Abstract: In a first aspect the invention comprises an apparatus for heat-treating products, comprising: a retort into which the products to be treated are receivable; heating means for heating the retort; coolant spray means for spraying a liquid coolant onto products received in the retort; and shielding means to substantially prevent coolant sprayed from the coolant spray means from impinging on the interior of the retort. In a further aspect the invention comprises a method of protecting a retort comprising a retort wall defining a volume into which products to be treated are receivable, heating means for heating the retort, and coolant spray means for spraying a liquid coolant onto products received in the retort against thermal shock, the method comprising mounting shielding apparatus within the retort to substantially prevent liquid coolant sprayed from the coolant spray means within the retort from impinging on the interior of the retort wall.