3 replies to this topic

[sitansu.shekhar15]

Hello friends,
this is shitanshu doing my 3rd year of chemical engineering from bangalore, india.
I choose this topic as i am very interested. you can post your opinions if you have any related to wine making at home.

[kkala]

The topic is not only interesting, but also probable for Chemical Engineer's specialization. A colleague of mine was occupied (1975 - about 1980) in a wine making company, although chemists (not chemical Engineers) are usually employed in Greece. But these customs vary from country to country, besides interest in food (and beverages) is always increasing.
Ancient god of wine here was Dionysus, having come from Asia, probably from India. I have heard of wine making in Kataragama, Sri Lanka, but also India seems to have good wines produced. Wines here are usually produced by small firms, frequently owning the grape trees too. One problem is lack of standard quality, due to weather variations from year to year. French wines seem to be successful in this standardization.
If you have a flow sheet on wine making (or a web site containing it), this would be welcomed. Searching the web, I have found http://www.begerow.c...seprobe_ENG.pdf, assumed to represent modern plants. I remember a local plant (1970) a bit, it was much simpler. Fermentation took place in concrete tanks. Then there was filtration and embottlement. The latter made the main equipment of the installation, supervised by a Chemist.
I have seen a man (in the country) stepping on the grapes to crush them, like in old times. Then you store the jus (must) in barrels, place them underground (no extreme temperature variation) and wait (say) about 40 days for the fermentation of sugar to alcohol. Collection of grapes occurs in September, before them barrels are washed with sea water. Alcoholic degrees of 12 o to 15 o (meaning % vol in total vol) in produced wines are common. I know that sugar is added to sweet wines to stop fermentation to the desired degree, but how fermentation is stopped in other wines? Probably by exhaust of sugar content?
Could I make a small quantity of wine by storing must (it is sold in the market) in a container? I would like it, to follow the process. I think it is possible.
Good wine is stored in oak barrels, according to local tradition. The older wine, the tastier. But I had observed a trick, when they say that e.g. this wine is from 1900. There is a barrel for each year, filled with the wine of the year. You add 1 l of new wine into 2011 barrel and remove 1 l into the 2010 barrel. Similarly you take 1 l from 2010 barrel and place it into 2009 barrel. In the same way you transfer 1 l of wine to 2008, 2007, .... 1900 barrel, then you take 1 l. Evidently this wine taken is not same as if it remained in the 1900 barrel since that time. Even though they do not transfer excessive quantities from barrel to barrel. I do not know if this procedure is general, a wine company explained it (it is not a matter of cheat).
What remains from grapes after crashing is the raw material for "rum" (local name is tsipouro, raki, etc, depending on the place), a tasty drink of so high alcohol (probably 40 o) that it is flammable. I do not know how it is made, probably they boil the remnants and then distill the liquid.
What surprised me in wine is the difference in quality and taste, even between wines from same location and same kind of grapes. One can be excellent, the other below average.
My knowledge on wine making is quite limited, but I would like to know more. Wikipedia is a good source for it http://en.wikipedia....wiki/Winemaking.

[ankur2061]

Sitanshu,

As a chemical engineer you might be more interested in the industrial wine making process which requires several unit operations of chemical engineering. The representation of the wine making process as a process flow diagram would be more appealing to any chemical engineer so have a look at the link below:

http://www.begerow.c...seprobe_ENG.pdf

Regards,
Ankur.

[kkala]

Wikipedia, as said before, is a good source of wine making knowledge, as you can see by looking in http://en.wikipedia....wiki/Winemaking. Some useful additional data can be the following.

1. From 1,000 kg of harvested grapes, primary must for first class wine (usually bottled) is about 500 kg; remaining must for second class wine about 300 kg.

Info from local radio, 1 Oct 2010, variations from place to place and kind of grapes.

2. The main fermentation is the alcoholic one, an anaerobic activity converting sugars to alcohol and CO₂ gas. The reactions are numerous and complex, but main products are CH3CH2OH and CO₂, according to the overall simplified reaction:

C₆H₁₂O₆ (glucose or fructose) --> 2CH₃CH₂OH (l) + 2CO₂ (g)

The fermentation enzyme supplied by yeasts is called zymase, actually composed of many enzymes, each catalysing a specific reaction. Byproducts in small quantities are glycerin, acetaldehyde, amyl alcohols.

The reaction indicates production of 92/180 = 0.51 ~ 0.5 kg ethanol per kg of sugars. Roughly 24% sugars w/w in liquid must will give a wine of 12/(76+12) = 13.6 % alcohol w/w (see also wikipedia). Usually the volume per cent alcohol is considered in alcoholic drinks, estimated from specific gravity of must and wine http://en.wikipedia....cohol_by_volume., formula by C Berry.

3. Way of producing red or white wines, sweet or not, etc are described in wikipedia article mentioned above.