calculating starting gravity before sugar

[detlion1643]

I've been doing a bunch of wines from fruit juices and concentrates mostly. I've been out of the hobby for a while, but getting back into it now. I'd also like to start moving up to using real fruit (well mostly, sometimes a mix of real and juice/concentrate).

My question is how to figure out the starting gravity of the must? With juice/concentrate I mix those with sugar and water and dissolve/stir until I can get my preferred sg. How would I know how much sugar to add when using real fruit? I imagine that the sg of the fruit won't be readily available until it ferments/breaks down?

My plan is to make a batch of banana to get back into it (since bananas are relatively cheap). If I chop them up and throw them in a straining bag with water/sugar, how will I know how much sugar to add if I don't know the sg of just the banana?

 

[bernardsmith]

The USDA says that on average one 7 inch banana has about 14 g of sugar. There's about 453.5 g in one pound so you will need about 33 bananas per gallon to raise the gravity of the water by 40 points. With other fruits you can simply take a reading of the gravity or use a refractometer to measure the sugar content.

 

[Mallerstang]

My question is how to figure out the starting gravity of the must? With juice/concentrate I mix those with sugar and water and dissolve/stir until I can get my preferred sg. How would I know how much sugar to add when using real fruit? I imagine that the sg of the fruit won't be readily available until it ferments/breaks down?

This is a problem I've been thinking about too, since I also make wines from whole fruit.

You can start by freezing the fruit so that the juice comes out more readily. Use a mesh bag to hold the fruit, dissolve the sugar in boiling water, and pour the hot sugar solution onto the fruit. Assemble all your ingredients except pectic enzyme and yeast in the primary - the pectic is added after 12 hours and the yeast after 24 hours. Before you add the yeast, give the bag of fruit a good poke or even use your (very clean) hands to squeeze it. The freezing, the pectic enzyme, and the 24-hour head start will release a lot of the juice so that you can take an SG reading and adjust the sugar before you add the yeast.

It's not exact - I tend to aim for a slightly higher SG than I want, to allow for some juice still in the fruit.

Not sure if that would apply with bananas since they don't exactly have juice, but I hope that it's of some help. The only time I've used bananas was to add body to a peach wine, and the recipe (Jack Keller's) involved cooking up a weird banana liquor and straining out the pulp before adding the yeast.

 

[detlion1643]

Bernard thanks for the calculations. Maller thanks for the information. With that in mind I can figure out how much sugar to add to get my sg and an efficient way of extracting them with the hot water and freezing method.

 

[bernardsmith]

But juice is juice. If a wine maker making wines from grapes wants to know how much sugar is in the grapes you do not need to press out every last drop of juice. On the contrary, you need only one or two drops of juice and you can use a refractometer to assay the sugar content. If you have only a hydrometer then you need more than a drop or two but a cup or so will be more than enough. The issue then is NOT the gravity of the juice but the VOLUME - if you are adding sugar. But that volume is knowable sooner or later and the amount of time it takes for you to know is totally independent of the action of the yeast.