Fuente: WIPO "tomato" The present invention provides a method of detecting microorganisms in a substance. The method includes the steps of providing a fluid sample of a substance containing particles, taking measurements of a characteristic of the particles at a first and second time, calculating the difference between the measurements of the characteristic at the first time and the second time, and determining, based on that difference, the microorganism content in the fluid sample. The method enables the detection of microorganisms in the substance based on measurements of a characteristic of particles in that same substance. Also provided is a method of generating a reference profile for a substance.