Non-invasive spectrophotometric sensing of carrot quality from harvest to consumption

The impact of different storage conditions and minimal processing on quality changes of freshly harvested carrots were recorded by means of non-invasive spectrophotometric techniques. Methods were adapted and evaluated with conventional chromatographic methods to test their feasibility for non-invasive monitoring of compounds determining the product quality. Sugar contents, which are a major component of carrot taste, were non-invasively monitored by means of diffuse reflectance readings (800-1700 nm) applying partial-least squares regression with a percentage standard error of cross validation (SECV) of 15.4, 4.6, and 2.3% for sucrose, glucose, and fructose, respectively. Using spectrophotometry in the visible wavelength range, non-invasive analyses of alpha- and beta-carotenes, as important contributors to the nutritional value of carrots, were obtained with an SECV <1%. An inter-cultivar validation highlighted the need for re-calibration in sugar analysis, while carotenes were measured with an SEP < 18% and a coefficient of determination in the validation of R-p2 > 0.9. Application of non-invasive product monitoring shows that storage at high temperature (16 degrees C) as well as a break in the cooling chain can cause decreases in carotene contents. Under these conditions, in comparison with cool storage (3 degrees C), reducing sugars contents remained stable or were slightly enhanced, while sucrose contents decreased. After minimal processing all nutrients decreased. A loss was inhibited when the oxygen partial pressure was reduced. Monitoring such quality changes with rapid spectrophotometric methods can provide a quality control tool in modem supply chain management. (C) 2007 Elsevier B.V. All rights reserved.