A question about specific gravity

[bernardsmith]

I am making a gallon of strawberry wine. I added enough water to 2 lbs of sugar to make 1 US gallon. That should give me an SG of 1.090. I poured this syrup over 5 pounds of strawberries and allowed the fruit to macerate on the syrup with some pectic enzyme. I then blended everything and the gravity is now about 1.080 with the total liquid volume close to 1.5 gallons. Obviously, the fruit holds a great deal of liquid but I wonder whether the gravity (density) of the liquid includes the particles of the fruit or is my hydrometer essentially measuring only the sugar content of my syrup AND the sugars that were in the strawberries? I do have a refractometer, but I already pitched the yeast, and the must started to ferment after a very short lag time, so I have not tried to measure the sugar content with the refractometer.
Thoughts? Thanks.

 

[Raptor99]

SG measures total dissolved solids. Everything dissolved in the liquid increases SG. So the measure of sugar content is only approximate.

The liquid from the strawberries probably had an SG lower than 1.090, so it probably lowered your SG somewhat. An OG (original SG) of 1.080 would give a potential 11% ABV, which is a good level for a strawberry wine.

 

[bernardsmith]

SG measures total dissolved solids. Everything dissolved in the liquid increases SG. So the measure of sugar content is only approximate.

The liquid from the strawberries probably had an SG lower than 1.090, so it probably lowered your SG somewhat. An OG (original SG) of 1.080 would give a potential 11% ABV, which is a good level for a strawberry wine.

Thanks. I guess my concern is that given the fact that the volume (of liquid - from the juiced fruit) has increased by 50% my concern was whether the 1.080 reading was based on the fermentable sugars OR on the sugars AND the chopped up fruit. When I took the OG, the whole fruit was not adding to the density of the liquid. If the total liquid volume is now about 1.5 gallons, does that suggest that the SG should be closer to 1.070 which is closer to 9% ABV and not the 11% the reading would suggest or would the 5 lbs of strawberries have enough sugar to add another 10 points to the gravity? When I make fruit wines I generally treat the fruit as having virtually no sugars, but this is the first time I have blended the fruit in a blender.

 

[mac_1103]

Strawberries definitely contain fermentable sugars. The question is how much of them did you extract. Hydrometer reading should be accurate as long as you let all the solids settle out of the sample.

If you extracted no sugar from the fruit and increased the volume to 1.5 gallons then the SG should go from 1.090 to 1.060 (that's just simple arithmetic). I could believe getting 10 points from the strawberries but I don't know about 20.

 

[Raptor99]

When I took the OG, the whole fruit was not adding to the density of the liquid.

When I make fruit wine, I usually freeze the fruit, then thaw and mash with a potato masher, and add to the fermenter with the sugar water. I add pectic enzyme (if needed) an Kmeta, and then wait 12-14 hours. At that point, I give it a stir and measure the OG. The OG needs to include the sugar and water from the fruit.

When I make fruit wines I generally treat the fruit as having virtually no sugars,

Some fruits contain a considerable amount of sugar, as well as some water. Both will affect the SG. So it is best to combine everything, give it some time for the juices to merge into the must, and then measure the OG. We can't predict the exact amount of sugar in the fruit. It can vary considerably from season to season.

I guess my concern is that given the fact that the volume (of liquid - from the juiced fruit) has increased by 50% my concern was whether the 1.080 reading was based on the fermentable sugars OR on the sugars AND the chopped up fruit.

Part of the volume is fruit solids, which will settle out. If you ran it through a filter right now, you would end up with less than 1.5 gal. But the volume does not matter as far as SG is concerned. What you want to know is the SG of the all the liquid in the must, once everything has been added and had a chance to extract the juices from the fruit. Unless the must is really thick with fruit, a hydrometer reading is close enough. I don't think that the undissolved bits of fruit will affect it very much.