Study the synergism of microwave thermal and non-thermal effects on microbial inactivation and fatty acid quality of salmon fillet during pasteurization process

Abstract

Microwave processing is a combined treatment of thermal and non-thermal effects on microorganisms and food ingredients. There may exist synergism between these two types of effects. The objective of this study was to explore the synergism of microwave thermal (i.e. temperature) and non-thermal effects on microbial inactivation and on fatty acids quality of pasteurized salmon fillets. Water bath processes with same time-temperature profiles and same microbial inactivation intensity were designed as control. Results showed that the microwave non-thermal effect on microbial inactivation was significantly (P < 0.05) enhanced by increasing temperatures. Compared with the microbial inactivation of thermal effect, the inactivation efficiency of microwave non-thermal effect increased from 22.18% to 35.25% while final temperatures of samples increased from 84 °C to 100 °C. Furthermore, with the same microbial inactivation intensity of 7.5-log CFU/g, microwave process retained better fatty acids quality in consideration of significantly higher (P < 0.05) PUFAs (especially for ARA, EPA and DHA) than those with water bath treatments. These results demonstrated that high temperatures could bring significant enhancement on microwave non-thermal effect, and microwave processing could provide better bacteria control and meanwhile retain higher product quality due to the synergism of microwave thermal and non-thermal effects.