checking the gravity of a pulp fermentation?

[james]

How do I know what my starting gravity is for a wine heavy on fruit and undergoing a pulp fermentation?
I've always just guessed that "some" sugar will be provided by the fruit, and so I go easy on the added sugar. This has always worked, but I never know exactly what I'm working with.

Likewise, same question regarding acidity.

cheers

[Mamgiowl]

For a pulpy wine try to let it settle a bit and use a wine thief or turkey baster to take out enough must to almost fill the hydrometer test jar. If it's a 'lumpy' must you can strain through muslin or a very fine seive. Sometimes a pulpy must is too fine for these methods so the last time I had this problem I added sugar to 1090 and hoped for the best. It turned out fine.

I'm not so hot on acid knowledge so can't help there. Sorry

[lockwood1956]

For a must containing suspended solids, take 7 off your hydrometer reading.

The table linked below will help you to work out (roughly) the levels of acid and sugar in your fruit.

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

you may also find the book "must" by Prof gerry Fowles useful in this regard. (£3.95...quite a technical book though....thats why i love it! )

hope this helps
regards
bob

[Her Lushness]

Geek!

(and it's not available on Amazon...)

[james]

thanks. Just tracked a copy down on ebay.

I presume if I use a refractometer, I wouldnt need to adjust my reading for solids?

How acurate would the gravity or brix measument be, given that much of the sugar is leaked out over time during the pulp fermentation (...at the same time that the yeast is using up the available sugar...)? I would imagine that taking an opening gravity reading on day 1 of the pulp fermentation wont give a true indication of the total fermentable sugar

[NorthernWiner]

I presume if I use a refractometer, I wouldnt need to adjust my reading for solids?

You're on the right track, except that you won't get a true reading unless you account for the sugar that's contained within the pulp.

What's normally done for grape musts (which contain a great deal of solids) is to extract a cupful, mash it all up real good, and then squirt a couple of drops onto the refractometer lens to get your Brix reading. This technique works for any pulpy fruit must.

[Zebedee]

For a must containing suspended solids, take 7 off your hydrometer reading.

How do you arrive at 7 ?

Is there a geeky formula I dont know about ?

[lockwood1956]

I am the geek of geeks Zeb....you doubt me?

source = Progressive winemakng (Acton and Duncan) if you dont have it.....buy it!

[lockwood1956]

Better still.....I have a spare copy, you can collect it at Ponte wine circle next month

[lockwood1956]

Geek!

(and it's not available on Amazon...)

No....but it is available from;

http://www.vigoltd.co.uk

http://www.hopandgrape.co.uk

£3.95 brand new

[lockwood1956]

and I believe

http://www.leylandhomebrew.co.uk

[lockwood1956]

And it is because the suspended solids (on average) increase the density of the must by approx 0.007 (in tests)

[Duffbeer]

How do you arrive at 7 ?

Is there a geeky formula I don't know about ?

Not a particular reliable way tbh, some musts will be higher in sugar than others, their are two ways that I find most reliable:
1 the refractometer will tell you the brix of the fruit so you can do a reasonably close estimation of what sugar to add.
2 take a reading over 2 to 3 days of the must and get a general idea of the sugar content, if you work on the low side you can add more before pitching the yeast. The must should be strained of heavy debris before using the hydrometer.

We must all remember though inacuracy is one thing we have to live with, we can get things near, but I doubt 100% accuracy is quite possible or nessicarry in a hobby.

[james]

You're on the right track, except that you won't get a true reading unless you account for the sugar that's contained within the pulp.

What's normally done for grape musts (which contain a great deal of solids) is to extract a cupful, mash it all up real good, and then squirt a couple of drops onto the refractometer lens to get your Brix reading. This technique works for any pulpy fruit must.

Thanks, thats a great help.