Abstract: Loose particulate material to be frozen is supplied to a rising current of refrigerating fluid such as cold air. The velocity of the refrigerating fluid is such that the particulate material to be frozen is supported dynamically, or substantially suspended, by the refrigerating fluid so that the particulate material to be frozen settles slowly through the rising refrigerating fluid, or is slowly transported by such refrigerating fluid either upward or translationally. The refrigerating fluid may carry the material to be frozen through successive freezing chambers through which the refrigerating fluid rises. Such chambers may be vertical or may be inclined upwardly.