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A near-infrared spectrophotometric method for estimating the soluble solids in honeydew melons is presented. The method is based on a body transmittance geometry in which the angle between the source incident beam and the detector is approximately 45°. The regression analysis of the spectral and chemical data utilizes a ratio of two second derivatives and resulted in a correlation coefficient of 0.85 and a standard error of calibration of 1.5. The numerator wavelength occurs in a carbohydrate absorption band, thus the method can be interpreted as a measurement of carbohydrates.
An instrument based on near infrared (NIR) reflectance techniques is described which is capable of determining nondestructively the percent soluble solids in whole honeydew, cantaloupe and watermelon samples. It utilizes a tilting interference filter technology for wavelength scanning and a silicon detector/amplifier for the detection of radiation which has penetrated through inner melon flesh. The standard error of prediction is of the order of 1.2 percent soluble solids for honeydew melons when compared with a standard refractometer analysis.
Abstract
Light transmittance curves of intact blueberries, ‘Wolcott’ and ‘Bluecrop’ cul-tivars, were recorded in the visible and infrared with the ASCO Biospect and correlated with anthocyanin content. Correlation coefficients were computed for a large number of possible maturity indexes to determine the optimum index. In all cases the index involves the measurement of the optical density of the intact fruit at 2 wavelengths and computation of the optical density difference. From the ‘Wolcott’ blueberry correlation data, the highest correlations, 0.925 and 0.967, were found in the infrared region between ∆OD(760–800 nm) vs anthocyanin content per berry and between ∆OD(760–800 nm) vs anthocyanin content per g fresh weight of tissue, respectively. For the ‘Bluecrop’ blueberry, the highest correlations, 0.933 and 0.916, were found in the infrared region between ∆OD(740–800 nm) vs anthocyanin content per berry and between ∆OD(740–800 nm) vs anthocyanin content per g fresh weight of tissue, respectively. Thus, optical density difference measurements of individual intact fruits afford a reliable maturity index for blueberries.
Whole dates (Phoenix dactylifera L.) were analyzed for moisture content using near infrared spectrophotometry in a direct transmittance geometry. In the calibration experiment using 72 samples, the correlation coefficient was 0.977 and the standard error of calibration (SEC) was 0.89%. When the calibration equation was used to predict the moisture in another set of 72 date samples, the standard error of performance (SEP) was 1.5%. When the method was used to sort these 72 dates into four industry-standard grades, 74% were correctly graded and 15% missed the grade by <1 SEC.