Microwave pretreatment as a promising strategy for increment of nutraceutical content and extraction yield of oil from milk thistle seed

Abstract

In this study, seeds of Milk thistle (Silybum marianum L.) as a biomedical plant were pretreated with microwaves (800 W) for 2 and 4 min, to evaluate the process of intensifying oil extraction efficiency, physicochemical properties, nutraceuticals content, and fatty acids profile of milk thistle seeds oil extracted from Iranian ecotype, Khoreslo. Results showed that microwave pretreatment of Milk thistle seed increased the oil extraction yield (by 6%), total phenolic content (by 12.2%), phytosterols (by 25%), and tocopherols (by 37.5%) of the oil obtained by solvent. Some physicochemical properties of seed oil such as chlorophyll content (0.55–1.73 mg pheophytin/kg oil) and saponification value (179–187 mg KOH/g oil) increased, but acid value (4.24−2.16 mg KOH/g oil), peroxide value (5.11−2.09 meqO2/kg oil), iodine value (107−99 g I2/100 g oil), and the poly unsaturated to saturated fatty acids (PUFA/SFA) ratio of all samples decreased by treatment with microwaves. Moreover, the α, β, γ-, δδ -tocopherols, and phytosterols content such as cholesterol, campesterol, stigmasterol, cleroesterol, β-sitosterol, and Δ7-sterol of milk thistle seed oils increased by microwaves treatment. In conclusion, the results indicated that microwave pretreatment is a promising strategy for amplification of oil extraction yield and the content of nutraceuticals in obtained oil from milk thistle seeds.