Studying the non-thermal effects of microwave on amino acids in sterilized rainbow trout (Oncorhynchus mykiss) fillets using a double side approximating method.

[Display omitted] • A mathematics-based method was developed to determine the boundaries of thermal effects. • Microwave non-thermal effects was differentiated from thermal effects that occur simultaneously. • Microwave non-thermal effects on 22 amino acids were determined. • Sterilization was carried out using a low frequency (896 MHz) microwave processing system. The aim of this study was to investigate the impact of microwave non-thermal effects on thermal sensitive amino acids in rainbow trout (Oncorhynchus mykiss) fillets. To distinguish non-thermal effects from thermal effects occurring simultaneously, a Double Side Approximating Method (DSAM) derived from computational mathematics was developed. Two corresponding water bath treatments were designed for each microwave processing to approximate the time–temperature profiles at the hot and cold spots of the microwave processed samples while maintaining a comparable thermal intensity (F 0). The microwave non-thermal effects on amino acids were determined by comparing the amount of each of 22 amino acids between the microwave processed and the two corresponding water bath treated rainbow trout fillets. The results indicated that the DSAM was successfully implemented, as the amino acid contents' order curve in the microwave processed samples was clearly exceeded the boundary formed by the two corresponding water bath treated samples. This finding confirmed the occurrence of microwave non-thermal effects on amino acids. The non-thermal effect resulted in a notable increase in the quantity of most amino acids, while it reduced the content of Lys and Hyp. Longer microwave processing times intensified these effects, while higher thermal processing intensities resulted in more damage to each amino acid. [ABSTRACT FROM AUTHOR]