Influence of environmental and agronomic factors contributing to increased levels of phospholipids in oil from UK linseed Linum usitatissimum

Abstract

Listen

Translate article

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 survey results indicate this may be linked to the relationship between physiological maturity and weather conditions at individual sites.