The Effect of Seed Pretreatment and Extraction Conditions on the Amount of Minor Components in Seed Oils II. Chlorophyll and Related Pigments

A large number of samples of rapeseed have been analysed for chlorophyll content, using various solvents and extractors. The moisture content of seeds was varied in hexane extraction of unheated seeds as well as “cooked” seeds (heat treated in a closed vessel). The results obtained indicate a marked influence of the nature of the solvent on the absorbance at 670 nm (strongly correlated to total chlorophyll); chloroform‐methanol (3 : 1, v/v) giving the highest values. Further, the “cooking” process markedly increased the value of A 670 when hexane was used as an extraction agent. The character details of the “chlorophyll” absorbance spectrum (chlorophylls and pheophytins) was also influenced by the extraction conditions. The data presented indicate that the hexane solution of the oil has to be evaporated with care and the oil stored in the dark if not immediately analysed in a photometer. The binary solvent mixture heptane/ethanol (3:1, v/v) was found to be very appropriate since the extract could be used both for the gravimetric determination of oil content and the photometric determination of the chlorophyll content of the oil. The absorbance maximum for the green pigment mixture varied slightly with the seed sample, but a majority of the samples had absorbance maximum at 667 nm. A method for the semi‐quantitative determination of the ratios of chlorophyll to pheophytin has beed devised. High quality rapeseed had predominantly chlorophyll whereas low‐quality seeds (mould‐infested, heat‐damaged etc.) had more of pheophytin than of chlorophyll. Based on these studies a highly automatic system for the simultaneous analysis of oil content and chlorophyll content, capable of handling several hundreds of rapeseed samples daily has been developed.