Authentication of Avocado Oil (Persea americana Mill.) Using Differential Scanning Calorimetry and Multivariate Regression
The potential application of Differential Scanning Calorimetry (DSC) combined with multivariate calibration was used to verify adulteration of avocado oil from Indonesian avocado cultivars with Refined Bleached Deodorized Palm Superolein (RBDPSO). Avocado oil and adulterant were characterized by significantly different cooling and heating DSC thermal profiles. The addition of RBDPSO makes the shift of overall transitions temperature toward lower temperature, enhancing crystallization, melting enthalpy and developing both process over a narrower temperature range. The change of characteristic exothermic and endothermic event in avocado oil with increasing adulterant was possibly associated with the increase of oleic and stearic acids along the decrease of palmitoleic acid. The multivariate calibration approach was applied to DSC data in order to build the quantitative calibration model for adulterant concentration in a range of 0-50%, (v/v). Partial Least Square Regression (PLSR) and Stepwise Multiple Linear Regression (SMLR) were tested to these mixtures. Generally, both calibration models showed good correlation coefficient (R) with low errors in both calibration and validation sets. But, SMLR model showed better criteria values than PLSR, not only on DSC crystallization profile data but also on heating profiles data. The crystallization models of SMLR and PLSR showed the higher R value (above 0.99) than melting calibration models. The results presented in this study suggest that DSC analysis may be a useful tool for detecting adulteration of avocado oil with RBDPSO. The DSC represent a rapid, environmentally friendly and alternative option for avocado oil quality screening without sample pretreatments.