Study on Material Basis and Processing Principle of Fishy Smell of Pheretima aspergillum by Electronic Nose and HS-GC-MS / 中国实验方剂学杂志

ABSTRACT

Objective:To analyze and compare the fishy components in raw, stir-fried, liquorice-processed, vinegar-processed and wine-processed products of Pheretima aspergillum, and explore the material basis and processing principle of fishy smell of P. aspergillum. Method:Heracles Ⅱ ultra-fasted gas chromatography electronic nose technology combined with chemometrics was used for the overall analysis of volatile components in raw P. aspergillum and its processed products. Headspace gas chromatography-mass spectrometry (HS-GC-MS) was used to analyze and identify the volatile compositions in the raw products and processed products. Gas chromatographic conditions were as following：temperature program (initial temperature at 60 ℃, kept for 5 min, up to 120 ℃ with the heating rate of 3 ℃·min-1, and then up to 230 ℃ with the heating rate of 10 ℃·min-1 and finished), the inlet temperature at 280 ℃, high purity helium as the carrier gas, the flow rate of 1.0 mL·min-1, the split ratio of 20∶1. Mass spectrum conditions were as following：electron impact ionization (EI), electron collision energy of 70 eV, ion source temperature of 230 ℃, quadrupole temperature at 150 ℃, scanning range of m/z 50-550. The relative content of each component was calculated by peak area normalization. Result:Principal component analysis (PCA) and discriminant factor analysis (DFA) of the electronic nose showed that the raw products and its processed products could be clearly distinguished from each other. Among them, the difference between raw products and stir-fried, liquorice-processed products was small, but the difference between raw products and vinegar-processed, wine-processed products was large. A total of 25, 27, 22, 26 and 33 components were respectively identified from raw, stir-fried, liquorice-processed, vinegar-processed and wine-processed products of P. aspergillum, there were 13 common components in these products, including 4 aldehydes (isovaleraldehyde, 2-methylbutyraldehyde, hexanal, benzaldehyde), 2 ketones (2-heptanone, 2-tridecanone), 1 carboxylic acid (lauric acid), 4 heterocyclic compounds (2-methylpyrazine, 2,5-dimethyl pyrazine, 2-pentylfuran, 2-ethyl-6-methyl pyrazine), 1 amine (trimethylamine) and 1 alcohol (1-octen-3-ol). Conclusion:The odorous components in the raw products are mainly derived from aldehydes (isovaleraldehyde, 2-methylbutyraldehyde, isobutyraldehyde, 2-ethylhexanal, hexanal) and amines (trimethylamine). Odorous components of P. aspergillum can be reduced effectively by stir-fried and liquorice, vinegar, wine processing, while flavoring substances can be increased by wine processing to cover its ugly odor. This paper can provide scientific basis for the deodorization of P. aspergillum by processing, and also provide reference for the analysis and correction of ugly odor of other animal medicines.