Help understanding an SG reading

[michael jordan]

Hi there

I was hoping somebody here could help me. I've just pressed 3.7kg of dabinettes today, which had been in the fridge for a couple of months since they were picked. I got about 1 litre of juice out of it, which suggests they were a bit dehydrated from storage.  

When I measured the SG, with two separate hydrometers, the reading was below the scale suggesting a value of 980 -990 or something like that. When half diluted with water the reading was 1005. The temprature on the hydrometer was 17°c, and it's calibrated for 20°c, so should only be off by about 1% if I'm reading it correctly. If water has an SG of 1000, then I don't really understand these numbers. Diluting it with water would suggest the SG of the juice was 1010.

They were grown in the cloudy west of Ireland so I wasn't expecting high sugar but other cultivars have given me SGs of up to 1045 in previous years. The pips were all black suggesting they had ripened. Ph reading of the juice taken with a paper strip had a colour that wasn't on the strip, suggesting it's outside the bounds of 2.8 - 4.6. That may suggest they're not ripened. 

If anybody had a view on what the situation might be here I'd be grateful. It seems like the tree just didn't get enough sun and so didn't produce enough sugar, however the rest of this year's crop (on very  heavy clay soil) ripened fine. The dabinette is the weakest grower of the lot, but produced a good crop and looked otherwise healthy. I don't live near the tree, so can only check in every now and then.

[Claude Jolicoeur]

These SG readings make no sense. I have no idea what is wrong...

Maybe show a photo of your hydrometer itself, and one showing the hydrometer in the juice would help identify the problem.

[Cory Widmayer]

Hi Michael,

Is the juice "jelled"?  That can interfere with getting good readings.

I make a point with all apples that are held for a long time to treat them with pectinase before pressing.  Getting only 1L out of that many apples is heartbreaking...

Grind the apples down to a rough sauce, mix in pectinase (I do ~2 tsp per gallon of sauce), let sit at room temperature for 2-4 hours.  You can also add ascorbic acid at this step to preserve color/prevent browning if you like.  You can press right away or, more ideally, cold steep in the fridge for up to a week.

For particularly stubborn apples, I will also add in 2 tsp of pectin lyase or polygalacturonase (check Alibaba for these), and sometimes a cellulolytic enzyme complex such as ViscoSEB.  The combined effort of these enzymes will eliminate jelling and dramatically improve your yield when you press.  You can cold-steep the juice in the fridge to help clarify the juice before fermentation.

~Cory

[Bennie]

If fermentation has not yet started, you can measure with a refractometer.

Op di 24 dec. 2024 16:17 schreef michael jordan <mickj...@gmail.com>:

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