Pigment polymerisation of Pinot noir wines : a dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Horticultural Science (Honours) at Lincoln University

Abstract

An investigation was conducted into the effects of varying levels wine tannin addition on the colour stability (pigment polymerisation) of Pinot Noir wine. Five levels of wine tannin (0, 20, 40, 60, and 80mL) were added to five litre batches of wine. Analysis of colour stability was measured spectrophotometrically (colour hue, colour density, age index, polymers monomers) and using HPLC (polymers, oligomers, monomers, total pigments) at both 420nm and 520nm, over an 88 day period. A greater amount of monomers were present in the wines treated with lower levels of tannin at 56 days (HPLC @ 420nm). This was probably because less tannin was available for polymerisation with these pigments. At 36, 56 and 70 days (HPLC @ 520nm) and at 56 days (HPLC @ 420nm), higher tannin levels were associated with decreasing levels of total pigments presumably due to precipitation of the larger molecular weight polymers. At 88 days the inverse was true. For all other parameters there was no significant difference between levels of tannin addition (LSD 5%). No evidence was obtained here to support the hypothesis that addition of wine tannin could be used to increase colour stability in Pinot Noir wine. Longer term research may be required.