The paper presents an ultrastructural analysis of sarcolemma in the smooth muscle of pig stomachs, raw, cooked at 90°C and sterilized at 121°C. The analyses were made using a transmission electron microscope (ТЕМ) which confirm the presence of characteristic, compact intracellular linkages in the raw material. The plasma membrane in the muscles cooked at 90°C is partially broken, and collagenous fibres are 'sinking' into the basement membrane. For this reason, sterilization is recommended for these by-products since it affects the destruction of cellular membrane.