Determination of convective heat transfer coefficient during frying of potato dough

In this study, the influence of oil temperature, water migration and surface temperature of potato dough ball on convective heat transfer coefficient was investigated. The convective heat transfer coefficient during deep-fat frying was determined at temperatures 160, 170, 180 and 190 °C. The dough ball of wheat flour with different amounts of whole potato flour having a radius of 2.5 cm was used as a sample. Heat transfer coefficient was the highest at the beginning of deep-fat frying process (197.25 ± 1.39 to 774.88 ± 3.90 W/m2 K), and the lowest in the case of setting up a uniform period of water migration from sample, which corresponded to surface temperatures slightly higher than 100 °C (94.22 ± 0.33 to 194.84 ± 0.91 W/m2 K). Addition of whole potato flour in dough considerably decreased heat transfer coefficient regardless of the frying oil temperature. Higher oil temperature for deep-fat frying increased values of heat transfer coefficient for the same composition of spherical shape dough.