Assessment of the Hazelnuts Roasting Process by Pressure Differential Scanning Calorimetry and MID-FT-IR Spectroscopy

The effect of the roasting process on the quality of hazelnuts (Corylus avellana L.) lipidic fraction was investigated by pressure differential scanning calorimetry (PDSC) and middle Fourier transform infrared (MID-FT-IR) spectroscopy. The data obtained were referred to and related with fatty acid composition, free fatty acids content, peroxide value, anisidine value and tocopherols concentration measured by standard techniques. These methods were used to decipher between the roasted hazelnuts (shelled and in-shell) treated in different thermal conditions (100 A degrees C, 130 A degrees C and 160 A degrees C) and time (10, 30 and 60 min). The results of free fatty acids (FFA), peroxide value (PV) and anisidine value remained low for all roasting conditions applied and were within quality requirement ranges. The shell left on hazelnuts during the roasting process limited hazelnuts oxidative deterioration, hence it showed protective function. Minor changes occurred in the fatty acid and tocopherol contents and compositions. PDSC, as an appropriate unbiased method for assessing the oxidative stability, revealed a slight elevation of oxidative stability as the temperature and time of the roasting process increased (p < 0.05). Discriminant models constructed with the use of principal components (PC) procedure confirmed the ability of MID-FT-IR to monitor the roasting process within a certain range of temperature and time applied.