Terpenes in food and plant samples: Updates on sampling, pretreatment and analysis techniques

Terpenes are the molecules synthesized or polymerized from isoprene or 2-methyl-1,3-butadiene. They are the most diversified families of secondary metabolites found in various foods and plant samples. These compounds have various bioactivities including antimicrobial, anti-inflammatory, analgesic, etc. Because of the utility of terpenes, rapid, reliable, sensitive, and selective pretreatment and analytical methods are being developed for quality monitoring and control. Diverse pretreatment and analytical approaches for terpenes have been reviewed since 2017. Terpene pretreatment is done by liquid-liquid extraction, matrix solid-phase dispersion extraction, supercritical fluid extraction, or emerging eco-friendly microextraction methods, such as liquid-phase microextraction, and solid-phase microextraction. In addition, the convenient automated online extraction method has also been presented. Meanwhile, analytical protocols involve gas chromatography-based methods, liquid chromatography-based methods, electronic nose methods, and others; among them, high sensitivity and selectivity mass spectrometry methods have been highlighted. In summary, the main trends in sample pretreatment are cost-saving, time-saving, low toxicity, and high efficiency, as well as the automation and miniaturization of the experimental device. Meanwhile, real-time, miniaturized, and sensitive technologies will be preferred in the analysis of terpenes in the future.