Pigmented tannin

Purified pigmented tannin (100 mg/mL, 1 1 acetone-d6 D20) was characterized by C-NMR (100 MHz, Bruker DPX400), with chemical shifts (5) in ppm referenced internally with acetone-d6. The proton-decoupled, inversegated sequence, with 30° pulse length, 25,000 Hz spectral widA, 64 K data points, 1.3 s acquisition time, relaxation delay of 3 ms, SO K scans and with 3 Hz line broadening was carried out at a temperature of300 K. 

Interestingly, the elution pattern of the pigmented tannin was bimodal. Given that the molecular weight distribution of seed and skin tannins is very different, one possible explanation for the bimodal distribution of the tannin is that it represents seed (later eluting material) and skin (earlier eluting material) extraction. 

From these results it could be confirmed that the tannin isolated from wine (in a manner consistent with techniques used in grape tissues), was deeply pigmented. It was confirmed that the isolate contained very little low molecular weight material indicating that most of the pigment was polymeric in nature. Finally, the pigmented tannin contained a significmit amount of proanthocyanidin material. 

Figure 3. NMR spectrum of pigmented tannin isolated from red wine, with anthocyanin signals indicated...

Figure 4. Electrospray mass spectrum of infused pigmented tannin. (Reproducedfrom reference 16, with permission from the Australian Society of Viticulture and Oenology)...

Stapa 2 Stapa 2 VS Stapa 5 Stapa 5 VS Stapaf 8 Stapa 15 VS Stapa 30 Stapa Luxai 4 Stapa Luxal 4 VS Stapa Luxal 15 Stapa Luxal 15 VS pigment, tannin stain inhibiting acryiic latex... 

If haze solubilizes, proceed using diagnostic scheme presented below. If haze remains, the instability is probably due to protein or complexes of protein, protein-phenolics, or phenolics-phenolics (i.e., pigment-tannin). For presumptive identification of the later group, see the subsection D-4, Protein/Phenolics above. 

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