Thanks Matt – you are a gent. Points taken.
But just to confirm no water is added to the blackberries before the yeast is pitched.
All the best.

Please let us know how it turns out Skip!

Hi Myles, here are my thoughts on your questions:

1 – the 3lbs of sugar is to raise the sugar level of the must sufficiently enough to produce a finished wine with enough alcohol. David mentions that after the wine is finished you may need more sugar to sweeten to your liking.

2 – I did some research on this and found that blackberries have roughly 4.88 grams of sugar per 100 grams of fruit. Table grapes have 16.25 grams of sugar per 100 grams of fruit. Wine making grapes typically have much more sugar than table grapes so the 3lbs of sugar would be needed to make a proper blackberry wine before adding the brandy.

3 – To guard against wild yeast fermentation you could crush / press the fruit, treat it with potassium metabisulfite, and pitch your yeast 24 hours later. That’s typically what’s done with wine grapes as well.

With 7kg of blackberries you could expect to get 1.03 gallons (3.9 liters) of juice. The pint of brandy will add another 0.5 liters so you would be good with a 5 liter container.

Topping up with marbles is certainly doable. Just be careful of dropping them into the carboy. I’ve heard of people doing this and they wound up cracking the bottom of their carboy. I’d consider using a mesh bag to hold the marbles.

Your other option would be to use an inert gas such as Private Preserve to displace the oxygen. Just purge the head space and seal the carboy up with an airlock. Solid plugs can lead to trouble if anything is going on in the wine still or if there are temperature changes.

Great questions Myles!

For the most part the sugar levels are going to be to taste. If you put more sugar in the must to produce a higher alcohol finished wine you can use a less potent brandy to get to 20% ABV. Back sweetening is of course to suite your own palate.

David doesn’t use acid blend but you could determine if your blackberries could use an acid boost by testing the titratable acidity. I don’t really have a good idea of what the acidity of a blackberry is unfortunately.

Lastly, sulfites levels will depend on the pH of your finished port. I would stick to the suggested normal sulfite levels outlined in this article: Adding Potassium Metabisulfite to Wine. The dose of brandy will help with stability though as this was the purpose of adding brandy to wine in the first place. It stabilized the wine so it could be stored in barrels in the bottom of a sailing ship to go back to Europe.

Adam, I ran some numbers using the Pearson Square and found the ratio of brandy to wine to be about right. Of course it depends on the alcohol content (ABV) of both the blackberry wine and the brandy. Here are two examples.

If the wine is 17% ABV you’ll need a pint of 40% ABV brandy to get to a 20% ABV port. If the wine finishes at 15% ABV then you’ll need a pint of brandy at 55% ABV. Brandy alcohol content can range from 35-60% ABV so these numbers are right in there.

I hope this helps!

Thank you again for sharing this recipe.