Comprehensive Evaluation of Drying Characteristics and Quality of Citrus aurantium Based on Intelligent Sensory Multi-source Information Fusion Technology

Objective: To investigate the drying characteristics of Citrus aurantium under various drying methods and their impact on quality, aiming to identify the optimal process conditions that balance drying efficiency and quality. Methods: Using vacuum freeze-drying as a reference, the drying kinetics and physical parameters of Citrus aurantium were examined under hot air drying, vacuum drying, microwave drying, and infrared drying. Seven empirical drying models (Midilli, Lewis, Page, Modified Page, Logarithmic, Overhults, Two-term Exponential) were employed to fit and validate the drying process, and to determine the effective diffusion coefficient (D_eff) of water in Citrus aurantium under different drying conditions. Multi-dimensional data on volatile compounds, total phenol and flavonoid content, antioxidant capacity, and sensory characteristics were collected using headspace-gas chromatography-mass spectrometry, enzyme labeling, electronic nose, electronic tongue, and colorimeter. Finally, multi-source information fusion techniques, including principal component analysis, partial least squares discriminant analysis, and correlation analysis, were applied to comprehensively evaluate the quality of Citrus aurantium. Results: The Midilli model provided the best fit, with the effective water diffusion coefficients of Citrus aurantium under hot air drying, vacuum drying, microwave drying, and infrared drying being 1.55×10⁻⁷, 1.00×10⁻⁷, 1.62×10⁻⁵, and 5.67×10⁻⁶ m²/s, respectively. These values were consistent with the drying time and rate. A total of 64 volatile compounds were detected, 20 of which were common across all methods. Among these, (+)-limonene (71.17%), laurin (4.02%), and ocimene (1.68%) showed the highest concentrations under vacuum drying, while linalool (10.13%) had the highest concentration under vacuum freeze-drying. The e-nose and e-tongue results indicated that the different drying methods could distinctly differentiate the odor profiles of Citrus aurantium. The retention of total phenols (113.72±6.75 mg GAE/g), total flavonoids (17.74±0.75 mg RE/g), and the scavenging capacity for DPPH free radicals (4.23±0.60 mmol TE/g DW), as well as the total antioxidant capacity (0.27±0.03 mmol Fe²⁺/g DW), was highest in Citrus aurantium subjected to microwave drying. Additionally, microwave drying resulted in optimal preservation of flavor and color. Conclusion: Microwave drying is the most suitable method for the drying and processing of Citrus aurantium, effectively enhancing its overall quality. This study offers valuable insights into the optimal drying technique and the comprehensive quality of Citrus aurantium.