Here is some background information that will be helpful.
This is an excerpt from the U.S. Army Quartermaster Museum Civil War Rations page.
MARCHING RATIONS
Only when a march took them beyond the range of army wagons, as happened from time to time with the fast-moving cavalry, or when a battle separated them from their primary depots did Union soldiers go without food. The most famous example of the latter was the aftermath of the 1 863 battle of Chickamauga, Georgia. There, by luck and a Union command error, the Confederates routed the Federals from the field and chased the Northerners into Chattanooga, where a siege followed. For about a month, Union soldiers in Chattanooga went on half rations and even ate feed grain meant for the Army's starving animals. When the siege lifted in October, 10,000 horses and mules had died. Still, the Federal ration was more than ample in terms of quantity and calories. It was larger than that of the British, French, Prussian, Austrian, and Russian armies of the same period.
The real trouble began when Billy Yank received the ration. On a march, it usually consisted of four parts: three-fourths pound of salt pork, one pound of hard bread (hardtack), coffee, and sugar. Few soldiers knew much about cooking, and the Army was still about a half century away from training cooks. Further, the soldier's issue of equipment did not include any cooking utensils beyond camp kettles and mess pans, for use by the company in camp or in garrison. Faced with few tools, little culinary skill, a hunk of pickled pork, and around ten thick and large hard crackers made of flour and water, Federal soldiers began to cook. As time went by, they acquired utensils such as cutlery and a tin plate and cup, fashioned boilers by adding a wire bail to an empty tin can, or rigged a frying pan from discarded canteen halves with a green stick to serve as a handle. They also discovered that by forming a mess of approximately five soldiers, preparing meals became a social occasion. The soldier who demonstrated the greatest culinary talent was often appointed the cook. This duty became the envy of other soldiers, because the cook was excused from all other camp chores. After much experimentation and many digestive complaints as a result, Federal soldiers settled on a few tried and true methods of food preparation. There was not much that could be done with salt pork beyond frying it, boiling it, or adding it to a stew. If there was no time for these small luxuries, it could be placed between two pieces of hardtack and eaten as a primitive sandwich. Salt beef, derisively labeled "salt horse" by the soldiers, was hardly fit for consumption. It was so heavily impregnated with salt that it had to be soaked overnight in a running stream. Even then, it was still often rusty from improper packing and gave off an incredible stench. Salt horse was so foul that upon occasion angry soldiers used it-as ammunition with which to pelt the commissary's tent, or staged a mock burial and laid the putrid stuff to rest, complete with feigned military honors.
Link:
Feeding Billy Yank: Union Rations Between 1861 and 1865 — Subsistence & Culinary Arts: History & Heritage of Quartermaster. Content provided by the Quartermaster Foundation. | U.S. Army Quartermaster Museum, Fort Lee, Virginia
qmmuseum.army.mil