There are a variety of torque limiting couplings on the market and they all either slip or disconnect to avoid breaking the shaft.  Many of the better manufactures will supply a slip clutch or a limiter with the equipment. I would contact your equipment supplier for the best device.  If they don't have one, just Google the term "torque limiting coupling."  However, a torque limiter may not be the best solution and can cause production problems (product quality, downtime to clean the screw) due to the slip of the drive.  It may be better to redesign the screw to avoid high torque.  I would do some shear testing of the material over the range of moisture in the screw to see what the correct screw design should be.  It may be a more reliable solution to replace or use a different screw design, which will not have periods of high torque.