Abstract: A method for concentrating a substance in a milk product, the method including the steps of: feeding the milk product from a tank to a filtering device, filtering the milk product into a permeate and a retentate: such that the substance is concentrated in the retentate, circulating a first part of the retentate over the filtering device, feeding a second part of the retentate to the tank, repeating the circulations to thereby gradually increase a concentration of the substance in the milk product, and stopping the repeating when the concentration of the substance in the milk product has reached a predetermined value.

Abstract: A plant and method of treating low-fat milk, such as skim milk, so as to obtain with a low content of spores and bacteria, wherein the milk is subject to a first microfiltration causing a separation into a first permeate, the first permeate being subjected to an additional microfiltration. This double microfiltration ensures that the acceptable limits for bacterial counts in milk products are not exceeded in case of a membrane breakdown.