target proteins like RuBisCO. This allows large-scale purification of proteins like RuBisCO from plant sources in a way that avoids the use of organic solvents or leaves green color.

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4. Single-Step Protein Extraction from Plant Residues Using Acid-Precipitation and Enzymatic Hydrolysis with Controlled pH Gradient

UNIV SOUTH CHINA TECH, 2023

A novel method for extracting high-quality vegetable protein from plant residues through a single-step process that preserves protein structure and functionality. The method employs a proprietary combination of acid-precipitation and enzymatic hydrolysis to extract protein from oil meal residues. The process involves a controlled pH gradient that selectively precipitates protein while preserving the natural polyphenol composition, followed by enzymatic hydrolysis to re-adsorb and stabilize the protein structure. This approach enables efficient extraction of light-colored, high-quality protein from plant residues without the need for multiple steps, adsorbents, or decolorization agents.

5. Method for Extracting High-Purity Protein Isolate from Sunflower Meal Using Sequential Acid and Alkali Treatments

FIBONACCI GROUP OF COMPANIES LIMITED LIABILITY CO, Limited Liability Company Fibonacci Group of Companies, 2022

A method to extract high-purity protein isolate from sunflower meal that has a protein content of over 90% and low phenolic compound content to make it suitable for food applications. The process involves grinding the meal, acid washing, alkali extraction, isoelectric precipitation, washing, and neutralization. Acid and alkali washes with antioxidants reduce color. The steps are optimized with specific temperatures, times, and pH levels to extract and purify the protein.

6. Protein Precipitation Method Using Controlled Non-Volatile Precipitant Concentration and Water Removal

PLASMA TECHNOLOGIES LLC, 2022

A method for enhancing protein precipitation efficiency in protein purification processes. The method involves adding a non-volatile precipitant to a protein solution at a controlled concentration that prevents precipitation while maintaining protein and precipitant concentrations. The precipitant concentration is precisely controlled by removing water from the solution while maintaining the precipitant concentration, resulting in a visible precipitate that can be separated from the supernatant fraction. This approach enables the selective precipitation of target proteins while minimizing contamination and preserving protein structure.

7. Red Bean Protein Isolates with Variable pH Extraction and Transglutaminase Modification

EAT JUST INC, 2022

Highly functional red bean protein isolates with improved properties like reduced oxidase activity and regulated sensory profiles for a wide range of food applications. The isolates are made by extracting red bean proteins at high pH, followed by isoelectric precipitation and filtration steps. Transglutaminase treatment can also be used to modify the texture and properties of the isolates. The isolates have protein contents of at least 60% and globulin-rich fractions. They replace egg in applications like emulsions, scrambled eggs, and baked goods. The isolates have reduced off-flavors and improved functional properties compared to unmodified red bean protein.

8. Mung Bean Protein Isolates with Enhanced Functional Properties via Isoelectric Precipitation and Transglutaminase Treatment

EAT JUST INC, 2022

Highly functional mung bean protein isolates for food applications like egg substitutes. The isolates have enhanced functional properties compared to unmodified mung bean protein. The isolates are produced by extracting mung bean protein, followed by steps like isoelectric precipitation, filtration, and concentration. This results in isolates with high protein content, reduced impurities, and modified properties like taste and oxidase activity. The isolates are also contact with transglutaminase to further enhance functional properties.

9. Protein Extraction from Potatoes Using Precipitation Gradient Based on Isoelectric Point

XIAN QUANAO BIOTECH CO LTD, 2022

A novel extraction method for protein from potatoes that achieves high-purity protein recovery while maintaining color and texture integrity. The method employs a unique precipitation gradient approach to selectively precipitate proteins based on their isoelectric point, allowing precise extraction of specific protein fractions. The process involves mixing potato with a precise brine composition, followed by controlled pH adjustments to optimize protein precipitation. The resulting protein is then recovered through centrifugation and subsequent freeze-drying. This approach enables the extraction of high-quality protein from potatoes in a highly alkaline environment while minimizing equipment costs and maintaining product characteristics.

10. Process for Producing Protein-Rich Composition with Coagulated Plant Proteins via Aqueous Solution Coagulation and Fraction Purification

TEREOS STARCH & SWEETENERS EUROPE, 2020

Process for producing a protein-rich composition comprising coagulated plant proteins from a plant material. The process involves mixing plant material with an aqueous solution, followed by coagulation of the aqueous solution to form a suspension, and then separating the coagulated protein fraction from the supernatant. The coagulated protein fraction is further purified through centrifugation, enzymatic treatment, and drying to produce a protein-rich composition containing both soluble and coagulated protein fractions.

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11. Protein Purification Method Using pH-Induced Precipitation and Centrifugation

SPIBER????, 2020

Simplified method to purify proteins like spider silk from biological sources without complex refining steps. The method involves increasing the pH of the protein solution to precipitate impurities while leaving the protein soluble. This is done by adding base to the acidic protein solution. The resulting precipitate is removed by centrifugation to leave behind the purified protein in the supernatant.

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12. Protein Extraction Process Using Alkaline Solvent Suspension and Pre-Acidification Precipitation

IMI TAMI INSTITUTE FOR RES AND DEVELOPMENT LTD, 2020

A process for extracting proteins from plant-based materials that improves separation efficiency compared to conventional methods. The process involves suspending the protein-containing material in a solvent, extracting it at pH>7, and then acidifying the solution to precipitate the protein. The acidification step is performed before adding acid, and the resulting precipitate is washed to remove impurities. The resulting protein precipitate is then processed directly into an extruder feed, where it can be transformed into a desired product through conventional extrusion processing.

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13. Method for Extracting Rice Protein via Multi-Step pH Adjustment and Centrifugation Process

CHENGMING JIANG, 2019

A novel method for extracting high-quality rice protein through a multi-step process that leverages the unique properties of rice residue. The process involves adding water to rice dregs, adjusting the pH to optimize protein extraction, followed by centrifugation to separate the protein solution. The resulting protein solution is then treated with acid to adjust its isoelectric point, allowing precipitation of the protein. The precipitate is then dried to produce rice protein, which retains its nutritional value and functional properties.

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14. Protein Extraction Method from Moringa oleifera Leaf Extracts via Isoelectric Precipitation and Lyophilization

UNIVERSIDADE FEDERAL DE SERGIPE, 2018

A method for extracting protein from Moringa oleifera leaf extracts using isoelectric precipitation followed by lyophilization, maintaining the protein's nutritional and sensory characteristics. The process involves creating two fractions: a soluble protein fraction through isoelectric precipitation in a buffer solution, followed by the isolation of the protein precipitate. The protein precipitate is then dried using a freeze dryer to produce a concentrated protein extract. This approach preserves the protein's functional properties while maintaining its nutritional value, particularly beneficial for food and pharmaceutical applications.

15. Protein Recovery Method from Wastewater via Controlled pH Regulation Using Nitrogen Gas

OCEAN UNIV CHINA, 2016

A method for efficient protein recovery from wastewater through controlled pH regulation using nitrogen gas. The process employs a nitrogen cycle to maintain a controlled pH environment, with nitrogen gas acting as a carrier for acetic acid. By regulating the nitrogen pressure, temperature, and time, the system can precisely control the pH to near-isoelectric point of target proteins, facilitating effective precipitation and recovery. This approach enables the recovery of high-concentration protein streams from wastewater, particularly in applications like surimi processing, where traditional methods struggle to achieve optimal protein removal.

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16. Method for Producing Soy Protein Isolate via Alkaline and Acidic Enzymatic Treatment with Phytate Reduction

JIANGNAN UNIVERSITY, Jiangnan University, 2016

A method for producing high-solubility, low-phytate soy protein isolate through a combination of alkaline and acidic enzymatic treatment. The process involves crushing and sieving soybeans to remove phytic acid-containing insoluble fiber, followed by alkaline extraction of water-soluble protein solution. The solution undergoes enzymatic hydrolysis of phytic acid to remove its chelating and solubilizing effects, followed by isoelectric precipitation of the resulting curd. The curd is then dried to produce high-solubility soy protein isolate with significantly reduced phytic acid content.

17. Method for Producing Soy Protein Isolate Using Ultrafiltration with Controlled pH Precipitation

XINJIANG WESTERN ANIMAL HUSBANDRY CO., LTD., Xinjiang Western Pasture Co., Ltd., 2016

A method for producing soy protein isolate that achieves a higher purity and yield compared to conventional methods. The process employs ultrafiltration technology to separate soy protein from its natural components, achieving a precipitate concentration of 45% while maintaining superior purity and color characteristics. The method optimizes the precipitation conditions by precisely controlling pH levels within the isoelectric point range of soy protein, ensuring optimal precipitation and protein retention.

18. Method for Extracting Apoplast-Derived Proteins via Enzymatic Degradation of Plant Cell Walls

MEDICAGO INC, 2015

A method for preparing plant-derived proteins and protein suprastructure from plant tissues by selectively extracting proteins from the apoplast region. The method involves enzymatically degrading plant cell walls to release apoplast-derived proteins, which are then recovered and purified from the apoplast fraction. This approach preserves the structural and immunogenic properties of the extracted proteins while minimizing cell wall disruption compared to traditional protein extraction methods.

19. Isoelectric Precipitation Method for Yam Albumen Extraction with Simplified Process Steps

UNIV LIAONING, 2015

A method for extracting yam albumen that simplifies the process while maintaining high purity and yield. The method employs isoelectric precipitation to extract yam albumen, a protein-rich component of the yam tuber. The isoelectric precipitation process eliminates the need for complex precipitation steps and dialysis, reducing production time and environmental impact. This method achieves protein purity of 60% and polysaccharide content of 20-30%, while preserving the characteristic white color and stable structure of yam albumen.

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