# Development and Analysis of an Intensified Batch-Fed Wine Fermentation Process
## 4 Discussion  
The results of the pilot and sensory studies indicate that the intensified wine processes can realize substantial cycle time improvements, while using already-available winemaking equipment and risking minimal impact to end wine quality. This represents a major leap forward in wine processing, as it enables wineries to increase their production with minimal capital investment. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Wine** & **Sauerkraut** & **Sulfur (egg)** \\ \hline Control 1 & 0.6 (c) & 0.3 (c) \\ \hline Control 2 & 1.2 (ab) & 0.7 (bc) \\ \hline Semi-Batch 1 & 0.7 (bc) & 0.7 (bc) \\ \hline Semi-Batch 2 & 1.3 (a) & 0.9 (b) \\ \hline Recycle Semi-Batch 1 & 1.3 (a) & 1.1 (b) \\ \hline Recycle Semi-Batch 2 & 1.5 (a) & 1.8 (a) \\ \hline Least Significant Difference & LSD = 0.5 & LSD = 0.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Significant aroma differences and their Least Significant Differences (LSD). Differences in aroma score greater than LSD indicate a meaningful difference between the samples. Note that letters represent significant groupings based on [PERSON]’s Least Significant Difference (LSD) test \(p<0.05\). Figure 3: Principal Component Analysis (PCA) of seven volatile compounds (red) and two sensory aroma attributes (blue) of six FPI Chardonnay wines (black) that discriminated them significantly at \(p<0.05\). The PCA explained 84.35% of the total variation, 68.21% was explained in the first dimension, and 16.14% in the second dimension. Flask studies show that specific YAN uptake drops over the course of fermentation. This is likely due to two phenomena: first, yeast change from primary to secondary metabolism over the course of batch fermentation. Second, the accumulation of ethanol serves to metabolically inhibit yeast cells, reducing the rate of nutrient uptake and division. The application of flask scale data to the pilot trials was successful, as evidenced by the low level of residual YAN in the accelerated fermentations. Ethyl carbamate analysis shows that there is not an associated risk with these large YAN additions. It is interesting that recycle-semi-batch had less healthy yeast at end of fermentation. Industrial breweries, where cell recycling between fermentations is common, typically use 3-9 \"generations\" of yeast recycling, due to accumulation of dead cells and strain drift. The semi-batch fermentation had the highest cell viability at the end of fermentation, even higher than the control. This may be due to the fermentation completing earlier, resulting in a shorter exposure time to a high ethanol environment. Additionally, while dry cell weight is highest in recycle-semi-batch fermentation, the cell number is highest in semi-batch. This implies smaller but more abundant cells in the semi-batch fermentation, indicating changes in yeast morphology due to processing conditions. In calculating YAN additions, fermentation progress was expressed in Brix instead of time. This is a useful independent variable to utilize in wine fermentations, as wine can be fermented over a wide range of temperatures (10-35 \({}^{\circ}\)C). [PERSON] showed that YAN-to-biomass and sugar-to-ethanol yields are not temperature sensitive, so this change of variables is justified and applicable, as the stoichiometries are invariant with temperature. When fitting the flask data, a purely empirical approach yielded an exponential decay fit. This purely empirical fit is convenient for manipulation, but likely does not reflect the underlying metabolic shifts--further investigation into how changing metabolic states impacts nutrient uptake is warranted. The sensory attributes 'Sauerkraut' and 'Sulfur (egg)' (generally considered negative attributes) are related to sulfur compounds in wines [19; 20; 21] that were not measured for this experiment, as they have low sensory detection thresholds. 'Sulfur (egg)' is corresponding to order descriptors of boiled or rotten egg and hydrogen sulfide (H2S) is the compound responsible for them ([PERSON] et al., 1999).