Effect of Ultrasound or Microwave-Assisted Germination on Nutritional Properties in Flaxseed (Linum usitatissimum L.) with Enhanced Antioxidant Activity

Germination and physical field treatments were effective methods to change the content of active substances in flaxseed, but their combined effects have been seldom investigated. The present study characterizes the influence of germination on lignan, tocopherol, phytosterol, fatty acids, and total fat in flaxseed. It was observed that 18–24 h of germination caused increases in γ-tocopherol, campesterol, stigmasterol, and sitosterol contents by 24.47, 12.66, 16.72, and 9.73%, respectively. With the noticeable reduction in total fat content, linolenic acid, oleic acid, and linoleic acid significantly decreased at 24 h germination. The secoisolariciresinol diglucoside peaked at 10.44 ± 1.00 mg g–1 dry weight after 6 h germination, which was an increase of 20.78% compared to nongerminated flaxseed. Furthermore, the combined effects of ultrasound or microwave and germination on the lignan and antioxidant activity were explored. The diphenyl-2-picrylhydrazyl free-radical scavenging rate of the lignan extract was significantly improved by the ultrasonic pretreatment at 60 W for 10 min or microwave at 130 W for 10 s in germinated flaxseed. The results revealed the positive impact of short-term germination on the active substances in flaxseed and indicated that the combined effect of germination and physical field treatments were effective approaches to improve the nutritional quality of flaxseed.