Organic vs Conventional Management on Soil and Sauvignon blanc Must and Wine Chemical Compositions

Abstract

The aim of the study was to determine if there are significant differences between organic and conventional Sauvignon blanc from Marlborough, New Zealand represented in the following parameters: soil elemental profile, soil acidity, basic cation exchange capacity, shoot density, shoot mass, must glutathione, must amino acid profile, and/or aromatic profile. Pruning weights and shoot numbers were measured according to Dr. Smart’s ideotypes and were found to be significantly different where organic canopies exemplified a more desirable vigor and density. Organic musts had more than 2 times the median concentration of glutathione (GSH), an important antioxidant, which was quantified by high performance liquid chromatography (HPLC) methodology. Although the amino acid concentration — quantified with HPLC- diode-array detector (DAD) — did not differ significantly, conventional musts had more yeast available amino acids. All aroma compounds were quantified by gas chromatography coupled with mass spectrometry (GC-MS), and the aromatic thiols — 3-mercaptohexan-1-ol (3MH) and 3- mercaptohexyl acetate (3MHA) — were quantified using a new ethyl propiolate method where the thiol compounds were first extracted using solid phase extraction (SPE) prior to GC-MS. Conventional wines showed significantly higher aromatic thiols and fatty acids, whereas significantly higher alcohols differentiated organic wines. Organic wines also showed elevated norisoprenoids, but not significantly. The soil study portion of research resulted in the quantities of 58 elements at a depth of 40-50 cm and used inductively coupled plasma mass spectrometry (ICP-MS). The soils are similar for the most part: acidic, very low fertility regarding the basic cation — K+, Ca2+, Na+, Mg2+ — exchange capacity (CECb), and show extraordinarily high levels of Al3+, which is known to be toxic to roots of grapevines. For the first time ever to the best of my knowledge, multiple aromatic compounds have been significantly correlated to individual elements in the soil. I hypothesized that there would be significant differences, that organic musts would have more glutathione, and confirm these in the conclusion.