Wine Conservation Research Articles

Norisoprenoids in Vitis vinifera White Wine Grapes and the Identification of a Precursor of Damascenone in These Fruits

Twenty-four norisoprenoids , which are either free volatile components of juices of Vitis vinifera cvv . Chardonnay, Semillon and Sauvignon Blanc, or are liberated by glycosidase enzyme, or acid hydrolysis of extracts of these juices, have been identified. Eleven of these norisoprenoids are reported as grape products for the first time. The hypothetical 7-oxomegastigmane precursors, grasshopper ketone (5) and megastigm-5-en-7-yne-3,9-diol (10), as well as the related allene, 9-hydroxymegastigma-4,6,7-trien-3-one (6), have been observed for the first time, cooccurring with damascenone (1), 3-hydroxy- β- damascone (2) 3-oxo-β-damascone (3) and 3-oxo-α-damascone (4). Hydrolytic studies have shown that megastigm-5-en-7-yne-3.9-diol (10) is a precursor of damascenone (1) and 3-hydroxy- β- damascone (2) during wine conservation.

Occurrence of Lactic Acid Bacteria During the Different Stages of Vinification and Conservation of Wines

We showed that the growth of lactic acid bacteria during alcoholic fermentation depends on the composition of the must. We illustrated how the addition of sulfur dioxide to the must before fermentation and the temperature of storage both affect the growth of these bacteria in the wine. Whereas species of Lactobacillus and Leuconostoc mesenteroides were isolated from grapes and must, Leuconostoc oenos was the only species isolated after alcoholic fermentation. This organism was responsible for the malolactic fermentation. Isolates of this species varied in their ability to ferment pentoses and hexoses. The survival of Leuconostoc oenos in wines after malolactic fermentation depended on wine pH, alcohol concentration, SO(2) concentration, and temperature of storage.