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62 P R A C T I C A L W I N E R Y & V I N E YA R D October 2015 W I N E M A K I N G freezing and lees removal compared to the higher protein concentration beforehand is most likely due to lees sediment removal. Yeast mannoproteins released during fermentation and autolysis have been described as the major foam promoters due to their structure, which favors adsorption to the foam gas/liquid interface. 1,12,14,15,22 LTPs associated with beer gushing have been identified in Riesling still wine as well as thaumatin-like proteins with molecu- lar masses of approximately 25 kDa. 19,24 Unfortunately there is currently no recom- mended grape protein concentration in base wine at bottling or in the finished sparkling wine (grape pro- teins and yeast m a n n o p r o t e i n s ) due to the many variables involved that include grape variety, yeast strain, length of lees aging and production techniques. 6 Further research into the types of proteins and their concentrations in Riesling juice, base wine and finished sparkling wine could reveal their foam- ing and gushing potential, but that was beyond the scope of this study. Yeast cell counts were much higher in the bottles of wine that gushed when disgorged before addition of the dosage, which is undoubtedly due to either incom- plete riddling and/or insufficient time in the neck freezer. If the lees sediment is fro- zen too quickly, yeast from the deposit can drift back up into the clear wine above the deposit. Ideally the lees sediment "plug" should be firm, not hard. The minuscule turbidity difference in our trial was likely due to rogue yeast sediment remaining in the bottle neck or bottle variation. A slight difference in malic acid level was found in the wine after the crown caps were removed. Given the lack of research reporting a change in malic acid level at this stage, it is most likely due to bottle variation. There was no difference in phe- nolic concentration or residual sugar level. Although the bottles that gushed after neck freezing and crown cap removal were not tartrate-stable, the tartrate-stable bottles did not gush at each light/temperature treatment. All bottles of wine were from the same tank and filtered and cold stabilized after blending. This result could simply be bottle variation due to the location in the riddling cage impacting bottle temperature or possibly from the low pH of 2.9 typi- cally found in sparkling wines (the spar- kling wine pH range is generally between 2.8 and 3.0 in finished wine) combined with the ambient temperature effect. Alternatively, effective riddling and neck-freezing prior to disgorging may have removed some tartrate crystals with the yeast sediment when the non-gushed bottles were disgorged. Although bottle variation is inevitable within méthode champenoise sparkling wine production, it is possible to reduce the incidence with careful management (see Table 4). Table 3. Overall compositional comparison of gushed bottles and non-gushed bottles (after neck freezing and lees removal). All values displayed as mean ± standard deviation of replicate samples. Non-gushed Gushed bottles Analysis bottles (mean ± SD) (mean ± SD) Bottle pressure (bars) ......................... 6.2 ±0.1 .............................. 5.9 ±0.2 Yeast cell count ...................................... 0.0 ±0.0 .......... 7.5 x 10 3 ± 7.5 x 10 3 Protein concentration (mg/L) .......... 5.2 ±2.3 .............................. 4.4 ±1.9 Protein stability (∆NTU) ..................... 0.2 ±0.1 .............................. 0.3 ±0.1 Malic acid (g/L) ....................................... 2.4 ±0.6 .............................. 2.6 ±0.1 Residual sugar (g/L) pre-dosage ..... 0.4 ±0.0 .............................. 0.4 ±0.0 Phenolic concentration (A.U.) ......... 4.6 ±0.1 .............................. 4.5 ±0.1 Tartrate/cold stability .................................... Yes .......................................... No Sanitary Stainless Welding Inc. is the exclusive North American distributor for the Marzola product line