On-line monitoring of fermentation processes by a new remote dispersive middle-infrared spectrometer

A middle infrared spectrometer coupled with a new attenuated total reflectance probe by optical fibres was developed to solve the problem of on-line analysis in the bioreactors. The measurement of sugars, ethanol and organic acid concentrations was investigated during alcoholic and lactic fermentations. This apparatus was able to operate between 5.5 and 10.5 μm with a reasonably good repeatability (CV<5%) between 6 and 10 μm. The standard errors of prediction were between 1.4 g l−1 (for galactose) and 4.5 g l−1 (for fructose).