J. K. Daun

Comparison of three whole seed near-infrared analyzers for measuring quality components of canola seed

Whole seed near-infrared (NIR) analyzers are capable of high-speed compositional analysis of oilseed commodities. This study compared the PerCon Inframatic 8144 (Perten Instruments, North America Inc., Reno, NV), the Tecator Infratec 1225 (Tecator AB, Hoganas, Sweden) and the NIR-Systems 6500 (NIR Systems, Inc., Silver Spring, MD) analyzers for measurement of oil, protein, chlorophyll and glucosinolates in intact canola seed of composite samples from the Grain Research Laboratorys (Winnipeg, Manitoba, Canada) annual Western Canada Harvest Surveys (1985–1989) for assembly of calibration and prediction sets. No significant differences were found between the three instruments for oil [standard error of prediction (SEP 0.43–0.55%)], protein (SEP 0.35–0.42%) and glucosinolates (SEP 2.4–3.8 mM/g). Neither the Tecator nor the PerCon instruments were effective for determining chlorophyll. By combining oil content and fatty acid composition data to give an estimate of the total level of each fatty acid in the sample, high correlations were obtained for total saturates, linolenic acid, and linoleic acid although the RPD (ratio of the S.E. of prediction to the S.D. of the original data) values were not high enough to enable routine use of the method to predict results.

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.

Use of gas liquid chromatography for monitoring the fatty acid composition of canadian rapeseed

Since 1972, Canadian rapeseed has been changing from high erucic acid types to low erucic acid types. In 1970, the Canadian Grain Commission instituted a program to monitor the fatty acid composition of rapeseed at the farm level, in railway carlot shipments and in export cargo shipments. Initially, in order to process up to 20,000 samples per year, a combined extraction and methylation procedure was developed in which methyl esters were analyzed within 5 min by manual injection on a nonpolar column. Since conversion to low erucic acid rapeseed types has been completed, other details of fatty acid composition have received more attention. In the system presently used, the rapeseed oil methyl esters are analyzed on a mixedphase column which gives good resolution of all of the major fatty acids. Through the use of a microcomputer-controlled autosampler, 50 samples can be analyzed per day. Reports are generated giving complete fatty acid composition as well as estimates of iodine value and saponification value.

Quality of yellow and dark seeds inBrassica campestris canola varieties Candle and Tobin

Yellow-coated seeds from theBrassica campestris cultivars Tobin and Candle were heavier and contained more oil and protein than the dark-coated seeds from the same sample. In addition, the yellow-coated seeds had lower levels of erucic acid, glucosinolates, chlorophyll and crude fiber. These differences were detected in both pedigreed and commercial (producer) samples, but to a larger extent in commercial samples. Reasons for the greater quality differences between yellow- and dark-coated seed could be admixtures of cultivars other than the declared ones of Tobin or Candle or changes in the seed itself as it went from the breeder’s stage to the producer stage.

Fatty acid composition of oils extracted from Canadian weed seeds

The fatty acid composition of the diethyl ether extract from nine varieties of Canadian weed seeds is reported. Fatty acid compositions forRumex pseudonatronatus L. Borbus,Setaria viridis L. Beauv., andChenopodium album L. have not been previously reported.

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.

Comparison of combustion and Kjeldahl methods for determination of nitrogen in oilseeds

The recent development of combustion-type nitrogen analyzers capable of handling relatively large samples with semi automatic operation offers a potential replacement for the Kjeldahl method for direct determination of nitrogen. Nitrogen analyses for canola seed, flaxseed, sunflower seed, mustard seed and soybeans on a LECO (St. Joseph, MI) FP-428 Nitrogen Analyzer were evaluated against results from the Grain Research Laboratorys (GRL) Kjeldahl system. The nitrogen analyzer gave significantly higher values than the Kjeldahl method, resulting in a correction of low values in the GRL Kjeldahl, caused by the inability to use mercury as catalyst. The standard error for results from the analyzer was comparable to that for the Kjeldahl method. The nitrogen analyzer also was faster than the Kjeldahl method and had less environmental impact. The combustion method has replaced the Kjeldahl method for routine nitrogen determinations in oilseed surveys conducted by the GRL.

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.

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.

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.