Abstract
This study investigated the effects of novel extraction technologies, including ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), pulsed electric field (PEF), high-pressure processing (HPP), enzyme-assisted extraction (EAE), and conventional extraction, on the recovery of phenolic compounds and associated antioxidant properties from buckwheat hull (Fagopyrum esculentum). Initially, twenty-four extraction strategies were investigated. Based on the results of the total phenolic content and antioxidant properties (DPPH and FRAP), twelve strategies (i.e., US (n = 2), PEF (n = 1), MW (n = 4), HPP (n = 4), and a control method) were selected for phenolic profiling carried out using liquid chromatography-mass spectrometry (LC-MS). Forty-one phenolic compounds were identified in the extracts, and a scanning electron microscope (SEM) analysis was also carried out on the treated residues to analyze the surface damage post-treatments. The results showed that samples treated with US (16.14 ± 0.06), PEF (9.94 ± 0.02), MW (12.63 ± 0.13), and HPP (21.76 ± 0.78) contained the highest total phenolic content (mg GAE/100 mg of DW). In the case of the antioxidant activities, the highest DPPH activities were obtained using HPP, MAE, and UAE, while no clear pattern was recorded in the case of FRAP activities. The highest DPPH and FRAP activities observed were 80.91 ± 0.22% and 23.98 ± 0.2 mg Trolox equivalents/100 mg, respectively. Additionally, the LC-MS results identified eleven different groups of phenolic compounds in buckwheat hull extracts, including anthocyanin, flavanol, flavanones, flavones, flavonol, phenolic acids, isoflavones, lignans, and quinones.