Impact of roasting on oxidation characteristics of less well-known hazelnut cultivar: Turkish hazelnut (Corylus colurna)

Abstract

In this work, the roasting processes on some quality parameters and oxidation of lipid fraction for a wild Turkish hazelnut (Corylus colurna) cultivar were studied and the sensitivity to lipid oxidation of the hazelnut samples stored under the accelerated conditions were determined. Changes in water activity, moisture content, oil content, colour values, free fatty acids, peroxide value and specific extinctions (K 232, K 270) were determined in the hazelnuts with different roasting conditions. The results showed that the roasting conditions significantly affected the fundamental characteristic parameters mentioned.In more detail, the water activity and moisture content of hazelnuts were found to decrease while L*- and b*-values of roasted hazelnut samples were observed to increase with roasting conditions. The higher values in free fatty acids and specific extinctions were experimentally measured in roasted samples at 165 degrees C for the durations of 15 and 30 min. The fatty acid compositions of oils extracted from the hazelnuts were obtained to change slightly with the roasting process. The major fatty acid was determined as the oleic acid (ca. 80%). In accelerated conditions, the rates of the increment in the PV, K 232, K 270 were noted to be significantly higher in the roasted as compared to the enhancement rates of those in the unroasted hazelnuts during the storage at 60 degrees C. In the same conditions, the linoleic acid contents of oils extracted from the hazelnuts decreased with the storage. All in all, the roasting of hazelnuts led to decrease the oxidative stability throughout the storage in accelerated conditions. The study showed the effect of roasting temperature and time on some quality parameters of Turkish hazelnut cultivar.