How can you prevent a cheesecake from cracking?
Cheesecakes crack because the filling expands during cooking and then contracts while it cools. If the filling is not able to relieve the stress caused by this contraction in some way, it cracks. There are a few ways to help prevent cracking, according to Harold McGee. They come down to ways to either reduce expansion or allow the filling to contract more uniformly.
To reduce expansion start by not over mixing ingredients. The longer the ingredients are blended, the more air is incorporated, which expands during cooking, causing the filling to expand. If you are using an electric mixer, use the lowest speed possible to do the job. The downside, though, is that the resulting cheesecake may be more dense.
Also, cook the cheesecake at as low a temperature as possible. A longer cooking time means more time for bubbles to escape. If you can, use a water bath to moderate the cooking temperature. If you are using a springform pan in a water bath, place the pan onto two or three layers of aluminum foil and then bring the foil up around the outside of the pan to keep water out. The water bath may extend the cooking time, but it is the best way to cook egg custards, like cheesecake.
To get the filling to contract uniformly after cooking, do not overcook the cheesecake. Shirley Corrihersuggests that there should be an area about three inches (7.5 cm) in diameter in the middle that is "still wobbly and shaky and ... looks undercooked." For a more accurate estimate, use an instant read thermometer. Insert the thermometer, starting at the corner edge so as not to poke a hole in the top of the cheesecake, angling down and in so that the tip is close to the center of the filling. For food safety, eggs should be cooked to 160°F (71°C), however too much above that and the filling may start to separate and become grainy (see the KitchenSavvy posting Custards and Sauces).
If you are using a water bath, you can cook the filling to about 145-150°F (63-66°C), remove the cheesecake from the oven and allow the cheesecake to remain in the water bath, out of the oven, for another hour. During that time residual heat will finish cooking the filling until it has reached the desired temperature. If the temperature reaches 155°F (68°C) before you take the cheesecake out of the oven and you are using a water bath, remove the cheesecake from the bath and allow it to cool on the counter. If you didn't use a water bath at all, cook the cheesecake to 155°F (68°C). In either case, heat transferred from the edges to the center will finish the cooking to a safe temperature.
Cooking to a higher temperature, or until the center is no longer wobbly makes the filling less elastic, and more likely to crack.
Once the cheesecake is cooled to lukewarm, cover and refrigerate.