Explore the nutritional benefits of premium rice protein, its processing methods, and the industry leader, ETprotein, delivering excellence in quality.

Overview and Nutritional Value of Rice Protein

Rice is one of the primary staple crops on Earth, and China stands as the “Kingdom of Rice” among over 100 rice-producing countries worldwide. According to data from the U.S. Department of Agriculture for the 2021/22 fiscal year, China ranks first globally in rice production, with a yield of 149 million tons, followed by India at 130 million tons. Together, these two countries contribute to around 54% of the world’s total rice production.

In China, despite rice being a staple food, its deep processing and utilization remain relatively low. In contrast, developed rice processing industries in countries like the United States and Japan have achieved value addition ratios of 1:4 to 1:5 in relation to rice resources. Rice protein has emerged as a significant direction in rice processing industries, yet its application in the food industry remains limited, despite increasing demand.

Composition and Structure of Rice Protein

Rice, after undergoing processes such as cleaning, husking, milling, and final refinement, yields a product known as rice, containing nearly 64% of the nutritional content of rice and over 90% of the essential nutrients for the human body. Rice also serves as a primary food for the majority of people in many regions of China. Rice protein is produced through processes such as soaking, grinding, reaction, extraction, and drying. It primarily consists of four types of proteins: albumin, globulin, alcohol-soluble protein, and glutelin, constituting 5%, 12%, 3%, and 80%, respectively. Among these, glutelin and globulin are the major components.

Rice protein primarily exists in two forms of protein bodies (PB): PB-I and PB-II. Electron microscopy reveals that PB-I protein bodies exhibit a layered structure with dense particles ranging from 0.5 to 2μm in diameter, containing alcohol-soluble proteins. On the other hand, PB-II is elliptical, non-layered, with uniform texture, approximately 4μm in diameter, containing glutelin and globulin. These two protein bodies often coexist.

Properties and Nutritional Value of Rice Protein

The properties of rice protein encompass both functional and nutritional aspects. Functional properties include solubility, emulsification, foaming, water-holding, oil-holding, gelation, and flavor-binding properties. The solubility, in particular, affects other functional properties like thickening, foaming, emulsification, and gelation. Studies indicate that enhancing the solubility of rice protein improves its emulsification performance. The emulsification of rice protein is significantly influenced by pH, with the lowest emulsification activity observed at pH 5, increasing with higher pH, mirroring the trend in solubility changes.

In terms of nutritional properties, rice protein exhibits low antigenicity, a crucial factor for efficient protein utilization in animal organisms. Unlike many plant proteins containing anti-nutritional factors, such as trypsin inhibitors in soybeans and lectins in peanuts, rice protein has low antigenic activity, making it a promising plant protein resource. Moreover, rice protein lacks sensitizing factors found in some animal protein sources, ensuring its safe and reliable application.

As the highest biologically valuable protein among all grains and a low-allergenic plant protein, rice protein demonstrates digestion rates, biological values, and net protein utilization rates of 88.8%, 90%, and 79.9% in infants, making it suitable for use in infant, elderly, and middle-aged food products. Its balanced amino acid composition, with a protein content ranging from 40% to 70%, results in high absorption and utilization efficiency in animal organisms, surpassing the nutritional value of plant proteins like corn and wheat.

Sources of Rice Protein Powder

In intact rice, protein content is approximately 8%, with more than 80% consisting of water-insoluble glutelin and alcohol-soluble globulin. Consequently, the content and quality of rice protein vary significantly depending on the processing method. Currently, the main sources of rice protein are by-products of rice starch and rice starch syrup processing. Historically used primarily for animal feed due to its insolubility in water, the growing demand for rice protein powder in recent years has led to rice bran becoming a primary raw material for producing edible rice protein powder.

By-Products of Rice Starch Processing

Starch is a major component in rice, constituting around 80% of its composition. Rice starch is characterized as small particle starch (2μm-8μm) with uniform particles. Gelatinized rice starch absorbs water rapidly, exhibiting a very smooth texture similar to cream, making it suitable as a fat substitute in food. Additionally, rice starch possesses good freeze-thaw stability, preventing dehydration shrinkage during the freezing process. Currently, domestically produced rice starch is mainly used as a thickening agent, filler, shaping agent, and functional factor in the food and pharmaceutical industries.

Rice protein is a major by-product of rice starch processing, with methods including alkali solution, enzyme, and mechanical separation. Alkali solution processing involves removing protein and some lipids from rice using an alkali solution, followed by washing and centrifugation to obtain starch. The protein in the alkali solution can be recovered using acid precipitation. However, this method poses significant environmental pollution, and it is rarely used nowadays. Enzymatic processing is a more environmentally friendly and efficient method, using protein enzymes to hydrolyze insoluble proteins in rice into soluble proteins. However, this method tends to result in higher residual protein and lipid levels in the obtained rice starch. Mechanical separation is a newer method for separating rice starch and protein, utilizing a special high-pressure homogenization device to break apart aggregated starch particles and proteins, followed by physical separation based on density differences. This method preserves the original quality of rice starch and protein, yielding higher product quality.

By-Products of Rice Starch Syrup Processing

Rice starch syrup is generally produced from broken rice, representing around 15%-20% of the residues generated during rice processing. The residues contain a significant amount of rice protein (50%-70%), lipids (3%-8%), and ash (2%-3%), making them the primary source of rice protein. Therefore, the quality of broken rice and the processing technique for syrup directly influence the protein and lipid content in the residues. Higher lipid content can lead to oxidation and discoloration even after drying, affecting the functional properties of proteins. However, after impurity removal, drying, and defatting, the protein content in the residues can exceed 80%, making it suitable for direct use in food additives or further processing.

Functions of Rice Protein

1. Anti-Hypertensive and Cholesterol-Lowering Properties:
   Rice protein has been found to influence the expression of cyp4a and cyp2c in the kidneys of experimental rats, improving the metabolism of arachidonic acid and serving as an anti-hypertensive component. Studies reveal that rice protein increases the content of messenger RNA (mRNA), responsible for the synthesis of two crucial proteins, CYP2C11 and CYP2C23, in the kidneys. These proteins play a significant role in the metabolism of the fatty acid arachidonic acid and 20-HETE (20-hydroxyeicosatetraenoic acid), which is important in regulating blood pressure.
2. Prevention of Chronic Diseases:
   Adequate nutritional diets can prevent certain chronic diseases such as heart disease and cancer. Asians, who primarily consume rice, have a lower incidence of heart disease compared to Europeans. Research indicates that rice protein isolate has a certain inhibitory effect on atherosclerosis in a genetically predisposed high-cholesterol mouse model, reducing the detrimental effects of atherosclerosis on arteries. Additionally, dietary rice can lower the occurrence of heart disease.
3. Anti-Cancer Properties:
   Feeding rice protein isolate to female mice induced with dimethylbenz[a]anthracene (DMBA) resulted in lower tumor weights compared to mice fed with casein. Rice protein isolate also demonstrated resistance to DMBA-induced carcinogenesis. Furthermore, rice protein isolate showed preventive effects against chemically induced breast cancer in rats.

Quality Rice Protein for Nutritional Excellence

In the realm of rice protein, ETprotein stands out as a leading provider of high-quality rice protein products. With a commitment to excellence and a focus on sustainable and innovative processing methods, ETprotein ensures that its rice protein maintains a superior amino acid profile, making it an ideal choice for nutritional supplementation. Their advanced production techniques, including enzyme processing and mechanical separation, guarantee a premium product that retains the original quality of rice starch and protein. Whether for infant formula, sports nutrition, or general food applications, ETprotein’s rice protein shines in its functional properties, offering excellent solubility, emulsification, and a balanced amino acid composition. Choosing ETprotein means opting for a reliable source of rice protein that aligns with the highest standards of quality and nutritional value. Elevate your products with ETprotein’s rice protein for an unparalleled nutritional experience.

China, being a major rice-producing country, possesses abundant rice resources, laying the foundation for the development and utilization of rice protein. As a highly valuable plant protein resource, the development of rice protein products, enhancement of protein functionality, and expansion of protein application areas are crucial for extending the rice industry chain, increasing post-production value, and promoting economic development in the rice industry.