What are the basic steps for oilseed production?
Answer: The basic processing steps are as follows:Seed cleaningPreparation of the raw material often includes removing husks or seed coats from the seeds and separating the seeds from the chaff. There are a wide variety of small- to intermediate-scale approaches to and technologies for effective seed cleaning. Seed preparation and conditioning For successful pressing, the seed must be: ? Clean. Fine dust in the seed may clog the oil press hardware. Chaff left in the seed will absorb some of the oil and keep it from getting squeezed out of the expeller. Sand in the seed will wear out the press. Stones damage the oil press screw or piston. ? Dry. Moist seed leads to low yields and clogs the screw or cage, a part of the press. Moist seed may also get moldy, as mold spores are present in all crops. A rule of thumb is that the moisture content of the seed should be close to 10 percent. The number varies considerably for specific oilseeds. For example, rapeseed should be dried to a 7-percent moisture content, camelina to about 6 percent and sunflower to 8.5 percent. Safflower needs only to be dried to 11 percent and soybean is safe for storage and processing at 12 percent. There are at least two methods of testing seed moisture levels. Hand-held moisture testers allow the user to simply place the seed in the tester, turn it on and select the type of seed to test. The tester provides an instant readout. These testers cost from $400 to $700. Here is a lower-tech, low-cost way of moisture testing: Weigh a sample of seed, and then heat the sample in an oven at 300 degrees Fahrenheit for one hour. Reweigh the sample. The weight lost in the oven is equal to the moisture content of the original sample. Calculate the percentage by dividing the weight lost by the original weight and multiplying the result by 100. Even dry seed can quickly get damp by being in contact with damp earth. Once the seed is dried and bagged, it must be carefully stored to keep it from absorbing moisture.? Warm. Warm seed will yield the most oil for the least effort. The optimum heat range for oil extraction is from 100 to 160 degrees. There are several ways to preheat the seed in advance of extraction. For very small batches, heating the seed in an oven or double boiler works, as does concentrated sunlight in a solar food dryer or some other solar collector. For larger batches, a heating element in a hopper located between the seed storage facility and the oilseed press works well.Extraction by cold pressingOil can be extracted mechanically with a ram press, an expeller or even a wooden mortar and pestle, a traditional method that originated in India. Presses range from small, hand-driven models that an individual can build to power-driven commercial presses. The ram press uses a piston inside a cage to crush the seed and force out the oil. Expellers have a rotating screw inside a horizontal cylinder that is capped at one end. The screw forces the seeds or nuts through the cylinder with gradually increasing pressure. The seed is heated by friction and electric heaters or a combination of the two. Once the cap is removed, the oil escapes from the cylinder through small holes or slots and the press cake, or meal, emerges from the end of the cylinder. Both the pressure and temperature can be adjusted for different kinds of feedstock.ClarificationClarification removes contaminants such as fine pulp, water and resins. You can clarify oil by allowing it to sit undisturbed for a few days and then removing the upper layer. If the oil needs further clarification, filter the oil through a fine filter cloth. Finally, you can heat the oil to drive off traces of water and destroy any bacteria. Very clean oil is important in all uses, including biodiesel.DegummingDegumming is the process of removing the phospholipids from the oil. Many people advise that you allow the resulting oil to settle out the gums, or hydratables, over a period of one to two weeks. However, you need more chemical processing to make high-quality culinary oil or biodiesel feedstock.Refining, bleaching and deodorizing The vegetable oil produced and processed to this point does not need refining, bleaching or deodorizing as long as the natural taste, smell and color are acceptable to the user. However, getting the oil to commercial food grade may be an important step in oilseed processing if your market demands it. For example, restaurants require oils that have a relatively high smoke temperature and may or may not want the taste of the natural oil.Oil packaging and storage Use clean, dry containers to package and store oils. Sealed glass or plastic bottles are adequate for small quantities. Colored containers in a dark box help increase shelf life. Steel or plastic tanks work well for large quantities. The shelf life of oil is usually six to 12 months if it is properly packaged and kept away from heat and sunlight. Keeping air away from oil is perhaps the most important step to prevent rancidity. Completely fill whatever size container you chose so there is no air space and then cap the container tightly. Shelf life of oil may vary depending on the type of oil as well as the storage conditions. For example, flax and grape seed have a shorter shelf life than canola or sunflower due to the large amount of polyunsaturates present. If the stored vegetable oil does not reach sustained temperatures of 100? F or more, its vital components will be preserved. Therefore, vegetable oil is excellently suited for natural nutrition. As long as the oil is stored in a dark, cool place, it will have a long shelf life.To learn more, consult the ATTRA publication Oilseed Processing for Small-Scale Producers. This publication describes the basic processes involved in oil processing and includes sources for more information and equipment.