Low nitrogen Chardonnay juice from an Oregon winery was fermented
with a series of nutrient supplements, including diammonium phosphate
(DAP), Fermaid K, Superfood, yeast extract, yeast hulls and thiamine.
These treatments were evaluated for their contribution to the yeast
assimilable nitrogen content (YANC) of the juice, which consists of the
ammonium ion and α-amino acid content by NOPA (nitrogen by ophthaldialdehyde).
The fermentation characteristics and the nutritional
and chemical status of the finished wines were compared.
Diammonium phosphate added 25 mg N/L from ammonia for every
pound/1000 gallons (12.5 g/hL) used. Commercial yeast nutrient
preparations were found to contribute around 10 mg N/L from
ammonium ion per pound/1000 gallons (12.5 g/hL). NOPA and HPLC
analysis of Superfood and Fermaid K indicated that they contributed only a
small amount of amino acids. NOPA analysis of PL-50 yeast extract
indicated that it may have added some nitrogen from amino acids.
Nitrogenous compounds were taken up within the first few days of
fermentation. Ammonium ion was depleted very quickly and did not
reappear later in fermentation. Alpha-amino acids reached a low within
approximately ten days of fermentation, then leveled out or increased
towards the end of fermentation. Treatments containing high amounts of
ammonia were observed to produce the most vigorous fermentations.
These treatments were found to have the highest apparent levels of amino
acids at the end of fermentation. The Control treatment, which had the
lowest YANC content, appeared to utilize proline during fermentation.
Sensory analysis was not conducted on the finished wines due to
replication differences in reduced sulfur aroma found in preliminary
screening. GC-MS analysis showed that the higher nitrogen treatments
had levels of reduced sulfide compounds that were above sensory
threshold, whereas moderate nitrogen treatments did not.
Ethyl carbamate was not found in any of the finished wines.
These data suggest that moderate levels of supplementation had a
positive effect on both fermentation and finished wine quality. Higher
levels of nutrient addition were effective at increasing fermentation rates
but negatively affected the sulfide profile of finished wines. / Graduation date: 2001
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26564 |
| Date | 25 May 2000 |
| Creators | Specht, Anna Louise |
| Contributors | Watson, Barney T. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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