Abstract:
Background Fresh oysters contain a high moisture content and are prone to spoilage during storage and transport. Drying effectively reduces its water activity and extends shelf life, however, traditional sun drying suffers from low efficiency, unstable product quality, and a lack of theoretical guidance.
Objective This study aims to clarify the drying characteristics of oysters under different drying methods, identify the most suitable technique and its kinetic model, and provide a theoretical basis for process design and production control.
Methods Triploid Fujian oysters Crassostrea angulata were dried by using sun drying (SD), vacuum drying (VD), hot air drying (HAD), and far-infrared radiation assisted hot air drying (FIRHAD). The moisture ratio (MR), drying rates, and effective moisture diffusion coefficient (Deff) were systematically investigated, and thirteen classic thin-layer drying models were fitted to the drying curves to establish the kinetics model for each method.
Results All four processes were governed by internal moisture diffusion, and exhibited a typical falling-rate drying characteristic without a distinct constant-rate period. Specifically, FIRHAD reaching MR=0.2 was the fastest (8 h), whereas VD achieving the constant weight was the earliest (22 h). The Deff ranked as SD (3.311×10−10 m2/s)<FIRHAD (1.704×10−9 m2/s) <HAD (2.590×10−9 m2/s)<VD (2.826×10−9 m2/s). Non-linear relationships between MR and drying time were observed in all methods. The Two-term model effectively described SD and FIRHAD processes, while the Midilli model provided a good fit for the VD and HAD processes.
Conclusion FIRHAD at 50 °C is optimal for producing low-moisture dried oysters (MR=0.2), whereas VD at 50 °C is the fastest route to fully dried oysters. The Two-term and Midilli models are recommended for describing and predicting the drying behavior of oysters.
下载:
