Effect of Different Roasting Methods, Blanching and Pasteurization Conditions on Physicochemical and Sensory Characteristics of Hazelnut Milk

High nutritional value and bioactive compounds in hazelnut has become a valuable nutrient. One of the ways to increase per capita consumption of hazelnut is processing of it with different methods such as production of hazelnut milk. In this study, application of different roasting methods (infrared, microwave and hot air oven) blanching time (0, 15 and 30 min) and pasteurization conditions (5 min at 95°C, 15 min at 85°C and 25 min at 75°C) in hazelnut production were investigated. Also, the asymmetric methods (completely randomized factorial and partial least squares regression) and symmetric methods (coefficients of determination and principal components analysis) were used for study of physicochemical characteristics, color parameters and sensory aspects. The results of this study showed that pH, physical stability index and L * significantly increased (p˂0.05) but the acidity, total solids content, protein, fat, viscosity and b * decreased with increasing of blanching time. Hazelnut roasting using infrared method, blanching for 15 minutes at 95 °C and then pasteurization for 15 minutes at 85 °C achieved the best physicochemical and sensory properties of hazelnut milk. It could be found from principal components analysis (PCA) that roasting methods of microwave and hot air oven results in the increase of sensory scores of cooked, chalky, roasted and bitter flavors. pH and acidity had the best significant correlation coefficients with physicochemical and sensory properties. Obtained R2 of partial least squares regression models were above the medium range. It shows the high efficiency of these models in prediction of sensory characteristics of infrared hazelnut milks from color analysis indices.