WVIT 365 MIDTERM EXAM QUESTIONS
AND ANSWERS
What is quality a result of ? - Answer-soil, genotype, microclimate, canopy, photosynthesis
what are the important points for grape sampling ? - Answer-maturity, Brix, TA, pH, phenolics
How does one assess maturity? - Answer-varietal characteristic intensity, phenolics, tannin, seed
ripeness (browning/crunchiness), berry softness, Brix, pH, ability to ripen further
Factors to take into consideration when doing a vineyard samples - Answer-macro, meso, and micro
climate variations; random vs targeted sampling, light, soil moisture, crop load
factors to consider when analyzing Brix - Answer-its a sugar to water ratio. weight can change without
change to brix, physiological conditions can change brix, important to also analyze sugar per berry
which parts of the grapes affect aspects of wine? - Answer-central zone: magic acid, no sugar
intermediate zone: tartaric acid and sugar
peripheral: potassium, aroma, astringency, no sugar or acid
,evaluation of data - Answer-accuracy, precision, consistency
What aspects do Nonsoluble (suspended) Solids affect? - Answer-increase phenolic
concentration/extraction, chemical stability, increase yeast growth
How to reduce NSS? - Answer-Low temperature clarification, fining agents, filtration, centrifugation
hydrometry - Answer-measures specific gravity of a sugar solution, measures sugar using brix, specific
gravity, baume, and oechsle. Read at the bottom of the meniscus, reading is at the correct temperature,
glassware is clean. calibrate using sugar water solutions
determine soluble solids with a refractometer - Answer-passes light through a sample, refractive index
translates to a brix scale. temperature and alcohol can skew this measurement
Total acidity vs titratable acidity - Answer-total: number of protons that organic acids would contain if
they were undissociated
titratable: number of protons recovered in titration with a strong base, always less than total
legal limits on acidity - Answer-TTB allows additions of citric, tartaric, and magic do not exceed 9 g/L
What aspects of wine does TA affect? - Answer-pH, color, chemical/biological stability, shelf life. normal
range in wine is 5-15 g/L
what will be the TA of a wine with a high buffering capacity? - Answer-TA will be high. Buffering capacity
is resistance to pH change and requires more hydroxide to reach titration equivalence point.
titration with diprotic and monoprotic acids - Answer-ph 7 works fine for mono protic acids like acetic,
but will not work for diprotic acids like tartaric because it has multiple pKas
, What skews TA measurement accuracy? - Answer-particulates (absorb NaOH titrant) and CO2 (carbonic
acid)
correct these by centrifugation and neutralization with deionized water. Use an endpoint detection of
pH 8.2
pH electrodes - Answer-measures electrochemical potential of hydrogen ions using known pH of liquid
as a reference point.
fragile, always keep immersed, dry electrodes can usually be rejuvenated
what aspects does nitrogen impact in wine? - Answer-healthy fermentation, clarity, microbial stability,
aroma, foam in sparkling wine
potentiometric titration - Answer-- a form of redox titration in which a voltmeter or external cell
measures the electromotive force (emf) of a solution
- no indicator is used
- the equivalence point is determined by a sharp change in voltage
- higher accuracy
nitrogen sources for wine - Answer-grape cell proteins and vineyard practices; Diammonium Phosphate,
Finn enzymes, mannoproteins
what can cause nitrogen losses in wine? - Answer-settling, clarification (bentonite, centrifugation), wild
yeasts (rot). this can ruin fermentation
which source of nitrogen can yeast use ? - Answer-only ammonium, maybe some amino acids. proline is
most present in grapes, but not utilizable by yeasts.
AND ANSWERS
What is quality a result of ? - Answer-soil, genotype, microclimate, canopy, photosynthesis
what are the important points for grape sampling ? - Answer-maturity, Brix, TA, pH, phenolics
How does one assess maturity? - Answer-varietal characteristic intensity, phenolics, tannin, seed
ripeness (browning/crunchiness), berry softness, Brix, pH, ability to ripen further
Factors to take into consideration when doing a vineyard samples - Answer-macro, meso, and micro
climate variations; random vs targeted sampling, light, soil moisture, crop load
factors to consider when analyzing Brix - Answer-its a sugar to water ratio. weight can change without
change to brix, physiological conditions can change brix, important to also analyze sugar per berry
which parts of the grapes affect aspects of wine? - Answer-central zone: magic acid, no sugar
intermediate zone: tartaric acid and sugar
peripheral: potassium, aroma, astringency, no sugar or acid
,evaluation of data - Answer-accuracy, precision, consistency
What aspects do Nonsoluble (suspended) Solids affect? - Answer-increase phenolic
concentration/extraction, chemical stability, increase yeast growth
How to reduce NSS? - Answer-Low temperature clarification, fining agents, filtration, centrifugation
hydrometry - Answer-measures specific gravity of a sugar solution, measures sugar using brix, specific
gravity, baume, and oechsle. Read at the bottom of the meniscus, reading is at the correct temperature,
glassware is clean. calibrate using sugar water solutions
determine soluble solids with a refractometer - Answer-passes light through a sample, refractive index
translates to a brix scale. temperature and alcohol can skew this measurement
Total acidity vs titratable acidity - Answer-total: number of protons that organic acids would contain if
they were undissociated
titratable: number of protons recovered in titration with a strong base, always less than total
legal limits on acidity - Answer-TTB allows additions of citric, tartaric, and magic do not exceed 9 g/L
What aspects of wine does TA affect? - Answer-pH, color, chemical/biological stability, shelf life. normal
range in wine is 5-15 g/L
what will be the TA of a wine with a high buffering capacity? - Answer-TA will be high. Buffering capacity
is resistance to pH change and requires more hydroxide to reach titration equivalence point.
titration with diprotic and monoprotic acids - Answer-ph 7 works fine for mono protic acids like acetic,
but will not work for diprotic acids like tartaric because it has multiple pKas
, What skews TA measurement accuracy? - Answer-particulates (absorb NaOH titrant) and CO2 (carbonic
acid)
correct these by centrifugation and neutralization with deionized water. Use an endpoint detection of
pH 8.2
pH electrodes - Answer-measures electrochemical potential of hydrogen ions using known pH of liquid
as a reference point.
fragile, always keep immersed, dry electrodes can usually be rejuvenated
what aspects does nitrogen impact in wine? - Answer-healthy fermentation, clarity, microbial stability,
aroma, foam in sparkling wine
potentiometric titration - Answer-- a form of redox titration in which a voltmeter or external cell
measures the electromotive force (emf) of a solution
- no indicator is used
- the equivalence point is determined by a sharp change in voltage
- higher accuracy
nitrogen sources for wine - Answer-grape cell proteins and vineyard practices; Diammonium Phosphate,
Finn enzymes, mannoproteins
what can cause nitrogen losses in wine? - Answer-settling, clarification (bentonite, centrifugation), wild
yeasts (rot). this can ruin fermentation
which source of nitrogen can yeast use ? - Answer-only ammonium, maybe some amino acids. proline is
most present in grapes, but not utilizable by yeasts.
