Determination of chlorophyll pigments in crude and degummed canola oils by HPLC and spectrophotometry

Chlorophyll pigments in crude and degummed canola oils were analyzed by spectrophotometry using a modified AOCS Method and by reversed phase HPLC. HPLC showed that crude canola oils contained very littlechlorophyll a orb, these pigments having been converted to pheophytins and other pigments with similar spectral properties. The ratio ofchlorophyll a∶b in the seed was found to be about 3∶1 while the ratio ofpheophytin a∶b in the oil was about 9∶1. As the AOCS Method for determining oil chlorophyll was calibrated for pure chlorophyll, the use of this method on crude canola oil results in a significant error. Recalibration of the spectrophotometric procedure with pheophytin gave better agreement with the HPLC method. Paper No. 635 of the Canadian Grain Commission, Grain Research Laboratory, 1404-303 Main Street, Winnipeg., Manitoba, Canada R3C 3G8. Presented at the A.O.C.S. 79th Annual Meeting, Phoenix.     

Characterization of chlorophyll pigments present in canola seed,meal and oil

Chlorophyll pigments present in canola seed, meal and crude and degummed oils were analyzed by high-performance liquid chromatography (HPLC) with a fluorescence detector. Chlorophylls a and b, low levels of pheophytin a, and occasionally traces of pheophorbide and its methyl ester were present in canola seed. Meals and oils contained magnesium-deficient chlorophyll pigments such as pheophorbide a, methylpheophorbide a, pheophytins a and b, and pyropheophytins a and b but not chlorophyll a or b. The amounts of chlorophyll pigments were oil > seed >> meal. Both crude and degummed oils contained pheophytin a and pyropheophytin a as main components, but the ratio of pyropheophytin a to pheophytin a was markedly higher in degummed oils. No pheophorbides were detected in degummed oils. These results suggest that oil processing steps such as extraction and degumming affect the composition of chlorophyll pigments. Publication No. 678 Canadian Grain Commission.     

Characterization of chlorophyll pigments in ripening canola seed (Brassica napus)

This study characterizes the chlorophyll pigments in ripeningBrassica napus seed. Seed samples, collected weekly as the crop ripened, were analyzed by high-performance liquid chromatography to characterize chlorophyll pigment composition. Chlorophyll A, chlorophyll B, pheophytin A and pheophytin B were the predominant pigments, while pheophorbide A, methylpheophorbide A and pyropheophytin A were minor components. No differences in pigment composition were observed between the three cultivars tested or between early and late seeding dates. There were differences in pigment composition between the two years of the study, which may result either from seed aging during storage or from environmental influences. Pigment composition was dependent on seed maturity, with physiologically mature green seeds containing both chlorophylls and pheophytins, but fully mature seeds containing only chlorophylls. Pheophytins and the minor components appeared transiently, presumably formed from the chlorophylls and subsequently degraded. The ratio of chlorophyll A/B increased during seed ripening, with fully mature canola seed having a chlorophyll A/B ratio twice that of physiologically mature green seed. The “B” derivatives degraded faster than the “A” derivatives, suggesting enzymatic reactions. The initial steps in the chlorophyll breakdown pathway in canola seed appear to be:      

Glucosinolate levels in western Canadian rapeseed and canola

Since the introduction of low glucosinolate rapeseed into Canadian production in 1975, the average level of glucosinolates has declined from about 80 μmol/g to 25 μmol/g in the 1985 Canadian new crop. Since 1983, more than 90% of the rapeseed planted in Western Canada has been of canola quality (less than 30 μmol/g glucosinolates). The Northern Alberta/British Columbia growing area is the only area in Western Canada which produced noncanola quality seed in 1984. Export shipments of rapeseed from Western Canada have not contained more than 30 μmol/g glucosinolates since December 1983, and at the end of the 1984/85 shipping year most shipments contained about 20 μmol/g glucosinolates. Western Canadian crushing plants have preferentially selected and crushed canola quality seed since 1979. This preferential selection may have slowed the reduction of glucosinolates in export seed. Crushers have produced canola quality meal from seed containing as much as 50 μmol/g glucosinolates, since between 40 and 60% of the glucosinolates present in the seed were removed during processing. Rapeseed has been introduced recently in Southern Ontario. Although the spring-planted crop is canola quality, the winter crop, which makes up 20% of the production, is still high in glucosinolates.     

The relationship between rapeseed chlorophyll,rapeseed oil chlorophyll and percentage green seeds

Oils with high levels of chrlorphyll have become a major problem in the Canadian crushing industry. It was not possible to compare visually the color of samples of rapeseed oil from various crushing plants in Western Canada with the nickel sulfate standard used as a trade standard. Comparison was easy using samples of oil prepared from seed in the laboratory. The difficulty in comparison was probably caused by conversion of green-colored chlorophyll to russet-colored pheophytin in the crushing process. An “apparent chlorophyll” standard with a maximum of 20 ppm (measured by AOCS Cc 13d-55) is recommended. The “percentage green seed” count used in the Canadian grading system was found to correlate poorly (r²<05) with the chlorophyll level in the seed or oil. A maximal chlorophyll level of 12 ppm was found to be allowable in the top grade of seed. It is recommended that a rapid, accurate and inexpensive procedure for chlorophyll measurement be developed to supplement the grading system. Contribution No. 478 from the Grain Research Laboratory, Canadian Grain Commission, 1404-303 Main St., Winnipeg, Manitoba, Canada R3C 3G9.     

Comparison of methods for the analysis of phosphorus in canola oils

Three chemical and two instrumental methods for determining phosphorus in crude and refined canola oils were compared with the official AOCS method. Of the three different digestion-spectrophotometric procedures examined, the oxygen bomb combustion method appeared to offer the best combination of speed, accuracy and precision. In contrast, the perchloric acid procedure was faulted for poor agreement with the AOCS procedure and poor reproducibility between batches, whereas the saponification procedure was very labor intensive and exhibited poor precision. Of the two instrumental methods examined, atomic absorption spectrophotometry was found to be more sensitive than molecular emission cavity analysis although both procedures were reported to be unsatisfactory in detecting inorganic phosphorus. Paper no. 472, Canadian Grain Commission, Grain Research Laboratory, 1404-303 Main St., Winnipeg, Manitoba, R3C 3G9.     

Chemical degumming of canola oils

Crude oil produced from 2 varieties of canola (low thioglucoside rapeseed), i.e., Candle and Tower, were chemically degummed using 54 reagents. Phosphorus, iron, calcum and free fatty acid levels, and Lovibond colors were measured. Inorganic and organic acids or their anhydrides gave the best results in terms of phosphorus removal. Phosphoric, nitric and citric acids, and maleic anhydride were used in laboratory refining tests to determine the effects of chemical degumming on the refining process and on refined oil quality. Citric acid and maleic anhydride gave residual phosphorus levels of less than 50 mg/kg, and after refining, resulted in the best quality oil in terms of color, flavor and stability. The chemical degumming agents behaved similarly for expressed, solvent-extracted and blended oils of both varieties tested. One anomalous result was observed: Candle oil was not efficiently degummed by hydrocholoric acid, whereas the Tower oil gave excellent results. The experiments suggest that chemical degumming can significantly improve the quality of crude canola oil, and will lead to improved final products at lower cost to the refiner.     

Evaluation of oxidative stability of canola oils by headspace analysis

Lipid oxidation is a major factor affecting flavor quality and shelf life of vegetable oils. Oxidative stability is therefore an important criterion by which oils are judged for usefulness in various food applications. In this study a method based on headspace analysis was developed to evaluate relative oxidative stability of canola oils. The method does not require the use of chemicals, involves minimal sample preparation, and can be performed on a relatively small sample size in comparison with traditional wet chemical methods. Canola oils freshly extracted in the laboratory from different seed samples were subjected to accelerated oxidation and analyzed for PV by standard methods and headspace volatiles by solid phase microextraction/GC-MS. Forward stepwise regression analysis of the data revealed a relationship between PV and headspace concentration of the volatile lipid oxidation products hexanal and trans,trans-2,4-heptadienal. The PV calculated using this formula correlated (R ²=0.73) with those measured by conventional methods. Presented in part at the 96th Annual Meeting of the AOCS, 1–4 May 2005, Salt Lake City, UT.     

Commercialization of high oleic canola oils

High oleic canola oils were developed through plant breeding in the 1980's as a trans fat solution. More than 25 years after its initial launch, high oleic canola oils include a series of products with fatty acid profiles tailored for both foodservice and food processing. High oleic canola oil has taken most of the market for trait enhanced oils while other specialty oils have either seen significant market share reduction or failure. High oleic canola oils with 23%–27% linoleic acid are ideal for fried foods, while those with less than 20% are most suitable in the manufacture of shelf stable foods. In addition to improved nutrition, the next generation of high oleic canola oils will significantly reduce packaging costs.     

Erucic acid levels in Western Canadian canola and rapeseed

Canadian exports of canola seed and oil are shown to meet the Generally Recognized as Safe (GRAS) standard of 2% erucic acid. Canadian seed exports averaged less than 2% erucic acid since 1980 and individual cargoes, with one exception, contained less than 2% erucic acid since 1982. Most Western Canadian crushing plants have produced oil with less than 2% erucic acid since 1981, and all since 1984. Areas whereB. campestris varieties of canola predominate may still have difficulty in meeting a 2% erucic acid standard without screening incoming seed. Further reductions in the erucic acid level ofB. campestris canola varieties are desired. This is paper No. 573 of the Grain Research Laboratory.     

Behavior of chlorophyll derivatives in canola oil processing

Chlorophyll derivatives in canola oil were analyzed quantitatively by reversed-phase high-performance liquid chromatography without any pretreatment. The main components were pheophytin (pheo) a and b and pyropheophytin (pyro) a and b. The factors affecting the types and concentration of chlorophyll derivatives in oil have been investigated during seed preparation, expelling, extraction, degumming and alkali-refining processes. Bleaching tests of alkali-refined canola oil with activated earth indicated the adsorption of each derivative to decrease in the following order: pheo a > pyro a >> pheo b > pyro b. In bleaching with activated carbon, however, the following order was observed: pyro b > pheo b > pheo a > pyro a.     

Polymerization of safflower and rapeseed oils

Rates of polymerization of oils from 2 safflower and 2 rapeseed varieties were measured in the air and under vacuum. Thermal polymerization rates showed a stronger dependence on the degree of unsaturation than on oxidative polymerization. Molecular weight distributions of polymerized oils were determined by size exclusion chromatography, and the relationship between viscosity and weight-average molecular weight was determined.     

Antioxidant activity of crude tannins of canola and rapeseed hulls

The antioxidant activity of crude tannins of canola and rapeseed hulls was evaluated by β-carotene-linoleate, α,α-diphenyl-β-picrylhydrazyl (DPPH) radical, and reducing power assays. Crude tannins were extracted from three samples of Cyclone canola (high-tannin) hulls and Kolner, Ligaret, and Leo Polish rapeseed (low-tannin) hulls with 70% (vol/vol) acetone. The total phenolic content in crude tannin extracts ranged between 128 and 296 mg of sinapic acid equivalents per 1 g of extract. The ultraviolet spectra of methanolic solution of canola extracts showed two absorption maxima (282 and 309 nm), whereas those of rapeseed extracts exhibited a single maximum (326 nm). Crude tannins isolated from canola hulls exerted significantly (P<0.025) greater antioxidant activity than those from rapeseed in all three assays. The scavenging effect of all crude tannins, at a dose of 1 mg, on the DPPH radical ranged from 35.2 to 50.5%. The reducing power of Cyclone canola hull extracts on potassium ferricyanide was significantly (P≤0.0025) greater than that of rapeseed hull extracts, and the observed data correlated well (r=0.966; P=0.002) with the total content of phenolics present.     

Characterization of wax sediments in refined canola oils

Turbidity components in refined canola oils were collected by filtration at 4 and 20°C. Major components (thin-layer chromatography) at both temperatures were wax esters (WE), hydrocarbons (HC) and triacylglycerols (TG) while free fatty acids (FFA) and fatty alcohols (FAL) were found in minor amounts at 4°C. WE had carbon numbers of 40 to 56 (made up of combinations of C16 to C30 alcohols and C16 to C28 fatty acids). HC were mostly C29 and C31 with lesser amounts of C24, C28 and C32. TG, compared to the corresponding liquid oil, still contained C18:1 as the major component, but had less C18:2 and particularly less C18:3 and at least two times higher levels of saturated fatty acids. The FFA were mainly long-chain C22:0, C24:0 and C20:0 (in order of amount). FAL were mainly long-chain C26:0, C28:0 and C30:0 but ranged from C16:0 to C32:0. Presented in part at the 1991 American Oil Chemists’ Society Annual Meeting and Exposition, Chicago, May 15. Received Outstanding Paper Award 1991, Chicago (82nd) Annual Meeting.     

Fatty acids and sterols in oils from canola screenings

One sample of canola seed (variety Tower) and five samples of screenings were commercially processed to yield first an “expeller oil” and subsequently an “extractor oil” by the hexane extraction of the residue. The screening samples contained 25–50% intact or broken canola seed. The balance included 21–31% weed seeds (especially lambsquarter and stinkweed), hulls, fragments of the embryo, and chaff. All the oil samples were analyzed for sterol and fatty acid composition. The extractor screening samples had slightly higher sterol contents than the corresponding expeller samples, while the Tower samples gave the lowest values. The averages (in mg/g oil or extract) for the extractor screening samples were: brassicasterol, 1.0; campesterol, 4.1; and β-sitosterol, 7.3. For expeller screening samples the average were: 0.9, 3.6 and 6.2 and for the Tower oils they were, respectively, 0.9, 3.8, 5.3 and 0.9, 3.5, 4.7. The fatty acid compositions of the screening samples for both extractor and expeller oils were similar to that of the Tower oil except for the higher proportions of docosenoic acid (22:1) and eicosenoic acid (20:1) and the more obvious presence of three C₁₈ conjugated dienes totalling up to 0.6% of one screening oil sample. The docosenoic acid level (mainly erucic acid) ranged from 3.0 to 7.0% for the extractor oils and from 2.5 to 8.0% for the expeller samples, compared to 0.1% for the two Tower oils. The oil contents of the screenings ranged from 20 to 30%, and the fatty acids and sterols appear to be nutritionally useful and innocuous in all respects. Presented in part at the ISF/AOCS World Congress, New York, April–May 1980.     

Frying performance of genetically modified canola oils

The frying performance of low linolenic and high oleic canola oils was compared to regular and hydrogenated canola oils. The antifoaming agent dimethylpolysiloxane (2 ppm) was added to all frying oils. Potato chips were fried in the four oils over a 5-d period for a total of 40 h of frying. Oil samples were collected each day and analyzed for conjugated dienoic acids, free fatty acids, polymers, oxidation products, and polar components. Polar components were determined by the gravimetric method and by thin-layer chromatography with flame-ionization detection. The initial quality of the four oils was similar except in the amount of tocopherols present. All oils deteriorated after 5 d of frying but differences were not as anticipated, possibly as a result of observed differences in tocopherol levels.     

Kinetics of oil extraction from canola (rapeseed)

The extraction of oil from canola (rapeseed) using hexane as a solvent can be described by a two stage washing/diffusion model. Oil which is at the surface of the seed as a result of pressing or cooking is removed rapidly at the beginning of the extraction process by simple washing by the solvent. This is followed by a slow extraction of the oil from the seed by a diffusional process. This latter process appears to be controlled by two mechanisms: slow, unhindered diffusion of oil held in the ruptured cells in the seed; and very slow, hindered diffusion of oil held within unruptured cells in the seed. To evaluate this model, rapeseed was extracted with commercial hexane in a simple bench scale batch extractor and the effects of variables such as particle thickness, temperature, cooking, degree of agitation, and solvent-to-seed ratio were studied.     

Hydrogenation of canola oil as affected by chlorophyll

Chlorophyll was added to refined and bleached canola oil before hydrogenation, and the effects on hydrogena-tion rate, fatty acid composition and the percentagetrans isomers were determined. The hydrogenation rate was greatly slowed down by chlorophyll under selective (200 C and 48 kPa) and nonselective conditions (165 C and 303 kPa). Higher levels of chlorophyll reduced the reaction rate more than the lower levels under both conditions. Dropping points were slightly higher for the nonselectively hydrogenated samples than for the selectively hydrogenated ones. Addition of 1 mg/kg or more chlorophyll decreased the solid fat content under nonselective conditions. Addition of chlorophyll reduced thetrans isomer content under nonselective conditions. Nonselective conditions also resulted in a greater decrease of 18:3 and faster production of 18:0 than selective conditions at all levels of chlorophyll addition.     

Specific gravities of rapeseed and canbra oils

New varieties of rapeseed oils grown in Canada have bess than 1% erucic (cis-13-docosenoic) acid and also a reduction in cis-11-eicosenoic acid. The replacement of these acids with C₁₈ acids increased the specific gravity (25 C/25 C) from 0.9123 for an oil with 23.1% erucic acid to 0.9171 for an oil with 0.7% erucic acid. Soybean oil data are presented for comparison.     

Characterization and evaluation of some rapeseed oils

Rapeseed oil is used mostly in edible products. Four rapeseed oils, brown sarson and toria oils from West Pakistan, a Swedish oil and a Canadian oil, were characterized and examined relative to their suitability as edible oils. The various analytical data obtained are reported. The hydrogenated oils have consistency characteristics and plastic ranges which make them suitable for use as plastic fats. This work supported by a fellowship grant awarded by South East Asia Treaty Organization, Bangkok, Thailand. A laboratory of the So. Utiliz. Res. & Dev. Div., ARS, USDA.