The effect of wheat boiling time, bulgur particle size, drying time and temperature on some physical properties of hot air dried tarkhineh

Abstract

Tarkineh is one of the traditional products of western part of Iran. This work was carried out to study drying behavior of Tarkineh. The effect of wheat boiling time (0, 1 and 3.5 hours), drying temperature (70, 80 and 90 ^°C), drying time (from 30 to 900 minutes) and bulgur particle size (fine, medium, coarse) on drying behavior of Tarkineh were analyzed. Different mathematical models were applied to evaluate the behavior of Tarkineh during hot air drying and color changes of Tarkineh during hot air drying was assumed using image processing. At the beginning of the drying process, the L* decreased rapidly and b* increasing quickly, but both were relatively stable afterward. a* slightly decreased initially but then depending on the type of sample increased or remain constant. When bulgur particle size increases, generally, the amount of L* increase but a* and b* decrease. The results indicated that At 70 ^°C, the logarithmic model can present better predictions for the moisture transfer than other models for ultra cooked samples but for raw and cooked samples, the two-term model were appropriate. At 80 and 90 ^°C, the two-term model was the best descriptive for ultra cooked samples but for raw and cooked samples, the Midilli-Kucuk model were appropriate. Mentioned variables had major effect on the drying behavior of Tarkhineh. For increasing the production rate and improving the color of Tarkineh, boiling of wheat for one hour and drying at 80^°C is recommended.