Determination of antioxidant capacity and phenolic content of chocolate by attenuated total reflectance-Fourier transformed-infrared spectroscopy

Chocolate Classification by an Electronic Nose with Pressure Controlled Generated Stimulation

In this work, we will analyze the response of a Metal Oxide Gas Sensor (MOGS) array to a flow controlled stimulus generated in a pressure controlled canister produced by a homemade olfactometer to build an E-nose. The built E-nose is capable of chocolate identification between the 26 analyzed chocolate bar samples and four features recognition (chocolate type, extra ingredient, sweetener and expiration date status). The data analysis tools used were Principal Components Analysis (PCA) and Artificial Neural Networks (ANNs). The chocolate identification E-nose average classification rate was of 81.3% with 0.99 accuracy (Acc), 0.86 precision (Prc), 0.84 sensitivity (Sen) and 0.99 specificity (Spe) for test. The chocolate feature recognition E-nose gives a classification rate of 85.36% with 0.96 Acc, 0.86 Prc, 0.85 Sen and 0.96 Spe. In addition, a preliminary sample aging analysis was made. The results prove the pressure controlled generated stimulus is reliable for this type of studies.

Antioxidant capacity of cocoa beans and chocolate assessed by FTIR

The total antioxidant capacity (TAC) and total phenolic compounds (TPC) of cocoa beans and chocolate produced from spontaneous and inoculated fermentations of different cocoa varieties were evaluated. Fourier transform infrared spectroscopy (FTIR), as well as conventional methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), was used to determine TAC and TPC. Chocolate showed higher (p<0.05) TPC (47.17-57.16mgGAE/g) and TAC (1.66-2.33mMTE/g and 8.86-11.35mMTE/g as measured by DPPH and ABTS, respectively) than cocoa beans (6.30-26.05mgGAE/g, 0.24-1.17mMTE/g and 1.29-4.83mMTE/g for TPC, DPPH and ABTS, respectively). Partial least square (PLS) model for infrared data showed a good calibration coefficient (R²cal>0.94), indicating that the FTIR technique represents a fast and reliable tool to evaluate TPC and TAC in cocoa beans and chocolate.