Stable carbon isotope fingerprinting of vietnamese passion fruit juice: A dual EA -IRMS and LC-IRMS approach for authenticity and adulteration detection

This study aims to develop and validate analytical protocols for the determination of the stable carbon isotope ratio (δ¹³C) in constituents of Vietnamese passion fruit juice, including pulp, juice, and individual sugars (fructose, glucose, and sucrose). This study integrates Elemental Analysis and Liquid Chromatography–Isotope Ratio Mass Spectrometry (EA-IRMS and LC-IRMS). A total of 630 passion fruit samples were analyzed, including 441 fresh samples collected from five major Vietnamese growing regions (Southeast, Central Highlands, North Central, Mekong Delta, and Red River Delta) and 189 commercial juice products obtained from retail markets. From the authentic dataset, a representative subset of 141 samples was selected for compound-specific isotope analysis using LC-IRMS. The δ¹³C values of pulp and juice, determined via EA-IRMS, ranged from –28.21‰ to –24.04‰ and –27.90‰ to –24.56‰, respectively. LC-IRMS analysis revealed that δ¹³C values ranged from –29.76‰ to –25.12‰ for fructose, –28.97‰ to –24.17‰ for glucose, and –27.62‰ to –22.24‰ for sucrose. Statistical analysis, including analysis of variance (ANOVA), Tukey’s honestly significant difference (HSD) test, and principal component analysis (PCA), confirmed statistically significant isotopic differentiation among geographic regions and revealed isotopic structuring patterns between authentic samples and several commercial samples exhibiting anomalous isotopic signatures (p < 0.05). The findings reveal that δ¹³C values of sugar fractions in authentic passion fruit juice differ significantly from those in samples adulterated with C₄ plant-based sweeteners. Notably, this represents the first application of stable isotope analysis for fruit juice authentication in Vietnam, marking a significant advancement in food analytical sciences, promoting the international competitiveness of Vietnamese agricultural commodities. • Developed the first δ¹³C isotopic fingerprinting protocol for Vietnamese passion fruit juice. • Combined EA-IRMS and LC-IRMS to analyze pulp, juice, and individual sugars (fructose, glucose, sucrose). • Established a δ¹³C reference database from 441 fresh passion fruit samples across five regions in Vietnam. • Detected adulteration in 62 of 189 commercial juices with C₄ plant-derived sugars. • Demonstrated dual utility of stable isotope analysis for both authenticity and geographic origin tracing.