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Influence of environmental and agronomic factors contributing to increased levels of phospholipids in oil from UK linseed Linum usitatissimum
Industrial Crops and Products 10 (1999) 201 – 207 www.elsevier.com/locate/indcrop
Influence of environmental and agronomic factors contributing to increased levels of phospholipids in oil from UK linseed Linum usitatissimum M.A. Froment a,*, J. Smith a, K. Freeman b a
ADAS Bridgets Research Centre, Martyr Worthy, Winchester SO21 1AP, UK b John L. Seaton and Co. Ltd., Bankside, Hull HU5 1RR, UK Accepted 19 May 1999
Abstract High levels of phospholipids in linseed oil result in production line hold-ups due to gum formation in machinery during processing and irreversible cloudiness when high phospholipid oil is left to stand. Specific problems with oil from UK crushed linseed were experienced by linseed oil refiners in both the 1993 and 1997 seasons. The 1993 harvest was characterised by wet conditions suggesting that enhanced phospholipid content may be associated with weather damage which was reported in some linseed crops in that year. A study was undertaken to investigate the effect of agronomic factors which may influence phospholipid content. In a replicated field experiment spring linseed cv. Barbara, which had been desiccated with diquat, was sequentially harvested at six timings from both rainfed plots and others which were misted during the seed filling stage. Additional plots which had not been desiccated were also sampled at a normal, early September and late October harvest date. Seed samples were crushed and the resulting oil was analysed for total, hydratable and non-hydratable phospholipid contents. Mean total phospholipid contents were greater in non-misted plots than misted plots and increased dramatically between the final harvest dates, however, there were large variations in total phospholipid content for individual treatments. Desiccation of linseed is standard practice in the UK, but total phospholipid content of the non-desiccated samples taken in early September were low at 170 ppm and did not increase despite a further harvest delay of 3 weeks. The level of non-hydratable phospholipids, which are not removed during normal processing and cause the most difficult production problems, were unaffected by delayed harvest date, but they were always greater in the misted, compared to non-misted treatment. An additional study of unreplicated seed samples collected from a range of sites and varieties indicated a large variation in total phospholipid content from 43 to 1436 ppm. The highest levels were reported at one site where the harvest was delayed past physiological maturity by wet weather. Results from these studies suggest that crop desiccation, which causes drying and fracturing of the capsule wall, allowing water ingress, could increase the risk of increased phospholipid content in linseed if wet weather delays harvest. Variety choice may also be important, but at individual sites. © 1999 Elsevier Science B.V. All rights reserved.
* Corresponding author. Tel.: + 44-1962-779-765; fax: + 44-1962-779-739. E-mail address: martin – [email protected] (M.A. Froment) 0926-6690/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 6 - 6 6 9 0 ( 9 9 ) 0 0 0 2 4 - 2
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M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
Keywords: Linseed; Linl11um usitatissimum; Phospholipids; Oil; Agronomy
1. Introduction The United Kingdom is the EU’s major producer of linseed, with :4000 growers farming 60 000–70 000 ha (MAFF, 1997), down from its peak in 1993 of 160 000 ha. UK linseed supplies both home and export markets where it must compete in terms of consistency of supply and quality, as well as price, if it is to remain competitive with imported supplies. High levels of phospholipids in linseed oil result in production line hold-ups due to gum formation in machinery during processing and irreversible cloudiness when high phospholipid oil is left to stand. Phospholipids are naturally occurring compound lipids (a lipid containing a phosphate residue) which are commonly found in oilseed crops (Lehninger, 1970; Ansell et al., 1973). Specific problems associated with phospholipids in UK crushed linseed were identified in 1993, when phospholipid content increased from B 50 ppm to between 300 and 1000 ppm. There were further problems in 1997. The 1993 season was characterised by a wet harvest suggesting that enhanced phospholipid content may be associated with sprouting which was reported in some linseed crops in that year. Desiccation of spring linseed using diquat or glyphosate is routine practice in the UK (Anonymous, 1996) to ensure rapid crop desiccation as a harvest aid. This practice is favoured in more northerly areas where crop maturity is delayed by cooler growing conditions and where farmers wish to harvest crops before the risk of autumn rains. The cost of removing phospholipids from the oil is reduced if this can be identified at the crushing stage, so prior warning of general (weather) or specific (variety or crop management) factors relating to enhanced levels would improve the overall efficiency of the oil processing operation. A research study was undertaken to improve understanding of the problem and investigate possible causes for variation in the phospholipid content of UK linseed.
2. Material and methods
2.1. Misting experiment, study 1 Plots of spring linseed cv. Barbara were marked out in a commercial crop at the ADAS Bridgets Research Centre, Winchester, UK. A split-plot design was used with misting and no-misting on main plots and sample date on sub plots. Main plot and sub plot treatments were randomised within each of three blocks. Individual sub plots were 2 m× 3 m in size, with 12 sub plots per block providing six sequential sampling dates. Additional non-desiccated plots were abutted to each block and these were sampled at a ‘normal’ commercial harvest date, early September and at a ‘late’ October harvest date. Misting equipment was used to enhance the effects of normal rainfall and encourage sprouting in linseed on misted main plots. This was achieved by the use of ACCESS Girosprinklers (micro irrigation nozzles mounted on 0.8 m tall risers). Capsule wetness was controlled by use of an electronic timer. Plots were misted for 3× 1 h sessions per day from Friday to Tuesday. Each Wednesday and Thursday the crop was allowed to dry and it was sampled by hand on Fridays. Misting began on the 15 August. Water used for misting was taken from a potable mains water supply. Misted and non-misted main plots were desiccated with Reglone (Diquat, Zeneca, 500 g a.i./l) applied at 3 l/ha plus Agral wetter (non ionic) at 100 ml per 100 l of diluted spray. The desiccant was applied at a single timing on the 12 August at 300 l/ha spray volume using a commercial farm sprayer. Spray timing was at seed maturity (capsules yellow brown, seeds light brown), crop GS85 (Smith and Froment, 1998). Normally, commercial harvesting would be expected to take place 10–20 days later. Linseed plants were sampled from each plot by hand. Plant stems were cut beneath the lowest capsule. The harvested material was laid out in
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
trays and oven dried for 12 h at 40°C. The linseed plants were threshed by hand and then cleaned using a ‘Clipper’ seed cleaner (Blount/FerrellRoss, Bluffton, IN). The cleaned seed was then allowed to air dry on the laboratory bench. From each sub plot, 2–6 m2 of harvested material was sampled. The entire sub plot was required at the later sampling dates to provide sufficient seed material for crushing, although this was not achieved at later sampling dates due to crop deterioration.
203
2.3. Pressing of linseed Linseed seed samples from both studies were taken to Statfold Seed Oil Developments, Tamworth, Staffordshire for cold pressing (no solvent extraction). Using a STATFOLD bench press, oil was extracted by expelling oil through a 5 mm aperture. The temperature of the press ‘cone’ was 46–50°C. A 50–100 ml sample of oil was collected for analysis.
2.4. Oil analysis 2.2. Linseed sur6ey, study 2 Seed samples were collected from existing variety comparison experiments harvested in 1997. These included sites at Winchester, Cambridge and Abbots Ripton in England and Inverness in Scotland. The seed material included winter linseed, spring sown industrial oil and fibre flax lines (see Table 1) (NIAB, 1998). At each site, a sample of :300 g of linseed was taken from the ex-combine sample collected for yield assessment. Crops were harvested at normal commercial harvest dates. There were differences in the crop husbandry at each site according to local practice, but all the crops were desiccated prior to harvest. No further cleaning of ex-combine samples was required. All samples were crushed and the resulting oils analysed in the same way as for study 1.
This was carried out at the laboratories of John Seaton, Hull. Total phosphorus was determined using the method described by Cock and Van Rede (1966). In this procedure 0.6 g of linseed oil was ashed with 0.03 g of magnesium carbonate. The ash was dissolved in 5 ml of hydrochloric acid and then neutralised using sodium hydroxide in a 100 ml volumetric flask. After the addition of 20 ml of reduction solution and 10 ml of ammonium molybdate the samples were placed in the dark for 20 min for the colour to develop. A 20 ml volume of sodium acetate was added and the solution was then made up with water. The absorbance of the solution at 720 nm was determined colourimetrically in a 1 cm cell and the result compared to that from a standard calibration graph. The non-hydratable phospholipids were determined by mixing 25 g of linseed oil with
Table 1 Location of sites and varieties evaluated in the linseed survey Site name
Supplier and location
Varieties
Type
Bridgets
NIAB, Winchester, UK
Antares Barbara Mikael Klasse Laura
Spring Spring Spring Spring Spring
Abbots Ripton
Semundo, Huntingdon, UK
Barbara Oliver
Spring oil Winter oil
Cambridge
NIAB, Cambridge, UK
Barbara Klasse Laura
Spring oil Spring sown fibre flax Spring sown fibre flax
Inverness
SAC, Inverness, UK
Oliver
Winter oil
oil oil oil sown fibre flax sown fibre flax
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
204
Table 2 Total, hydratable and non-hydratable phospholipid content (log transformed) of linseed from misting experiment Sample date
Total
Hydratable
Non-hydratable
Misted
Non-misted
Misted
Non-misted
Misted
Non-misted
Desiccated 26 August 28 August 2 September 4 September 9 September 11 September
1.78 1.72 2.11 1.68 2.14 2.40
1.95 1.98 1.33 1.91 1.68 2.42
1.42 1.59 2.00 1.45 2.08 2.38
1.91 1.97 1.33 1.73 1.66 2.42
0.80 0.81 1.02 1.29 0.90 1.00
0.39 0.53 0.00 0.71 0.11 0.54
SEM (20df)
0.482
Not desiccated 7 September 1 October
0.576
1.77 1.69
75 ml of water. The mixture was spun in a centrifuge at 2000 rpm for 60 min. Two to three grams of the oil was then analysed by the normal method. Hydratable phospholipids were calculated from the difference between total and nonhydratable phospholipids.
2.5. Statistical analysis Individual plot data from study 1 on the total, hydratable and non-hydratable phospholipid contents were analysed using ANOVA (Genstat). No analysis of the unreplicated data for study 2 was undertaken.
3. Results
3.1. Misting experiment, study 1 Misting began on the 15 August. The first sample from misted and non-misted sub plots was taken on 22 August, 20 days after desiccation, but this was rejected due to mould development during drying. Further samples were taken on 26 and 28 August and on 2, 4, 9 and 11 September. The ‘normal’ harvest date for the non-desiccated, nonmisted treatments was 7 September and the ‘late’ harvest date was on 1 October.
0.446
1.66 1.14
0.66 0.96
There was 52.8 mm of rainfall in August and 11.2 mm in September. August rainfall was evenly distributed with significant (\ 4 mm) daily rain events on six occasions before sampling commenced in late August. Visible sprouting in misted treatments was first observed on 26 August. On 28 August (second sampling date) there was 2% sprouting which increased to 10% by 2 September (third sampling date). The overall level of visible sprouting did not increase from this level (fourth to sixth sampling dates). There was no visible sprouting on non-misted plots. The level of non-hydratable phospholipids, which have been associated with production line hold ups, were always higher in the misted (16 ppm) than non-misted samples (2 ppm), but levels as a proportion of total phospholipids were very low. Overall, mean total phospholipid content was greater in the non-misted samples (286 ppm) than misted samples (172 ppm) and increased dramatically between the two final sample dates, peaking at 702 and 467 ppm, respectively. However, there were large variations in phospholipid content and inspection of the raw data indicated that transformation was justified. The data was log transformed and re-analysed. A summary of the log transformed data is shown in Table 2.
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
205
Fig. 1. Total phospholipid content (ppm) of seed collected from linseed survey.
Phospholipid content of the desiccated misted and non-misted linseed increased between the fifth and sixth sampling dates, but overall there was no significant difference between treatments for the log transformed means. Phospholipid content at the final sampling date was, however, consistently greater at the final sampling date than for any other dates. In contrast, the phospholipid content at the final sampling date of the desiccated, misted or non-misted treatments was higher at 584 ppm than that from the non-desiccated samples taken at the same date of 170 ppm. Additionally, the level of total phospholipids in the non-desiccated treatment remained consistently low, even when harvest was delayed until 1 October, 3 weeks after the normal harvest date.
high at the Aberdeen site (685 ppm) and in a single variety, Laura (473 ppm), at Cambridge. However, whilst Laura recorded the highest total phospholipid content at Cambridge, at Bridgets it gave the lowest total phospholipid content of all the varieties compared. Levels of non-hydratable phospholipids (Table 3) were low in all the samples analysed. A visual assessment of all the seed samples collected for the survey suggested that they were Table 3 Hydratable and non-hydratable phospholipid content (ppm) of linseed collected from survey Site
Variety
Phospholipids (ppm) Hydratable
3.2. Linseed sur6ey, study 2 Oil analysis results from seed samples collected from different varieties and sites are shown in Fig. 1 and Table 3. Due to the unbalanced nature of the sample set no statistical analysis was undertaken, but there were differences both between sites and between varieties at individual sites. Total phospholipid contents were highest at Bridgets (Fig. 1), the five varieties compared averaged 670 ppm, but there were also large differences between varieties at this site, which ranged from 43 to 1436 ppm. Total phospholipids were also
Non-hydratable
Bridgets Bridgets Bridgets Bridgets Bridgets
Antares Barbara Klasse Laura Mikael
1262 225 1429 67 507
4.3 0.0 7.4 0.0 0.0
Cambridge Cambridge Cambridge
Barbara Klasse Laura
43 61 473
0.0 0.0 0.0
Abbots Ripton Abbots Ripton
Barbara Oliver
71 46
0.0 0.0
Aberdeen
Oliver
675
10.6
Inverness
Oliver
285
0.0
206
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
in good condition. However it is noteworthy that the actual harvest at the Bridgets site was delayed by about two weeks after crop maturity, due to rain. This site recorded the highest levels of total phospholipids.
4. Discussion Results from the misting experiment suggested that delayed harvesting increased total phospholipid content and that this effect was occurring in both non-misted and misted treatments, both of which had been desiccated. Although the increase in total phospholipid content between sampling dates was not significant, they were consistently high, additionally the absence of such an increase in non-desiccated plots suggests that the change was related to physiological changes in the seed associated with germination and sprouting in the capsule. Crop desiccation had taken place 28 days previously, allowing plenty of time for drying and fracturing to occur in the capsule wall, presumably allowing ingress of water into the capsule leading to more rapid sprouting in desiccated plots. Such effects have been observed in other experiments using crop desiccants (Froment, 1993). There was an absence of visible sprouting in the non-misted plots, despite an increase in total phospholipids. This is not a surprising result, as seed samples were dried, threshed and cleaned prior to crushing, a process which removed those seeds which were in the most advanced stages of sprouting. It is likely that the same biological processes were taking place in both treatments, albeit at slightly different rates, the sample process merely narrowing the measured treatment differences. Non-hydratable phospholipids, which cause the greatest processing problems, were always greatest in the misted seed samples, although this difference was not significant due to sample variability. It cannot therefore be concluded from these results that non-hydratable phospholipids increased with misting. It was evident however, that seed sample quality declined with later harvests, as did oil recovery. A standard seed crushing method
was adopted for all samples in this experiment, but it is possible that modifying this process to maximise oil recovery would significantly affect the quality of the resulting oil. The results from the survey of linseed samples supported the findings of the misting experiment. The high total phospholipid content of the Bridgets seed samples can be explained by the delayed harvest due to wet weather. The Bridgets seed samples were dull in appearance having lost the traditional lustre of seed harvested in dry conditions. Results for the variety Laura at the Bridgets and Cambridge sites suggest that there was no simple relationship between variety and phospholipid content. The physiological status of the crop related to timing of desiccation, weather conditions and normal maturity date are likely to explain these effects. Aspects of oil quality, such as phospholipid content, are important to processors and farmers, although price premiums are poorly related to quality in the UK due to the economic support regime adopted in the EU. The results from this study suggested that crop desiccation and perhaps variety choice can influence oil quality by their impact on the risk of sprouting in the crop. Therefore, appropriate use of desiccants related to timely harvesting by farmers should contribute to the aim of maintaining the quality of UK linseed oil. If relationships between field measurements such as visible or incipient sprouting could be identified this would aid both farmers and their buyers to identify potentially problematic supplies. It may then be possible to manage these samples using appropriate drying or crushing processes to maximise quality and maintain the consistent quality of oil from the UK crop.
5. Conclusion This study has shown that the phospholipid content in linseed oil varies between varieties and sites and that delayed harvesting and desiccation appear to be important aspects influencing these changes, either directly or indirectly due to their effects on sprouting.
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Acknowledgements The financial support of the Sugar, Tobacco, Oilseeds and Pulses Division of the UK Ministry of Agriculture Fisheries and Food who funded this research is gratefully acknowledged. Thanks are also due to NIAB, Semundo and SAC, who provided linseed for pressing and Martin Collins for laboratory analysis of the oil.
References Anonymous, 1996. Pesticide Usage Survey Report 141. In: Thomas, M.R., Garthwaite, D.G., Banham, A.R. (Eds.), Central Science Laboratory, Sand Hutton, York, YO4 1LZ.
.
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Ansell, G.B., Hawthorne, J.N., Dawson, R.M.C. 1973. Form and Function of Phospholipids. BBA Library, vol. 3, 2nd ed. Elsevier Scientific Publishing Company, Amsterdam. Cock, L.V., Van Rede, C. 1966. Determination of Phosphorus in Oil. The Laboratory Handbook for Oil and Fat Analysis. Academic Press, London, pp. 137 – 142. Froment, M.A., 1993. Effects of desiccants on seed yield and plant dry matter in linseed, Linum usitatissimum: tests of agrochemicals and cultivars no. 14. Ann. Appl. Biol. 112 (Suppl.), 100 – 101. Lehninger, A.L. 1970. Biochemistry, The Molecular Basis of Cell Structure and Function: Lipids, Lipoproteins and Membranes. Worth Publishers, New York, chapter 10, pp. 189 – 215. NIAB, 1998. UK Descriptive List for Linseed. National Institute of Agricultural Botany, Cambridge, UK. MAFF, 1997. Linseed areas in the UK. MAFF Statistics Branch. Peasholme Green, York, UK. Smith, J., Froment, M.A., 1998. A growth stage key for winter linseed Linum usitatissimum. Ann. Appl. Biol. 133, 297 – 306.
Influence of environmental and agronomic factors contributing to increased levels of phospholipids in oil from UK linseed Linum usitatissimum M.A. Froment a,*, J. Smith a, K. Freeman b a
ADAS Bridgets Research Centre, Martyr Worthy, Winchester SO21 1AP, UK b John L. Seaton and Co. Ltd., Bankside, Hull HU5 1RR, UK Accepted 19 May 1999
Abstract High levels of phospholipids in linseed oil result in production line hold-ups due to gum formation in machinery during processing and irreversible cloudiness when high phospholipid oil is left to stand. Specific problems with oil from UK crushed linseed were experienced by linseed oil refiners in both the 1993 and 1997 seasons. The 1993 harvest was characterised by wet conditions suggesting that enhanced phospholipid content may be associated with weather damage which was reported in some linseed crops in that year. A study was undertaken to investigate the effect of agronomic factors which may influence phospholipid content. In a replicated field experiment spring linseed cv. Barbara, which had been desiccated with diquat, was sequentially harvested at six timings from both rainfed plots and others which were misted during the seed filling stage. Additional plots which had not been desiccated were also sampled at a normal, early September and late October harvest date. Seed samples were crushed and the resulting oil was analysed for total, hydratable and non-hydratable phospholipid contents. Mean total phospholipid contents were greater in non-misted plots than misted plots and increased dramatically between the final harvest dates, however, there were large variations in total phospholipid content for individual treatments. Desiccation of linseed is standard practice in the UK, but total phospholipid content of the non-desiccated samples taken in early September were low at 170 ppm and did not increase despite a further harvest delay of 3 weeks. The level of non-hydratable phospholipids, which are not removed during normal processing and cause the most difficult production problems, were unaffected by delayed harvest date, but they were always greater in the misted, compared to non-misted treatment. An additional study of unreplicated seed samples collected from a range of sites and varieties indicated a large variation in total phospholipid content from 43 to 1436 ppm. The highest levels were reported at one site where the harvest was delayed past physiological maturity by wet weather. Results from these studies suggest that crop desiccation, which causes drying and fracturing of the capsule wall, allowing water ingress, could increase the risk of increased phospholipid content in linseed if wet weather delays harvest. Variety choice may also be important, but at individual sites. © 1999 Elsevier Science B.V. All rights reserved.
* Corresponding author. Tel.: + 44-1962-779-765; fax: + 44-1962-779-739. E-mail address: martin – [email protected] (M.A. Froment) 0926-6690/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 6 - 6 6 9 0 ( 9 9 ) 0 0 0 2 4 - 2
202
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
Keywords: Linseed; Linl11um usitatissimum; Phospholipids; Oil; Agronomy
1. Introduction The United Kingdom is the EU’s major producer of linseed, with :4000 growers farming 60 000–70 000 ha (MAFF, 1997), down from its peak in 1993 of 160 000 ha. UK linseed supplies both home and export markets where it must compete in terms of consistency of supply and quality, as well as price, if it is to remain competitive with imported supplies. High levels of phospholipids in linseed oil result in production line hold-ups due to gum formation in machinery during processing and irreversible cloudiness when high phospholipid oil is left to stand. Phospholipids are naturally occurring compound lipids (a lipid containing a phosphate residue) which are commonly found in oilseed crops (Lehninger, 1970; Ansell et al., 1973). Specific problems associated with phospholipids in UK crushed linseed were identified in 1993, when phospholipid content increased from B 50 ppm to between 300 and 1000 ppm. There were further problems in 1997. The 1993 season was characterised by a wet harvest suggesting that enhanced phospholipid content may be associated with sprouting which was reported in some linseed crops in that year. Desiccation of spring linseed using diquat or glyphosate is routine practice in the UK (Anonymous, 1996) to ensure rapid crop desiccation as a harvest aid. This practice is favoured in more northerly areas where crop maturity is delayed by cooler growing conditions and where farmers wish to harvest crops before the risk of autumn rains. The cost of removing phospholipids from the oil is reduced if this can be identified at the crushing stage, so prior warning of general (weather) or specific (variety or crop management) factors relating to enhanced levels would improve the overall efficiency of the oil processing operation. A research study was undertaken to improve understanding of the problem and investigate possible causes for variation in the phospholipid content of UK linseed.
2. Material and methods
2.1. Misting experiment, study 1 Plots of spring linseed cv. Barbara were marked out in a commercial crop at the ADAS Bridgets Research Centre, Winchester, UK. A split-plot design was used with misting and no-misting on main plots and sample date on sub plots. Main plot and sub plot treatments were randomised within each of three blocks. Individual sub plots were 2 m× 3 m in size, with 12 sub plots per block providing six sequential sampling dates. Additional non-desiccated plots were abutted to each block and these were sampled at a ‘normal’ commercial harvest date, early September and at a ‘late’ October harvest date. Misting equipment was used to enhance the effects of normal rainfall and encourage sprouting in linseed on misted main plots. This was achieved by the use of ACCESS Girosprinklers (micro irrigation nozzles mounted on 0.8 m tall risers). Capsule wetness was controlled by use of an electronic timer. Plots were misted for 3× 1 h sessions per day from Friday to Tuesday. Each Wednesday and Thursday the crop was allowed to dry and it was sampled by hand on Fridays. Misting began on the 15 August. Water used for misting was taken from a potable mains water supply. Misted and non-misted main plots were desiccated with Reglone (Diquat, Zeneca, 500 g a.i./l) applied at 3 l/ha plus Agral wetter (non ionic) at 100 ml per 100 l of diluted spray. The desiccant was applied at a single timing on the 12 August at 300 l/ha spray volume using a commercial farm sprayer. Spray timing was at seed maturity (capsules yellow brown, seeds light brown), crop GS85 (Smith and Froment, 1998). Normally, commercial harvesting would be expected to take place 10–20 days later. Linseed plants were sampled from each plot by hand. Plant stems were cut beneath the lowest capsule. The harvested material was laid out in
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
trays and oven dried for 12 h at 40°C. The linseed plants were threshed by hand and then cleaned using a ‘Clipper’ seed cleaner (Blount/FerrellRoss, Bluffton, IN). The cleaned seed was then allowed to air dry on the laboratory bench. From each sub plot, 2–6 m2 of harvested material was sampled. The entire sub plot was required at the later sampling dates to provide sufficient seed material for crushing, although this was not achieved at later sampling dates due to crop deterioration.
203
2.3. Pressing of linseed Linseed seed samples from both studies were taken to Statfold Seed Oil Developments, Tamworth, Staffordshire for cold pressing (no solvent extraction). Using a STATFOLD bench press, oil was extracted by expelling oil through a 5 mm aperture. The temperature of the press ‘cone’ was 46–50°C. A 50–100 ml sample of oil was collected for analysis.
2.4. Oil analysis 2.2. Linseed sur6ey, study 2 Seed samples were collected from existing variety comparison experiments harvested in 1997. These included sites at Winchester, Cambridge and Abbots Ripton in England and Inverness in Scotland. The seed material included winter linseed, spring sown industrial oil and fibre flax lines (see Table 1) (NIAB, 1998). At each site, a sample of :300 g of linseed was taken from the ex-combine sample collected for yield assessment. Crops were harvested at normal commercial harvest dates. There were differences in the crop husbandry at each site according to local practice, but all the crops were desiccated prior to harvest. No further cleaning of ex-combine samples was required. All samples were crushed and the resulting oils analysed in the same way as for study 1.
This was carried out at the laboratories of John Seaton, Hull. Total phosphorus was determined using the method described by Cock and Van Rede (1966). In this procedure 0.6 g of linseed oil was ashed with 0.03 g of magnesium carbonate. The ash was dissolved in 5 ml of hydrochloric acid and then neutralised using sodium hydroxide in a 100 ml volumetric flask. After the addition of 20 ml of reduction solution and 10 ml of ammonium molybdate the samples were placed in the dark for 20 min for the colour to develop. A 20 ml volume of sodium acetate was added and the solution was then made up with water. The absorbance of the solution at 720 nm was determined colourimetrically in a 1 cm cell and the result compared to that from a standard calibration graph. The non-hydratable phospholipids were determined by mixing 25 g of linseed oil with
Table 1 Location of sites and varieties evaluated in the linseed survey Site name
Supplier and location
Varieties
Type
Bridgets
NIAB, Winchester, UK
Antares Barbara Mikael Klasse Laura
Spring Spring Spring Spring Spring
Abbots Ripton
Semundo, Huntingdon, UK
Barbara Oliver
Spring oil Winter oil
Cambridge
NIAB, Cambridge, UK
Barbara Klasse Laura
Spring oil Spring sown fibre flax Spring sown fibre flax
Inverness
SAC, Inverness, UK
Oliver
Winter oil
oil oil oil sown fibre flax sown fibre flax
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
204
Table 2 Total, hydratable and non-hydratable phospholipid content (log transformed) of linseed from misting experiment Sample date
Total
Hydratable
Non-hydratable
Misted
Non-misted
Misted
Non-misted
Misted
Non-misted
Desiccated 26 August 28 August 2 September 4 September 9 September 11 September
1.78 1.72 2.11 1.68 2.14 2.40
1.95 1.98 1.33 1.91 1.68 2.42
1.42 1.59 2.00 1.45 2.08 2.38
1.91 1.97 1.33 1.73 1.66 2.42
0.80 0.81 1.02 1.29 0.90 1.00
0.39 0.53 0.00 0.71 0.11 0.54
SEM (20df)
0.482
Not desiccated 7 September 1 October
0.576
1.77 1.69
75 ml of water. The mixture was spun in a centrifuge at 2000 rpm for 60 min. Two to three grams of the oil was then analysed by the normal method. Hydratable phospholipids were calculated from the difference between total and nonhydratable phospholipids.
2.5. Statistical analysis Individual plot data from study 1 on the total, hydratable and non-hydratable phospholipid contents were analysed using ANOVA (Genstat). No analysis of the unreplicated data for study 2 was undertaken.
3. Results
3.1. Misting experiment, study 1 Misting began on the 15 August. The first sample from misted and non-misted sub plots was taken on 22 August, 20 days after desiccation, but this was rejected due to mould development during drying. Further samples were taken on 26 and 28 August and on 2, 4, 9 and 11 September. The ‘normal’ harvest date for the non-desiccated, nonmisted treatments was 7 September and the ‘late’ harvest date was on 1 October.
0.446
1.66 1.14
0.66 0.96
There was 52.8 mm of rainfall in August and 11.2 mm in September. August rainfall was evenly distributed with significant (\ 4 mm) daily rain events on six occasions before sampling commenced in late August. Visible sprouting in misted treatments was first observed on 26 August. On 28 August (second sampling date) there was 2% sprouting which increased to 10% by 2 September (third sampling date). The overall level of visible sprouting did not increase from this level (fourth to sixth sampling dates). There was no visible sprouting on non-misted plots. The level of non-hydratable phospholipids, which have been associated with production line hold ups, were always higher in the misted (16 ppm) than non-misted samples (2 ppm), but levels as a proportion of total phospholipids were very low. Overall, mean total phospholipid content was greater in the non-misted samples (286 ppm) than misted samples (172 ppm) and increased dramatically between the two final sample dates, peaking at 702 and 467 ppm, respectively. However, there were large variations in phospholipid content and inspection of the raw data indicated that transformation was justified. The data was log transformed and re-analysed. A summary of the log transformed data is shown in Table 2.
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
205
Fig. 1. Total phospholipid content (ppm) of seed collected from linseed survey.
Phospholipid content of the desiccated misted and non-misted linseed increased between the fifth and sixth sampling dates, but overall there was no significant difference between treatments for the log transformed means. Phospholipid content at the final sampling date was, however, consistently greater at the final sampling date than for any other dates. In contrast, the phospholipid content at the final sampling date of the desiccated, misted or non-misted treatments was higher at 584 ppm than that from the non-desiccated samples taken at the same date of 170 ppm. Additionally, the level of total phospholipids in the non-desiccated treatment remained consistently low, even when harvest was delayed until 1 October, 3 weeks after the normal harvest date.
high at the Aberdeen site (685 ppm) and in a single variety, Laura (473 ppm), at Cambridge. However, whilst Laura recorded the highest total phospholipid content at Cambridge, at Bridgets it gave the lowest total phospholipid content of all the varieties compared. Levels of non-hydratable phospholipids (Table 3) were low in all the samples analysed. A visual assessment of all the seed samples collected for the survey suggested that they were Table 3 Hydratable and non-hydratable phospholipid content (ppm) of linseed collected from survey Site
Variety
Phospholipids (ppm) Hydratable
3.2. Linseed sur6ey, study 2 Oil analysis results from seed samples collected from different varieties and sites are shown in Fig. 1 and Table 3. Due to the unbalanced nature of the sample set no statistical analysis was undertaken, but there were differences both between sites and between varieties at individual sites. Total phospholipid contents were highest at Bridgets (Fig. 1), the five varieties compared averaged 670 ppm, but there were also large differences between varieties at this site, which ranged from 43 to 1436 ppm. Total phospholipids were also
Non-hydratable
Bridgets Bridgets Bridgets Bridgets Bridgets
Antares Barbara Klasse Laura Mikael
1262 225 1429 67 507
4.3 0.0 7.4 0.0 0.0
Cambridge Cambridge Cambridge
Barbara Klasse Laura
43 61 473
0.0 0.0 0.0
Abbots Ripton Abbots Ripton
Barbara Oliver
71 46
0.0 0.0
Aberdeen
Oliver
675
10.6
Inverness
Oliver
285
0.0
206
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
in good condition. However it is noteworthy that the actual harvest at the Bridgets site was delayed by about two weeks after crop maturity, due to rain. This site recorded the highest levels of total phospholipids.
4. Discussion Results from the misting experiment suggested that delayed harvesting increased total phospholipid content and that this effect was occurring in both non-misted and misted treatments, both of which had been desiccated. Although the increase in total phospholipid content between sampling dates was not significant, they were consistently high, additionally the absence of such an increase in non-desiccated plots suggests that the change was related to physiological changes in the seed associated with germination and sprouting in the capsule. Crop desiccation had taken place 28 days previously, allowing plenty of time for drying and fracturing to occur in the capsule wall, presumably allowing ingress of water into the capsule leading to more rapid sprouting in desiccated plots. Such effects have been observed in other experiments using crop desiccants (Froment, 1993). There was an absence of visible sprouting in the non-misted plots, despite an increase in total phospholipids. This is not a surprising result, as seed samples were dried, threshed and cleaned prior to crushing, a process which removed those seeds which were in the most advanced stages of sprouting. It is likely that the same biological processes were taking place in both treatments, albeit at slightly different rates, the sample process merely narrowing the measured treatment differences. Non-hydratable phospholipids, which cause the greatest processing problems, were always greatest in the misted seed samples, although this difference was not significant due to sample variability. It cannot therefore be concluded from these results that non-hydratable phospholipids increased with misting. It was evident however, that seed sample quality declined with later harvests, as did oil recovery. A standard seed crushing method
was adopted for all samples in this experiment, but it is possible that modifying this process to maximise oil recovery would significantly affect the quality of the resulting oil. The results from the survey of linseed samples supported the findings of the misting experiment. The high total phospholipid content of the Bridgets seed samples can be explained by the delayed harvest due to wet weather. The Bridgets seed samples were dull in appearance having lost the traditional lustre of seed harvested in dry conditions. Results for the variety Laura at the Bridgets and Cambridge sites suggest that there was no simple relationship between variety and phospholipid content. The physiological status of the crop related to timing of desiccation, weather conditions and normal maturity date are likely to explain these effects. Aspects of oil quality, such as phospholipid content, are important to processors and farmers, although price premiums are poorly related to quality in the UK due to the economic support regime adopted in the EU. The results from this study suggested that crop desiccation and perhaps variety choice can influence oil quality by their impact on the risk of sprouting in the crop. Therefore, appropriate use of desiccants related to timely harvesting by farmers should contribute to the aim of maintaining the quality of UK linseed oil. If relationships between field measurements such as visible or incipient sprouting could be identified this would aid both farmers and their buyers to identify potentially problematic supplies. It may then be possible to manage these samples using appropriate drying or crushing processes to maximise quality and maintain the consistent quality of oil from the UK crop.
5. Conclusion This study has shown that the phospholipid content in linseed oil varies between varieties and sites and that delayed harvesting and desiccation appear to be important aspects influencing these changes, either directly or indirectly due to their effects on sprouting.
M.A. Froment et al. / Industrial Crops and Products 10 (1999) 201–207
Acknowledgements The financial support of the Sugar, Tobacco, Oilseeds and Pulses Division of the UK Ministry of Agriculture Fisheries and Food who funded this research is gratefully acknowledged. Thanks are also due to NIAB, Semundo and SAC, who provided linseed for pressing and Martin Collins for laboratory analysis of the oil.
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