Supercritical Fluid Extraction of Bilberry Seed Oil

Abstract

Supercritical fluid extraction is an extraction technique that utilizes solvents in its supercritical state, a state in which the solvent acts as a liquid and a gas simultaneously, resulting in a more efficient extraction process compared to conventional extraction techniques. The most commonly used solvent is carbon dioxide. Carbon dioxide has benefits of being inexpensive, non‐toxic and reaches its supercritical state at relatively moderate conditions of 74 bar pressure and 31°C. Extraction of oil from the oil‐rich bilberry seed utilizes a by‐product from the berry production with the goal to produce a new product with use in the food, pharmaceutical or cosmetic industry. In this thesis, extractions were performed with both laboratory scale and pilot scale equipment to assess how the process conditions affect the oil yield and quality. Optimal yield was determined by the use of a full factorial experimental design investigating the influence of pressure, temperature and particle size. Oil quality from the different extraction experiments was evaluated with respect to thermal and oxidation stability while storing the oil in different environments. The yields from the laboratory scale experiments corresponded well with previous studies using other raw materials, where high pressure combined with high temperature gave the highest yield. Results from the pilot scale extraction were inconclusive due to operational difficulties. Oil from the pilot scale was used to assess stability and quality during storage. Cold storage was most successful in preventing oxidation of the oil while addition of antioxidants unexpectedly accelerated oxidation. The thermal stability of the oil did not change significantly during storage. However, a slight decrease was observed for the oil with added antioxidants. Meanwhile, oil extracted at 60°C showed a significantly improved thermal stability compared to the oil extracted at 35°C, that might be due to a change in the oil composition. This thesis has provided useful data on how to optimize the extraction process and developed promising methods to evaluate the oil’s quality for future research.