acid content

[bill]

using my richies acid test kit i get a figure of 5.5ppt acid content in my gallon fermenter . first does this acid level sound right , in that i mean will using so much juice naturally be high acid

3l red grape juic
1l apple juce
5 conference pears , peeled and cored
1lb sugar
water to a gallon




i have some precipitated chalk which states 7g per gallon will reduce acid by 1.5ppt.

i read a good acid content to be between 3 and 4.5 so what should i aim for?? and also is a teaspoon around 5g?

is it ok to add it now its nearing finishing fermenting or should i leave till finished.. i would of done this before but didnt have the kit..

btw, i intend ferm this dry and sweeten with grape juice before bulk ageing.
billy

[goldseal]

The Ritchies kit mesaures acid 'as sulphuric'.

5.5 g/l as sulphuric is OK for whites, maybe towards the upper end of the range.

The easiest way to work out acid, I find, is to measure using the kit, convert to Tartaric, then you can work out how many grammes of tartaric acid you need to add.

5.5 g/l sulphuric is 8.5 g/l tartaric.

See here:

http://www.winesathome.co.uk/downloads/TAtestsheet.pdf

Example to INCREASE acidity:

You have 5 litres must at 4.2 g/l sulphuric. You want to get to 5.2 g/l sulphuric.

4.2 g/l sulphuric is 6.5 tartaric. 5.2 is 8.0 tartaric. You need to add 1.5 grammes Tartaric acid per litre, giving you a total of 7.5g for your 5 litres.

I would strongly recommend

a) doing the calculations at least twice to ensure you have the right answer

b) add half the calculated acid, then measure again. It is more difficult to get out than to put in





Because yours appears to be at the upper end of the range for whites, your plan to sweeten is a good idea - it should take the edge off it. I would not reduce its acidity at the moment.

(Now waits for someone to come along and tell him that his calculations are rubbish )

[bill]

ok cheers , that confused me for a minute till i read the attached file properly and understand the chart..

so whats the reccommended figure sulphuric or tartaric for reds

and whats the figure for whites???

i ask because i have an acid content of 5.5 and it tastes acidic yet the chart says this figure is fine , my figure is probably a litle high as i was a bit quick with the last 1/2 mill or so of solution and if done again would probably be around 5 ..

.................................................. .......................

this bit may need to much deatail to answer here..

if my acid content is above reccommended levels do i drop the level using something like precipitated chalk or another acid to counteract ?.. i

[granda]

if you have added to much acid how can you reduce it

[lockwood1956]

Depends on the sort of acid....

if it is tartaric you can make it drop out via cold stabilisation (see tutorial thread)

otherwise precipitated chalk can reduce the acidity, as can blending with a non acidic wine

[NorthernWiner]

The Ritchies kit mesaures acid 'as sulphuric'.

This is something I've always found confusing.

To begin with, it's confusing that acid in wines be measured as sulphuric, since there are no fruits or vegetables that contain sulphuric acid (at least that I'm aware of). I'm guessing that some French guy is probably to blame.

But that aside, what I'm wondering is HOW does the Ritchies acid test kit measure as sulphuric when it apparently uses all of the same chemicals as the American kits that measure as tartaric?

Is there a formula that converts the amount of NaOH used into g/L or percentage?

[lockwood1956]

I'm not sure if there is a formula, but I just use this sheet to compare

http://www.winesathome.co.uk/downloads/TAtestsheet.pdf (page 2)

[NorthernWiner]

Well... let me put it another way.

In the US, we measure acid in wine as tartaric.

In the UK, you measure acid in wine as sulphuric.

Both US and UK test kits contain the same solutions: a phenolphthalein indicator solution (for detecting color change), and a bottle of sodium hydroxide (NaOH) solution reagent. In the US, the strength (normality) of the NaOH solution is typically .1N or .2N (I don't know the strength of the solution found in the Ritchie's kit).

To determine TA in the US, we use the following formula:

TA% (as tartaric acid) = [75 x (N of NaOH) x (ml of NaOH)] ÷ (ml of sample)

So, if we both have the same chemicals in our kits, how do you arrive at a different number for TA than we do? I'm assuming the formula used in Europe is simply a variation of the one we use over here.

Hopefully that makes more sense.

[NorthernWiner]

The reason I'm wondering this is because I hope to modify my TA spreadsheet so it can be used by both UK and US winemakers.

[NorthernWiner]

Hmmm.... I suppose I could always just multiply the result by 0.65 to make the conversion to sulphuric.

[lockwood1956]

hmmm.... I suppose i could always just multiply the result by 0.65 to make the conversion to sulphuric.

geek!

[NorthernWiner]

geek!

True!

[NorthernWiner]

To determine TA in the US, we use the following formula:

TA% (as tartaric acid) = [75 x (N of NaOH) x (ml of NaOH)] ÷ (ml of sample)

So, if we both have the same chemicals in our kits, how do you arrive at a different number for TA than we do? I'm assuming the formula used in Europe is simply a variation of the one we use over here.

Well, I found the answer to my question, thanks to a book Bob sent to me ("Modern Winemaking Techniques" by Gladys Blacklock - thanks again Bob!).

After a bit of futzing around, I found that, in order to calculate TA as sulphuric, one only has to replace a single variable in the above formula:

TA in g/L (measured as sulphuric) = [50 x (N of NaOH) x (ml of NaOH)] ÷ (ml of sample)

So, if you have a 20 ml sample and it takes 17 ml of 0.1N NaOH solution to titrate to neutral, then your formula will look as follows:

TA = [50x 0.1 x 17] ÷ 20
TA = 4.25 g/L

And as Ms. Blacklock wisely points out, once you determine which standard to use (sulphuric, citric, tartaric), it's best to stick to it throughout the entire process, lest you confuse yourself.

[lockwood1956]

YAY

the book arrived....


I hope you enjoy it as much as I did dud, she was well ahead of her time

regards
Bob