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Quantification of Free 2-Furfurylthiol in Coffee Brew Using a Prefabricated Coffee Model Zhenchun Sun 1 & Khizar Hayat 2 & Jingyang Yu 1 & Eric Karangwa 1 & Emmanuel Duhoranimana 1 & Xiaoming Zhang 1 & Shuqin Xia 1

Received: 26 June 2017 / Accepted: 6 September 2017 # Springer Science+Business Media, LLC 2017

Abstract A reliable and sensitive method was developed to quantify the free 2-furfurylthiol (2-FFT) in coffee brew. Using cysteine addition combined with vacuum distillation, a coffee model with trace 2-FFT and similar physicochemical properties as coffee brew was prepared for standard curve construction. During the model preparation, 2-FFT in bound form was released to free 2-FFT and removed from coffee brew through vacuum distillation. The method sensitivity, precision, accuracy and selectivity were evaluated. The limit of quantification (LOQ) was 3.0 μg/L. The coefficient of variation (CV) was 7.1%. The average recovery rates were 86.8–106.2% at spiked concentrations of 22.6, 135.8 and 181 μg/L. Coffee brews prepared using Robusta and Arabica roasted coffee beans were analyzed, and results showed that coffee brew from Robusta coffee beans had a greater amount of free 2-FFT (20.94 μg/L) than Arabica coffee beans from Yunnan (11.34 μg/L) and Columbia (15.33 μg/L), respectively. This method would be beneficial to investigate the free amount of 2-FFT in coffee brew and the sensorial assay based on free 2FFT concentration.

Keywords Free 2-furfurylthiol . Coffee brew . Quantification . Model preparation

* Xiaoming Zhang [email protected]

1

State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi 214122, Jiangsu, People’s Republic of China

2

Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia

Introduction Sulfur compounds play an important role in the formation of coffee flavor (Budryn et al. 2011; Nebesny and Budryn 2006; Schutte and Teranishi 1974). Among these compounds, thiols, due to their extremely low thresholds and strong odor (Buffo and Cardelli-Freire 2004), make a significant contribution to coffee sensory characteristics (Dulsat-Serra et al. 2016). Among thiols, 2-furfurylthiol (2-FFT) is considered as the key coffee aroma compound, and its identification is considered a milestone in coffee flavor field (Akiyama et al. 2008; Bel Rhlid et al. 2002; Dulsat-Serra et al. 2016; Semmelroch and Grosch 1995; Semmelroch and Grosch 1996). 2-FFT, which is formed through Maillard reaction (Buffo and Cardelli-Freire 2004), provides a desirable sulfury-roasty and toast-like odor (Buffo and Cardelli-Freire 2004; Hofmann and Schieberle 2002; Semmelroch and Grosch 1995). Its low threshold (0.01 μg/L in water) and pleasant sulfury-coffee-like smell exert an important effect on coffee flavor profiles (Akiyama et al. 2008; Dulsat-Serra et al. 2016; Semmelroch and Grosch 1995; Semmelroch and Grosch 1996). Previous studies reported that 2