engleski

Influence of conditioning temperature on the volatile profile of virgin rapeseed oil

Research from the past decade suggest that virgin rapeseed oils have higher nutritional value than the ones produced by cold pressing. Heating of the seeds prior the oil extraction increases the amount of bioactive compounds such as tocopherols, sterols and polyphenols. Furthermore, applying heat during conditioning of the rapeseed can have effect on the sensory characteristics of the produced oil. The aim of our study was to determine changes in volatile components caused by increase of the conditioning temperature during the production of virgin rapeseed oil. For this experiment oils were produced by using the expeller press after condition the seeds at 60, 80 and 100 °C for 30 minutes. Cold pressed oil was produced by pressing the unconditioned seeds. Isothiocyanates were the dominant volatiles of cold pressed rapeseed oil making more than 55% of total volatile components. Conditioning the seed at 60 °C increased isothiocyanates concentration due to enhanced myrosinase activity. Using higher temperatures (80 and 100 °C) caused myrosinase inactivation, consequently decreasing isothiocyanates concentration in these oils. Although isothiocianates were still dominant components of the oil produced after conditioning at 80 °C, their concentration were about 7, 5 times lower than in the oil produced at 60 °C. Increasing the conditioning temperatures to 80 and 100 °C caused higher concentrations of nitriles and epithionitriles because of the thermal decomposition of glucosinolates. So the dominant components of virgin rapeseed oil produced after conditioning at 100 °C were nitriles making 53% of total volatiles. As expected, concentrations of aldehydes and ketones increased with temperature and pyrazines and furan derivates were only present in oil produced at 100 °C. All oils produced for this experiment differed significantly in volatile profile, indicating that optimizing the conditioning process can enable production of virgin rapeseed oil of a different and very specific sensory characteristics.

rapeseed oil; conditioning; volatile components

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