Can walnuts, soybeans, rice, and pumpkin seeds be pressed for oil? How much oil can one jin yield?
Walnuts, soybeans, rice, and pumpkin seeds are all things we commonly eat, so can they all be pressed for oil? How much oil can one jin yield? It is understood that pumpkin seeds and rice cannot be pressed for oil, while walnuts and soybeans can. Below is a detailed introduction.
Walnuts and soybeans can be pressed for oil; how much oil can one jin yield?
Walnuts:
Walnut is an oil crop with a very high oil content; the oil yield of walnut kernels can reach 40%-50%, and walnut oil has the effects of strengthening the body, nourishing the brain, preventing cardiovascular and cerebrovascular diseases, improving endocrine system function, and supplementing calcium.
The oil pressing method is basically the same; it mainly depends on whether the walnut oil content is high enough to meet the requirements for oil pressing. However, wild walnuts seem to have low oil content and cannot yield much oil either. Nowadays, high-quality walnuts are generally used for oil pressing; first, the kernel yield is high, and the oil yield is also high, so only then is there economic value.
Under normal circumstances, 4 jin of walnuts can press 1 jin of oil, because the oil yield of walnut kernels is about 70%, 500*0.7=350 grams, and one jin of walnut kernels yields only 7 liang of oil.
Walnuts of different qualities have different oil yields. The oil yield of walnuts used for oil pressing on the market is about 30%, which is basically the highest oil yield.
Soybeans:
Soybean oil processed and produced from soybeans is one of the important edible oils. It belongs to semi-drying oil and is a good vegetable oil.
1. Moisture adjustment and cleaning to remove impurities. Soybeans and yellow soybeans from different regions have different moisture levels and different types, so the moisture of these raw grains needs to be adjusted. This process is not optional. The moisture requirement for extracting soybean oil with a soybean oil press is that it must not be higher than 12%, and the impurity content must be below 0.5%. The content of moisture and impurities directly affects the quality of the oil. Although the soybean oil press can be equipped with a refining process, the degree of refining is limited. Moreover, excessively high impurity content can also cause oil passage blockage and accelerate the wear of oil equipment parts.
2. Peeling and shelling of soybeans and yellow soybeans. If soybeans are not shelled during extraction, it will affect the oil yield of the oil press and the production efficiency of the oil machinery. Moreover, there will be some impurities and pesticide residues on the soybean skin. Once they enter the oil, they will affect the color and quality of the oil.
3. Soybean crushing and flaking. This process can be set up or not. The main function of this process is to press the soybeans into flakes, increase the oil extraction area, and improve the processing capacity of the oil equipment. Of course, flaky soybean blanks will also reduce wear on the press screw of the oil press.
4. Seed roasting. This process is a signature technique in hot pressing, but it is not needed for cold pressing. Generally speaking, the oil yield and production efficiency of hot pressing are both higher than those of cold pressing.
Depending on the soybean variety, the oil yield is mostly between 18--22%. Generally speaking, the genetically modified soybeans currently from the United States and Brazil are mostly high-fat beans, so their oil yield is higher.
Rice and pumpkin seeds cannot be pressed for oil
Rice itself cannot be pressed for oil, but the layer of rice bran between the rice and the rice husk contains rice skin and rice germ, which include many nutrients from a rice grain. In fact, many nutrients in the rice we usually eat are lost, and rice bran oil is extracted from this nutrient-rich rice bran, so this oil is very nutritious.
Pumpkin seeds have low oil content. So currently no one uses them to press oil.