Soy has become a major source of protein food for both animals and humans. Most notably, soy protein has a high nutritional value and provides a variety of vital amino acids for humans. Furthermore, soy protein is frequently used in the food business because of its high yield, low cost, and suitable functional qualities.
An essential component of the soy industry is the soy protein extraction process. Alkaline extraction and isoelectric precipitation have historically been used to extract soy protein. With the development of more extraction techniques, this conventional method has been surpassed in effectiveness. Finding and improving new environmentally friendly technologies is a pressing necessity for lowering the price and impact of the extraction of vegetable oils on the environment. As detailed below, technology has significantly changed the extraction and processing of soy protein.
1. Alkali Solution–Acid Precipitation Method
Undoubtedly, soy protein is a complete source of proteins. But, the primary problem of the traditional approach is that soy protein concentrate (SPC) and soy protein isolate (SPI) could be better soluble when rehydrated. That is because protein extraction involves harsh conditions such as acids, bases, heat treatment, or centrifugation, which causes protein denaturation. Furthermore, traditional-process SPC and SPI may containlarge quantities of phytic acid.
Phytate minerals or protein mineral phytate complexes are formed when phytic acid complexes with divalent cations impact mineral bioavailability. Protein solubility may be diminished as a result of phytic acid. Another downside of traditional approaches is environmental degradation. Large amounts of acidic and alkaline wastewater are produced during protein extraction, resulting in water pollution.
2. Enzyme-assisted Extraction
Enzyme-assisted extraction extracts protein from soybeans using water and protease and is regarded as an alternate extraction method to alkaline extraction, which causes pollution. Enzyme-assisted extractions are regarded as ecologically friendly technologies since they provide a green extraction option for the food industry seeking greener approaches. Recent research on enzyme-assisted extraction has revealed that it provides faster extraction rates, larger recoveries, less solvent use, and lower energy consumption than non-enzymatic methods, making it a viable alternative to classic solvent extraction methods.
Protein hydrolysis caused by enzymes causes a decrease in protein size compared to alkaline extraction. As a result, proteins can be removed more readily. Enzymes can also be employed to reduce the pH during processing, preventing extreme instances of protein denaturation.
3. Membrane Ultrafiltration Extraction
The purification of proteins using ultrafiltration membranes is a desirable substitute for the usual isoelectric precipitation, among other novel and unorthodox procedures. In the early to mid-1970s, membrane ultrafiltration technologies were first applied to separate soy protein.
Proteins can be separated from salt, sugar, and each other using ultrafiltration. Proteins with various molecular weights are produced due to the partial hydrolysis of SPI and are separated by ultrafiltration membranes with various pore diameters. Membrane ultrafiltration selectively separates and eliminates unwanted components, such as soy oligosaccharides, from soy-based on the difference in molecular size between proteins and other components. Additionally, the majority of the protein in soy is retrieved without creating a byproduct resembling whey.
4. Ultrafiltration Membrane Method Possess Great Advantages
Compared to traditional soybean processing methods, the ultrafiltration membrane method offers significant advantages as a relatively new technology. The main advantages of ultrafiltration are the mild operating conditions and the high selectivity. Using a gentle process produces less denatured protein than traditional disappointing precipitation.
Food product preparation calls for various specific properties from intact soy proteins, including water binding, adhesion, fat absorption, solubility, texture, emulsification, foaming, and flavor creation. Using an ultrafiltration membrane, protein is directly extracted from the soy extract, bypassing the whey created by conventional isoelectric precipitation techniques. As whey protein is recovered from the isolate, this method not only boosts the yield of the isolate but also creates a product with improved functionality and nitrogen solubility.
5. Reverse Micelle Extraction
A reverse micelle is a nanometer-sized aggregate generated by a surfactant, an organic solvent, and a small amount of aqueous solution. It is a potential extraction method for protein extraction from soy. It might be round, oval, or even rod-shaped. When surfactants reach concentrations above the critical micelle concentration in nonpolar organic solvents, they disintegrate and create reverse micelles.
Because surfactant and nonpolar solvents can be recovered, reverse micelles are inexpensive, thermodynamically stable, and optically transparent. They are also simple to scale up and have straightforward reaction variable control. Most crucially, the reverse micelles could stop the denaturation of encapsulated biomolecules since their aqueous cores are analogous to the physiological environment. According to a recent study, the reverse micelle approach is more effective than the conventional alkali solution-acid precipitation method at maintaining the natural molecular structure of proteins.
6. Use Solvents in the Extraction of Oil from Soybean
Expulsion or using an organic solvent are two ways to extract soybean oil. To boost the yield of the lipid extraction, however, the solvent will always be used after expelling. At the same time, solvent extraction using hexane is the most effective process for oil production due to its high productivity and low cost, while expelling has the biggest influence on emissions of environmental pollutants, such as carbon dioxide. However, the techno-economic benefits of using this solvent are closely related to environmental difficulties and issues with public safety.
Industrial-scale extraction needs solvents, which must be available in large quantities, safe, affordable, non-flammable, effective at extracting oil, and practical. Many businesses advise using green solvents since they help create more environmentally friendly procedures. Several pharmaceutical firms, including GlaxoSmithKline, Pfizer, and Sanofi, have recommended solvents.
Researchers have created cutting-edge soy protein extraction techniques to solve the shortcomings of conventional extraction procedures. Modern extraction methods, such as reverse micelle extraction, enzyme-assisted extraction, and ultrafiltration membrane extraction, are described in the earlier debate. The extraction and processing of soy protein and other products have undergone a revolution because of these techniques.