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p r a c t i c a l w i n e r y & v i n e ya r d J U n e 2 0 1 4 65 also decreased. Both the reduction in tan- nin concentration and size would contrib- ute to astringency softening with aging. A decrease in tannin concentration has long been speculated as the reason for the change in wine texture with aging, how- ever this is the first study to confirm that this does occur. A s t h e t o t a l a m o u n t o f t a n n i n decreased, the proportion of tannin that is pigmented gradually increased (Figure 1b). This indicated that the anthocyanins in red wine were being converted into pigmented tannins, which contribute to the longer term color stability of wine. Wine color density, which relates directly to the purple color of wines, decreased gradually over time, reflecting the decrease in anthocyanins (Figure 1c). Wine hue, which relates more to an orange color in the wine, increased with further aging, indicating that pigmented tannins are formed from the purple anthocyanins (Figure 1d). Impacts of wine pH and closure on color and tannins with aging Wine pH and selected closure type did not change the general trends observed with wine aging, but they did have a dramatic impact on the speed of these reactions. Within six months, the differences in pH had started to influence wine color and tannin structure, with these changes even more apparent after 24 months (Figure 2). The lower pH wines (pH 3.2) contained substantially fewer anthocyanins than the pH 3.8 wines (Figure 2a), and this related to the formation of more SO 2 non-bleach- able pigments (percent stable pigments) in the lower pH wines (Figure 2b). Slight oxygen exposure through the lined screw- cap (Sx) exacerbated the impact of the more acidic wine with a further decrease in overall anthocyanin concentration. Changes in the tannin structure were also affected by pH and closure type. One of the main measures for assessing tan- nins is how readily they break apart into smaller fragments in the presence of acid. This is referred to as percent yield of the reaction or percent tannin fragmentation. The more readily the tannin can be frag- mented (greater percent tannin fragmen- t a t i o n ) , t h e s i m p l e r t h e t a n n i n composition and, potentially, the more astringent the tannin. With wine aging, the perrcent tannin fragmentation decreased substantially in all wines, indicating that the tannin was becoming more complex, probably due to interactions with itself and other compo- nents of the wine such as anthocyanins and acetaldehyde. These changes were much more apparent in the pH 3.2 wines (Figure 2c) and particularly under Sx compared with ST screwcaps. Such changes to the wine tannin structure may also relate to the softening of astringency with wine aging. Another notable change in tannin structure was the proportion of grape seed-like tannin (percent epicatechin gallate, Figure 2d). Generally with aging, the proportion of these tannins decreases due to oxidation. This occurred in the higher pH wines (pH 3.5 and 3.8), but at lower pH this proportion remained fairly constant. Conversely, the propor- tions of the grape skin-like tannins (per- cent epigallocatechin) did not change. Seed tannins are generally considered to be more astringent and more bitter than skin tannins, and therefore a decrease in concentration would soften wine astringency, as is generally observed with wine aging. The effect of more seed- like tannin in the lower pH wines in this case is likely to be offset by the lower per- cent tannin fragmentation. Conclusions Low wine pH and a closure that allowed a slight ingress of oxygen resulted in w i n e M a K i n g www.jansoncapsules.com EntEr thE 30 x 60 DimEnsion