Effects of Household Processing on Rutin and Fagopyrin F in Common and Tartary Buckwheat

Buckwheat contains rutin, a flavonoid, and fagopyrin F, a photosensitizer. This study compared household processing methods to determine how fagopyrin F content could be reduced while limiting rutin loss. Common and Tartary buckwheat (CB and TB) grains were processed using seven household methods: boiling, steaming, microwave heating, pan roasting, oven heating, deep frying, and air frying. Extractable phenolic and total flavonoid contents were determined colorimetrically; rutin and fagopyrin F were quantified by ultra-performance liquid chromatography with ultraviolet detection and tandem mass spectrometry, respectively. In CB, steaming and several dry-heating treatments increased the measured rutin content. In TB, microwave heating for 120 s, oven heating at 180 °C for 5 min, and air frying at 180 °C for 5 min maintained rutin at 95.7-105.9% of the control. All treatments reduced measured fagopyrin F content. The largest reductions occurred after medium-flame pan roasting, oven heating at 200 °C, deep frying at 190 °C, and air frying at 180-200 °C. Under corresponding processing conditions, the relative decrease in fagopyrin F was greater in CB than in TB. The rutin-to-fagopyrin F ratio increased under all calculable conditions. These results provide a basis for selecting processing conditions that reduce fagopyrin F with limited rutin loss.