title: Ultrastructural changes of sparkling wine lees during long-term aging in real enological conditions.
abstract: Ultrastructural changes of lees of three series of sparkling wines produced using the traditional method during long-term aging (4 years) were assessed by high-pressure freezing in combination with transmission electron microscopy. The stratified structure of the cell wall disappeared throughout aging. After 18 months, the microfibrous material of the cell wall appeared more diffuse and the amorphous midzone of the inner wall layer was progressively degraded. From 30 months onward, the cell wall consisted of a tangled structure of fibers. In spite of these changes, the cell wall of yeasts remained unbroken at 48 months of wine aging. Cell membrane breakage was observed for the first time in lees of Saccharomyces cerevisiae. An increase in the thickness of the periplasmic space owing to plasmolysis and of the number of cells with less cytoplasmic content was observed during aging. Morphological evidence of microautophagy was detected for the first time in S. cerevisiae in enological conditions.
authors.affiliation: Departament de Nutrició i Bromatologia, Xarxa de Referència en Tecnologia dels Aliments (XaRTA), Universitat de Barcelona, Barcelona, Spain.
authors.forename: Rebeca
authors.initials: R
authors.lastname: Tudela
authors.forename: Joan J
authors.initials: JJ
authors.lastname: Gallardo-Chacón
authors.forename: Núria
authors.initials: N
authors.lastname: Rius
authors.forename: Elvira
authors.initials: E
authors.lastname: López-Tamames
authors.forename: Susana
authors.initials: S
authors.lastname: Buxaderas
mesh_terms: D001343:Autophagy; D002462:Cell Membrane / Q000648:ultrastructure; D002473:Cell Wall / Q000648:ultrastructure; D005615:Freezing; D046529:Microscopy, Electron, Transmission; D019897:Periplasm / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000648:ultrastructure*; D013997:Time Factors; D014920:Wine / Q000382:microbiology*