Oilseed Presses

Oilseed Presses

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Introduction

An oilseed press is essential for any oilseed pressing enterprise, capable of extracting oil from seeds such as sunflowers, canola, and soybeans, along with less common seeds like pumpkin, grape seeds, and brazil nuts.

The oil produced from these presses is unrefined and can be utilized in food or industrial applications. Culinary uses include salad dressings, frying, and baking. Common oils produced are soybean oil (often called "vegetable oil"), corn oil, sunflower oil, canola oil, peanut oil, olive oil, and safflower oil. This variety highlights the adaptability required from an oilseed press to efficiently process a wide array of seeds and nuts. Prior to purchasing, it's vital to scrutinize the manufacturer's claims and seek feedback from previous users.

The vegetable oils prevalent in the market are often RBD oils, meaning they are Refined, Bleached, and Deodorized post extraction. For small oil producers, understanding these processes can aid in integrating useful methods into their operations while recognizing which processes may not be feasible.

Types of Oilseed Presses

There are two primary types of small oilseed presses: screw presses (expeller presses) and reducing screw/cage presses. Many of these machines are manufactured abroad, although a few are now produced in the United States. Ongoing research in the Northeastern United States aims to collect information on oilseed presses available in that region.

Oil Production Capacity

The size of oilseed presses varies, alongside the expected oil yield, which fluctuates with different seed types. Consequently, the press's capacity is typically measured in weight of seeds processed hourly.

Oil output can differ significantly based on the material. For canola seeds, approximately one-third of the seed weight results in oil, with the remaining two-thirds becoming meal. Different seeds yield various oil-to-meal ratios, and presses are often rated for input materials ranging from 3 kg (6.6 lb) to 100 kg (220 lb) per hour.

Essential Requirements for Successful Oilseed Pressing

This article compiles insights from numerous discussions with oil producers and oilseed press suppliers. As users become familiar with their specific press, they will discover the optimal settings through a trial-and-error approach. It is advisable to document successful adjustments for future reference.

Moisture Content of Seeds

Proper operation of an oilseed press necessitates clean seeds with appropriate moisture levels. A separate article titled "Cleaning and Storage of Oilseed" provides insights on this topic.

A general guideline suggests maintaining a moisture level of around 10% for the storage of seeds. While seeds can store well at this moisture, they may not perform efficiently during pressing. Seeds with excessive moisture can create gummy meal with poor oil yields, as the moisture binds with oil and inhibits separation.

Each grain has an optimal moisture content for pressing, typically between 7-8%. Experience has shown that canola seeds do best in the 6-8% moisture range, with similar requirements for other oilseeds. Low moisture levels can raise the temperature in the press significantly, hampering cold pressing operations.

Moisture content may also affect pressing efficiency. In one instance, canola seeds stored in a heated environment were found to have dried out to 4% moisture, greatly affecting their pressability. Consulting with seasoned users or the manufacturer can provide valuable insights on ideal moisture levels for specific seeds.

Seed Quality

Seed quality plays a pivotal role in determining the flavor and characteristics of the oil. Harvesting seeds prematurely or too late can adversely affect the oil's quality. For instance, pressing immature seeds results in different aroma and flavor profiles than ripe seeds, leading to lower quality oil.

Additionally, seeds affected by mold due to high moisture levels during harvest or storage can impart unwanted odors and toxins, affecting both the oil quality and safety.

Pressing Temperature

When examining food ingredients, you may notice terms like "expeller pressed" or "cold-pressed". Expeller pressed oil is extracted using a press, while cold pressed means it is produced at temperatures below 49°C (120°F).

Lower temperature oils are often perceived to have better health attributes. Moreover, cold pressed oils exhibit lower phosphorus levels when used as straight vegetable oil (SVO) fuel in internal combustion engines.

Press Settings

Manufacturers design presses to include adjustable settings for accommodating various seed types. While not all presses offer comprehensive settings, most allow for some adjustments. Always remember to turn off and disconnect power before making changes.

For screw-type presses, the settings that can be adjusted include:

• Distance between the end cap and screw end
• Speed of the press
• Tip size (diameter of the expulsion hole)
• Type of screw (spacing between and depth of auger flights)

Adjusting each characteristic can impact extraction rates, making press operation more of an art than a science. An understanding of how moisture content and other factors influence the press settings is crucial for optimal oil recovery.

Distance Between Press Head and Screw End

Adjusting the clearance between the end of the screw and the press head can significantly affect the pressure within the press, impacting oil extraction rates. Striking the right balance between meal passage and oil extraction is key for press efficiency.

Press Speed

Many presses feature variable speed options that allow for adjustments in pressing speed. While faster speeds can increase feedstock processing rates, they often lead to reduced oil extraction efficiency. A careful balance between speed and temperature is critical, particularly for cold pressing.

Diameter of the Tip

Presses typically come with various tip diameters, enabling adjustments for different feedstocks. The diameter impacts the back pressure and oil extraction rate. Testing various sizes can optimize your specific pressing conditions.

Type of Screw

Presses might use screws with varying pitches and depths, tailored to handle specific seed kinds effectively. Before purchase, inquire about any additional components necessary to maximize versatility in processing diverse seeds.

Beginning Operations

Each press may require distinct sequences for startup. Generally, the following steps apply:

• Ensure the feed gate is closed for preheating.
• Set the desired tip diameter and adjust the clearance as necessary.
• Preheat the press head to approximately 120°F (60°C) before feeding seeds.
• Start the press and allow the seeds to flow once the correct temperature is reached.

Shutting Down

• Close the feed gate.
• Wait for oil and meal production to cease.
• Disconnect the press.
• Turn off any heating elements used during operation.

Conclusion

As a crucial component in the oilseed conversion process, the oilseed press allows for the extraction of oil from various seed types. Quality outcomes are influenced by multiple factors including press settings, moisture content, and seed storage practices.

Resources

Press Manufacturers

This is not a comprehensive list of all manufacturers.

Vegetable Oil Processing Equipment

Northeast Oilseed Information

This resource list is not exhaustive, nor do any partners endorse the products listed. It's merely a starting point for those interested in small-scale oilseed processing.

For more information regarding commercial nut roasting equipment, please do not hesitate to reach out.