Hazelnut skin powder: A new brown colored functional ingredient

- Hazelnut skin is a rich source of dietary fibers and phenolic compounds.
- Its oil fraction is very rich in tocopherols and oleic acid.
- Defatted hazelnut skin may be used as natural brown coloring agent.
- High-shear homogenization is useful to obtain low-micron sized skin powder.

Hazelnut skin arises as a by-product in the roasting process of hazelnuts. This study aimed to investigate the potential of its utilization as a brown colored functional ingredient. Chemical composition analyses revealed that hazelnut skin is a very rich source of dietary fibers (67.7%) and phenolic compounds (233 mg GAE/g). Its oil fraction (14.5%) was found to contain very high amounts of tocopherols (2.77 μg/g) and oleic acid (75.2%). After defatting, coarse and fine hazelnut skin powders were obtained by low and high shear homogenization. High shear homogenization was performed at different pressures (10, 20 and 30 ksi) for different pass cycles (1, 3, 5 and 10). The powder samples were analyzed for particle size distribution, color, individual phenolic compounds, total phenolic content, and total antioxidant capacity. A desirable low micron particle size for the hazelnut skin for incorporation into food formulations was achieved by means of high shear homogenization, meanwhile there was no significant change in phenolic composition and antioxidant capacity.