Foamy liver is seen as -

In putrefaction liver becomes soft and later studded with blisters due to production of gas by Cl.welchii. Initially the gas appears as yellowish grey dendritic figures in parenchyma. Later bubbles develop and gives liver a honeycomb or foamy appearance. Later liver turns coal black. Dr. Narayana Reddys Synopsis of Forensic Medicine & Toxicology 27 th edition pg. 85.