Effect of chemometrics to accuracy of NIR spectroscopy in predicting total soluble solid and hardness of dragon fruit

Abstract

NIR spectroscopy and chemometrics were assessed to determine the total soluble solids (TSS) and hardness of the dragon fruit nondestructively. Dragon fruit reflectance (n=117) were measured nondestructively by FT NIR spectrometer, and after that TSS and hardness of dragon fruit were measured destructively with digital refractometer and rheometer, respectively. Six spectra pretreatments and some number of PLS factors were applied to analyze the chemometrics effect to NIRS accuracy in predicting TSS and hardness of dragon fruit. The values of reflectance spectra of dragon fruit are high in 1000-1400 nm and after that decrease gradually. On the contrary, the values of absorption spectra are low in 1000-1400 nm, but in 1400-2500 nm the values are high with high variation. The hardness range of dragon fruit is 8.73-24.91 N and TSS of 9.20-17.60 brix. Reflectance spectra is better than absorption spectra in predicting TSS and hardness of dragon fruit. Only detrending spectra pretreatment increased the accuracy of NIR spectroscopy in predicting TSS of dragon fruit. However, there is no spectral pretreatment that can improve accuracy in predicting dragon fruit hardness. Increasing the number of PLS factors may increase the accuracy for a while but after that it decreases. The best chemometrics to determine TSS of dragon fruit is using detrending pretreatment of reflectance spectra and 16 PLS factors (r=0.93, SEP=0.66 brix, RPD=2.09). For hardness, the best chemometrics is using original reflectance spectra and 17 PLS factors (r=0.89, SEP=1.75 N, RPD=2.02). NIR Spectroscopy and chemometrics can be used to predict TSS and hardness of dragon fruit accurately and nondestructively.

Determination of Chemical Content of Porang Flour (Amorphophallus muelleri blume) by Near Infrared Spectroscopy

“…Therefore, a rapid and more efficient method is required to cope with the problem, one of which is the near infrared spectroscopy (NIRS) method. NIR spectroscopy has been successfully applied to determine chemical content of agricultural products such as catechin in gambir powder [4], fat and free fatty acid in Jatropha [5], major chemical content of dragon fruit peel flour [6], total soluble solid (TSS) of mango [7], hardness of mangosteen [8], TSS of papaya [9], trigonelline, chlorogenic acid, caffeine content of coffees [10] [11], TSS and firmness of persimmon [12], TSS of dragon fruit [13], classification of coffee origin [14] and patchouli oil [15] as well. NIRS method has also been studied for determining the molecular composition of glucomannan yeast product (GYP) and glucomannan extracted from iles-iles or porang (Amorphophallus oncophylus) using NIRLab N-200 [16].…”