**12. Grape juice clarification and filtration**

In fact, white grape juice clarification was one of the first applications of enzymes in enology. After pressing, the grape juice is turbid as it contains numerous particles that confer a negative trait. Clarification can be achieved by gravity spontaneous setting, but in most occasions, it should be induced and facilitated by the addition of commercial pectolytic preparations [70, 71]. In all cases, the addition of pectolytic enzymes accelerates the clarification process; its technological efficacy is easily determined by pilot experiments measuring juice turbidity, and the methodology to be employed can be optimised for each specific type of elaboration. Further clarification after fermentation will facilitate the subsequent filtration of the resulting wine. Filtration is a key procedure to obtain a premium wine, and it is also most delicate because at this stage the colloidal matrix of the wine is very complex. The aim of adding pectolytic preparations at this stage is to increase wine filterability by degrading pectins and a variety of colloids (other polysaccharides, protein aggregates, glucans from *Botrytis cinerea*, yeast mannoproteins) responsible for clogging filtration membranes. Enzyme addition allows filtering larger wine volumes before filter clogging, and the enzyme cost is compensated for by the reduction in filtering costs and time reduction. Moreover, filtration is a process that all wines and most grape juices should undergo before bottling.
