Influence of hull and impurities in the seed on sensory quality of cold-pressed oleic type sunflower oil

Abstract

Cold-pressed oils are characterized by specific sensory characteristics, especially the odour and taste of the original raw material, making it completely different from the refined one. Beside the type of materials, the quality of oil obtained by cold pressing is influenced by many other factors, such as quality of raw materials, processing technology, the hull, or impurities (foreign matter) content in the material for pressing, oil storage conditions, etc. In order to prolong the expiry date of the oil, breeders make constant efforts to create hybrids with modified fatty acid composition, i.e. with high oleic acid content. Different portions of the hull (0-20%) and impurities of organic matter (0-10%) in the material for pressing influence the sensory quality of cold-pressed oleic type sunflower oil, in which the content of oleic acid was 83.32%. Sensory evaluation was carried out by three member panel of experienced tasters. Effect of the hull and impurities on the colour of oil has been investigated by spectrophotometric measurement at 455 nm transparency in relation to carbon tetrachloride and the determination of pigment content: total carotenoids and total chlorophylls. The total score for the sensory quality of oils ranged from 14 to 23 (maximum score was 25). The carotenoids content in tested samples ranged from 2.86 to 9.48 mg kg-1, and chlorophylls content from 0.00 to 3.15 mg kg-1. Between the values of transparency and total carotenoids content, there was a negative correlation with a high correlation coefficient (R2>0.9). The presence of high quantities of hull and impurities in the material for pressing has a very negative influence on sensory quality of oils obtained by pressing with the screw press. This influence is, in a far greater extent expressed in the aroma of oils (odour and taste) than in his appearance and colour. The presence of hull and impurities increase the content of total carotenoids and chlorophylls in the oil, and thus the reduction of transparency.