Oilseed Fact Sheet: Oilseed Presses

nuts. Some presses offer more flexi- Oilseed Presses bility than others, so examine care- Available small oilseed presses are of fully the claims of the press manufac- two major types; screw presses turer before purchasing a press for (expeller press) (Fig. 2) or reducing a particular purpose. If possible, screw/cage presses. Many are made conversations with others who overseas while at least one is now have used a particular press available from a United States manu- will be valuable. facturer. Information about many of the presses used in the Northeastern Vegetable oils typically found United States is being collected by in the marketplace are RBD this NESARE project and will be avail- oils. This means that the oils able as a separate informational bul- have been Refined, Bleached letin. Operation of an oilseed press is and Deodorized after the initial the objective of this sheet. removal from the oilseed. A sepa- rate factsheet describes these terms Oil Production and the procedures that may be used Oilseed presses vary in size and the Introduction for each process. For a small oil pro- amount of oil expected varies be- An oilseed press (Fig. 1) is the heart ducer, some of these processes may tween types. As a result, the of an oilseed pressing operation. This be useful to incorporate into the oil capacity of an oil seed press is often fact sheet focuses on small oilseed production line and others may be given in the weight of that can presses used for edible oil production outside the scope of the operation. be processed per hour. Depending on or for producing oil for fuel or bio- the material processed, the expected diesel production. Oilseed presses separate oilseeds such as sunflowers, canola, and into oil and oilseed meal. Pumpkin or grape seeds and brazil nuts are examples of materials that are less known and can be pressed for their oil in these machines.

Oil from the press is raw oil, and is used either as a food product or as an industrial product. Food products include raw oil in dressings or alone, pan frying applications, or in deep frying. oil (usually called “”), corn oil, sunflower oil, , oil, oil, and oil are the most com- mon. This large range of oils points to the flexibility necessary in an oilseed press if it is to be used to press oil from a wide variety of seeds and Fig. 1: Oilseed press Oilseed Fact Sheet: Oilseed Presses

All grains have moisture contents at which they press best. A general rule to start from is that the ideal mois- ture for pressing is in the 7-8% range. Experience shows canola presses best in the 6-8% moisture content range, with other oilseeds requiring similar moisture contents. If the moisture content of the seed being pressed drops too low the tempera- ture of the press head increases when pressing and will make it diffi- cult to stay under the 120F (50C) Fig. 2: Expeller Press (screw press) diagram temperature limit for cold pressed oil if that is important to the operation. oil output will vary greatly. For cano- Moisture Content of Seed Lower moisture content seeds result la, about 1/3 of the seed weight go- For an oilseed press to operate in higher press temperatures and a ing into the press will be produced in properly, the incoming seed must be lower yield of oil. oil, while the remaining 2/3 will be clean and of the proper moisture meal. Other seeds will give different content. Seed cleaning and storage Moisture content is often the culprit oil and meal ratios. information is provided in a separate if pressing is difficult. On one occa- fact sheet, “Oilseed Cleaning and sion, bags of canola at 7% moisture Presses of these types are typically Storage”. content to be pressed were placed rated in the 3 kg (6.6 lb) to 100 kg on the floor of the pressing area. (220 lb) of input material per hour Generally 10% is used as a rule of When pressing time came a week range. thumb for the moisture content at later, the seed would not press. After which to store grain and seeds. While numerous failed attempts at getting Requirements for Effective the seed will store well at this mois- the press started with this seed, the Oilseed Pressing ture content, it most likely will not moisture content was tested again Information provided in this fact press well. Seed sheet has been gathered from expe- that is too moist rience and discussions with numer- will produce meal ous oil producers and providers of that is gummy and oilseed presses. As experience is will not produce oil gained with a particular press the as it passes through settings that work best will be deter- the press. The mined. Much of this work is on a trial moisture in the and error basis, and when proper seed ties up the oil settings are determined they should and does not allow be recorded so they are saved for the oil and meal to reference and as a starting point for separate as it the next harvest. should. Different examples of oilseed, including (from left to right) camelina, soybeans, and canola. Oilseed Fact Sheet: Oilseed Presses and had dropped to 4%. Unknowingly ins that carry through into the the seed had been stored directly pressed oil. under a heating vent and had dried considerably by heated air blowing Seed Quality Pressing Temperature across the bags. Seed quality is also important, as When reading the ingredients on seed harvested either before or after food, have you noted how vegetable For information on moisture con- optimal ripeness can impart unwant- oils are listed? Sometimes oil is listed tents for pressing, consult someone ed flavor or chemical characteristics as “expeller pressed” or “cold- familiar with press operation. Often to the oil produced from that seed. pressed”. Expeller pressed oil means an email or phone call to the press When green (not fully ripened) seed that the oil is extracted from the manufacturer will help in getting is pressed for oil, the smell it produc- seed by a press as described in this started on a new type of seed. When es when pressed is not the same as fact sheet. Cold pressed adds an ad- an opportunity to press Brazil nuts the smell of ripe seed being pressed. ditional requirement that the oil is was presented, an email to the man- Oil produced from green seed will extracted at a temperature of less ufacturer delivered the news that the not have the characteristics such as than 49 C (120 F). Many people be- press barrel needed to be heated to smell or taste desired in the finished lieve that the oil produced at a lower about 93 C (200 F) for pressing to oil. It is difficult to produce high qual- temperature have better health char- work correctly with this high oil con- ity edible oils when starting with low acteristics. Additionally, cold pressed tent nut. Without this information a quality seed. oils have a lower phosphorous level great deal of time was used unpro- which is required if using the oil as ductively as various lower tempera- Likewise, seed that contains mold straight vegetable oil (SVO) fuel in an tures, speeds and tip sizes were un- from too much moisture during har- internal combustion engine. successfully tried. vest or storage (Fig. 3) will have a

noticeable odor and may contain tox- Press Settings Manufacturers produce presses that have characteristics that can be changed to accommodate different sizes, shapes or types of seeds or nuts. Not all manufacturers accom- modate all of the following setting changes, but most allow at least some of the settings. Remember that the press should be shut off and the power disconnected before changing the settings. For screw type presses: distance between end cap (press head) and screw end speed of press tip size (diameter of hole through which meal is expelled) type of screw (distance between Fig. 3: Properly stored seed (left) as compared to moldy canola seed (right) and depth of auger flights) Oilseed Fact Sheet: Oilseed Presses

Considering each of these character- istics in more detail provides the ef- fects of each setting. Because each setting can have an impact on other settings it takes time, record keeping and patience to find the acceptable setting for each type of seed, or even each batch within a type of seed. It is for this reason that operating a press is more of an art than a science. Changes in moisture content or other characteristics may also require changes to press settings for accepta- ble oil recovery.

Distance Between Press Head and Screw End Fig. 4: Example of a press head. The clearance between the end of the screw and the press head itself (Fig. 4) is one common adjustment, creases the clearance between the this material tighter, and that’s not though not an adjustment available end of the screw and the press head. always easy to do. Removing the on all presses. As this clearance is Even a small adjustment (1/16 of a press head and clearing the material made smaller, the force needed to turn) can change the press from be- may be the only way to relieve this push the seeds through the press ing productive to being plugged. pressure enough to be able to turn increases, creating a greater pressure Once an adjustment is made it can the press head in. overall on the oil/meal mixture. Too usually be left for the duration of the much pressure, though, and the pressing of that seed. It is not a set- Speed of Press press will no longer allow the meal to ting that needs to be altered continu- Many presses have a variable speed pass through effectively blocking the ously. drive. This may be an electronically meal flow and stopping the flow of variable speed drive, a variable pitch material through the press. Too large Turning the press head out to in- drive, or another type of drive that a distance and the meal will pass crease clearance looks like an easy allows the pressing screw(s) to be through easily, leaving a large process, and usually it is. If the ma- driven at different speeds. amount of oil in the meal. Finding the chine has been run for a long period correct setting is a balance between of time, or the heating element has Turning the screw(s) faster will put the meal passing reliably through the been used on the barrel and head more feedstock through the press in press and extracting the maximum while pressing then turning the press a set amount of time and increase amount of oil while doing so. head may be difficult. Turning the the oil production rate (gallon or li-

press head in can be a trying proposi- ters per hour). This sounds like a On a Kern Kraft press, this setting is tion because meal is already packed great idea, but there are downsides changed by turning the pressing head into the space between the end of to running the machine faster (Fig. in or out. As the head is turned, the the screw and the presshead. Reduc- 5). As the screws turn faster, more threading either increases or de- ing this clearance means squeezing Oilseed Fact Sheet: Oilseed Presses

tion rate, as there may not be a way to change the press head to screw end clearance or the screw speed.

Tip diameters that have been used successfully are presented in Table 1. Remember that every batch of seed and every machine are slightly differ- ent, so these diameters are a place to start but may not be the best sizes for your feedstock and conditions. Experiment with different tip diame- ters until the oil extraction rate is acceptable. Also realize that as new tips become worn in, they become Fig. 5: Effect of speed on oil production smoother and produce less “back pressure” on the meal passing material is moving through the press moving through the press. Too large through. and this provides less time for the oil a diameter tip and the feedstock is to migrate out and be separated not held back adequately and flows Reducing screw/cage presses use a from the meal. As a result, the slow- freely from the press with little oil different technique for pressing the er the press is run the higher the extraction. Too small a tip and the oil than the expeller screw presses. extraction rate for oil; the less oil is tip plugs, effectively ending that Operational requirements are simi- left in the meal. If cold pressing of pressing session. On smaller presses, lar, but adjustments are made by the oil is a requirement, then a slow- tip diameter may be the only varia- tightening (reducing) the distances er speed is often necessary because ble present to change the oil extrac- between the bars to increase the as screw speed increases, the tem- back pressure and increase oil ex- perature of the oil and meal moving traction. through the machine also increases. Table 1: Successful Tip Temperature and efficiency of oil Diameters Type of Screw extraction need to be balanced Manufacturers may provide screws against overall oil production to de- Feedstock Tip Diameter with different pitches (distance be- cide on a screw speed. Brazil nuts 5 mm tween high points of the screw) or depths to better handle the variety Tip Diameter Camelina 7 mm of seed shapes and types available. Tips are available in varying diame- For example, the Kern Kraft press ters for each press. Many presses Canola 5, 6, 7 mm provides a screw that will handle come with a range of tip diameters 7 mm soybeans more readily than the to allow pressing of different feed- screw that handles canola, camelina Sunflower stocks. Typically tips are available 5, 7 mm and other smaller seeds. Check with from ~ 5 mm to ~ 15 mm diameter. (Hulls off) the supplier of the press before pur- Press tip diameter is one factor that chase to be certain you understand Sunflower greatly influences the amount of 10 mm the possible need for additional (Hulls on) “back pressure” on the meal/oil components to handle the range of Oilseed Fact Sheet: Oilseed Presses products you are considering pressing. the gate allowing seed to flow to the press. Oil and meal production Starting the Press is not immediate; it may take sev- Bear in mind that every press will have eral seconds to over a minute to slightly different requirements for start having oil drip or flow from starting and stopping. Steps below are oil holes in the barrel. Different for one particular type of press, but oilseeds contain different should translate well to any press with amounts of oil, so the oil that is slight modification. produced may range from a steady drip to a steady stream. Be certain the gate allowing seed to the press is shut. This allows Shutting Down the Press the barrel and press head of the Close the gate that allows feed- press to be heated without seed stock to flow to the press. present. Wait until the meal flow slows Be certain the desired tip diame- considerably or stops, and oil no ter is in the press head and set the longer drips from the barrel. press head to screw end clearance Shut off the screws. if a change is needed. Different Turn off heaters if they have been clearances can be noted by count- used during pressing. ing the number of threads show- ing or by measuring this distance. Manufacturers suggest removing and Most oilseeds that will be pressed cleaning the barrels and screws of the require that the press be initially presses after shutting down the press. heated to a temperature of ~120 F Experience has shown that if the seed (60 C). Typically this is done with flow to the press is shut off and the heating bands that cover each press is run long enough to expel the press head of the press and a con- material in the press, this may not be troller. Some heat band control- necessary. If the press is to be restart- lers thermostatically control the ed soon (within a week?) then leaving heat of the heat band, while other the press without removing the barrel heat bands are simply on or off. and cleaning is all right. The press will Typically about 10 minutes are start up again with only the steps out- needed to get the press head up lined above. to the preheat temperature. This Summary can be measured with a thermom- As the center point of the oilseed con- eter inserted into a hole in the version process, the press can be used press head or more simply with an to extract oil from a variety of seeds. infrared thermometer aimed at The quality of the product is deter- the press head. mined by many factors, including the Start the press and select the de- settings of the press, as well as mois- sired drive speed. ture content and proper storage of the Once the press head is at the cor- oilseed. rect starting temperature open Oilseed Fact Sheet: Oilseed Presses

Resources This project supported by the North- Press manufacturers (not an exhaus- east Sustainable Agriculture Research tive listing) and Education (SARE) program. SARE Ag Oil Press (www.agoilpress.com) is a program of the National Institute Egon Keller (www.keller-kek.de) of Food and Agriculture, U.S. Depart- Kern Kraft (www.oelpresse.de) ment of Agriculture Komet (www.ibg-monforts.com) Piteba (www.piteba.com) This publication is available in alterna- Tabypressen (www.oilpress.com) tive media on request. Tokul (www.tokultarim.com) Penn State is committed to affirmative Vegetable oil processing equipment action, equal opportunity, and the Tinytech (www.tinytechindia.com) diversity of its workforce.

Northeast Oilseed Information University of Vermont: www.uvm.edu/extension/cropsoil/ oilseeds

Note: This is not an exhaustive re- source list nor do any of the oilseed project partners endorse any of the products or companies on this list. It is intended as a resource and starting point for those interested in small- scale oilseed processing.

Fact sheet prepared by: Douglas Schaufler, Dept. of Agricultur- al and Biological Engineering, Penn State College of Agricultural Sciences.

Reviewed by: Russell Schaufler, Farm Operations, Penn State College of Agricultural Sci- ences.