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Assaying the carotenoid content in corn and sweet potato flours by photoacoustic spectroscopy

This is the first attempt to use photoacoustic spectroscopy (PAS) for quantification of carotenoids in powder-like samples, namely in corn and sweet potato flours. In this study spectrophotometry has been used as an established absolute method. PAS measurements were performed at room temperature at 488 nm of the argon laser (f=9 or 30 Hz, tc=1 s, incident laser power 70-74 mW). Central semispherical cavity of the PAS cell (diameter 8 mm accommodated flour specimen ; this latter was loaded flush with the surface of the plate using a spatula. PAS measurements were repeated within a run and within several days or months. Thirty-three corn flours were investigated ; linear analytical response was obtained for the samples containing 0.1-26 ppm total carotenoids(R=0.91-0.92), for upto 36 ppm TC power function was obtained (R=0.95-0.97). DL values obtained at 9 and 30 Hz were 2.14 and 6.51 ppm TC. Nine sweet potato flours were also analyzed. Two linear regions were established: upto 18 ppm beta carotene (R=0.92-0.96) and from 40-240 ppm (R=0.94-0.95). Respective DL values were 0.70 and 0.90, namely 12.43 and 19.86 ppm beta-carotene. Comparable repeatability (n=3-12) and intermediate precision (n=6-28) were evaluated for both frequencies: 0.1-17.1% and 5.3-14.7% for corn flours and 1.4-9.1% and 4.2-23.0% for sweet potato flours, resp. Our results show that PAS might be successfully used as an analytical tool for quick and simple screening of flour samples for their nutritional value through the content of carotenoids.

total carotenoids assay; corn flours; sweet potato flours; photoacoustic spectroscopy

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