Optimization and Application of Automatic Cryogenic Vacuum Distillation System for Fruit Water Extraction for Isotope...

Stable hydrogen (δ²H) and oxygen (δ¹⁸O) isotopes in plant tissue water provide effective indicators for tracing fruit origin. This study optimized automatic cryogenic vacuum distillation (ACVD) system parameters (temperature, extraction time, and sample volume) to achieve a near-complete water recovery and high analytical accuracy. Systematic deviations of isotopic values between the original water and the water extracted from the spiked strawberry samples (Δδ²H: 4.56‰; Δδ¹⁸O: 1.14‰) were observed, likely due to matrix effects during extraction. Nevertheless, the optimized ACVD protocol enabled clear discrimination of the geographical origins of strawberries, apples, and kiwifruits based on their δ²H and δ¹⁸O values. These results indicate that, despite extraction-induced isotopic fractionation, tissue water isotopes remain reliable markers for fruit provenance when ACVD parameters are carefully controlled.