The reason why Jews eat corned beef is because corned beef became a staple food in Jewish delis in the United States.
Corned beef became a staple food in Jewish delis in the United States, mainly due to the fact that brisket, the cut of meat which is used for corned beef is a kosher cut of meat and was relatively inexpensive.
This made it accessible to Jewish immigrants that often lived in close proximity to Irish immigrants that adopted corned beef with both communities.
However the origins of corning beef is not specifically Jewish, the widespread consumption of corned beef is linked to Jewish delis in America.
Corned beef is a roast or brisket that has been salt cured with the optional addition of sugar and spices to the cure for added flavor.
Corned beef is often made from a tough beef roast (often a brisket or round roast) that has been slow cured and cooked to tender, salty perfection.
Corned beef often contains high levels of cholesterol , fat and sodium, so that makes corned beef not the healthiest of foods.
It's not typically viewed as a healthy ingredient, but lean cuts of corned beef can be purchased upon request.
And the fat can also be trimmed off, and steaming can also help melt the fat off.
The white stuff in the corned beef is just fat that solidifies as the meat cools off.
It's a natural process and part of the canning process and does not mean the corned beef is spoiled.