a question of acid

[godfrey]

as you may or may not have read I am making a plum port style wine

I have posted my progress so far in this thread

http://www.winesathome.co.uk/forum/showthread.php?6449-Hello-and-help-please

my acid test kit arrived yesterday, and I was up until the small hours trying to get a reading

I have used about half the kit already with no sucsess :-(

I believe the acid is too high to get a reading from the kit

I have ordered a digital ph meter yesterday as I understand ph and acid are linked

the ph meter just arrived in the post so I can updated the reading after work :-)

I also believe the ph is very low but difficult to read on the blotter as the must is red

the must was very sour before adding sugar, but the sugar will be converted to alcohol

from what I have read port style wines can be high in acid
and in fact high acid is desirable
to balance against the high sugar level after fermentation

I have some precipitated chalk on order , but only 50g
the instructions indicate that 7g per gallon will reduce acid by 1.5
so my 50g can reduce the acid in my 4-5 gallon must by about 2-3

the yeast was pitched yesterday and I measured an SG drop
from 1.110 to 1.100 in the first 24 hours

any advice or help would be greatly appreciated

EDIT: there is a guide to port making here

http://www.northernbrewer.com/documentation/MakingPortWine.pdf

the guid suggests an acid level of ~0.75% or 0.65-1.0%

multiply by 10 to get g/l is ~7.5

gram per litre (g/l) is the same as part per thousand (ppt)

I believe the acid in the must is greater than 12 ppt
at 12 ml of sodium hydroxide with 5ml must and 1 ml distilled water
there is very little space left in the test tube to shake
I guess I need a bigger vestle for the test lol

[godfrey]

I have just got home from work....

I measured the volume of the test tube supplied with the acid test kit
and the test tube will only hold 20ml of fluid to the brim
no wonder I was having trouble testing last night !!!

any thoughts on using a champagne flute as the test vestal...
the instructions say to use distilled water to make measurement easier in red wines
so I plan to take a 5ml must sample, 5ml distilled water and the acid indicator drops
and something more than 12ml of sodium hydroxide, I will add 10ml straight off
and start drop testing from that point.

alternatively... could i use 1ml of must instead of 5ml and do some maths to compensate ?
perhaps a chemistry major here will have the answer to this.....

I guess I only need an approximate first reading as I will need to make adjustments to reduce acid.

I am just away to have some dinner and sterilise all my equipment before I open the FV
final pH and acid levels will be posted soon!

[lockwood1956]

Which acid test kit is it?

If it is a ritchies one and you are beyond 12ppm thats incredibly high as those kits express as sulphuric acid

Regards
bob

[godfrey]

yes it is richies test kit

best to get the acid level down earlier rather than later in this case....

got another 100g of chalk on order already

[lockwood1956]

I suspect this fruit might have been under ripe?

Careful with chalk additions, they can leave the resultant wine gritty and well.....chalky

If you are sweetening then the acid can be quite high, but expressed as tartaric you are off the scale, somewhere like 20ppm, that will take a lot of sugar to balance....

not saying it cant be done, but it will be a lot of work. we will of course be happy to help you along the way

regards
bob

see here

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

regards
bob

[lockwood1956]

You might want to consider addition of grape juice to lower the acidity by dilution?

it wouls also lower the SG which (in my opinion) is a little high a start gravity

hope that helps

regards
bob

[kirk]

I could be wrong but you say:

the guid suggests an acid level of ~0.75% or 0.65-1.0%

multiply by 10 to get g/l is ~7.5

gram per litre (g/l) is the same as part per thousand (ppt)

The guide does not mention "acid level of ~0.75% or 0.65-1.0%"
The term % is not present.

The guide says:

TOTAL ACID (TA) ~0.65 – 1.0 G/L
PH 3.2 – 3.6

So that is the g/l required you appear to have decided, from the original post information, to multiply this by a factor of 10.

You would multiply by about 20-25 for the quantity in 4-5 gallons (15-18 gms in a 4-5 gallon quantity), but if you are working to 7.5g/l to be added then the quantity is a factor of 10 too high.

[godfrey]

OK some good news, looks like i made a school boy error last night by not boiling off the must before testing

SG 1.095
pH 3.2
TA 6.5 ppt

I am just boiling off another sample to confirm the first TA result
this time I will use the test tube not the champagne flute


EDIT:
the next test i think i miss counted or didn't boil off enough as I got 9 ppt

so I did a 3rd test and got 6.5 ppt again

kirk, you are correct the guid does say G/L not %
but this must be an error.....
as TA 0.75 ppt would be far to low for any wine !

it looks like i got 150g of chalk for nothing

[godfrey]

this vendor list several port with breakdown of ABV / Residual Sugar(RS) / pH / TA

http://www.grootconstantia.co.za/our-wines/groot-constantia-wines/by-type/fortified/?id=4&catId=16

for RS something between 3 and 12 BRIX depending if i want a sweet or dry port

I guess the PDF guide posted above is listing TA in gram per 100ml not gram per litre

[lockwood1956]

ppt and grams per litre are interchangeable terms

The chart i posted is G/litre but it givces you the conversion betweeh acidity expressed as sulphuric and acidity expressed as tartaric

regards
Bob

[godfrey]

thanks Bob

so I have 6.5 sulfuric or about 10 tartaric

looking at the range I posted from the port guide
both sulfuric and tartaric are in the target range
even though the target range is not specific on TA type lol

[godfrey]

damn it is near impossible to find if values are expressed in sulphuric or tartaric

why do vintners not say what TA type they are testing against

now I am unsure if I am on the low side of acid
and have some room to adjust up with some lactic acid

or if I am on the high side and best use some molastic culture

[robwrx]

The pdf that Bob posted the link to shows where the acid levels of the must needs to be.

I imagine that the figures quoted would be tartaric.

If your must is 10g/l or 10ppt Tartaric then it has a bit too much acid in. You need to get it down to around 7g/l.

I would be inclined to follow Bobs advice and dilute the must first before you think about adding chalk. The one time I used chalk I had to bin the wine as the chalk stripped all the grape flavour and left a horribly gritty chalky taste.

I don't know what the main acids in plums are so I cannot comment on MLF or whether you could chill the wine to get any tartaric to drop out.

[godfrey]

most of the fruit used in my must are malic acid

although a few ingredient on the berries are citrus acid

the PDF bob posted is great but it does not list port style wine

the whole point of this style is the volume of fruit
dilution is really not a good solution in this case

not planning on adding any chalk
after the comments detailing the side effects
the money wasted on chalk would have got me a nice ML culture
like this one

http://www.brewuk.co.uk/store/ingredients/ingredientsyeast/new-wyeast-wine/wyeast-activator-malolactic-cultures.html

my concern here is the high ABV I plan,
I doubt the culture will be happy in an environment of over 20% ABV

[lockwood1956]

Port style wines would allow for higher acidity, you can of course use Lalvin 71B-1122 or Gervin D which would both chew through and metabolise some of the malic acid

you will find guides to acidity in this thread

http://www.winesathome.co.uk/forum/showthread.php?3436-Wines-by-style

you will notice that dessert or port styles are to be around 7 grammes per litre or 7 parts per thousand or acidity of 0.7% all meaning the same.

That would be TA expressed as tartaric (which most of the winemaking world uses, except the French and ritchies products)

hope that helps

regards
bob