Term
| Parameters that must be evaluated to determine optimal time to harvest |
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Definition
sugar content: soluble solids, degrees brix
Aciditiy: TA and pH
Color of Skins, color intensity and uniformity
Color of seeds and stems (from green to brown)
Development of varietal aromas and flavors |
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Term
| Practical considerations to make for harvest decisions |
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Definition
condition of fruit, vine condition, weather, berry shriveling, dehydration, berry swelling, weather, presents of rot/mold, insect or bird damage,
weather, winery demands (winemaker, tank space) |
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Term
| Changes during ripening (gains and losses) |
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Definition
| reduction of acid, increase in berry size, rise in pH, rise in sugar, rise in anthocyanins |
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Term
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Definition
| colors, tannins, aroma and flavor |
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Term
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Definition
| water, acids, mineral salts, sugars, aroma and flavor |
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Term
| components of grape Seeds |
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Definition
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Term
| Components of grape Stems |
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Definition
| Tannins, Aroma and Flavor |
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Term
| Components of "Technological maturity" versus "Physiological Maturity" |
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Definition
Technological: sugar, acid and pH parameters
Physiological: optimal development of color, skin and seed tannins, and varietal aromas and flavors
Do not always occur at the same time (varietal character develops and lower sugar levels in cool seasons and at higher sugar levels in hot seasons), wine quality may be affected if all berry components are not physiologically mature |
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Term
| Generalized Ripening order of seed, skin and pulp berry components |
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Definition
| Pulp first, skin second and seed last (within about a 3 week period) |
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Term
| Optimal Grape Maturity (From a winemaker/growers point of view) |
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Definition
| the point at which the composition most closely matches that required to make the style of wine required |
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Term
| What happens during the first growth period of grape development? |
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Definition
Berry formed and seed embryos, rapid cell division, vine is producing a viable seed
compounds of significance:
organic acids (tartaric, malic)
tannins (skin and seed)
Flavor compounds (green characters) |
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Term
| What happens during the second growth period of grape development? |
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Definition
Vine goal is to make berries appealing to birds- needs to negate negative effects of astringent tannins and acids
-sugar increases
-organic acids, esp. malic acid decrease
-potassium increases
-pH increases, TA decreases |
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Term
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Definition
| Berry loses chlorophyll, synthesizes and accumulates flavonols (white grapes) and anthocyanins (red grapes) |
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Term
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Definition
Synthesis during first growth phase but maturation/modification after verasion
seed tannin content decreases may be related to oxidation of seed coat (browning)
skin tannins may decline, remain constant, or may be modified with pectins or anthocyanins
may affect mouthfeel and texture |
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Term
| Ripening effects on Flavor and Aroma |
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Definition
aroma compounds produced during the first growth period decline (methoxypyrazines, vegetal)
other important aroma and flavor compounds produced late in fruit ripening
varietal aromas and flavors develop and non-volatile flavor precursors also increase in conc. late in ripening (many as precursors bound to sugar- glycosides) |
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Term
| Flavor Evolution in red grapes |
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Definition
| Herbaceous-> Red Fruit-> Black Fruit->Jam |
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Term
| Importance of Nitrogen in Grapes |
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Definition
N is essential for yeast growth
low N can result in stuck of sluggish ferments
not all N is "yeast available N" |
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Term
| Types of N usable by Yeast |
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Definition
Ammonia N (NH4+)
Alpha amino acids (FAN)
combined= YAN
DOES NOT INCLUDE PROLINE OR PROTEINS |
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Term
| Effect of Ripening on N content |
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Definition
as more ripe (indicated by increased sugar) there is a decrease in Ammonium but an increase in Amino Acid content (including a sharp increase in proline)
(YAN goes down the more ripe) |
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Term
| Vineyard factors that influence YAN |
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Definition
Arginine has a negative correlation with Brix
FAN increases then decreases near harvest
Ammonia N increases then decreases
Wet years with high incidence of rot will result in low YAN as well as hot dry years |
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Term
| Summary of Ripening changes |
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Definition
sugars increase as acids drops, maturation/modification of tannins, flavor development from green to red fruit to prune raisin
Total N content increases to a point
-ammonium drops
-AA increases but shifts towards proline rich so YAN drops |
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Term
| Oregon Regulations on addition of sugar |
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Definition
Oregon regulations allow additions of 2% (20g/L) of sugar to increase the potential alcohol content by about 1%; addition of 4% is allowed by industry petition in very poor ripening years; in California no sugar additions are allowed
ATTB regulations: the quantity of sugar or concentrated juice added may not raise the original density of the juice above 25 degrees Brix
Calculate additions based on juice volume for white wines and estimated press yields for red wines (not must volume) |
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Term
| Disadvantages of high Brix |
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Definition
high alcohol levels (unbalanced wine)
stuck fermentations |
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Term
| Considerations when adding water to must |
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Definition
use spring, well or DI water, (Not clhorinated)
acidity will also be reduced as well as sugar
make additions based on juice volume for white and press yields for red
tartaric acid can be used to increase acid after dilution |
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Term
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Definition
| degree to which light is refracted is proportional to concentration of dissolved solids compared to water, calibrated at 20 C, can be corrected for T, cannot be used to estimate decreasing sugar content during fermentation due to effect of alcohol on refractive index of solutions |
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Term
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Definition
| measure soluble solids by comparing the density of juice to that of water, as more alcohol is produced the readings no longer are accurate- brix will go negative at the end |
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Term
| Assessment of Organic Acids |
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Definition
pH- measured strength of solution
TA- measures amount of acids
primary acids are malic and tartaric- ratio changes during ripening
possible to have high pH AND high TA |
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Term
|
Definition
measured with pH meter or litmus paper
increases with berry growth |
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Term
|
Definition
pH increases with berry growth (dilution of acids), with the decrease in malic acid due to respiration, and with the uptake of potassium and the formation of weak acid salts (potassium tartrate)
The quantity of organic acids present and their weak acid salts (potassium acid tartrate) largely determine the pH and the buffering capacity (resistance to change) by addition of acid or base |
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Term
| Objective assements of maturity in some other components |
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Definition
seed color- more lignified over time, brown
skin bleeding- breakdown of cellwalls
anthocyanin and tannin content in redgrapes
aroma compounds (difficult to measure) |
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Term
| What to consider before harvest? |
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Definition
| Brix, TA, pH, flavor, seed color, skin bleeding, historical experience, site, climate, variety, desired wine outcome |
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Term
| Importance of Sensory Evaluation |
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Definition
quality control tool to manage winemaking
driver behind many winemaking decisions
chemical analysis can only reveal so much- experience and training are most important |
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Term
| Why do sensory evaluations? |
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Definition
For decisions on:
harvest
fermentation problems
fining addtions
experimental procedures
blending |
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Term
| Sensory properties of wine |
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Definition
Apearance: clarity, intensity
Aroma: volatile compounds
Tastes: sweet, sour, bitter,
Flavor by mouth: retronasal smell
Mouthfeel: astringency, drying,
Aftertaste |
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Term
| Indications of lack of Clarity in a wine |
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Definition
- improper finishing
-instability
-spoilage
(tartrate crystals, yeast/bacteria cells, filterpad fibers, haze) |
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Term
| Stuck or sluggish ferment definition |
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Definition
slow or incomplete
premature cessation of yeast growth and fermentation leading to unfermented sugars (above .4%)
may take weeks or months to never to ferment |
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Term
| Risks/Effects of stuck/sluggish fermentations |
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Definition
sweet tasts, lower than desired alcohol
inferior sensory qualities
higher risk of microbial spoilages
require additional attention to prevent spoilage or oxidation
tie up fermentor space |
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Term
| Major causes of stuck/sluggish ferments |
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Definition
1. Nutritional Deficiencies (N, vitamins, O, minerals)
2. Inhibitory substances (Ethanol, acetic acid, sugar, fugicides)
3. Physics factors (temperature, excessive must clarification) |
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Term
| Effect of too high EtOH conc. |
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Definition
| inhibition of amino acid translocation |
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Term
| When N additions should be made: |
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Definition
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Term
| Sachromycese is capable of making all essential vitamins except? |
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Definition
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Term
|
Definition
O is required for lipid production, essential for cell membranes
addition of O early in ferment is beneficial to yeast |
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Term
| Effect of EtOH on fermentation |
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Definition
EtOH disrupts cell membranes causing leakage and placing stress on yeasts' ability to maintain pH homeostasis
yeast strains have different tolerances |
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Term
| Preferable temperature ranges for fermentation |
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Definition
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Term
| Effect of overclarification of grape must |
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Definition
| decrease in nutrients and loss of sterols |
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Term
| How to avoid stuck/sluggish ferments: |
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Definition
adequate nutrition
-YAN, vitamins, O
-Timing of additions
-prevention of spoilage yeasts
-prevention of lactobacillus
-understanding of risk in high Brix must
-proper yeast strain selection
-avoidance of temperature extremes |
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Term
| Ways to restart a stuck ferment |
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Definition
-add yeast hulls to adsorb inhibitory subs
-may need to add lysozyme to kill lactobact
-may add yeast nutrient
-build up starter culture and acclimate
-reinoculate |
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Term
| Hydrogen Sulfide description |
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Definition
-rotten egg smell
-produced during active early ferment
-most is blown off by CO2
-mercaptans and disulfides can arise from modifications to H2S
-yeast intermediate to biosynth of sulfur containing cmpds. |
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Term
| Factors that influence Hydrogen Sulfide Production |
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Definition
-Nitrogen
-Vitamins
-Temperature
-Elemental Sulfur from vineyard
-Yeast Strain
-Tank Shape
-Oxygen |
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Term
| Nitrogen in relation to H2S production |
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Definition
Lack of N may lead to a build up of Sulfide in cell wells which is toxic and diffuses from cell as H2s
can be alleviated by addition of DAP |
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Term
| Relation of of Pantothenic Acid to H2S production |
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Definition
| more panthothenic acid, less H2S |
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Term
| Ways to deal with H2S in the winery |
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Definition
-splash racking young wines (can also cause formation of disulfides if mercaptans are available)
-addition of copper sulfate for removal of H2S and mercaptans, but not disulfides |
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Term
| How to Prevent H2s Production |
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Definition
-adequate grape must nutrient
-early must aeration
-not stressing yeast
-minmimize vineyard sulfur
-avoid "problem" yeast
-not leaving wine on heavy lees |
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Term
| Types of fermentation vessels |
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Definition
-general purpose tanks or barrels
-open top vats or bins
-purpose built fermentors
-variation greatest for red wine ferms |
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Term
| General All purpose tanks |
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Definition
flexible cap management
usually stainless steel
smaller wineries may use plastic
wooden tanks uncommon |
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Term
| Required Features for Red wine fermenters |
|
Definition
sloped bottoms
door for pomace removal
racking doors and valves
larger tanks need temp control |
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Term
| White wine fermenter requirements |
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Definition
| temperature cooling jackets |
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Term
|
Definition
preferred for pinot noir
stainless steel, plastic, concrete
use of cooling vains or coils for temp control |
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Term
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Definition
- passive, special geometry (egg)
-active systems, rotary fermenters, automated punch downs, pumpover systems, active submerged cap systems, pulse air cap management |
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Term
| Ratios of Red wine fermentors height:width |
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Definition
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Term
| Ratio for white wine fermenters |
|
Definition
1:3 to 1:8
want to minimize top surface area and have efficient cooling |
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Term
| Most important in determining fermentor |
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Definition
| price point, wine varietal, size of fermentation lot, cap management regime |
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Term
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Definition
important to red wine quality, color mouthfeel, age-ability
present in grape juice but more in wine (greater solubility in etoh)
most important cmpds are anthocyanins, flavanols and polymeric pigments (anthocyanin+tannins) |
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Term
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Definition
| anthocyanin reacted with acetaldehyde or pyruvic acid to form a color stable cmpd |
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Term
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Definition
colorless phenolics such as quercitin and caffeic acid interacting with anthocyanins to form stable color compounds
can account for 30-50% of a young wines color |
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Term
|
Definition
formed by linkage between anthocyanins and tannins
more stable than free anthocyanins
after 1 yr 50-70 of pigments will have reacted into a polymeric form |
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Term
|
Definition
gallic and elagic acid based
not naturally found in grapes but in oak and are main commercial tannin adds |
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Term
|
Definition
mainly polymers of flavan-3-ols
basic units are catechin and epicatechins
found in grape skins, seeds and stalks |
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Term
| Derivation of wine tannins |
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Definition
| 36% from skin tissue, 64% seed tissue |
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Term
| Anthocyanin rates during fermentation |
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Definition
| start low and rise dramatically early on but pitter off relativley early on |
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Term
| Tannin rates during fermentation |
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Definition
| rise quickly in the begining and then steadily unit the end of ferment |
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Term
| Cold Soak- Preferment Maceration definition |
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Definition
must held at 10-15C for several days
to improve color and flavor due to extraction of more water solubles
popular for pinot noir but inconclusive research
only skin tannins extracted (seed tannins are EtOH soluble) |
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Term
| Thermovinification Definition |
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Definition
Hold must at high T 60-80C for short (seconds) period of time
increase color extraction, increase phenolics
characteristic flavor changes occur
can increase vegginess |
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Term
|
Definition
prevent heat build up
increase contact between skin and juice
prevents microbial spoilage
aeration
can be punch down or pump over (variety dependent) |
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|
Term
|
Definition
technique for cap management, juice is drained entirely from tank into another tank and poured back over skins
can remove seeds
increases aeration of must |
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|
Term
| Temperature relation to phenolics |
|
Definition
higher temps= greater phenolic extraction
increased permeability of hypodermal cells releases anthocyanins and tannins |
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Term
| Most important factors for Tannin Extraction |
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Definition
| temperature, time, ethanol conc |
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Term
| Non Saccharomycese yeast- Kloeckera |
|
Definition
dominant species early in ferment
can ferment glucose
can grow as a film
can cause spoilage issues
produces ethyl acetate, acetic acid, acetaldehyde
can be cold soak problem
lemon shaped
control with temp, SO2 and oxygen exclusion |
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Term
| Effects and indicators of Spoilage by Non Sacch. yeasts |
|
Definition
depletion of essential nutrients
competition with desired yeasts
stuck fermentations
look for:
clumps or scum on surface
off odors (banana, VA, nail polish)
unexpected fermentation starts |
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Term
|
Definition
slow growing generally
requires very low levels of sugar (275mg/L)
can survive on wood sugars
rarely found on grapes
cant compete with sacch.
not found in new barrels
can occur in tank as well as barrels |
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Term
| Metabolites of Brettanomyces |
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Definition
Volatile phenols, 4-ep, 4-eg, 4-ec
(ep- bandaid medicin; eg-smoke, clove, spicey; isovaleric- rancid vomit, barnyard)
acetic acid
isovaleric acid |
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Term
|
Definition
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Term
| Possible cause of 'mousey" wine defect |
|
Definition
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|
Term
| cause of buttery, bitter, sauekraut off aromas as well as cloudyness and ropiness |
|
Definition
|
|
Term
|
Definition
formed by decarboxylation of amino acids
some LAB and Oenococcus implicated
dulls/mutes fruit
some are gross: putrescine, cadaverine |
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