Crude Degummed Canola Oil

 

Crude Super Degummed (CSD) Canola Oil is oil that unedible and requires further processing before being used by the food industry. The color of Crude Canola oil is dark yellow. Domestic and international Buyers of crude degummed canola oil typically have a facility where they would further process the canola oil before moving it to consumption. Further information, specifications and commercial trade rules for Crude Degummed Canola Oil are available through the Canadian Oilseed Processors Association.

Crude Super Degummed Canola Oil is composed mainly of tria-cylglycerols but contains considerable amounts of desirable and undesirable minor components. Crude canola oil is refined in order to remove undesirable minor compounds that make this oil unusable in food products. However, refining can also cause the removal of desirable health promoting minor components from the oil. The first section of this review describes the chemical composition of canola oil, followed by a brief introduction to the effects of minor components on canola oil quality and stability. Following a review of traditional canola oil refining methods, the effects of individual refining stages on the removal of both desirable and undesirable components from canola oil are presented and contrasted with other common vegetable oils.

 

Crude oil
Crude Super Degummed Canola Oil

Introduction

Vegetable oils and fats are the raw materials in the manufacture of shortenings, margarines, frying oils, and other edible products used by both the food manufacturer and the household. Vegetable oils can also be used to formulate specialty lipids such as human milk fat substitutes for infant formula, low calorie fats and oils and edible oils enriched in essential long chain omega3 fatty acids and mediumchain fatty acids. They also have applications in the oleochemical, leather, paint, rubber, textile and pharmaceutical industries. Vegetable oils and fats are the densest source of food energy, more than any other food group. Vegetable oils are also carriers of fat soluble vitamins, and provide essential fatty acids.

Crude vegetable oils and fats consist predominantly of triacylglycerols along with other minor components such as Free Fatty Acids (FFA), monoacylglycerols, diacylglycerols, Phospholipids, free and esterified Phytosterols, Polyphenols, Triterpene alcohols, Tocopherols, Tocotrienols, Carotenes, Chlorophylls, Hydrocarbons (e.g. squalene), Trace metal ions (e.g. Iron, Sulfur and Copper), Oxidation products, Gums, Waxes, Pesticide residues and flavor compounds.

 

Understanding How Crude Oil Is Processed
Understanding How Crude Oil Is Processed

Canola oil was introduced in Canada in 1974. Since 2000, canola oil in Canada is extracted mainly from the seeds of genetically modified Brassica Napus L. Some canola oil is still extracted from Brassica rapa L. The rapeseeds currently in use are bred specifically to be low in both Erucic Acid and Glucosinolates (0.1 % Erucic Acid in the oil and 8.5 lM/g Glucosinolates in the seed). The reduction of Erucic Acid in the rapeseed oil causes a dramatic increase in the oleic acid content of canola oil. Different types of modified canola seeds have been developed by plant breeders (high oleic, high stearic/lauric and low linolenic canola). High lauric and high stearic canola oils are currently not in commercial production but they have potential for use in confectionery coatings, coffee whiteners, whipped toppings, and baked products as a substitute for hydrogenated oils.

Crude canola oil is unique, compared to the other major vegetable oils, for its high chlorophyll content. The specification for chlorophyll content of crude oil in Canada is less than 30 mg/kg. It has been shown that chlorophyll and its derivatives (especially Pheophytin and Pheophorbide) are powerful prooxidants when exposed to light (photooxidation). Thus, chlorophyll pigments in canola oil are highly undesirable. The total chlorophyll content of canola oil should be reduced to less than 1ppm after bleaching with activated bleaching clays. The stability of canola oil decreases with an increase in the chlorophyll content.

 

Canola Seed Oil Extraction Process
Canola Seed Oil Extraction Process

Free Fatty Acids

Free fatty acids in vegetable oils can act as prooxidants. The carboxylic group accelerates the rate of hydroperoxide decomposition. Free fatty acids have a higher vapour pressure compared to triacylglycerols. As a result, oils with high FFA contents usually have a lower smoke point. Crude canola oils are either water degummed or acid degummed prior to neutralization. The FFA content just prior to neutralization is generally between 0.4% to 1.0% w/w. After chemical or physical refining, the FFA content in crude canola oil is usually reduced to 0.05% w/w. In virgin canola oils that have a high FFA content, which may result in an undesirable taste and flavor.

Trace Metals

Vegetable oils contain some trace metal ions such as Iron, Copper, Zinc and Lead. These elements can act as prooxidants and should be reduced in the refined oil. Canola oil contains sulfur in the form of organic compounds. These are hydrolysis products of glucosinolates that are transformed into a variety of sulfur compounds such as iso thiocyanates, thiocyanates, nitriles and oxazolidinethiones. Sulfur compounds are responsible for the unpleasant odor of heated canola oil. Crude canola oil contains about 1535ppm sulfur compounds that, after refining, is reduced to about 27ppm. During hydrogenation, these sulfur components poison the nickel catalysts. The sulfur components also act as antioxidants by converting hydroperoxy radicals into stable termination products. Sulfur compounds can also inactivate metal ions and other prooxidants.

Canola Oil Refining Methods

Degumming

Traditional Degumming

Degumming is the first stage in edible oil refining. Degumming removes phospholipids, trace metal ions and other mucilaginous materials. Phospholipids are oil soluble but are rendered insoluble in oils after hydration. Canola oil contains up to 3.5% phospholipids, primary lecithin (Phosphatidylcholine) and Cephalin (Phosphatidylethanolamine). These are both hydratable and can be removed by a water degumming process. Other Phospholipids such as Calcium or Magnesium salts of Phosphatidic acid and phosphatidylethanolamine are nonhydratable and require acid degumming.

 

Degumming - An Overview
Degumming – An Overview

 

Although, some kinds of Phosphatides such as Phosphatidylcholine have several health benefits, they should be removed from oil during refining as they settle during crude oil storage as well as make an emulsion during processing that may lead to an increase in the refining loss. Soluble phospholipids also cause crude oils to darken during storage and if they are not removed from oils prior to deodorization, can lead to dark color formation in deodorized oils and tend to enhance the formation of off flavors. Traditional methods of degumming are: (1) Water Degumming and (2) Acid Degumming (Super Degumming). During water degumming, 2% w/w water is added to oil with a 1530 min agitation to form hydrated gums, which are insoluble in oil and can be separated by centrifugation. Acid degumming is a combination of water and acid treatment (predominantly Phosphoric or Citric Acid). In this process, nonhydratable Phospholipids can be removed by adding a 85% Phosphoric acid solution Phosphatide content of crude canola oil to 2535ppm. Acid degumming is necessary before physical refining. It was found that using citric and Malic Acids resulted in lower residual phosphorus levels in oil and improved the quality of the degummed canola oil in terms of color, flavor, and oxidative stability. Other authors reported that phosphoric acid was exceptional at removing chlorophyll during acid degumming while citric acid was the least efficacious at removing chlorophyll. In the acid degumming of canola oil, a citric acid concentration of 0.25% in the oil was optimal for degumming canola oil. The residual phosphorous level in the degummed oil was about 50ppm.

Other Industrial Degumming Methods

Several other degumming methods such as:

(1) Enzymatic Degumming,

(2) Membrane Degumming,

(3) Soft Degumming (using a chelating agent such as Ethylene Diaminetetra Acetic Acid (EDTA), and an emulsifying agent),

(4) TOP Degumming (TOP is a Dutch acronym derived from ‘‘Totaal Ontslijmings Process’’ which means total degumming process), and;

(5) Dry Degumming are used to remove Phospholipids. During dry degumming, crude oil is first mixed with Phosphoric or citric acid to dissolve the metal Ion/Phosphatide complexes.

The oil is then mixed with bleaching earth to remove Phosphatides, Pigments, and other impurities. Dry degumming is rarely used to degum canola oil but is useful for low Phosphatide oils such as Palm and Coconut oils.

In enzymatic degumming, Phospholipase A1 is used to split Phosphatides. This enzyme converts Phospholipids to Lysophospholipids and Free Fatty Acids (FFA). Phospholipase A1 (Lecitase Ultra) was quite effective at removing phospholipids from rapeseed oil. The phosphorous content of degummed oil was about 7ppm. During TOP degumming, the crude oil is water degummed and the hydratable phospholipids are removed. Thereafter, acid degumming removes the calcium and magnesium salts of phosphatidic acid. Finally, a dilute base such as NaOH, sodium carbonate or sodium silicate was used to neutralize phosphatidic acid. It has been reported that the amount of phosphorous in canola oil after water degumming decreased to 70ppm. After acid degumming, the amount of phosphorous was reduced to 21ppm. TOP degumming reduced the amount of phosphorous to 15ppm. 

Membrane degumming is especially useful for miscella degumming. Up to 90% of total phospholipids in soybean miscella can be removed via ultra filtration. In this study, the phosphorous content of the oil was reduced to 20–58ppm. Other degumming processes of interest include supercritical CO2 degumming, ultrasonic degumming and two solvent phase extraction.

Oil Extraction, Degumming and Refining Process
Oil Extraction, Degumming and Refining Process

Standard Specification of Crude Degummed Canola Oil

Standard Specification of Crude Degummed Canola Oil