The Wine Makers Toy Store carries two post fermentation tannin products that were obtained from Scott Laboratories: Tan'Cor and Tan'Cor Grand Cru.  Both products are a blend of proanthocyanidic (grape) and ellagic (oak) tannins.  The products were developed to aid in color stabilization and protection against oxidation.  In addition Tan'Cor Grand Cru increases structure and mouth-feel through the creation of long-chain polyphenols.
 
We decided to try the tannins on a Castel del Papa, the 10-Liter Vinifera Nobel kit from Mosti Mondiale.  Since these tannins are to be added post-fermentation, we added them after the wine had been degassed and fined.  The amount of tannin added can be increased with each racking, however the final adjustment should be made at least three to six weeks before bottling.  For our test we made only one addition.
 
For both products Scott Laboratories recommends a dosage of from 10 to 30 grams per hundred Liters.  For our test we selected the low end (10g/hL) and the mid-point (20g/hL).  The wine was divided into five one-gallon batches.  One batch had no tannin added and was our control sample.  Tan'cor was added to two of the one-gallon batches, one received 0.4 grams and the other 0.8 grams.  Tan'Cor Grand Cru was also added to two one-gallon batches in the same amounts.  The wine was then allowed to age for about six months.
 
The wines were tasted after three months of aging.  The wines with the tannin additive were somewhat smoother than the control sample but there was no significant difference in aroma and taste between the samples.  When tasted at bottling, the wines with the tannin addition were noticeably smoother that the control.  During this period, all the individual wines had improved aroma and taste.  The tasters were mixed as to which tannin product and which dosage produced the better aroma and taste.  All did agree that the wines with the tannin additions had a more pronounced fruit aroma and taste than the control.
 
After three months of bottle age, the wines were again tasted.  The body of all wines was consistent with expectations from a 10-Liter kit.  The tannin additions did however; create the perception of increased body.  This perception was from the wine being more fruit forward and the improved mouth-feel.  All wines with the tannin addition were noted as having more pronounced fruit aroma and taste than the control.  The larger the dosage, the more fruit forward the wine.  The wine treated with Tan'Cor Grand Cru showed better mouth-feel than the control or the wine treated with Tan'Cor.
 
Another tasting was conducted after eight months of bottle aging.  The tannin treated wines were still smoother than the control but the difference was not as significant as it had been when the wines were younger.  The wines treated with either Tan'Cor Grand Cru or Tan'Cor continued to show better mouth-feel and were more fruit forward than the control.   Tan'Cor Grand Cru had better mouth-feel and was fruitier than the Tan'Cor treated wine.  The tasters were not able to discern a significant difference due to the increased dosage of the tannin products.    
 
In summary, the wines with the tannin addition were smoother and more fruit forward than the control wine.  As the dosage of tannin increased, the fruit became more emphasized although this emphasis seemed to diminish with time.  Both products improved the mouth-feel of the wine; however, the improvement was more apparent in the wines that had the Tan'Cor Grand Cru added.  The difference between the treated and the untreated wine is not subtle; the difference is very evident.  The tannins integrated well into the wine and there was no noticed harshness or excess astringency.  Based upon our tasting, these tannin additions can make an improvement in a young wine.  Unfortunately, because of frequent sampling we do not have enough wine left to determine the longer term effects of these tannin products. 
 
These two tannin products were developed to be added to the wine after fermentation is complete and at least three weeks before bottling.  As previously indicated, Scott Laboratories recommends a dosage of 10 to 30 grams per hundred Liters.  Based upon our trials, one teaspoon of either Tan'Cor or Tan'Cor Grand Cru in six gallons will approximate a dosage at the low end of the recommended range, two teaspoons is about the mid-point and three teaspoons is the high end of the recommended range.