Abstract: This study elucidated the mechanism by which ultrasonic treatment (at 20 kHz and 2 400 W for 20 min) enhanced the synthesis and stability of phenolic compounds in tender coconut water (TCW) during storage. Integrated metabolomic and transcriptomic analysis revealed that ultrasound indirectly regulated gene expression in coconut flesh to promote polyphenol synthesis in TCW. Ultrasonic treatment significantly increased the contents of total phenolic (up to 1.38-fold) and total flavonoid (up to 1.36-fold), while enhancing the antioxidant capacity. Targeted metabolomics identified significant upregulation of key phenolic compounds including catechin, epicatechin, luteolin, and anthocyanins. Transcriptomic analysis showed that ultrasound induced the expression of core phenylpropanoid and flavonoid biosynthesis genes (COMT, 4CL, CHS, F3H, and DFR), particularly on the 6th day of storage. A strong correlation was observed between gene expression and metabolite accumulation, confirming that ultrasound promoted phenolic biosynthesis by indirectly regulating gene expression in coconut flesh. These findings suggest that ultrasound, as a non-thermal processing technology, holds great promise for maintaining the nutritional quality of TCW during storage.

Key words: tender coconut water; ultrasound treatment; post-harvest preservation; metabolomics; transcriptomics