Experimental investigation of the relationship between the core temperature of hazelnuts and ambient conditions in the drying process

Öz

Hazelnut, which is one of the major export products in Turkey, can be generally evaluated and preserved in dried form. There are difficulties encountered in keeping its internal temperature and humidity constant at desired values because it is commonly exposed to solar energy and dried in outdoor environment. Especially due to rainy and variable weather conditions, it is possible to decay and decompose the inner hazelnut without full drying. Because of improper drying, hazelnuts are known to lose their nutritional value. In this study, the attitude of hazelnut was observed in different ambient conditions and the drying temperatures in hazelnut drying processes performed under laboratory conditions. For this purpose, insulated drying booths for experimental setup were created and air circulation was provided for forced convection by fans. Approximately equal sized hazelnuts were placed in the cabin. The main properties of hazelnuts before and after conditioning were recorded for each experiment. The internal temperature, surface temperature and mass loss of the hazelnut were evaluated together. Drying attitudes were recorded for different types of hazelnuts (round, pointed and long). The optimum ambient conditions and drying temperatures were determined during hazelnut drying process. Drying times at 25-50 0C temperature were determined for hazelnuts with 60% relative humidity under ambient air conditions at 3 m/s rate. It has been understood that keeping the drying speed and temperature high or low causes uncontrolled and insufficient drying. It has been observed that different drying conditions can be applied depending on hazelnut storage properties.

Anahtar Kelimeler

• Hazelnut drying
• Drying rate
• Drying temperature

Kaynakça

1. [1] Marti, Joan Tous. "World hazelnut production”. Available online at:(accessed 11 March 2003), 2001
2. [2] Hoffman, Richard, and Mariette Gerber. "Food processing and the Mediterranean diet”. Nutrients 7.9 (2015): 7925-7964.
3. [3] Pannico, A., et al. Non-destructive detection of flawed hazelnut kernel sand lipid oxidation assessment using NIR spectroscopy. Journal of Food Engineering 160, 2015, 42-48.
4. [4] Mercanligil, S. M., et al. "Effects of hazelnut-enriched diet on plasma cholesterol and lipoprotein profiles in hyper cholesterolemic adult men." European Journal of Clinical Nutrition 61.2 (2007): 212.
5. [5] Yucesan, F. B., et al. "Hazelnut consumption decreases the susceptibility of LDL to oxidation, plasma oxidized LDL level and increases the ratio of large/small LDL in normolipidemic healthy subjects. Anadulu Kardiyoloji Dergisi: AKD 10.1 (2010): 28.
6. [6] Dutta, S. K., V. K. Nema, and R. K. Bhardwaj. "Drying behaviour of spherical grains”. International journal of heat and mass transfer 31.4 (1988): 855-861.
7. [7] Steffe, J. F., and R. P. Singh. "Diffusion coefficients for predicting rice drying behaviour." Journal of Agricultural Engineering Research 27.6 (1982): 489-493.
8. [8] Keey, R. B. Drying of loose and particulate materials. CRC Press, 1991.

9. [9] Gröber, E. G. Warmeübertragung; 3. Auflage, Springer-Verlag, Berlin-Heidelberg, New York, 1963
10. [10] Keey, R. B., and M. Suzuki. "On the characteristic drying curve." International Journal of Heat and Mass Transfer 17.12 (1974): 1455-1464.
11. [11] Daloğlu, A., Çok katmanlı kürede geçici rejimde ısıtransferinin nümerik hesaplanması, Yüksek lisans tezi,. KTU, Trabzon, 1982
12. [12] Ünal, A. and Daloğlu, A., Küresel şekilli kompozit cisimlerde ısı transferi, 10. Ulusal Isı Bilimi ve Tekniği Kongresi, Ankara, 1995, 139-148
13. [13] Demirtas, C., Teoman A., and Kaygusuz, K., "Drying behaviour of hazelnuts." Journal of the Science of Food and Agriculture 76.4 (1998): 559-564.
14. [14] Kaya, A. Aydın, O. and Demirtaş, C., "Experimental and theoretical analysis of drying carrots." Desalination 237.1-3 (2009): 285-295.