Aliquots (0.5 mL) from thawed tomato juice samples
were centrifuged at 12,000 rpm for 5 minutes at 25 °C,
and two drops were applied to the surface of the ATR
crystal for spectral data collection. The absorbance
spectra of the room temperature samples consist of 64
co-added interferograms at 4 cm-1 resolution measured
in the 4000 to 600 cm-1 mid-IR wavelength range. The
spectrum of each individual sample, which took less
than 2 minutes to acquire, was corrected against a
background spectrum of air. Duplicate independent
measurements were taken on each sample and
background spectra were collected after every sample
to account for environmental variations. Between
measurements, the ATR surface was cleaned with a
70% ethanol solution.