SG is way less with the same juice and sugar as last time?

[Grape Expectations]

Last batch:
In my last batch of wine, I used Aldi 2L orange juice from concentrate. That juice measured 1.048 SG. To that, I added 1080g sugar per 3.75L of juice and that created 4.56L of juice ready for the yeast. This ended up starting at 1.131 SG which is high but I have done it before and had no problems. That all turned out fine, the wine ended at 0.997 SG and it was at around 17.4% ABV.

Current batch:
I bought the exact same juice - Aldi 2L orange juice from concentrate. That juice measured 1.046 SG. To that, I added 1125g sugar per 3.75L of juice and that created 4.60L of juice ready for the yeast. Now it gets weird: This only measures 1.114 SG. That's way lower than the 1.131 SG from last time! In fact, there is slightly more sugar added to this mixture, so how can the SG be so different?

It's fermenting like a madman and everything's going well, with the usual tsunami of yeast flowing around.

What about air in the juice?
I thought, maybe blending the sugar (in a Vita-Mix) introduced so many microscopic bubbles into the juice, if the juice is less dense, that's going to make the hydrometer sink lower and give a lower SG reading than reality?

So I put 120ml of the mixture into a casserole dish, so the juice was only about 5mm deep, then I left it standing for 20 minutes. After that time, it can't possibly still be full of bubbles, so I took it out of the casserole dish and put it in my cylinder to measure the SG... it was still at 1.114 SG.

I don't mind the wine coming out at 15%-16% ABV as opposed to 17%-18% ABV but I can't work out how this SG level can be so far out from last time. It's not like I'm going off the juice carton label, I am testing the SG and triple checked I was reading it correctly, with the same hydrometer as last time at around the same temperature. I even checked the bags of sugar thinking maybe I bought 500g bags or they reduced the weight like is the case with nearly everything else these days, but it's still 1KG bags, like last time. It's perplexing.

 

[Jim Welch]

That is strange, I’ve a couple thoughts.
Is all the sugar fully dissolved?
Did you actually weigh ALL the sugar on a scale? If so have you checked the scale with known test weights or compare results to another scale?
Seems the only explanation is either the sugar isn’t fully dissolved or you did not get the actual weight of sugar you think you did.
Also, just reread and notice the OJ is from concentrate, are you positive you used identical or nearly identical volume of water to reconstitute the OJ?

 

[Grape Expectations]

That is strange, I’ve a couple thoughts.
Is all the sugar fully dissolved?
Did you actually weigh ALL the sugar on a scale? If so have you checked the scale with known test weights or compare results to another scale?
Seems the only explanation is either the sugar isn’t fully dissolved or you did not get the actual weight of sugar you think you did.
Also, just reread and notice the OJ is from concentrate, are you positive you used identical or nearly identical volume of water to reconstitute the OJ?

The OJ was straight out of the carton, it's just called "from concentrate" on the carton, but it's ready to drink. I blended the sugar with a Vita-Mix for at least a few minutes each time, but even if that didn't dissolve it, it's the same thing I did last time around. 1 KG sugar was thrown straight in from the bag and I weighed the other small amount on digital scales, same as last time.

 

[Jim Welch]

The simplest explanation is that the 1 kg bag was light then, it is the only thing not measured or weighed right?
You can chapitalize to get to the previous batch’s OG if you want, there is a chapitalization calculator at brewers friend.

 

[Grape Expectations]

In addition to the SG not shifting according to the sugar added, this batch has also ended up not going fully dry, but I did start a new tub of yeast so I think it's probably that, although it's the same brand.

Instead of it coming out at the usual 17.5% ABV it's more like 14% ABV. It's actually come out better for it, more drinkable, slightly sweet, but something (an iffy tub of yeast I bet) made it stall and finish at 1.010 SG.

 

[Rice_Guy]

@Grape Expectations ,,, if I am formulating a nutritional statement, I need to test actual samples of the food product. A wet chemistry test for sugar is REDUCING SUGAR via a chemical oxidation test. This is not the same as measuring specific gravity. Gravity is a fairly dirty test which includes ash, fats, proteins, long chain carbohydrates,,, essentially the good stuff which produces really really good flavor and aroma. ,,, If you are really concerned about starting sugar and finished alcohol you need to change the test method to actually measure sucrose and fructose and glucose etc.

Specific gravity of a crop will vary by crop year, how much irrigation, how much fertilizer, soil type, days of sunlight, temperature in ripening, processing method used to create the concentrate, variety, how clean the truck was delivering to the factory, etc, etc, etc. The variation in sugar versus ash (flavor compounds) is significant.
OK so what?. ,,, Gravity is good enough for making wine which resists bacterial infection, and considering that a hydrometer is $10 the test is basically free. AND,,, In the eight or nine hydrometers I have variation is 0.004. ,, BUT You still have a crude test which two centuries ago was done by measuring how deeply an egg floated in the juice