Quantitative analysis of minerals and electric conductivity of red grape homogenates by near infrared reflectance spectroscopy

The use of near infrared (NIR) reflectance spectroscopy to measure the concentration of minerals and electric conductivity (EC) in red grape homogenates was investigated. Wine grape samples (n = 209) from two vintages, representing a wide range of varieties and regions were analysed by Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES) for the concentrations of calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), sulphur (S), iron (Fe), and manganese (Mn) and scanned in reflectance in a NIR instrument (400-2500 nm). The spectra were pre-processed using multiple scatter correction (MSC) before developing the calibration models using partial least squares (PLS) regression and cross validation. Coefficients of determination in cross validation (R(2)) and the standard errors of cross validation (SECV) obtained were for Fe (0.60 and 1.49 mg kg(-1)), Mn (0.71 and 0.41 mg kg(-1)), Ca (0.75 and 60.89 mg kg(-1)), Mg (0.84 and 12.93 mg kg(-1)), K (0.78 and 285.34 mg kg(-1)), P (0.70 and 40.19 mg kg(-1)), S (0.88 and 14.45 mg kg(-1)) and EC (0.87 and 7.66 mS). The results showed that Mg. S and EC in grape berries might be measured by NIR reflectance spectroscopy. (C) 2011 Elsevier B.V. All rights reserved.