Identification of Red Dragon Fruit Peel Flour Adulterated with Purple Sweet Potato Flour Using FTIR Spectroscopy Combined with Chemometrics

Abstract The vibrant peel of the red dragon fruit, with its striking magenta hue and unique texture, is rich in antioxidants, making it a valuable addition to a healthy diet. It can be processed into flour, which simplifies storage and expands its applications. A significant advantage of this material is its ability to biodegrade alongside other substances. Therefore, this study aimed to identify red dragon fruit peel flour that has been adulterated with purple sweet potato flour using FTIR spectroscopy combined with chemometrics. This study used a model of adulteration, mixing red dragon fruit peel flour (RDFPL) with purple sweet potato flour (PSPF). The study examined adulteration rates ranging from 3 – 100%. A colorimeter can significantly identify color changes in RDFPL adulteration with PSPF (p<0.05). The presence of (C-H) bending alkene-specific bonds to starch was indicated by spectral peaks at wavenumber 862 cm-1, which was specific indicator of RDFPL adulteration. Based on the results, the first derivative spectrum at wavenumbers 650–3603 cm −1 as the calibration and validation model for the adulteration rate prediction, with R2 values of 0.9999 and 0.9880, respectively, and RMSEC and RMSEP values of 0.304 and 2.86, respectively. The results of the multivariate analysis using Principal Component Analysis (PCA) categorize the level of adulteration in red dragon fruit peel flour (RDFPL) into three groups: low, medium, and high, achieving an accuracy rate of 98.7%. Additionally, when combined with chemometrics, Fourier Transform Infrared (FTIR) spectroscopy successfully identified the degree of adulteration in red dragon fruit peel flour when mixed with purple sweet potato flour.