Impact of Increasing Levels of Oxygen Consumption on the Evolution of Color, Phenolic, and Volatile Compounds of Nebbiolo Wines

Since the end of the last century, many works have been carried out to verify the effect of\r\ncontrolled oxygen intake on the chemical and organoleptic characteristics of red wines.\r\nIn spite of the large number of studies on this subject, oxygen remains a cutting-edge\r\nresearch topic in oenology. Oxygen consumption leads to complex and not univocal\r\nchanges in wine composition, sometimes positive such as color stabilization, softening\r\nof mouthfeel, increase of aroma complexity. However, the variability of these effects,\r\nwhich depend both on the oxygenation conditions and the composition of the wine,\r\nrequire more efforts in this research field to effectively manage wine oxygen exposure.\r\nThe present study is focused on the evolution of the chemical composition of four\r\ndifferent Nebbiolo wines, each of them added with 4 different doses of oxygen (7, 14,\r\n21, and 28 mg/L total intake) during the first month of storage. In this perspective,\r\nthe evolution over time of wine color and polyphenols was studied. Acetaldehyde,\r\nglyceraldehyde and glyoxylic acid were quantified by HPLC. These compounds can\r\nplay a role in wine aging creating condensed colored and stable products involving\r\nanthocyanins with or without tannins. Moreover, some volatile aldehydes correlated with\r\noxidized olfactory notes, including methional and (E)-2-alkenals, have been quantified by\r\nGC-MS. Overall, during storage a decrease of color intensity, total and free anthocyanins\r\nand an increase in polymeric pigments (in particular the contribution to the red color of\r\npigments not-bleachable by SO2 or dTAT%) and some minor aldehydes was observed.\r\nNevertheless, the differences in color parameters between the samples with different\r\ndoses of oxygen were modest. These evidences were in contrast with an evident\r\nand detectable increase of free acetaldehyde content at increasing doses of oxygen\r\nmeasured after 60 days of storage. The effect of oxygen on color and production of\r\nSO2 non-bleachable pigments during aging varies with wine composition, with Nebbiolo\r\nwines appearing not very reactive in this respect, probably due to their low content in\r\nanthocyanins and high content in tannins.