Laser mass spectrometry as on-line sensor for industrial process analysis: process control of coffee roasting.
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, approximately 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 degrees C).
Institute of Ecological Chemistry, GSF-National Research Center for Environment and Health, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.
Ralph
R
Dorfner
Thomas
T
Ferge
Chahan
C
Yeretzian
Antonius
A
Kettrup
Ralf
R
Zimmermann
D001628:Beverages / Q000592:standards; D003069:Coffee / Q000737:chemistry*; D003296:Cooking / Q000592:standards*; D005504:Food Analysis / Q000295:instrumentation / Q000379:methods*; D006358:Hot Temperature; D007834:Lasers; D013058:Mass Spectrometry / Q000379:methods*; D008970:Molecular Weight; D025341:Principal Component Analysis; D011786:Quality Control; D013232:Steel; D013696:Temperature; D013997:Time Factors
D003069:Coffee; D013232:Steel