Processing Canola Oil

Canola is an oilseed crop that was developed from traditional rapeseed by Canadian plant breeders during the 1970's. It is grown widely across Canada, several European countries, and Australia, and to a lesser extent in the United States. Canola is distinguished from traditional rapeseed by the greatly reduced levels of the fatty acid, erucic acid and anti-nutritional compounds called glucosinolates.

These alterations have led to the widespread use of canola oil in Canada and today it is the most popular all-purpose vegetable oil. Canola oil is sold as a salad and frying oil and is also used in margarines, shortenings and in prepared foods that contain vegetable oil (such as baked goods, potato chips, french fries, etc.). Canola oil accounted for approximately 78% of total Canadian production of edible oils in 1996 (Statistics Canada, 1996).

In terms of domestic production of food products, canola oil accounts for approximately 88% of salad and cooking oils, 71% of shortening oils, and 53% of margarine oils. Canola oil is used for similar purposes in the United States, where it represents 7% of total vegetable oil use.

Canola oil is the preferred oil for use in both countries because it is the oil lowest in saturated fats. Canola meal is the by-product of canola oil processing. It is used as a high-protein feed ingredient in the rations of poultry, swine, cattle and fish.

These food and feed applications are possible through strict procedures used in the processing of canola seed into oil and meal. This document describes the processing methodologies that are used by the canola industry to produce high quality oil and meal products.

The production of edible vegetable oils including canola oil involves two overall processes, mechanical pressing and extraction, and further processing to remove impurities. The techniques used are similar for most vegetable oils produced from the seeds of plants. The crushing and extraction processes utilized by the canola industry today produce very little change to the fatty acid profile of the oil and the nutritional qualities of the meal.

The majority of canola seed is grown by Canadian farmers as a commodity crop, meaning that canola seed is commingled and not separated by variety or other specific traits. Following harvest, canola seed is purchased by Canadian and American processors on the basis of grading standards set by the Canadian Grain Commission and, in the U.S., by the National Institute of Oilseed Processors. A number of criteria are used to grade canola seed, including the requirement that the seed must meet the canola standard with respect to erucic acid and glucosinolate levels.

Canola Seed Cleaning

Graded seed is cleaned by a number of different methods including air aspiration, indent cylinder cleaning, sieve screening, or a combination of these. Cleaning ensures that the seed is free of extraneous plant and other foreign material which is referred to in the industry as "dockage". Seed generally contains less than 2.5% dockage following the cleaning process. Seed that has been cleaned is ready for subsequent export or for crushing into canola oil and meal.

Canola Seed Preconditioning

Seed which will be processed for oil and meal is preconditioned using mild heat treatment, and moisture is then adjusted to improve subsequent oil extraction.

Canola Seed Processing

Following preconditioning, canola seed is next crushed and flaked and then heated slightly. These processes help to maximize oil recovery. The canola flakes are then "prepressed" in screw presses or expellers to reduce the oil content from about 42% in the seed (on an 8% moisture basis) to between 16-20%. Screw pressing also compresses the flakes into more dense cakes (called "press cake") which facilitates oil extraction.

Canola Oil Extraction

Press cake which results from seed processing is next subjected to one of two types of oil extraction to remove much of the remaining oil. Oil may be extracted using either hexane ("solvent") extraction or by "cold-pressing" (also referred to as "expeller pressing"). The end-market into which the oil is sold generally dictates which form of extraction will be used. Hexane is the extraction medium used for the bulk of canola oil which is sold into the commodity grocery chain market as well as to the food industry. Cold-pressed canola oil represents a much smaller volume sold to consumers and is generally marketed in specialty food stores. Both extraction processes result in an oil essentially bland in taste, light yellow in color, and with excellent nutritional and stability properties.

Hexane Extraction of Canola

Hexane extraction reduces the oil content of the press cake to very low levels. Oil recovery from canola seed is approximately 96% when this form of extraction is used. This is accomplished by maximizing contact of the hexane with the press cake through a series of soakings or washings. Residual hexane in the extracted press cake and oil is easily removed by evaporation at low temperature. Solvent residues in oils and meals, when produced in accordance with good manufacturing practice, can be said to be truly insignificant.

Canola Oil Refining

The oil which is produced during the extraction process is referred to as "crude oil" because it contains various compounds which must be removed to ensure a product with good stability and shelf-life. These impurities include phospholipids, mucilaginous gums, free fatty acids, color pigments and fine meal particles. Different methods are used to remove these by-products including water precipitation or organic acids in combination with water. Once removed, these by-products are added to the canola meal fraction in order to increase its feeding value (energy) and make it an even more nutritious product.

Following water precipitation and/or organic acid processing, the oil will still contain color compounds which, if not removed would make it unattractive to the consumer and also reduce its stability. These compounds are extracted through a process called bleaching. In contrast to what may be implied by the term, bleaching does not involve the use of harsh chemicals. Instead, during the bleaching process, the oil is moved through a natural, diatomaceous clay to remove color compounds and other by-products.

Deodorization is the final step in the refining of all vegetable oils, including canola. Deodorization involves the use of steam distillation with the objective being the removal of any residual compounds which, if retained, could impart an adverse odor and taste to the oil. The oil produced is referred to as "refined oil".

Further Processing of Canola Products

Refined canola oil is utilized in a large variety of edible oil products. Generally, no further processing is required for canola oil used as a liquid product for salads, dressings and home frying. The refined oil is sold under a number of brand names for both household and industrial purposes. A special process called hydrogenation is used in the production of margarine, shortening and other specialized products. Hydrogenation solidifies the oil and therefore greatly increases the range of products in which it can be used. As a rule, the more "solid" a product is, the greater has been the degree of hydrogenation.

Canola oil may also be processed into more solid products using a method called interesterification. Interesterification involves mixing canola oil with other oils that are more solid by nature, including palm kernel oil. Special processing parameters are utilized and result in a semi-solid product which does not need to be hydrogenated.

Cold Pressing of Canola

The production of cold pressed canola oil involves essentially the same steps as those used in hexane extraction. The most significant difference is that the hexane extraction step is omitted and the oil is removed primarily through mechanical pressing. In addition, the temperature of the cake during the mechanical pressing of the oil from the seed is controlled at 60 degrees C by water cooling. A drawback to cold pressing is that the recovery of oil is lower than from hexane extraction. This is because the mechanical pressing of the cake is less effective at low temperatures. Oil recovery when using cold-pressing techniques most often ranges between 75% to 85 %. The price of cold pressed canola oil tends to be slightly higher because of the lower recovery of oil. Cold pressed canola oil is generally sold in bottled form directly to consumers and is usually not used in further food processing.

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