Setting a protocol for hazelnut roasting using sensory and colorimetric analysis: influence of the roasting temperature on the hazelnut quality of Tonda Gentile delle Langhe cv

The North Western Italy has a tradition in handmade and industrially processed sweets prepared with roasted hazelnuts. The aim of this study was the evaluation of the influence of roasting temperature on the final quality of Piedmont hazelnut (cultivar Tonda Gentile delle Langhe, TGL). Sensory and colorimetric analyses were performed to define a quality profile of the fruit relating to the roasting technique parameters. Sensory analysis was conducted on roasted kernels through a trained panel. The effects of the different temperatures on colour were evaluated with two different techniques, colorimeter and scan-marker (scanner), in order to define the best method to individuate correlations between roasting temperature and colorimetric results. The quality traits of nuts roasted at different temperatures were compared: the samples roasted at lower temperature showed lighter colour; the hue values were higher in the roasted chopped nuts, while the chroma was higher in the paste samples. For both paste and chopped kernels a larger range of values was found in comparison with the results given by the colorimeter. As for the sensory analysis, we found that “hazelnut odour” varied significantly among the samples: this descriptor is able to significantly differentiate between different samples Our study showed that the modulation temperature is a very important parameter with a strong influence on the characteristic roasted flavour and colour of the product.