459 Journal ofFood Protection, Vol. 44, No.6, Pages 459-470 (June 1981) Copyright©, International Association of Milk, Food, and Environmental Sanitarians Detoxification of Rapeseed Products P. N. MAHESHWARil, D. W. STANLEY! andJ. I. GRAY2• Department ofFood Science, University of Guelph, Guelph, OntarioNI G2Wl, Canada, and Department ofFood Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824 (Received for publication June 19, 1980) ABSTRACT oil as it relates to the fatty acid composition that becomes The full potential of rapeseed products has not yet been the primary concern as it determines the value and utility Downloaded from http://meridian.allenpress.com/jfp/article-pdf/44/6/459/1654352/0362-028x-44_6_459.pdf by guest on 02 October 2021 realized because of the presence of certain toxic compounds. of the vegetable oil. There are wide variations in the fatty This paper reviews development of low erucic acid rapeseed, acid composition of the world's major edible oils and the extensive experimental scrutiny to which this oil has (fable 1). Rapeseed and mustard oils produced from been subjected. The significance of the presence of gluocosino­ conventional varieties differ from most other vegetable lates as well as their decomposition products (isothiocyanates oils by containing significant amounts of long-chain and oxazolidinethiones) in rapeseed meal is also discussed. monoenoic fatty acids with 20 and 22 carbon atoms. Various methods for removing these toxic constitutents from Indeed, the rapeseed and mustard oils produced in the the meal are reviewed. Far East still contain as much as SO% erucic acid and 8-lOo/o eicosenoic acid in their total fatty acid composition. Because of this unique fatty acid composi­ Rapeseed is an important oilseed crop and ranks fifth tion, rapeseed oil has been used in several industrial in the world production of oilseeds. India is the world's applications as well as in the manufacture of margarines, largest single producer of the crop (55), while Canada is shortenings and salad and cooking oils (42). the biggest exporter and supplier of the crop to the world The unique composition of rapeseed oil intrigued market (18). This crop has been cultivated for at least nutritionists to study its dietetic properties. Consequent­ 3500-4000 years in India, and today it is the second major ly, some Canadian nutritional investigations carried out oilseed crop (preceded only by peanuts), supplying about in the early 1950's by Carroll and his colleagues (34-36) 20% of the total edible oil supply in the country. In suggested that oils high in erucic acid, if fed to laboratory Canada, rapeseed was first grown commercially in 1942 animals as a large proportion of the diet, can result in as a wartime measure to supply oil for lubrication of retarded growth and poor animal performance. It was marine engines. Extraction of oil for edible purposes first the result of these early studies that led to a Canadian occurred in 1956. Since then production has expanded plant breeding program to either reduce or alter the rapidly so that rapeseed now represents a very important erucic acid levels in the rapeseed oil. crop for Canadian farmers, and accounts for more than Genetic investigations ascertained that the fatty acid SOo/oofthe oilseed crops grown. composition of the seed oil was determined by the Unfortunately, the full potential of rapeseed products genotype make-up of the developing embryo and not by has not been realized because of the presence of toxic the maternal plant (46), and that the erucic acid content compounds. This paper reviews progress in development ofthe seed oil was controlled by genes (39,64). By 1963, of erucic acid-free rapeseed oil as well as the problems this breeding program in Canada had produced strains associated with rapeseed meal. The various techniques in summer rape and summer turnip rape which involved in detoxification of this meal will also be contained less than 1 o/o erucic acid in their oil (40,129). reviewed. Commercial testing and industrial evaluation of the pro­ cessing quality and storage stability of the oil from these COMMERCIAL PROCESSING OF RAPESEED new strains of rapeseed was completed by 1966, and was Rapeseed oil found to be highly satisfactory. However, exploitation of The commercial processing of rapeseed in modern oil the low erucic rapeseed in Canada was very much limited mills yields approximately 40% oil and SO% protein-rich due to an unfavorable pricing situation for its oil on the meal. Oil quantity and quality are usually of the greatest world ma.rket. In the late 1960s and early 1970s, several interest to the oilseed processor since oil prices are reports of nutritional investigations from Canadian and normally several times higher than that of the by-product European laboratories were published which showed that meal. With the fixed quantity of oil, it is the quality of the the high erucic acid rapeseed oil was poorly used by young laboratory animals. When used as a major source 1 University of Guelph. of energy in the diet. it resulted in reduced growth and 2 Michir;an State University. undesirable physiological and histopathological changes JOURNAL UFFOO!J PROJECTION. VOL.44,JUNE 19H1 460 MAHESHWARI, STANLEY AND GRAY in the heart (cardiac lesions) and the skeletal muscles in biosynthesis of eicosenoic and erucic acids was confirmed the rat (2), ducks (1,3,133,147), guinea pigs (147) and by Downey and Craig (44). While low erucic acid (less monkeys (62). The nutritional properties of rapeseed oil than 1 o/o) rapeseed strains are being cultivated in Canada have been thoroughly reviewed by VIes (146) and Slinger and some European countries, goals have been set up for (122). These reports clearly established that a high level future quality improvement by breeding and include of erucic acid in the oil is undesirable from a nutritional advances such as palmitic acid up to 10o/o, linoleic acid point of view and abruptly changed the status of low above 40o/o and linolenic acid below 3o/o. Altering the erucic rapeseed in Canada and subsequently in Europe. levels of linoleic and linolenic acids appears feasible The changeover to low erucic acid varieties was (107), but it will probably require a few years to initiated in Canada in 1971 (42) and was soon followed by incorporate this characteristic into commercial varieties Sweden (10), Germany (50,68), France (89), Poland and (122). other European countries. The Canadian conversion was Low erucic acid rapeseed oil has also been subjected to essentially completed in 1974. The European conversion extensive experimental scrutiny. Rocquelin and Cluzan has been hampered by sharply increasing erucic acid (1 08) found that rapeseed oil from low erucic acid levels during seed and commercial multiplications varieties with 1-2 o/o levels of erucic acid in the oil also Downloaded from http://meridian.allenpress.com/jfp/article-pdf/44/6/459/1654352/0362-028x-44_6_459.pdf by guest on 02 October 2021 (perhaps as a result of volunteer high erucic plants resulted in cardiac lesions in rats when included in the originating from seed of old varieties lying dormant in the diet. These findings have been subsequently confirmed fields) but is expected to be completed shortly. by several groups of workers (4,23, 78, 79,109,111). It has Conversion to low erucic acid rapeseed and mustard also been shown that early lipidosis in the heart is strains in Asia has not yet been initiated. directly related to the concentration of erucic acid in Genetic isolation of rapeseed plants with less than 1 o/o dietary oils (5,21,22, 79,86), and the erucic acid erucic acid in their seed gave simultaneous selection for accumulation in cardiac lipids is proportional to the low eicosenoic acid and a corresponding increase in oleic concentration of this acid in the diet (79). Since the acid (fable 1). These observations suggested that oleic incidence of myocardial lesions on feeding rapeseed oil to acid was the precursor of eicosenoic and erucic acids in weanling male rats for about 16 weeks was observed their biosynthesis and that addition of an acetate group irrespective of the level of erucic acid, it has been to the carboxylic end of oleic acid would result in suggested that additional factors such as unsaponifiable eicosenoic acid. Addition of a second acetate group components or a fatty acid imbalance may be involved would give rise to erucic acid. This pathway for (78, 79,109, 111). However, Abdellatif and VIes (5) TABLE 1. Percent fatty acid composition of rapeseed oils and some selected vegetable oils. a Rapeseed oil Indian mustard b Low erucic before 1969 Commer- B. camp· Sun- Saf- Corn Fatty acid Canada Europe B.juncea cial oil B. napus estosis Soybean Peanut flower flower USA 1. Palmitic 3.5 3.5 2.1 1.7- 2.1 3.8 3.2 15.0 9.2 5.9 7.2 11.5 (16:0) 2. Stearic 1.4 1.2 1.2 1.1- 1.2 1.5 1.5 4.0 3.1 5.2 1.9 2.2 (18:0) 3. Arachidic 1.4 (20:0) 4. Behenic 2.6 (22:0) 5. Lignoceric 1.8 (24:0) 6. Oleic 30.5 12.0 11.2 11.2-16.2 62.6 60.2 24.0 57.2 15.9 12.4 26.6 (18: 1) 7. Linoleic 21.5 15.0 15.9 11.2-16.3 19.7 21.3 49.0 23.4 72.5 78.5 58.7 (18:2) 8. Linolenic 6.6 8.7 10.0 4.9-10.0 8.9 10.9 8.0 0.8 (18:3) 9.