Effect of Processing Temperature on Storage Quality of In-Shell Hazelnut

Drying is the one of the oldest methods for increasing the shelf life of food products. The objective of the present study was evaluation of effect of different drying temperatures on drying time and storage quality parameters of in-shell hazelnut.

Hazelnuts were dried as a thin layer at three temperatures (40, 50, and 60 °C). The time required for drying and quality parameters (lipid and protein content, acidity, and peroxide value) were evaluated. Besides, sensory and oxidation evaluations were performed in order to evaluate the effect of the drying temperatures on quality of hazelnuts before and after 6-month storage. Data were analyzed by SPSS software (V. 16.0).

The mean drying times at 40, 50, and 60 °C were 29.75, 25, and 20.25 h, respectively. In fact, an inverse significant (p<0.05) relationship was observed between temperature and time of the hazelnuts drying process. The mean protein content of the hazelnuts dried at 40, 50, and 60 °C were 13.06, 12.83, and 13.62 (% dry basis), respectively. Lipid content of the samples were significantly (p<0.05) increased with drying temperature. The lowest acidity and peroxide values were recorded for the samples dried at 60 °C with the values of 0.15% oleic acid and 1.3 meq/kg, respectively. Sensory results showed that all of the treated hazelnuts were acceptable after six months storage.

The evidences of the present study point that in-shell hazelnuts drying at temperature of 60 °C can lead to production of good quality products.