D OUGH T HICKNESS FOR KURTOSKALACS By: Timothy Ruggles and Heath Whittier

C HIMNEY S WEETS - K URTOSKALACS Kurtoskalacs is a centuries old dessert from Transylvania, a type of sweet bread wrapped around a wooden dowel and baked quickly over an open fire or in a rotisserie oven. Over the summer I worked at the Provo Farmer’s Market baking them. The process has been unchanged for centuries and is difficult to get right. The challenge to making the perfect kurtoskalacs is making the dough the right thickness so they cook quickly and the sugar on the outside caramelizes while the dough inside stays soft.

T HE P ROBLEM : P REDICTING THE REQUIRED DOUGH THICKNESS Sugar carmelizes at 160 C Dough is cooked at 93 C Using these two temperatures for the boundaries on each side of the dough we set up an equation to predict the perfect thickness. Because the dough is wrapped around a dowel we used the Approximate analytical solution for transient conduction through an infinite cylinder.

A DAPTING THE M ODEL This analytical solution was not meant for a non- homogenous cylinder. Because the dough and the dowel have differing properties, this model will not necessarily be accurate. The conduction coefficient was taken to be an average between dough (apprx. 0.4 W/mK) and wood (0.16 W/mK), 0.28 W/mK. We set the time for the inside to finish cooking and the time for the outside sugar to caramelize equal to each other.

S OLUTION AND RESULTS The equation simplified to the following: We found ζ from table 5.1 using Bi=h*r/k, and assumed it did not change with t. Estimated h=20, k=.28, r=.0381m Bi=2.72 ζ=1.7 Using Mathcad we then solved for t Which gives us t= inches

C ONCLUSIONS Our model predicted the ideal thickness for a crispy outside and a soft inside to be about a quarter of an inch. This value is close to common practice, but still too small. Our model needs further refinement to accurately predict baking parameters.

R ECOMMENDATIONS The inaccuracy of our solution may be due in part to the inadequacy of the model and poorly estimated properties and parameters. Oven temperature and convective coefficient were estimated because the oven was unavailable. If they were measured, more precise results could be obtained. The non-homogenous nature of the problem lends itself to a finite element analysis. Although our model was good for an initial guess, FEA would yield better results.

A PPLICATIONS Right now, Chimney Sweets, the company I worked for, is developing new ovens. A working model for the temperature of a kurtoskalacs as it bakes could help in oven design, setting target oven temperatures and convective coefficients in order to preserve the traditional taste of the kurtoskalacs.