How does the physics of the rotation behaviour of the Roti can be explained?

Question

Many times we see in kitchen when someone makes Roti, they first take the atta (flour) and make a circle shape (not perfect but ideal case let it be) we often see when the roller is moved above it to make the roti more flatter and circular, the roti rotates by itself to make the portion which is not yet flattened more to get the chance of flattening, how does this happens?

A video demonstrating the process: https://youtu.be/BPeY0XloQ0Y?t=76.
Update: The method seems to be rolling forward and backward through hands and at some critical times the Roti starts rotating a bit . Maybe somehow some force is providing a torque about centre , could the reason be friction?

Answer 1

In the video you linked, it looks almost like the person is turning it around manually. When the rolling-pin moves up, she seems to be pressing on the left side, and when it moves down, she seems to be pressing it on the right side.

Have you asked somebody who rolls Roti if this is indeed how they roll it? Are you sure people don't do this manual rotation when they are rolling Roti?

Answer 2

I think the rolling pin slightly rotates the dough when rolling, perhaps in some random direction, because it is hard to roll perfectly straight out from the centre. Continuing rolling in the same pattern causes the dough to continue to spin.

In fact, it is possible that certain rolling patterns reach a sort of resonance with the dough spinning, similar to pushing someone on a swing set, such that the rate of rotation increases with each back-and-forth of the rolling pin (up to a point).

Answer 3

Let us imagine that we have some shape made of dough on xy plane, and the rolling pin is initially on axis x. Let us assume that the dough currently covers a segment on axis x from x=-5 to x=5. Let us also assume that the cook intends to roll the pin to the points on dough that are all currently have coordinate y=1. If the thickness of the dough is larger for x=-5 than for x=5 and if the thickness of the dough will become the same in every place where the rolling pin will have run, then the pin will move farther at x=-5 than at x=5, as a result, the dough not affected by the pin (with the initial coordinates y>1) will turn to the right.