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

2019, Industrial Crops and Products

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 meqO 2 /kg oil), iodine value (107−99 g I 2 /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-, δ δ-tocopherols, and phytosterols content such as cholesterol, campesterol, stigmasterol, cleroesterol, βsitosterol, 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. shown cholesterol and blood pressure lowering activity, anti-proliferative activity against cancer cells, and chemo-protective activity (Pepping, 1999; Talbott and Hughes, 2007). Milk thistle seeds have a relatively high content of oil (26-31%). Considering this point, it is needed to remove the oil from seed before the extraction of silymarin. Actually, the oil is considered as a by-product of silymarin production (Fathi-Achachlouei and Azadmard-Damirchi, 2009). Milk thistle seed oil as a suitable edible oil contains long chain fatty acids (C16-C24), phytosterols such as campesterol, cleroesterol, stigmasterol, Δ-sterol and β-sitosterol, and it is also rich in vitamin E (