Detection and quantification of apple adulteration in diluted and sulfited strawberry and raspberry purées using visible and near-infrared spectroscopy.
Adulteration of sulfited strawberry and raspberry purées by apple is a commercial problem. Strawberry (n = 31) and raspberry (n = 30) purées were prepared from Irish-grown fruit and adulterated at levels of 10-75% w/w using cooking apples. Visible and near-infrared transflectance spectra were recorded using a 0.1 mm sample thickness. Classification and quantification models were developed using raw and scatter-corrected and/or derivatized spectral data. Classification as pure strawberry or raspberry was attempted using soft independent modeling of class analogy. The best models used spectral data in the wavelength ranges 400-1098 nm (strawberry) and 750-1098 nm (raspberry) and produced total correct classification rates of 75% (strawberry) and 95% (raspberry). Quantification of apple content was performed using partial least-squares regression. Lowest predictive errors obtained were 11.3% (raspberry) and 9.0% (strawberry). These results were obtained using spectral data in the wavelength ranges 400-1880 and 1100-1880 nm, respectively. These results suggest minimum detection levels of apple in soft fruit purées of approximately 25 and 20% w/w for raspberry and strawberry, respectively.
Downey
Gerard
G
Teagasc, The National Food Centre, Ashtown, Dublin 15, Ireland. gdowney@nfc.teagasc.ie
Kelly
J Daniel
JD
D005506:Food Contamination / Q000032:analysis*; D005511:Food Handling; D031985:Fragaria / Q000737:chemistry*; D005638:Fruit / Q000737:chemistry* / Q000145:classification; D027845:Malus / Q000737:chemistry*; D027824:Rosaceae / Q000737:chemistry*; D013053:Spectrophotometry; D019265:Spectroscopy, Near-Infrared; D013447:Sulfites / Q000032:analysis*
D013447:Sulfites