 Assessing a wine's bouquet can also reveal faults such as cork taint; oxidation due to age, overexposure to oxygen, or lack of preservatives; and wild yeast or bacterial contamination, such as those due to Acetobacter or "Brettanomyces" yeasts.Although low levels of "Brettanomyces" aromatic characteristics can be a positive attribute, giving the wine a distinctive character, generally it is considered a wine spoilage yeast.The bouquet of wine is best revealed by gently swirling the wine in a wine glass to expose it to more oxygen and release more aromatic etheric, ester, and aldehyde molecules that comprise the essential components of a wine's bouquet.