Vitamin C content estimation of chilies using Vis/NIR spectroscopy

Vitamin C has value in treatment or prevention of scurvy and it can be obtained from vegetable and fruit. Vitamin C is usually determined by traditional chemical methods which are destructive, time-consuming. This paper was conducted to study the vitamin C (VC) content estimation in chilies using quantitative analysis technique based on visible/near infrared (Vis/NIR) diffuse reflectance spectroscopy. Total 141 fresh chilies were purchased from market. After the samples have been washed and air-dried, Vis/NIR spectral data were collected using a QualitySpec^® Pro Vis/NIR spectrometer (ASD Inc.). Then the vitamin C contents in samples were determined by 2, 6-dichloro-indophenol titration method. Spectral preprocessing techniques, including standard normal variate (SNV), multiplicative scatter corrections (MSC), first derivative (FD), second derivative (SD) and smoothing methods were applied to the spectral data and examined for their effectiveness at reducing or eliminating scatter effects. Partial least squares (PLS) regression was applied to examine the impact of the preprocessing transforms on assessing the content of vitamin C in chilies. The result shows that the best calibration model can be obtained by the first derivative preprocessing method in the spectral range of 450-1000 nm. The prediction results are 0.803 and 0.509 for correlation coefficient (r) and root mean square errors of prediction (RMSEP), respectively. The study shows that vitamin C (VC) content in chilies can be effectively estimated using Vis/NIR spectroscopy technology.