Monthly Archives: March 2010

How Far Can You Trust Your Hydrometer?

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Hydrometers measure soluble solids density, and we use this to closely approximate soluble solids content of fruit juice. Because almost all the soluble solids in wine grapes are sugar, we use hydrometers to determine sugar content. I’m not telling you anything you don’t already know, every book on wine making I have says something like this, but did you maybe tuck the “in wine grapes” qualifier into the back of your head and just remember the “… almost all the soluble solids are sugar” part? I know I did, and it was while researching raspberries that I discovered just how much hydrometers can overstate sugar content.

Great data on raspberries upends an old rule of thumb

I was checking university extension offices, googling, and looking anywhere I had found information on fruit composition before when I came across this great paper on raspberries. It’s got excellent data on sugar and acid content, and I highly recommend it if you’re interested in making raspberry wine. I want to zero in on the Brix and Total Sugar measurements:


Brix vs Sugar Content in Raspberries
Varietal Brix Total Sugar Sugar Brix Ratio
Meeker site 1 11 2.83 25.7
Meeker site 2 8.6 1.01 11.7
Meeker site 3 9.2 2.38 25.9
Meeker site 4 9.8 3.28 33.5
Chilliwack 9.6 3.84 40.0
Tulameen 9.5 3.09 32.5
Willamette 8.7 2.31 26.6
Yellow Meeker 10.8 4.60 42.6
Average 9.7 2.92 29.8

Total Sugar is reported as grams per 100 grams, and if the soluble solids were 100% sugar, then Brix would equal Total Sugar. The last column, Sugar Brix Ratio, is my own calculation and expresses sugar as a percentage of soluble solids. I also reported average values in the last row.

We go from soluble solids being “almost all” sugar in wine grapes to less than 30% (on average) for raspberries! I asked Michael Qian, one of the authors, about this. He said that the data were good but some fruit, like raspberries and blackberries, just have a lot of pectin and other non-sugar soluble solids. I really appreciate him taking the time to help me out; I’m sure he’s a busy guy and this was a pretty basic question from someone outside his target audience (so, if you’re reading this – thank you!).

We know more than before – it just doesn’t feel like it

It’s exciting to learn something new, even if it does make things more complicated. When can we rely on our hydrometers? Wine grapes are probably a safe bet. Raspberries and blackberries are not. We need more information about other fruits, and I’ll be looking into that. If you know something about sugar content and soluble solids of other fruits, please say so in the comments.

Alright, what do we do when we know our hydrometers will read high? I don’t have a good solution yet. For raspberries, we might just adjust the reported Brix by 30% – still not accurate, but closer than the hydrometer reading. If you have an idea, I’d love to hear about it.

Jack Keller once said that a hydrometer is like a compass. Maybe it’s like a magnetic compass. It works well enough much of the time, but the question is, how do we find true north when we really need to?

Colony Collapse Disorder: Another reason for optimism

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The number of managed honeybee colonies in the United States rose to 2.46 million in 2009 (see the just-released USDA honey report). That’s more than in 2005, the last full year before CCD struck, and more than in 2006 when CCD was first reported. I’ve summarized USDA data on colony count, per-colony yield, and honey production in the table below.


US Honeybee Colonies And Honey Production
Year Production (millions) Producing Colonies Yield
2005 174 lb (79 kg) 2.41 million 72.4 lb (32.8 kg)
2006 155 lb (70 kg) 2.39 million 64.7 lb (29.3 kg)
2007 148 lb (67 kg) 2.44 million 60.8 lb (27.6 kg)
2008 161 lb (73 kg) 2.30 million 69.9 lb (31.7 kg)
2009 144 lb (65 kg) 2.46 million 58.5 lb (26.5 kg)

Colony Collapse Disorder is real, we don’t know what causes it or how to treat it, and it’s causing losses and hardship for beekeepers. But each passing year of stable colony counts, this is the fourth, is another reason for optimism that CCD is not threatening our honey supplies or pollination capacity. News media coverage seems to be moving away from the shrill cries of “disappearance” and “extinction”, as in this ABC report on the declining incidence and severity of CCD over the 2008/2009 winter.

I make a lot of mead and buy honey in bulk. I’d like to keep doing that, so I’ve been following the CCD phenomenon ever since I heard about it. I’m also interested in production and and the outlook for honey prices. From that perspective, the rest of the honey report is a good news/bad news story.

More honeybees but less honey in 2009

In 2008 we saw managed colonies decline, but per colony yield and total honey production rise. 2009 gave us a mirror image of that with the number of colonies rebounding but producing less honey. Much less. In fact per colony yield was the lowest since 1989 and total US honey production was the lowest ever. That’s the bad news. The good news is that lower production didn’t lead to higher prices.

Honey prices up a bit, inventories down a lot

Producer honey stocks fell to 37.2 million pounds (16.9 million kg), down from 50.4 million pounds (22.9 million kg)a year ago – a 27% decline. My own honey price survey showed no change in 2009, and the USDA’s “all honey” price was up 2% to 144.5.

Revisions of 2008 data

It looks like the USDA has revised some of it’s 2008 data this year. The all honey price was originally reported to be 141.0 in the 2008 honey report, but is said to have increased from 142.1 in the 2009 report. Also, the number of producing honeybee colonies was originally reported to be 2.30 million at the end of 2008, but are said to have risen by 5% to 2.46 million at the end of 2009. The USDA does not provide a new figure for the 2008 colony count, but 2.46 million is about 7% higher than 2.30 million. So it looks like honey prices rose more, and the colony count fell less, than first reported in 2008. Since the USDA was not explicit about all these revisions, I use the data as reported in my table. After all, the 5% figure or the 142.1 could have been typos.

Further reading

The ABC news story that I mentioned was based on A survey of honey bee colony losses in the United States, fall 2008 to spring 2009.