Volatile Analysis of Coffee Flowers before and after Pollination Using a Portable Electronic Nose and Gas Chromatography

Development of a portable electronic nose based on eight metal oxide gas sensors and gas chromatography (GC) analysis for classification of a difference in coffee flower odors are reported. Volatile organic compounds (VOCs) of arabica coffee ( Coffea arabica Linnaeus) flowers before and after pollination were investigated. Principal component analysis (PCA) was performed for pattern recognition. The results showed that all metal oxide gas sensors exhibited sensitivity to odors of the coffee flower samples. PCA result showed good classification of coffee flower odors correctly corresponding to the samples before and after pollination. Based on GC analysis, it was found that pyrazine may be one of impact volatile organic compounds in arabica coffee flowers before pollination and amount of 2-methyl-1-butanol largely decreased after pollination. The pyrazine and 2-methyl-1butanol may be used as a key compound for qualitative measurement using the electronics nose system with several advantages including rapid and accurate measurement, low cost and easy to use. We hope that this work will be useful for guidance on further studies of production of tea-like beverages using arabica coffee flowers.