An insect-repellent and/or insecticidal product is described obtained by concentration of by-product vegetable water from olive milling, characterized in that it has a dry matter content of 10% or higher and a pH of 5 or higher a method for the preparation of such a product is also described comprising the step of making a continuous stream of said vegetable water flow in the state of a turbulent thin layer, in contact with a heated wall of a turbo-concentrator comprising a horizontal-axis cylindrical tubular body (1), having an inlet opening (5) for said vegetable water and a final product discharge opening (7), a heating jacket (4) to bring the inner wall of said tubular body at a predetermined temperature, and a bladed rotor (8), rotatably supported in the cylindrical body (1).
