COLD OR HEATED OIL PRESSING?

We’ll analyze the technologies for processing canola (rapeseed) and sunflower that are similar as they’re both based on the non-chemical oil obtaining.

Cold oil pressing involves crushing the seed and forcing out the oil. Presses come in a range of sizes, from small sizes to huge commercial presses. The seeds are dropped inside a cylinder that contains a rotating screw. This screw grinds and crushes the seeds until the oil is extracted. Small holes in the bottom of the cylinder allow the oil to yield into a collection container

The processing of rapeseed (canola) into oil is much similar to sunflower seeds processing. The difference is that we actually don’t dehull the rapeseed.

Rapeseed or canola is small and black, much like a poppy seed, with a golden-yellow center. The oil is locked up in the carbohydrate at the center of the seed, and pressing is the method we use to extract this oil, by gently squeezing it out of the seed.

Cold oil pressing is the mechanical oil extraction where the oilseeds are not heated prior being pressed out or the seeds must be kept in a quite low temperature prior to the oil pressing. Usually, the maximal heating temperature is 55°С or not less than 60°С.

There is also the double oil press method of canola oil processing which is as follows:

Step №1 the first oil press used for preliminary mechanical oil extraction

Step №2 oil roaster

Step №3 the oil press used for final mechanical oil extraction

The ‘meal’ or oil cake that comes out of the end of the press, known as the leftover once the oil has been squeezed out, is collected and used for animal feed.

The characteristics of the ready oil cake:

• the residual oil content in the oil cake is 10-12%

• fiber content is 25-27%

Talking about hot oil pressing we should clearly understand that the seeds are heated up to 100-130°С. Due to heating, the shell could be peeled off from the seeds up to 60- 90%. The seed shells become hard mixture which also can additionally improve the oil yield from the oil press.

This process of rapeseed oil production can be done to the following scheme:

Step №1 oil roaster

Step №2 the first oil press used for preliminary mechanical oil extraction

Step №3 oil roaster

Step №4 the oil press used for final mechanical oil extraction

The characteristics of the ready oil cake:

• the residual oil content in the oil cake is 7-10%

• fiber content is 10-15% which can be considered as the advantage of the hot oil pressing method

The disadvantage is the high processing temperature 100-130°С which can adversely affect the biochemical properties of oil and oil cake.

We offer the combined method of rapeseed oil processing from Bronto where you use the oil press with processing temperature which corresponds to cold oil pressing 55°С combining it with a short cooking time (20-40 seconds only) in the extruder and finish the process with the final oil pressing.

Simply saying, the mechanical oil extraction occurs according to the following scheme:

Step №1 oil press for the preliminary oil pressing

The processing temperature is low and perfect for careful cold oil pressing.

Step №2 extruder

Extrusion cooking has been practiced for decades as a means of processing feed or food. During extrusion cooking, temperatures can be relatively high (100-120˚C) but the residence time at this elevated temperature is very short (20 to 40 seconds).

These kinds of processes tend to maximize the beneficial effects of the oil while minimizing the detrimental effects on its nutrients.

Step №3 oil press for the final oil pressing

This step helps to obtain the good oil yield and achieve the right oil cake characteristics.

The characteristics of the ready oil cake:

the residual oil content in the oil cake is  8-12%.

fiber content is 16-20%.

The processing temperature due to the short cooking time 20-40 seconds does not adversely affect the biochemical properties of oil and oil cake. The temperature may be controlled and quickly regulated.