Impact of ultrasound on the quality of tender coconut water during storage revealed by LC-MS-based metabolomics, HS-SPME-GC-MS and E-tongue

Tender coconut water (TCW) refers to the liquid endosperm of coconut developed in 6-9 months, which is prone to deterioration during postharvest storage. This study explored the impact of ultrasound (20 kHz, 2400 w and 20 min) on the quality of TCW during postharvest storage. Results showed that ultrasound was effective in preserving the quality of TCW. Especially at the end of storage (15 d), TSS value was increased by 18.38%, titratable acid was increased by 25.17%, turbidity was decreased by 10.58%, and soluble sugar and reducing sugar content were increased by 23.36% and 45.77%, respectively. According to HS-SPME-GC-MS results, a total of 28 volatile organic compounds were identified and the content of volatile organic compounds in TCW showed no significant difference before and after ultrasonic treatment. The E-tongue data demonstrated that ultrasound could effectively affect the taste of TCW, especially enhanced the astringency, aftertaste-A and aftertaste-B values. A total of 56 compounds were identified as differentially expressed metabolites by LC-MS based metabolomics, which were mainly connected with the tricarboxylic acid cycle and flavonoid biosynthesis pathway. These findings provide valuable insights into the potential use of ultrasound in the storage and preservation of other fruits.