WINETECH Technical Yearbook 2019

process is limited by the low temperature. Flotation can be a handy process to add the fining agents, without unnecessary oxygen uptake. Many Provence winemakers add the fining agents during the first third of alcoholic fermentation. Each fining agent has specific characteristics regarding size and results. Some can react with the polyphenols in the juice, while other will react with polymerised tannins. Combinations with PVPP can be used to remove the full spectrum of phenols, which can oxidise colour and flavours. Casein and PVPP combinations are critical when the juice is already oxidised and has an orange colour. Rosé wine is associated with fruitiness. The use of sound good quality is a basic requirement for this attribute. Red grapes can contain the same concentration of thiol precursors as Sauvignon blanc, but phenols in the juice can bind it and make it non- volatile. It is consequently important to remove such phenols and use yeast strains, which can convert the precursors into thiols to produce fruity rosé wines. The mouthfeel of rosé wines can be improved by keeping the juice at 0°C for 7 to 14 days and circulating the lees twice daily

with dry ice or nitrogen. It can increase the polysaccharide concentration in the juice, which will have an impact on the mouthfeel. An acceptable colour is a basic requirement for rosé wines. The colour is influenced by the cultivar, fining agents, sulphur dioxide concentrations, harvesting methods, enzyme additions, destemming and crushing. If all the phenolic compounds, that are responsible for oxidation are removed, the colour should not change, but if it is not the case the colour will gradually change to brown or orange. In Provence cellars usually have rosé wines with different colours and intensity, which can be blended to ensure an acceptable colour in the wine. Stabilisation of Provence rosé wines are done in standard ways. Sodium bentonite is used during fermentation and after final blending for protein stabilisation. Carboxymethylcellulose (CMC) is used for tartrate stabilisation (Rossi et al. , 2019). REFERENCE Rossi, C., Seabrook, A. & Mariani, A., 2019. Vegan rosé – lessons from Provence. Australian and New Zealand Grapegrower and Winemaker , February 2019: 54-57.

PHOTO 2. Different rosé colour nuances.

thiol flavours. Comprehension must also exist for the difference between chemical and enzymatic oxidation. Sulphur dioxide and ascorbic acid can control enzymatic oxidation to a certain extent, but chemical oxidation can still occur over time. It is

consequently essential to remove phenolic acids, which can otherwise be oxidised at a later stage. The effective fining of juice usually requires dosing with a venturi, when the juice is still cold. The uptake of oxygen during this