Laser Mass Spectrometry as On-Line Sensor for Industrial Process Analysis:  Process Control of Coffee Roasting

• Published in: Analytical chemistry (Washington) Vol. 76; no. 5; pp. 1386 - 1402
• Main Authors: Dorfner, Ralph, Ferge, Thomas, Yeretzian, Chahan, Kettrup, Antonius, Zimmermann, Ralf
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.03.2004
• Subjects: Analytical chemistry; Beverages - standards; Chemical bonds; Chemistry; Coffee; Coffee - chemistry; Cooking - standards; Exact sciences and technology; Food Analysis - instrumentation; Food Analysis - methods; General, instrumentation; Hot Temperature; Lasers; Mass spectrometry; Mass Spectrometry - methods; Molecular Weight; Principal Component Analysis; Process controls; Quality Control; Spectrometric and optical methods; Steel; Temperature; Time Factors; VOCs; Volatile organic compounds; Trace analysis; Process control; Volatile organic compound; Multivariate analysis; Chemical sensor; Real time; Roasted coffee; Laser beam; Time of flight method; Vacuum ultraviolet radiation; Multiphoton ionization; Mass spectrometry; Principal component analysis; Direct injection
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac034758n

The objective of the project is to develop on-line, real-time, and noninvasive process control tools of coffee roasting that help deliver a consistent and high-quality coffee aroma. The coffee roasting process was analyzed by direct injection of the roaster gas into a time-of-flight mass spectrometer and ionized either by resonance enhanced multiphoton ionization (REMPI) at 266 and 248 nm or vacuum ultraviolet single-photon ionization (VUV-SPI) at 118 nm. The VUV ionization scheme allows detecting mainly the most volatile and abundant compounds of molecular mass below 100 m/z, while REMPI ionizes mainly aromatic compounds of molecular mass larger than 100 m/z. Combining the compounds ionized by resonant and single-photon ionization, ∼30 volatile organic compounds are monitored in real time. Time−intensity profiles of 10 important volatile coffee compounds were discussed in connection with their formation chemistry during roasting. Applying multivariate statistics (principle component analysis) on time−intensity traces of nine volatile coffee compounds, the roasting degree could be traced as a consistent path in the score plot of the two most significant principle components (including 68% of the total variance), for a range of roasting temperatures (200−250 °C).