Ougan juice debittering using ultrasound-aided enzymatic hydrolysis: Impacts on aroma and taste

The optimal sonication conditions (40 kHz, 80 W/L and 60 min) during Ougan juice debittering by Aspergillus niger koji extract were established. Enzymatic hydrolysis degrees of naringin and limonin were enhanced to 89.90% and 36.16%, and enzymatic hydrolysis time was shortened by 33%. Sonication significantly enhanced activities of alpha-L-rhamnosidases, beta-glucosidases and limoninases from A. niger koji extract and facilitated break of C-O bonds in naringin (p < 0.05). These accounted for the enhanced enzymatic hydrolysis degrees and velocities of bitter compounds. Meanwhile, sonication lowered 40%, 7% and 21%, 13%, 11%, 25% of bitter, sour tastes and green, citrus-like, floral, woody notes, but enhanced 18% and 15% of fruity and sweet notes, resulting in 38% and 33% increases in over-all taste and aroma scores. Lowered levels of bitter compounds, organic acids, green, citrus-like, floral, woody aroma compounds and enhanced levels of fruity, sweet aroma compounds caused by sonication accounted for the flavor improvements.

Automated summary

The optimal sonication conditions were established for debittering Ougan juice using Aspergillus niger koji extract, enhancing enzymatic hydrolysis and reducing bitter compounds. Sonication improved enzyme activities, decreased bitter and sour tastes, while increasing fruity and sweet notes, resulting in overall taste and aroma improvements.