"...Leigh Francis returned for another study presentation with "The Effect
of Ascorbic Acid, Closure Type and Storage Conditions on the Composition and
Sensory Properties of a Chardonnay and Riesling Wine." The study used
unoaked riesling, and oaked chardonnay. Francis notes that ascorbic acid is
used exclusively in white wine production, but cannot replace SO2 as a
preservative; in Australia some studies have questioned the efficacy of
ascorbic acid because visible browning was thought to correlate with
ascorbic acid levels; this study wanted to verify if ascorbic acid was a
problem.
At bottling, both wines had 45 mg/ L ascorbic acid, with similar free SO2
levels. A spectrometer was developed which could measure light wavelength in
bottled wines; the 420 nm wavelength is used to correlate with visible
browning in wine and with low free SO2 levels. Storage also affects the 420
nm levels in chardonnay; upright storage increased levels for one of two
natural corks used; synthetics used have more 420 nm levels than do natural
corks.

Chardonnay with ascorbic added actually had less browning visible and with
lower 420 nm levels. Ascorbic acid reduces the 420 nm levels when added at
bottling; high 420 nm levels also correlates with oxidized aroma scores, but
a single wavelength e.g. 420 nm is not as reliable as multi-wavelength
levels for measuring wines with and without ascorbic acid measurement. The
study conclusion was that ascorbic acid addition together with sound free
SO2 levels at bottling contribute significantly to reducing 420 nm levels,
or visible browning..."

This seems to contradict the earlier studies. Anyone ??





"miker" wrote in message
oups.com...
Here's more on this topic:

http://www.vwm-online.com///Magazine...6/28thASEV.htm