**Acknowledgements**

The author Antónia Macedo acknowledges to the project LACTIES (Innovation and eco-efficiency in the dairy sector), PDR2020-1.0.1.-FEADER-030773, and the research group LEAF (Linking Landscape, Environment, Agriculture and Food) for funding this work.

## **Conflict of interest**

The authors declare no conflict of interest.

of lactose near the membrane surface, causing a higher increase in the osmotic pressure and concentration polarization phenomena. On the other hand, since the pH was 6.06 and the initial concentrations of calcium and phosphate were also higher than those of PUF-G, most probably, mineral fouling occurred due to the formation of insoluble calcium phosphates. In the case of PUF-G, the lower pH (5.43) and calcium and phosphate concentrations, due to the effect of dilution by diafiltration, were less prone to mineral fouling, leading to a more stable permeate flux. In spite of that, the permeate fluxes were lower during all the run, likely because of the highest concentration of chloride ions in goat cheese whey, which caused a greater initial osmotic pressure and therefore a lower effective transmembrane pressure. Beyond this, it is likely that also protein fouling contributed to this behavior since the pH of PUF-G was closest to the isoelectric point of β-lactoglobu-

*), at T = 25°C [20].*

*Variation of average (three replicates) permeate fluxes with the volume concentration factor (VCF) for the*

*) and PUF-G*

*concentration by nanofiltration of PUF-S (ΔP = 3.0* � *106 Pa; <sup>&</sup>lt;v<sup>&</sup>gt; = 1.42 m s*�*<sup>1</sup>*

*Recover of lactose (lactose concentrate) and whey proteins from cheese whey: WPC = whey protein concentrate; DF concentrate = whey protein concentrate of UF/DF; lactose concentrate (obtained after NF/DF) [20].*

These results suggest that, in order to reach a better NF performance for recovering lactose, the following procedures should be applied: (1) precipitate calcium or use ionic exchange resins with the objective to reduce calcium concentration in the

lin, the most abundant whey protein.

*(ΔP = 2.0* � *106 Pa; <sup>&</sup>lt;v<sup>&</sup>gt; = 0.94 m s*�*<sup>1</sup>*

**Figure 3.**

*Lactose and Lactose Derivatives*

**Figure 4.**

**30**

*Lactose and Lactose Derivatives*
