New barrel

Flow Surging Caused by a Worn Feed Casing and a New Barrel... 

Figure 12.27 The solids-conveying section of a single-screw, plasticating extruder with a worn feed casing. The schematic is not to scale, and it shows a ledge formed between the oversized (worn) feed casing and the flange of a new barrel...

The commercial extruder was modified by tapering the entrance to the new barrel such that a ledge did not occur between the feed casing and the barrel. As predicted by the experimental research, the commercial line was able to operate stably and at a high specific rate of 4.2 kg/(h-rpm), and at a screw speed of 150 rpm the plant was operating at a rate of 630 kg/h. Plant personnel ordered a new feed casing and planned to Install the casing at the next planned shutdown. 

The Inside diameter of the feed casing should be measured each time a worn barrel Is removed and replaced with a new barrel. The problem described here could have been diagnosed more quickly had the measurements been made. 

Calculation with the barrel surface/liter (Table II) shows that for each millimeter that wine penetrates into the side of the barrel, it would extract about 16.4 grams wood/liter wine in a 20-liter, 12.7 in 50-liter, 9.6 in 100-liter, 7.6 in 200-liter, and 5.6 in a 500-liter barrel. These data mean that the typical oak barrel near 200 liters in size can contribute 3800 mg wood for extraction at a depth of penetration of 0.5 mm or in about two months for a new barrel. Based on the tasting results this is about three to 10 times the amount necessary to produce a tastable difference in wine. We have measured the depth to which wine has visibly penetrated into staves from used wine barrels and found that 6-mm penetration is not unusual. This could represent extraction of 45.6 grams wood/liter wine in a... 

Other volatile compounds present in oak wood can transmit unpleasant aromas to the wine, such as the sawdust aroma of dry wood that is perceptible in some wines aged in new barrels. The substances that cause these aromas have been identified in both American and European oak wood, for instance, ( )-2-nonenal, 3-octen-l-one, ( )-2-octenal, and 1-decanal. Their connection with the sawdust aroma has been established by olfactometry, and they have been identified in wines suffering from this flaw, though toasting the wood (Chatonnet and Dubourdieu 1998). 

Impact of aging in new barrels on the wines content of toasty -aroma volatile compounds... 

The evolution of color may be affected by the characteristics of the oxidative process, that is, the barrel which has been used. Oak barrels are porous recipients that allow oxygen to enter continuously. The dissolved oxygen in wines matured in new barrels is higher than in used barrels because prolonged use causes a progressive colmatation of wood pores and a consequent decrease in the wine oxygen content. After the barrel has been used three to five times, the quantity of dissolved oxygen in wines will be very close to that of wines stored in tanks, so different wine color characteristics will be obtained (6). 

The twelve new and twelve used barrels used in this experiment were made of American white oak (Quercus alba, fine grain) or French oak (Quercus petraea from the Allier forest in France), and were obtained from the same cooperage firm in Spain with the same specifications (medium toast level). The used barrels had been used three times for the aging of Monastrell wine and they were sanitatied before use by burning sulphur inside. The following barrels were used in the experiment 220 liter French oak barrel (3 new barrels and 3 used barrels) 220 liter American oak barrels (3 new barrels and 3 used barrels) 500 liter American oak barrels (3 new barrels and 3 used barrels) and 1000 liter American oak barrels (3 new barrels and 3 used barrels). 

This decrease in the monomeric anthocyanins content was not reflected in color density (Table II). Whereas the concentration of monomeric anthocyanins in wines after six months of wood aging was only 23% of the initial value in wines stored in new barrels, and 36% in wines stored in used barrels, in the same period of time, the color density only decreased by 5.5% in wines from new barrels and by 16% in wines stored in used barrels. After one year in the bottle, the decrease in CD value was 30% and 36% in wines stored in new and used barrels, compared with the initial wine, while the decrease in monomeric anthocyanins accounted for 93% and 85%, respectively. 

The decrease in monomeric anthocyanins was greater in new barrels while the decrease in color density was more pronounced in wines aged in old barrels. This can be explained assuming that the color density of aged wines is essentially due to polymerized anthocyanins and is not related to free anthocyanins. Also, Revilla and Gonzalez-San Jos6 (20) found that wines stored in used barrels had a lower color density and higher tint values. 

The chemical analysis showed that polymerization and color stability seemed to be favored in small and new barrels. The results of the sensory analysis showed that the origin of the wood did not lead to important sensorial differences and that wines held in 500 and 1000 L barrels had a significantly lower score, wines from 220 liter barrels being, in general, preferred. 

This value may be somewhat distorted due to an increase in the wine s gallic acid and ellagic tannin concentration during aging in new barrels. The coefficients corresponding to these molecules are certainly very high, approximately 38. This increase only lasts a limited time, due to the rapid oxidative degradation of these compounds. 

The appearance of ethyl-phenols dnring aging is mnch more common, especially in used barrels, although phenol off-odors may also develop in red wines aged in new barrels, or even in vats. Fignre 8.10 shows an example of the increase in ethyl-phenol concentrations in a red wine in the barrel dnring the snmmer months. This phenomenon is promoted by the rise in cellar temper-atnre and the decrease in the wine s snlfur dioxide content dnring this period. 

Used barrel Used barrel New barrel New barrel ... 

Special care should be taken in maintaining wooden barrels. New barrels must be conditioned to eliminate any bitter, astringent off-flavors (Section 13.9.1), by cleaning with steam or boiling water, or by keeping the barrels full of slightly sulfured cold water for a few days. 

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