A foodstuff refrigerating machine comprising: a boxlike casing which is provided, on the inside, with a large thermo-insulated compartment adapted to contain the foodstuff product to be preserved; an electrically-operated cooling assembly adapted to cool down what contained inside the thermo-insulated compartment; and an electronic control unit that commands the cooling assembly; the cooling assembly being provided with a heat-pump unit that comprises: a high-pressure heat exchanger where the high-pressure refrigerant cools down; a low-pressure heat exchanger where the low-pressure refrigerant heats up; a gas expansion device that is interposed between the outlet of the high-pressure heat exchanger and the inlet of the low-pressure heat exchanger, and is adapted to cause the rapid expansion of the refrigerant that flows from the high-pressure heat exchanger towards the low-pressure heat exchanger; a compressor which is interposed between the high-pressure heat exchanger and the low-pressure heat exchanger, and is adapted to compress the refrigerant that flows out of the low-pressure heat exchanger and returns to the high-pressure heat exchanger; and a supplementary heat exchanger provided with a high-pressure branch crossed by the refrigerant directed from the high-pressure heat exchanger to the gas expansion device, and with a low-pressure branch crossed by the refrigerant directed from the low-pressure heat exchanger to the compressor intake, so as to transfer heat from the high-pressure refrigerant directed towards the gas expansion device to the low-pressure refrigerant directed towards the intake of said compressor; said refrigerating machine being characterised in that the heat pump unit additionally comprises: a draw-off line which is adapted to selectively divert, towards the inlet of the low-pressure branch of the supplementary heat exchanger, a part of the high-pressure refrigerant flowing out of the high-pressure branch of the supplementary heat exchanger, simultaneously subjecting said refrigerant to a rapid expansion in order to reduce both temperature and pressure; and a bypass line, which is arranged in parallel to the low-pressure branch of the supplementary heat exchanger, and is adapted to divert at least part of the gaseous-state refrigerant towards the intake of said compressor, while bypassing the low-pressure branch of the supplementary heat exchanger; and in that the electronic control unit controls said compressor and said draw-off line. the cooling assembly being provided with a heat-pump unit that comprises: a high-pressure heat exchanger where the high-pressure refrigerant cools down; a low-pressure heat exchanger where the low-pressure refrigerant heats up; a gas expansion device that is interposed between the outlet of the high-pressure heat exchanger and the inlet of the low-pressure heat exchanger, and is adapted to cause the rapid expansion of the refrigerant that flows from the high-pressure heat exchanger towards the low-pressure heat exchanger; a compressor which is interposed between the high-pressure heat exchanger and the low-pressure heat exchanger, and is adapted to compress the refrigerant that flows out of the low-pressure heat exchanger and returns to the high-pressure heat exchanger; and a supplementary heat exchanger provided with a high-pressure branch crossed by the refrigerant directed from the high-pressure heat exchanger to the gas expansion device, and with a low-pressure branch crossed by the refrigerant directed from the low-pressure heat exchanger to the compressor intake, so as to transfer heat from the high-pressure refrigerant directed towards the gas expansion device to the low-pressure refrigerant directed towards the intake of said compressor; said refrigerating machine being characterised in that the heat pump unit additionally comprises: a draw-off line which is adapted to selectively divert, towards the inlet of the low-pressure branch of the supplementary heat exchanger, a part of the high-pressure refrigerant flowing out of the high-pressure branch of the supplementary heat exchanger, simultaneously subjecting said refrigerant to a rapid expansion in order to reduce both temperature and pressure; and a bypass line, which is arranged in parallel to the low-pressure branch of the supplementary heat exchanger, and is adapted to divert at least part of the gaseous-state refrigerant towards the intake of said compressor, while bypassing the low-pressure branch of the supplementary heat exchanger; and in that the electronic control unit controls said compressor and said draw-off line.