What Is a Squeeze Job?

The squeeze method uses a screw press to rely on the propelling effect of the rotating spiral body in the squeeze cage, so that the peel is continuously compressed, the essence and oil in the peel cells are squeezed out, and then the impurities are removed by leaching and oil-water separation. ^[1]

Oil extraction by pressing is a method of extracting oil from the oil by means of mechanical force. Pressing the depth of the pressed oil and the pressure on the material during pressing, the pressing oil can be divided into a single pressing and pre-pressing combined with extraction oil extraction. Compared with other oil extraction methods, squeeze oil extraction has the advantages of simple process, less supporting equipment, strong adaptability to oil varieties, flexible production, good oil quality, light color, and pure flavor. However, after pressing, the cake has a high residual oil content, high power consumption, and easy to wear parts. This method can be used to extract fat from seeds or nuts such as cocoa beans, coconuts, peanuts, palm kernels, soybeans, rapeseed and the like. In addition, another important use of pressing is to make fruit juices, such as apple, citrus, and tomato juice. Juice extraction methods are as follows: Spiral juice extraction is characterized by simple structure, few failures, high production efficiency and low price. The disadvantage is that the juice yield is low, the juice is easy to be oxidized, and the content of the mixture in the prepared juice is high. It is generally suitable for processing immature fruits and vegetables, and is often used for juice extraction of grape, tomato and berry fruits. Belt juicer is characterized by saving floor space, high juice yield, low water content in slag, but high equipment cost. Because it is an open operation, the juice is easily oxidized, and it is suitable for grape juice, apple, and berry fruits. The juice yield when grapes and apples are squeezed is about 70%. Rotary split-type juicer. The fat layer, sponge layer, vein tissue, and seeds of citrus fruits contain some substances that make the fruit juice bitter. Juice is the brown juice extraction method, and the other is the whole fruit juice extraction method of FMC Company. Wrapped juice is mainly used to make fruit and vegetable juice. Generally, fruit and vegetable pulp is wrapped with synthetic fiber cloth, stacked one by one, and pressed to make the juice flow out. This method has low cost, convenient operation, high juice yield, but low efficiency, high labor intensity, and easy to oxidize the juice slurry.

According to whether the material is heat-treated before pressing, pressing can be divided into hot pressing and cold pressing. According to whether the residue is squeezed again after extraction, it can be divided into secondary crushing and primary crushing.

Clean up peanuts. Untreated peanuts often carry a lot of impurities. If not removed, it will not only reduce the quality of the fat, but also affect the oil yield. If ropes, sand, etc. are entrained in the peanut fruit, the machine will be worn away and a safety hazard will arise. Therefore, in order to ensure smooth production, impurity removal is essential.

When cleaning up impurities, you can choose different cleaning methods according to different situations. If most of the impurities are light, they can be removed by wind; if the impurities are small, they can be removed by screening. If it is a metallic impurity, it can be separated with a tool such as an electromagnet.

Husk before squeezing. Peanut hulls will absorb oil, reduce the oil output rate, and increase the wear and tear of the machine, lowering the quality of cakes and crude oil. Therefore, it is necessary to remove the shell before pressing. Operating the peanut sheller is easy and simple, but care must be taken not to damage the peanut kernel. Therefore, prior to this, simple classification based on peanut size was needed to facilitate the machine's efficient and high-quality classification of husks and nuts.

Crushing and rolling of slabs before pressing. In order to make the peanut nut oil better, the peanut needs to be crushed, that is, it is broken into four to six petals, which is conducive to rolling billets. Rolled billets, also called flakes, are an operation that presses peanuts into flakes. The processed peanut flakes are often called green compacts. Rolling the billet will damage the cellular structure of the peanut, which will facilitate the heat treatment. At the same time, after the granular peanuts become flakes, the process of extracting fat is simplified, which is conducive to crushing and leaching for oil extraction. Peanut flakes should be as uniform as possible, and its thickness is generally 0.8mm and below.

Heat treatment before pressing. Heat treatment can be divided into steamed billet and fried billet. The green billet after heat treatment is called cooked billet. The necessity of heat treatment is that it has a direct relationship with oil yield, oil and cake quality. Heat treatment can completely destroy the oil cells, and at the same time, denatures the protein under the effect of water pressure and temperature, thereby facilitating the extraction of oil from the protein. The better steaming and frying method adopted by domestic oil plants is the wet steaming and frying method, which heats the green body by moistening, steaming, and frying the green. However, the heating and steaming method uses more steaming and frying methods. It is more suitable for hydraulic presses and small presses. The heating and steaming steps are used to achieve the purpose of heat treatment. ^[2]