Effect of high intensity pulsed electric fields on physical changes of fishbone liquid

Abstract: High-intensity pulsed electric field (PEF) is characterized by transfer uniformity, nonthermal performance, high efficiency, short processing time and low component pollution. PEF shows unique advantages in the processing of liquid foods and thus can be widely applied to sterilization, extraction and enzyme inactivation of foods. PEF is a key processing technique that is most promising for industrial application in the past decade. Nevertheless, the effects of PEF on the physical state changes of foods have never been reported. With the rapid development of fishery worldwide, the fishbone from the majority of fish products is treated as tailing, which is restricted by low price, low processing capacity, low technical content, few high-value-added products, and low level of comprehensive processing and utilization. Higher requirements have been raised for the effective utilization of fish resources along with the development of modern food science and technology, especially the aquatic product processing industry. In this study, a texture analyzer was used to clarify the rheological properties of fishbone liquid and investigate the effects of PEF on the physical state changes of fishbone liquid. The indices used included the first and second compression work, elasticity, cohesiveness and gumminess. The principal component analysis was used to comprehensively assess the physical states of fishbone liquid. This analytical process was simplified into a comprehensive index equation. Single-factor tests were used to clarify the effects of PEF parameters on the physical state changes. The Box-Behnken design and response surface methodology (RSM) were used to investigate the effects of PEF on the electric field intensity, pulse number, and liquid-material ratio of fishbone liquid. Taking comprehensive index as the response value, we finished a 3-factor 3-level central composite design and acquired the optimal parameters of PEF: liquid-material ratio was 9.81 mL/g, field intensity was 23.10 kV/cm and pulse number was 10, and in such conditions, comprehensive index reached 2.3312. Correspondingly, the physical indices of the fishbone liquid were: first compression work was 1.2 N, second compression work was 1.3 N, cohesiveness was 1.21, elasticity was 9.25 mm and gumminess was 0.11 N. On the contrary, the rheological indices of the unprocessed fishbone liquid were: first compression work was 0.1 N, second compression work was 0, cohesiveness was 1.84, elasticity was 8.0 mm and gumminess was 0.18 N. These results indicated that after processing with PEF, the physical state indices of the fishbone liquid were changed during the first and second cycles, including higher energy needed for specified deformation, higher elasticity, lower internal bond strength of structural composition, and lower energy needed before swallowing. Moreover, PEF could significantly improve the physical states of fishbone liquid. PEF brought economic benefits for processing and utilization of fishbone. Therefore, PEF could be used to the processing of fishbone liquid. This study provides a theoretical basis for the application and promotion of PEF.