Pretreatment with microwaves and its effect on extracted oil quality from Milk thistle (Silybum marianum L.) seed from Iranian ecotype, namely Babak Castle

Application of novel technologies such as microwaves pretreatment of oil seeds might increase efficiency of oil extraction, a higher quantity of nutraceuticals, and a better oxidative stability of oil. In this study, Milk thistle seeds were pretreated with microwaves (800W) for two different times(2min and 4min), to investigate the process of enhancing oil extraction yield, physicochemical properties, tocopherols and fatty acids profile of milk thistle seeds oil extracted from Iranian ecotype, namely Babak Castle (in East Azarbaijan). To compare the results, oil was also extracted from non-treated Milk thistle seed by solvent as control sample. Results showed that microwave pretreatment of Milk thistle seed increased the oil extraction yield, Total phenolic content, and tocopherols of the oil extracted by solvent. Some physicochemical properties of seed oil such as chlorophyll content (1.03-1.91 mg pheophytin/kg oil) and saponification value (181-188 mg KOH/g oil) increased, but acid value (4.20-2.14 mg KOH/g oil), peroxide value (6.22-3.23 meq O2/kg oil), and iodine value (109-100 g I2/100g oil) decreased by treatment with microwaves. Microwave pretreatment of milk thistle seeds showed negligible influence on profile and the amount of fatty acids in obtained extracts, while among the fatty acids, oleic and linoleic acids decreased, but palmitic and stearic acids increased by treatment with microwaves. Moreover, the results showed that the longer pretreatment with microwaves resulted in slightly lower unsaturated fatty acids contents from Milk thistle seed oil. In conclusion, the results recognized microwaves pretreatment as a promising technique for intensification of oil extraction and tocopherols of oil from milk thistle seeds.