2 research outputs found
Profiling the Hydrolysis of Isolated Grape Berry Skin Cell Walls by Purified Enzymes
The
unraveling of crushed grapes by maceration enzymes during winemaking
is difficult to study because of the complex and rather undefined
nature of both the substrate and the enzyme preparations. In this
study we simplified both the substrate, by using isolated grape skin
cell walls, and the enzyme preparations, by using purified enzymes
in buffered conditions, to carefully follow the impact of the individual
and combined enzymes on the grape skin cell walls. By using cell wall
profiling techniques we could monitor the compositional changes in
the grape cell wall polymers due to enzyme activity. Extensive enzymatic
hydrolysis, achieved with a preparation of pectinases or pectinases
combined with cellulase or hemicellulase enzymes, completely removed
or drastically reduced levels of pectin polymers, whereas less extensive
hydrolysis only opened up the cell wall structure and allowed extraction
of polymers from within the cell wall layers. Synergistic enzyme activity
was detectable as well as indications of specific cell wall polymer
associations
Following the Compositional Changes of Fresh Grape Skin Cell Walls during the Fermentation Process in the Presence and Absence of Maceration Enzymes
Cell
wall profiling technologies were used to follow compositional
changes that occurred in the skins of grape berries (from two different
ripeness levels) during fermentation and enzyme maceration. Multivariate
data analysis showed that the fermentation process yielded cell walls
enriched in hemicellulose components because pectin was solubilized
(and removed) with a reduction as well as exposure of cell wall proteins
usually embedded within the cell wall structure. The addition of enzymes
caused even more depectination, and the enzymes unravelled the cell
walls enabling better access to, and extraction of, all cell wall
polymers. Overripe grapes had cell walls that were extensively hydrolyzed
and depolymerized, probably by natural grape-tissue-ripening enzymes,
and this enhanced the impact that the maceration enzymes had on the
cell wall monosaccharide profile. The combination of the techniques
that were used is an effective direct measurement of the hydrolysis
actions of maceration enzymes on the cell walls of grape berry skin