EFFECT OF SEED DEHULLING ON SENSORY AND PHYSICAL-CHEMICAL QUALITY AND NUTRITIONAL VALUE OF COLD-PRESSED RAPESEED OIL

Rapeseed of '00' cultivars is the main oleaginous material processed on an industrial scale in Poland. Rapeseed contains about 40 - 45 % of fat and 20 -25 % of protein. The content of hulls in the seeds varies from 10.5 % to 20 % depending on the cultivar. The dehulling of seeds causes the content of proteins to increase and the content of fibre to decrease in the rapeseed meal, and, at the same time, the colour and quality of the extracted oil to improve. The objective of this research study was to determine the effect of dehulling rape seeds on the efficiency of cold pressing process of rapeseed oil as well as on its sensory and physical-chemical quality and nutritional value. The experimental material consisted of cultivated rape seeds of `Monolit' and 'Bojan' cultivars. The dehulling of seeds was carried out in a disk hulling machine: Oils were pressed using a 'Farmer oil expeller for cold pressing. It was proved that the dehulling of rape seeds impacted the sensory quality and colour of oils produced, decreased their nutritional value, and increased of pressing efficiency. Statistically significant differences were reported in the basic quality parameters, i.e. acid and peroxide values of oils from the dehulled and whole seeds of the 'Monolit' cultivar. However, no such differences were reported in the case of oils from the `Bojan' seeds. The oils produced from the whole and dehulled seeds of the two cultivars did not statistically significantly differ as regards the anisidine value, UV absorbance (K232 and K268), and oxidative stability measured using the Rancimat test. In the oils from dehulled seeds, it was found that the percentage content of saturated and polyunsaturated fatty acids was slightly lower and the percentage content of monounsaturated fatty acids was higher. On the other hand, the content of total tocopherols was significantly lower in the oils from the seeds of both the `Monolif cultivar (54.6 from the dehulled seeds and 59.2 mg/100 g from the whole seeds) and the `Bojan' cultivar (56.9 and 62.7 mg/100 g, respectively).