Possibilities of using photoacoustic spectroscopy (PAS) in the classification of raw materials and additives of the food industry
1990
Nohos, F. | Kocsanyi, L. | Varadi, M. | Biacs, P. (Kozponti Elelmiszeripari Kutato Intezet (Hungary))
With the photoacoustic spectroscope developed and improved by the author the Pa-spectrum and NIR and Pa-spectrum of Rodamin-B were recorded. The apparatus used consisted of the following parts: casing of the xenon arc lamp and its feeding unit, a pair of condensers, grated monochromator, a set of filters to separate a higher order of screen fractions, light chopper, reference signaller, microprocessor control, convex lens, pyroelectric detector, photoacoustic cel, lock-in amplifer, analogue dividing circuit, X-Y writer. Milk, potatoes and wheat starch were analyzed. The potato starch was tested for reproducibility. Specific advantages of photoacoustic spectroscopy:even in the case of high absorption the spectrum obtained need not be saturated (this can be achieved by accelerating the chopping), the method is highly sensitive, by changing the chopping frequency, resolution according to depth may be realized in addition to resolution according to wave length, it is insensitive to scattered light, because scattered light does not initiate signal.
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