parkstone at lds.co.uk wrote in article <854622079.25760 at dejanews.com>...
> Hi, I'm an A-level student currently studying chemistry. I am presently
> involved in an extended investigation, which makes up part of my final
> grade, on the comparison of the rate of fermentation with use of
different
> sugar substrates. Below is my outline proposal . . . .
>> During alcoholic fermentation, yeast metabolises glucose to form ethanol
> and carbon dioxide using a metabolic pathway consisting of a number of
> enzymes. By making the assumption that the yeast cell is a single
> catalytic reactant, glucose (as a control), mannose, galactose and
> fructose will be added separately to yeast solution.
>> Because the multi-based pathway consists of steps, the rate of reaction
> will be heavily reliant on the slowest rate determining step. Comparison
> of reaction rates of each sugar with yeast will give an indication as to
> whether different pathways, (for example not that of glucose) were
> utilised.
I do not know if this is necessary to tell you but, you have a big task on
your hands. I tried to do the same analysis once, many years ago when I
first started making wine.
I was smart enough then to realize that I had to reduce the number of
variables. In my first test, I used sugar (same brand and quantities),
same water source, same containers, and varied only the yeast (note no
fruit). Of the five yeast, I selected two for the next set of experiments.
The second test involved only variation with water sources. The water
sources were Minneapolis city water and Hamms (now Stroh) brewery artesian
water. Brewery water was fastest. I did not take into account the
chlorinated water in my testing (big mistake- should have waited until
chlorine evaporated). The 3rd test involved sugar sources (cane vs. beet).
Cane was faster.
I now believed I knew the best yeast, waters, and sugars so I used two
different one US gallon containers as the primary fermenter. One was low
and wide in diameter, the other was tall and narrow. The low, wide
container fermented faster. At this point I thought I knew all about the
fermentation process. Fastest yeast, fastest water, fastest sugar, fastest
container. Who knows, maybe I invented something. Ha. More about this
later.
Well, I bought twenty pounds of peaches; fifteen pounds of sugar, got my
artesian water, bought a five gallon low, wide stainless steels pot for a
primary fermenter, did all the things necessary for making the best of
wines and went on vacation. Two weeks later I got back home. God was I
anxious to get home. I swung open the door, was greeted by a swarm of
fruit flies, and the smell of fermentation. I entered the kitchen to look
at my creation. There it was! Dried, sugary material on the table (this
is where I placed the fermenter since I would not be using the table for
two weeks), on the floor, on the chairs, down the legs of the chairs.
Every seam and crevice a liquid could possibly go, it went. My wife's
words to me were, "clean that %#@%$#@ up".
Lessons learned:
1. Use hot water to clean things up.
2. Place primary fermenter as close to floor as possible.
3. Fruit added to must causes more violent fermentation.
4. Allow ullage to exist between top of must and top of primary fermenter
5. Use tall primary fermenter to slow down rate of fermentation
Back to the more serious part.
As you can detect, there are a lot of variables I did not even take into
account. Acidity, types of fruits, specific gravity, energizers, etc.
As stated earlier, you have one big job. Best of luck.
