No abstract

Precise controlling and monitoring the status of the coffee roasting process is essential for consistent product quality and optimization towards targeted coffee properties. In small-scale roasting experiments, the chemical composition of the roasting off-gas was analyzed by online single-photon ionization time-of-flight mass spectrometry (SPI-TOFMS) at 118 nm with 5 s time resolution. Subsequently, mass spectra at the drop of the coffee beans were combined with off-line measurements of roast degree, described by color value "Colorette", and the antioxidant capacity, obtained from Folin-Ciocalteu (FC) assay, in an explanatory PLS regression model. While the roast degree gives an indication of the coffee flavor, antioxidants in brewed coffee are regarded as beneficial for human health. Colorette and FC values could be derived from the SPI mass spectra with root-mean-square errors from Monte Carlo cross-validation of 6.0 and 139 mg GA-eq. L -1 , respectively, and explained covariance (R 2 CV ) better than 89%. Finally, the regression models were applied to the SPI mass spectra over the entire roast in order to demonstrate the predictive ability for online process control in real-time.

No abstract

Fast and reliable information is crucial for first responders to draw correct conclusions at crime scenes. An ambient pressure laser desorption (APLD) mass spectrometer is introduced for this scenario, which enables detecting substances on surfaces without sample pretreatment. It is especially useful for substances with low vapor pressure and thermolabile ones. The APLD allows for the separation of desorption and ionization into two steps and, therefore, both can be optimized separately. Within this work, an improved version of the developed system is shown that achieves limits of detection (LOD) down to 500 pg while remaining fast and flexible. Furthermore, realistic scenarios are applied to prove the usability of this system in real-world issues. For this purpose, post-blast residues of a bomb from the Second World War were analyzed, and the presence of PETN was proven without sample pretreatment. In addition, the analyzable substance range could be expanded by various drugs and drug precursors. Thus, the presented instrumentation can be utilized for an increased number of forensically important compound classes without changing the setup. Drug precursors revealed a LOD ranging from 6 to 100 ng. Drugs such as cocaine hydrochloride, heroin, (3,4-methylendioxy-methamphetamine) hydrochloride (MDMA) hydrochloride, and others exhibit a LOD between 10 to 200 ng.

Process control with high time resolution is essential to maintain high product quality in coffee roasting. However, analytical techniques for quality assurance or measurements of desired coffee properties are often labor-intensive and can only be conducted after dropping the coffee beans. Resonance-enhanced multi-photon ionization time-of-flight mass spectrometry (REMPI-TOFMS) at 248 nm and 266 nm was applied to analyze the composition of the roast gas from small-scale Arabica coffee roasting. Coffee beans were dropped after different roasting times, ground and analyzed by Colorette to obtain the roast degree. Additionally, the antioxidant capacity of the coffee brew was determined by Folin–Ciocalteu (FC) assay. Models for the prediction of Colorette and FC values from REMPI mass spectra were constructed by partial least squares (PLS) regression. REMPI-TOFMS enables the prediction of Colorette values with a root-mean-square error in prediction (RMSEP) below 5 for both wavelengths. FC values could be predicted using REMPI at 248 nm with an RMSEP of 80.3 gallic acid equivalents (GA-eq) mg L−1, while REMPI at 266 nm resulted in RMSEP of 151 GA-eq mg L−1. Finally, the prediction of Colorette and FC value at 5 s time resolution were demonstrated with online measurements.