Finally, the proposed method was applied to analyse the effluents generated at different stages of a CIP process in a pilot plant aimed at the manufacturing of cheese. As an example, in Fig. 7 are shown the spectra obtained for some samples analysed. One of the register (7a) corresponds to the sample which contained the highest fat content. This sample was collected during the intermediate rinsing step, and it had to be diluted with water (factor dilution, 1:10) to adjust the fat content to the linear working interval. The fat content found for this sample was (79±7) mg/L (n=3). The other two samples were collected during the wash ( 7b) and final rinsing ( 7c) steps; the spectra showed that these samples contained fat levels below the LOQ and below the LOD, respectively. Some of the samples analysed contained a significant amount of suspended solids. However, these samples could be easily passed through the membranes, and reproducible absorbances were measured after an effective sample homogenization.