Scientific Study

BACKGROUD: For the processing industry, it is crucial to know what effect the roasting process and conditions have on hazelnut quality. The present study investigates, for the first time, on the effects of hot-air and infrared (IR) roasting at different time-temperature combinations on Tonda Gentile Trilobata hazelnut: whole kernels and derived processing products (paste and oil). RESULTS: Nutritional and physical characteristics of hazelnuts and processing products were determined to study the influence of the different roasting conditions as a function of the intended use. The antioxidant profile (DPPH, ORAC and total phenolic content) were analyzed on roasted hazelnut and paste extracts. For a comprehensive understanding of the complex bio-chemical phenomena occurring during roasting, E-nose and near-infrared spectroscopy were also applied. All analytical data were processed using univariate (ANOVA) and multivariate data analyses (PCA) . Hazelnuts derived from IR roasting at higher temperatures (195°C) showed a richer antioxidant profile and a more intense flavour. On the other hand, the yield associated to the oil extraction under the same conditions was unsatisfactory making this process completely inadequate for oil production. Oil obtained by hot-air roasting and IR roasting at lower temperature (135°C) resulted to be of good quality, showing rather similar acidity grade, peroxide number and acidic composition. In particular, a slightly but significantly lower acidity was related to lower roasting temperatures (0.21-0.22% vs 0.27 % for higher temperatures). All roasting conditions tested, allow to quantitatively obtain homogeneous hazelnut paste and from a rheological point of view, higher roasting temperatures gave pastes characterised by higher density and viscosity values. CONCLUSION: IR proved to be a promising alternative method for hazelnut roasting, thanks to its capability in preserving nutritional values and enhancing organoleptic quality.