Microwaves affect the formation of volatile compounds in peper powder by changing the nucleophilic addition reactions in Maillard reactions

Abstract

We explored the effect of microwave heating (MWH) and electric heating (ETH) on the volatile compounds (VCs) of pepper (Capsicum annuum L.). The spectral of the produced melanoidins by baking were used to screen samples with similar baking degrees. Mass spectrometry was used to detect the differences of VCs in samples. The results showed a dose-dependent effect between the intensity of absorption and fluorescence of melanoidins, which can be utilized as indicators for assessment baking degree. MWH samples produced larger variety of VCs than ETH. Changes in the variety and content of VCs infer changes in the flavor of pepper. According to the mechanism of Maillard reaction (MR) and MWH, it was deduced that MWH changes the type of chemical reaction in MR by affecting the distribution of valence electrons in the compounds. Therefore, MWH can be used as a novel method to modify the VCs and flavor of peppers.

Keywords: GC–MS; Melanoidin; Microwave heating; Pepper; Volatile compounds.

Fig. 1

UV–Vis absorption and fluorescence spectra of pepper samples prepared using different methods, which contain similar content of melanoidins (A-C: UV–Vis absorption spectra; D-L: fluorescence spectra, 3D model).

Fig. 2

Total ion current diagram of pepper samples prepared using different methods, with similar content of melanoidins (CT1-4, SZ1-4, XJ1-4: the unbaked pepper; the baking times of other samples are shown in Fig.

Fig. 3

PCA and HCA of volatile compounds in samples prepared using different methods, which contain similar content of melanoidins (A, C and E: PCA; B, D, F: HCA; CT1-4, SZ1-4, XJ1-4: the unbaked pepper; the baking times of other samples are shown in Fig. 1).