Characterization and Classification of Almond Cultivars by Using Spectroscopic and Thermal Techniques

Abstract

Three different almond cultivars (Spanish Guara, Marcona, and Butte from U.S.A.) were characterized by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and thermal analysis techniques (differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). All samples were directly analyzed without the need of a previous oil extraction. Similar FTIR bands were observed for all studied cultivars corresponding to specific functional groups characteristics of almond ingredients (water, fat, protein, and carbohydrates). Significant differences were observed between cultivars according to absorbance and maximum wave number values of specific bands observed by FTIR and melting and crystallization parameters obtained by DSC. TGA showed that samples were stable up to around 220 °C. Different stages of degradation were observed with increasing temperature corresponding to the degradation of the complex matrix of the samples. Successful discrimination was obtained for all samples by applying multivariate stepwise linear discriminant analysis (LDA) separately to data obtained from FTIR and DSC. A satisfactory multidisciplinary approach was also performed by inserting together all parameters obtained from the 3 techniques as predictors ensuring higher reliability of the obtained model. The obtained results proved the suitability of the studied analytical techniques combined with LDA for an easy and fast discrimination among different almond cultivars in food processing. Practical Application: The study of spectroscopic and thermal parameters could be used as a control tool for the direct and fast assessment of almond samples in food processing, particularly for protected designation of origin products.