Influence of cold plasma and ultrasonication on the extraction efficiency and quality of oil from milk thistle seeds (Silybum marianum L)

Abstract

The current study was attempted to evaluate the effect of cold plasma (CP; 10 and 15 min) and ultrasonication (UT; 20 and 30 min) on the oil extraction efficiency (OEE) from Milk Thistle Seed (MTS) along with determining the quality parameters of the extracted oil, e.g. Rancimat oxidative stability, acidity value (AV), peroxide value (PV), total phenolic content and antioxidant capacity over storage times (1, 30 and 60 days, T:4 °C). Our results revealed that treatment of MTS by CP and UT increased the OEE up to 29% (15 min) and 24% (30 min), respectively. In addition, applying these treatments to oil extraction led to lower AV (CP:49%, UT:46%) and PV (CP:38%, UT:35%) following 60 days’ storage. Moreover, the oil of treated MTS had higher phenolic content (CP:74%, UT:66%) and antioxidant activity (CP:156%, UT:127%) compared to samples extracted without any treatment. Besides, applying CP for 15 min increased the amount of α-tocopherol (157%), while UT (30 min) reduced its content (76%). Also, examination of fatty acid profile showed that CP (15 min) increased linolenic acid (2.8%) and arachidonic acid (35%) and decreased oleic acid (1.66%) and linoleic acid (2.1%), whereas UT (30 min) increased linoleic acid (0.27%), linolenic acid (8%) and arachidonic acid (41%) and decreased oleic acid (2%) in final oil samples. To conclude, results of this study noticed that introducing CP and UT have remarkable capabilities to improve both the OEE and oil quality which could be beneficial from both economic and quality viewpoints for the industry.