Abstract: A process for cutting food products, especially brittle food products such as frozen fish. The process involves mounting a cutting blade on an ultrasonic system in a manner such that the blade is vibrated parallel to the out face and the aspect of travel of ultrasound down the blade is approximately 90.degree. to the cutting edge of the blade. The cutting blade has a significantly blunted tip. The cutting is effected, at least in part, by localised heating of the food product. The process permits cutting of brittle food products into portions with minimum wastage. Fracturing is also reduced thus allowing the portion size to be accurately controlled and providing a final portion having smooth surfaces.