The possible effect of oxidation [processing with or without sulfur dioxide
(±S0₂)] and of pre-ultrafiltration treatment of juices with enzymes and fining
agents on flux, and on juice color, composition and stability was investigated. White
Riesling juice was ultrafiltered with a Romicon system operated with a nominal
molecular weight cut-off (MWCO) of 10,000 daltons. In addition, UF White Riesling
juices processed ±S0₂, were stored for 2 months (1985 vintage) and 12 months
(1984 vintage) at 2°C and 20°C, and evaluated by a trained panel using descriptive
analysis. Pre-UF treatment with enzymes and fining increased flux. Sediment
formation and instability to heat testing of UF permeates processed -S0₂ was
prevented with pre-fining. Up to 99% of protein, 90% of pectin, 84% of color and
low variable phenolics were retained by the membrane of 10,000 dalton MWCO.
During UF there is a significant increase in the soluble protein and water soluble
pectin passing through the membrane with increasing volume concentration ratio
(VCR, process time). It is concluded that it is not only the amount but the
nature/state of compounds such as proteins, phenolics, pectins, and their interaction
that results in instability. UF juices processed with minimum oxidation and stored
for 12 months had lower intensity aroma (apple/apple cider, sweet, and
honey/caramel) and overall intensity flavor by mouth descriptors than those processed with oxidation. Moreover, juices processed with minimum oxidation and
stored for two months (1985 vintage) had significantly lower intensity of
apple/apple cider, sweet, honey/caramel aroma descriptors when compared to those
processed with oxidation. There was no effect of temperature of storage on any of
the aroma and flavor-by-mouth descriptors for the 1985 juice after two months of
storage. Only one aroma descriptor (vegetative) was significantly increased for the
1984 White Riesling juice after 12 months at 2°C. This indicates the possibility
that UF juices may be stored at higher temperature (20°C) for less cost with
minimal changes in aroma and flavor.
White Riesling (WR) and Gewurztraminer (GEW) wines were ultrafiltered with
Romicon and Millipore pilot-scale systems, respectively. The effect of
ultrafiltration (UF), membrane MWCO from 10,000-50,000 daltons, and of VCR on
composition and wine stability was investigated. The effect of 1) pilot-scale UF
processing and Bentonite fining on WR and GEW wines, and 2) commercial-scale UF
processing on GEW wine was sensorially evaluated by a trained panel using
descriptive analysis. UF processing significantly reduced color (A [subscript 420nm]), total
phenol, protein and heat/cold test (HOT) haze of both WR and GEW wines. Stability to
HOT haze formation was obtainable with MWCO of 10,000 daltons, but trace
instability can remain. With increasing VCR (process time) there was a significant
decrease in membrane retention of color (A [subscript 420nm]), protein, and HCT haze formation
in the WR wine and the color (A [subscript 420nm]) of the GEW wine. UF processing of the WR
wine significantly decreased the perception of overall aroma intensity, fruity, fresh
fruity citrus, floral, sweet and honey/caramel character but it also increased the
intensity of the vegetative aroma descriptor when compared to the control unfiltered
WR wine. In addition, significant differences were detected for these descriptors
between the bentonite-fined WR wine and the ultrafiltered WR wine except for fresh
fruity citrus and honey/caramel which were less intense in the ultrafiltered WR ultrafiltered WR wine. UF processing of GEW wine significantly decreased the
intensity of fruity, fresh fruity aroma descriptors; and increased the chemical
aroma descriptor compared to the control unfiltered GEW wine. However, no
significant differences were detected for these descriptors between the bentonite
fined GEW wine and the ultrafiltered GEW wine except for fresh fruity which was
less intense in the ultrafiltered GEW wine. Commercial processing of GEW wine by
UF did not have any significant effect on the aroma and flavor by mouth descriptors
evaluated as compared to standard processing procedures. / Graduation date: 1988
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27154 |
| Date | 08 September 1987 |
| Creators | Flores Gaytan, Jose Humberto |
| Contributors | Heatherbell, David A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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