Winemaking Chemistry Flashcards
what does the flesh of grapes contain?
h2o
Acids (malic - hard acid green apple, tartaric, citric - small amounts)
sugars (fructose, glucose and others)
what are in the skins of grapes?
white
red
red: anthocyanins - red-brown colour in nature
white: carotenoid, varies from water white to yellow gold
what are the requirements for an alcoholic solution?
- complex carbs (sugars)
- aqueous solution: h20
- ambient temp approx 18-22
- a vessel
- yeast (not any yeast, most common is Saccharomyces cerevisiae)
what is ethanol?
alcohol that can be metabolised by the healthy adult human liver
reds are typically higher in alcohol than whites, by what percentage?
23% higher
what is the alcohol percentage of most wines?
12-15%
when is residual sugar created?
when ferment stops before Dryness (before all sugars are consumed by yeast)
what are the by-products of alcoholic fermentation?
heat CO2 aroma and flavour compounds... include: - acetic acid and acetaldehyde (vinegar-like) - hydrogen sulphide (natural gas) - glycerol, adds to the mouthfeel - volatile esters, essential flavour compounds - lees - dead yeast cells
are there different strands of Saccharomyces cerevisiae?
if so give examples
Yes
S. bayanus
S. beticus
what are the two things that influence how much sugar is in wine?
how much sugar there is and how vigorous the yeast are
in the last 20 years, what percentage of alcohol in wine has it gone up?
why is this
- 5%
- getting warmer and the yeast that have been cultured are getting stronger/more effective at doing their job
which is a drier white wine?
riesling or chard?
riesling
a very dry wine doesn’t exist, what is the consumer actually asking for?
white: high acidity in the wine
red: high tannins in the wine
regarding dry wine, what are the only two ways wine can turn out?
either a dry wine (no fermentable/residual sugar)
or there is some amount of residual sugar so degrees of sweetness
if there is residual sugar, how do we ensure there is no more fermentation in the bottle?
- super chill the wine so the yeast cannot operate