CONCLUSIONS
Silflower oil was extracted from unhulled silflower seeds with hexane
and compared with the oil extracted from unhulled sunflower seeds. The
oil content in unhulled silflower seeds was 15.2 % (w/w), and its fatty
acid composition was very similar to that of sunflower oil. Silflower
oil had high contents of TPC (12.35%, w/w), total phenolics (1.12 mg
GAE/g oil), and chlorophyll (1002.8 mg/kg). It should be noted that it
had a high squalene level (4.89%, w/w, isolated yield) indicating its
potential application as a new plant source of squalene. Crude silflower
oil had lower radical scavenging activity and oxidative stability than
crude sunflower oil as indicated by ABTS assay, OSI, and TGA. The
chlorophyll level of silflower oil was lowered, but still high (725.5
mg/Kg) after refining by a general refining process involving degumming,
alkali refining, and bleaching with Fuller’s earth. The oxidative and
thermal stabilities of silflower oil decreased after the refining
process.
Further treatments with bentonite, sepiolite, and Tonsil® significantly
lowered the chlorophyll level to 4.2, 474.5, and 38.5 mg/kg,
respectively. Some aspects of oxidative stability improved by these
bleaching agents. For example, the ABTS assay increased by treatments
with bentonite and Tonsil®, the OSI slightly increased by Tonsil®, and
the thermal stability determined by TGA increased by all three bleaching
agents.
More studies should be conducted to understand the factors affecting the
oxidative stability of silflower oil and to further improve the oil
quality. Oils from unhulled and hulled seeds may have different
properties, crop year and harvest time may affect the level of
chlorophyll, and different extract methods may result in different oil
properties. With the given seeds and the oil extracted under the
experimental conditions used in this study, it could be concluded that
silflower oil, which can be produced from the perennial plant with many
advantages such as higher drought tolerance and less tillage required,
has a great potential as a new edible oil. This study also found that
silflower oil can be a great plant source of squalene.