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Keywords:

  • Bleaching;
  • Camellia oil;
  • Quality;
  • Volatile profile

Abstract

Bleaching is a necessary step in the production of refined camellia oil (Camellia oleifera Abel) since crude oil has a dark brown color, due to pigments extracted from the seed coat during pressing, which is unacceptable to consumers. In order to understand the quality change and oxidative state of camellia oil in the bleaching step, measurements of various quality parameters, i.e. peroxide value (POV), free fatty acids (FFA), UV absorbance, and the volatile profiles of crude and bleached oils, were carried out. The results showed that FFA, K270, and K232 increased, whereas POV decreased, with increase of the activated earth dosage of 0–4% and of bleaching time from 0 to 40 min at 110 °C. As the amount of activated earth was increased from 0 to 4% with bleaching at 110 °C for 30 min, various classes of volatile compounds increased in concentration: aldehydes (23.7 µg/g), alcohols (13.2 µg/g), esters (8.0 µg/g), alkenes (2.0 µg/g) and ketones (1.9 µg/g). Likewise, when bleaching was carried out at 110 °C with 3% activated earth and the bleaching time varied between 0 and 40 min, the concentrations of volatile compounds also increased: aldehydes (27.7 µg/g), alcohols (18.2 µg/g), esters (7.3 µg/g), ketones (3.2 µg/g) and alkenes (0.6 µg/g). These findings indicate that hydroperoxides in the oil were decomposed into lower-molecular-weight products in the process of bleaching and that the extent of this decomposition can be controlled by time and amount of activated earth.