High pressure impregnation‐assisted drying of abalone ( Haliotis rufescens ) slices: Changes in protein conformation, thermal properties, and microstructure

This study aimed to evaluate the effect of high pressure impregnation (HPI) (pressure: 350, 450, and 500 MPa; time: 5 min; osmotic solution: 15% NaCl) as a pretreatment to the drying process of abalone samples (temperature: 60°C) and subsequent evaluation of physicochemical properties thereof. The protein conformational changes of HPI-dried samples were evaluated by Fourier transform infrared (FT-IR) spectroscopy. The molecular weight profile and amino acid composition were determined. Thermal analysis was performed by differential scanning calorimetry (DSC). Process drying rates were reduced up to 33%, and dried abalones had lower moisture content and water activity as the pressure level increased. In addition, less degradation effects were found in amino acid compositions. In the β-sheet structure, HPI-assisted drying process caused partially folded conformations at 350 and 450 MPa, and aggregation at 500 MPa. A compacted structure was identified as pressure increased (350 ➔ 500 MPa), confirming that the structure of abalone muscle treated with HPI-assisted drying differed significantly from raw material. The results presented in this research could support the potential application of high hydrostatic pressure treatment as combined treatments for other compound impregnation under high pressure. In addition, HPI technology could be used to enhance the quality properties of dried abalones and dried marine products of the aquaculture and fishery industry. Practical applications This research deals with the influence of high-pressure impregnation pretreatment on protein conformational changes of abalone samples subjected to convective air drying. Results showed that applying this combined innovative technology improved abalone slice dehydration rates compared with an atmospheric pressure operation, producing dried abalone with the moisture content required to be used as input material for subsequent processes. The different thermal properties were also determined to assess the importance of the changes in the protein structure that occur during heating and could influence process time. The HPI pretreatment can change the secondary structures of proteins as function the pressure level. The results of this study provide valuable information for the potential application of HPI pretreatment on the development of dried red abalone with high-added value. Thus, the aquaculture and fishery industry when using HPI technology would preserve the quality properties of further dried abalones.