Determination Of Soy Protein Contents In Soybean Milk Biology Essay


Soy is probably most well known for its protein content because soy has a high Protein Efficiency Ratio, which means that the amino acids that are contained in soy protein are made from a large percentage of "essential amino acids". Essential amino acids are known as amino acid that cannot produce by our body but need be provided by the diet. Soybean milk is a milk substitute which is consists of soybean flour and water. Besides, it also used in some infant formulas and in making tofu. Soybean milk is a rich source of high quality protein and vitamin B. Although soybean milk is not a rich source of calcium, but the most of commercial soybean milk products are fortified with calcium. Soybean milk naturally is contains isoflavones which is a plant chemicals that help lower LDL known as the "bad" cholesterol and it does not affect the good blood cholesterol, HDL. However, drinking too much soybean milk could possibly increase the risk of cancer because isoflavones are weak estrogens.

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There are many benefits to consuming the soybean milk compare to cow milk. First, soybean milk contains only vegetables protein which has the advantage that cause less loss of calcium through the kidneys and provides a lower risk for osteoporosis compare to the animal protein. In addition, soybean milk contains no lactose which is better alternative to people who lose the ability to digest lactose, the carbohydrate found in cow milk this situation is known as lactose intolerance which causes stomach cramps, flatulence and diarrhea. However, there are very fewer people are allergic to soybean milk only. Furthermore, the soy protein in soybean milk can reduce cholesterol. According to the FDA (Food and Drug Administration of US), they concluded that soy protein included in a diet low in saturated fat and cholesterol may reduce the risk of CHD by lowering blood cholesterol levels. Besides, The FDA recommends that consumers should have a daily diet ­with a total that at least 25 grams of soy protein each day. Besides, in the soybean milk does not contain hormones whereas in the cow milk that contains natural hormones and also synthetic hormones such as rBGH (recombinant bovine growth hormone) which used to increase milk production.


Nowadays and in future, soybean must be an important foodstuff as the protein source and health foods, because it has been recognized that the soybean protein has an adequate amino acid pattern and that this foodstuff can reduced serum cholesterol level according to the recent reports.

Soy protein refers to the protein that is found in soybeans that is often used to replace animal proteins in an individual's diet. The soybean is a legume that contains no cholesterol and is low in saturated fat. Soy proteins can be divided into different categories according to their production method: soy protein isolate, soy protein concentrate and textured soy protein.

Soy protein isolate is the soy protein with the highest content of protein. It is made from defatted soy meal by removing most of the fats and carbohydrates, yielding a product with approximately to 90 percent protein. Therefore, soy protein isolate has a very neutral flavour compared to other soy products. Due to the most of the carbohydrates are removed, the intake of soy protein isolate does not cause flatulence. Besides, soy protein isolate is also known as a complete vegetable protein. It contains all essential amino acids for growth and it is equal in quality to the protein in meat, milk and eggs. On the other hand, it has a very low fat content. Soy protein isolate may reduce the risk of coronary heart disease. There are also indications that soy protein can help in the prevention of osteoporosis, some cancers and menopausal symptoms. However, soy protein isolate may have less health benefits compare to the whole soybeans or soy protein concentrates. During the production of soy protein isolate the protein is washed with alcohol, and this cause removing most of the isoflavones. The isoflavones have many health benefits such as improving arterial vasodilatation, lowering cholesterol and inhibiting atherosclerosis.

Soy protein concentrate is made by removing a portion of the carbohydrates (sugars) from dehulled and defatted soybeans. There are three different methods to produce soy protein concentrate: aqueous alcohol wash process, acid wash process and water wash process with heat denaturation. These methods will yield soy protein concentrate with similar composition: 70 percent protein, 20 percent carbohydrates, 6 percent ash and about 1 percent oil. The solubility of the protein can differ between the different extraction processes. One ton of defatted soybean flakes will give about 750 kg (75 percent yield) of soybean protein concentrate. Soy protein concentrate retains most of the fiber of the original soybean. Soy protein concentrate is widely used as functional or nutritional ingredient in a wide variety of food products, mainly in baked foods, breakfast cereals and in some meat products. Soy protein concentrate is used in meat and poultry products to increase water and fat retention, and to improve nutritional values (more protein, less fat).

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Textured soy protein is made from defatted soy flour that is compressed and processed into granules or chunks. During this process, the structure of the soy proteins changes in fibres. Most textured soy protein is produced from defatted soy flour, soy flakes or soy concentrates with an extrusion process. This extrusion technology can form a fibrous matrix which is almost similar than that of meat.


Soybean milk is a rich source of proteins which are necessary for our body growth and survive. The objective of doing the topic of determination of soy protein content in the soybean milk is to determine the actual protein content in different types of soybean milk. This is because protein content in soybean milk may be lost or concentrated when undergoes in different processes.


In this topic, I will present an experiment to test and determine the soy protein in the soybean milk. There will get three types of soybean milk to test which are the homemade soybean milk, commercial soybean milk and sour soybean milk. First, I will extract the soy protein by using acid-wash process. In the first step, the water will remove from the soybean milk by oven heating and then washing the residue with water near the isoelectric point of pH 4-5 so the soluble sugars are removed from the matrix of proteins and polysaccharide. After acid-water washing, the remaining materials are adjusted to near neutrality and dried. In the next step, the Bradford assay is used to react with soy protein and using the spectrometer at the wavelength of 595nm to determine the absorbance. In the same time, a protein standard curve is required to determine and calculate the actual concentration of soy protein content in the soybean milk.