My New Toy: Refractometer (and bonus Christmas Cider recipe)

A couple of weeks ago, I was looking through Google Plus communities and I came across a post on using a refractometer for measuring sugar concentration (i.e. Brix). For me, this was a lightning bolt. I didn't need to read anything beyond the title of the post to know exactly why I wanted my own refractometer and why. I immediately started looking online, and found out that Lee Valley Tools in Edmonton had one in stock, advertised as a "Sugar Tester", priced at $76.50. I acquired one the next day.

Portable Refractometer. The item came with a case, an eyedropper, a small

screwdriver (for the calibration screw), instructions, and a cleaning cloth.

A refractometer measures the index of refraction of a medium. The index of refraction, n, is the ratio of the speed of light in a vacuum compared to the speed of light in the medium of interest. For example, n for water is 1.333, which means that light travels 1.333 times slower in water than in a vacuum. Refraction is when light "bends" on entering a medium with a different n. When I described this to my daughter, she immediately gave the example of looking at a plastic straw in a glass of water - it looks like it's bent.

The key thing to know is that sugar solutions have a larger n than water. And, if you increase the sugar concentration, n increases. This can be calibrated and you can use a relatively simple optical measurement to determine sugar concentration, as opposed to measuring specific gravity with a hydrometer.

Personally, I find the measurement of specific gravity with a hydrometer to be a chore. For one, you need to sanitize the hydrometer and the cylinder or wine thief used to hold the liquid during the measurement. So, every time you want to measure s.g., you need to sanitize stuff. Second, hydrometers are made of glass, so they are fragile and it's no fun if you break one by accident. Third,  s.g. measurements are a bit imprecise due to the size of the meniscus relative to the calibration marks on the hydrometer. And, if there are bubbles stuck to the hydrometer, the s.g. reading will be higher than it should. You need to measure s.g. two or three times to make sure the reading is consistent.

Measuring Brix with a refractometer is just simple. All you do is place a few drops (yes, DROPS) of liquid on the prism, close the "daylight plate", and look through the eyepiece for the reading. In this particular refractometer, the dual scale is given in Brix and "Approximate % of Alcohol". The images below show what you see in the eyepiece.

Refractometer Brix scale with water on the prism.

(Photo obtained by placing the eyepiece up to the camera on a MS Surface tablet)

Refractometer Brix scale with freshly pressed apple juice (for cider, of course!)

My first use of the refractometer was in preparing a batch of cider. I decided to use the same 'recipe' as a batch from last year, which I'm going to name "Christmas Cider" (see recipe at the end of this post). That batch of cider was delicious and I wanted to reproduce it. The refractometer comes in handy because I diluted the apple juice by a factor of two with water, and then adjusted (increased) the sugar content in order to get enough alcohol. By having a quick & easy way to measure Brix with a refractometer, this sugar adjustment was painless compared to repeatedly measuring s.g. with a hydrometer. The readings were precise in the sense that they did not fluctuate during the reading (unlike a bobbing hydrometer!) or between readings of the same sample.

The one big limitation of measuring the index of refraction is that it's only really useful for measuring sugar content before fermentation starts. When fermentation starts, the sugar concentration decreases, and alcohol increases. Alcohol, just like sugar, increases the index of refraction. That means that the n measurement is no longer proportional to sugar concentration. Rather, n is affected by sugar and alcohol concentrations. Apparently there are online calculators that allow you to calculate sugar and alcohol concentrations from a mid-fermentation refractometer reading, so long as you know the starting Brix. This sounds fine in theory, but I have a bias against "black box" calculations like that. Even though it's a chore, you are probably going to get a more reliable measure of fermentation progress from a direct measurement of s.g. with a hydrometer. Give me the choice, and I would rather have a direct measurement than a value from a black box. That being said, it would be interesting to compare s.g. measurements with corrected refractometer readings using an online calculators.

From a quick survey of YouTube videos on refractometers, it seems that a number of home brewers like to use refractometers when they are making up their wort, and then they use hydrometers once fermentation is under way. This makes a lot of sense.


Christmas Cider

1.5 gallons freshly pressed apple juice
1/2 tsp peptic enzyme
2 tsp yeast energizer
3 crushed Campden tablets
1.5 gallons water
approx. 3 cups granulated sugar
1 packet of champagne yeast (Lalvin EC-1118)
1 tsp. nutmeg
5 cinnamon sticks
3/4 cup dextrose (priming sugar)

Instructions*:
Add peptic enzyme, yeast energizer, and Campden tablets to the apple juice and let it sit in the closed primary fermentation bucket for 24 hours. Then, add water and stir thoroughly. Add sugar in 1 cup increments, stirring thoroughly after each addition, and measure Brix with a refractometer until Brix = 9. (If measuring s.g. with a hydrometer, aim for s.g. = 1.035 - 1.040.) Sprinkle yeast on surface of the juice and close the lid loosely on the primary (you can also use a primary with airlock). When the foam collapses, siphon the cider into a sanitized 3 gallon carboy for secondary fermentation. At this point, add the nutmeg and cinnamon sticks. Seal the carboy with an airlock. When fermentation is complete, siphon the cider into bucket and mix in the dextrose (1/4 cup per gallon of cider). Bottle in beer bottles and seal with bottle caps.

*Note: This is a customized version of the apple cider recipe in the Winemaker's Recipe Handbook, known as the purple booklet

Peach Melomel - Tasting & Bottling

Three months have passed since I racked the peach melomel to let it clarify. Passive clarification was effective in this case. The melomel was crystal clear at the time of bottling.

I siphoned the melomel into a sterilized carboy, and stirred it vigorously for about ten minutes. This was to remove residual carbon dioxide. I actually did a taste test before and after stirring, and it was easy to detect the reduction in carbonation. I also took a specific gravity reading, and found it unchanged from the previous measurement.

Bottling was a snap. The three gallon batch is a good size for my purposes. This yielded 14 (and half) bottles in the end. Some volume is always lost in the racking, but that's fine.

Bottles of peach melomel.

I like the taste of this batch. The taste is light and reminiscent to some dry white wines. It has a mild honey aroma, and the honey taste seems most noticeable at the front and middle. Then, a gentle fruit flavour emerges at the end. The acidity is just right. But the odd thing is that I have a hard time identifying a peach flavour!

Fruit flavours come from organic compounds called esters, and the pure compounds have very specific tastes and aromas. One of the fun things about esters is that they are easily transformed into other esters, under certain chemical conditions. That means you can transform an ester with one particular flavour into another ester that has a totally different flavour. All you have to do is mix up the ester with a little acid and an alcohol compound (the alcohol that we drink is an alcohol known as ethanol).

So, here's one hypothesis: peach flavour comes from "linalyl" esters. In the presence of ethanol and acid, these could be converted to the corresponding "ethyl" esters. The ethyl esters in question are present in bananas, lemons, pineapples, and strawberries. When I sip this peach melomel, I taste hints of all of these. (Caveat: this is just a hypothesis.)

Another, perhaps more likely, scenario is that the peach linalyl esters decomposed into carboxylic acids, which do not have fruit flavours at all. :(

"Peach" Melomel. More like "Fruit" Melomel.

 

Stuck Fermentation

What is it about mead and stuck fermentation? If you google search "mead stuck fermentation", you find that this is a widespread problem for home mead makers. I recently had to deal with it in my most recent attempt at mead.

Back in August, secondary fermentation of this mead had more or less stopped. Things had been going pretty well, and I assumed that most of the sugar must have been used up by the yeast. As I noted in an earlier post, I broke my hydrometer and therefore had no quick way to measure the specific gravity. (Actually, I could have measured out a volume of mead and measured the mass, from which you can easily calculate density. I have a cute little jeweller's electronic balance that measures to 0.01 g.) So, without knowing the completeness of the fermentation, I racked the mead with the intention to let it age and clarify.

As the mead was "aging", I noticed that there was a constant, very slow rate of gas production in the carboy. In the meantime, the batch of peach melomel was getting to the end stage of secondary fermentation, and it was time to rack it. Last week, I decided to rack the melomel and the mead, checking the specific gravity of each using my new hydrometer. Here's what I found:

Peach Melomel s.g. = 0.990 (Conclusion: fermentation is complete, and it's time to let it age)

Mead s.g. = 1.038 (Conclusion: oh crap, fermentation is stuck)

So, I had to intervene. I added two Campden tablets (crushed and pre-dissolved), 1 tsp of yeast nutrient, and a packet of Lalvin EC-1118 yeast. Bubble formation seemed to pick up within a few hours. The next day, gas production still wasn't as fast I would like, so I raised the temperature in the room using an oil heater, and also added 2 tsp of yeast energizer. Yeast energizer has a slightly different nutrient mix as yeast nutrient. Three days later, the fermentation in the mead was chugging along nicely, and continues:

Gas production after kick-starting the fermentation

with yeast nutrients and higher temperature.

Did fermentation resume because of added nutrients for the yeast, the higher room temperature (from 17 up to 22 degrees C), or both? I don't really know, but I suspect it was mostly the nutrients. After all, the peach melomel, which presumably had more nutrients from the peach juice, seemed to work out fine in the relatively cool room in which I keep this stuff. Lesson for next time: add more nutrient, with the proviso that "yeast energizer" is likely the more effective.

Mead v.2

My first attempt at mead left me unsatisfied. Looking back, there were three things that I did incorrectly:

1. Failed to add yeast nutrient. Honey does not have the range of minerals and other nutrients that yeast require. Fermentation only really started once I added the yeast nutrient. Further, all of my  fussing around to get fermentation started would have introduced unwanted oxygen, which would have led to undesirable compounds that affect taste.
2. Starting specific gravity was too high at the beginning (1.120) and the end (1.019) of fermentation.This gave a mead that was sweet, heavy, and very alcoholic. The balance of taste wasn't right (and still isn't!).
3. Honey quality. A friend from my undergraduate days at university now runs a honey business, and she pointed out that Costco honey is rubbish - if I want to make good mead, I need to start with quality honey. ("Okay. Point taken.")

So, it is now over two years after my first attempt at mead, and I finally got around to my second attempt. This time, I'm not making any of the mistakes I made the first time.

We have a great farmers market in St. Albert, and there are always three or four honey producers there. My wife and I went shopping one Saturday morning and obtained 7 kg of unpasteurized, local honey for $50. The vendor was Good Morning Honey Ltd.

Mead recipe:

3 Campden tablets
2 tsp yeast nutrient
10 L distilled water
Honey
1 packet of Lalvin EC-1118 yeast

Campden tablets and yeast nutrient were added to the water in the sterilized primary (bucket). Honey was added, with stirring, until s.g. = 1.088. After 24 hours, the yeast was hydrated and added to the must. Fermentation bubbles were observed within one hour of pitching the yeast.

After four days in the primary, s.g. = 1.065. I decided to rack the mead to a carboy. Fermentation has continued since then (6 days ago).

Mead, after racking to carboy.

I think most chemists will know what I'm talking about when I describe this fermentation as "clean". What I mean is this: when chemists conduct a chemical reaction the lab, especially when they are trying to synthesize a compound, they strive for a "clean" reaction. A clean reaction is something we recognize easily from the absence of unwanted precipitates, the absence of guck on the sides of reaction flasks, the relative transparency of solutions, and colours that you want to see (e.g. you don't want to see your mixture turn brown when the product you want is colourless). These are simply physical clues that a reaction is going right.

This mead has been "clean" from the beginning: the colour hasn't changed, the liquid is as transparent as you could expect if there were only little bits of yeast and bubbles that were scattering light. You can tell that clarification is going to be a snap. And, there was hardly any foaming, which suggests a very pure honey (i.e. no surfactants of any kind - natural or artificial).

The plan is to let this mead ferment all the way to dryness and then I will rack it and let it bulk age in a carboy for a couple of months. I'm looking forward to enjoying some of this mead over the Christmas holidays.

Dragon Blood Trial & Error

Back on May 21, I racked my first batch of Dragon Blood and did a taste test.  My notes say everything that needs to be said:

"Taste Test:
Dry, slightly acidic, and the taste was like diesel.  There is something in it that doesn't taste right.  Perhaps one of the fruit components like pomegranate or cherry?"

It is early, and the taste may evolve over time.  However, I am now a little cautious about experimenting with out-of-the-ordinary frozen fruit mixes such as the one I used on this particular batch.  Dragon Blood is usually made with common triple berry mixes (blueberry, blackberry, raspberry).

With that cautionary lesson, I went ahead and purchased a frozen triple berry mix and used the same basic recipe as the previous batch:

Dragon Blood v.2

3 gallons distilled water
17 cups granulated sugar
1 tsp peptic enzyme
2 tsp yeast nutrient
1.5 tsp acid blend (tartaric, citric, malic acids)
3 campden tablets (crushed)
2 kg of "Triple Berry Blend", in a nylon mesh bag (tied-off)

(The only differences are in the slightly higher amount of sugar required to get to the same starting s.g., and the larger mass of berries - which is simply because that was the amount in the bag!)

I started this one week ago.  The starting specific gravity was 1.087.  It is now 1.048.  I'm going to wait a couple of days, check the s.g., and rack to a carboy.

Apple Wine Racking & Tasting

It was just under three weeks ago that I racked the apple wine into a carboy where it could ferment to dryness.  At that time, I added three cinnamon sticks to add some flavour.  The bubble rate died off after a week, but there has been a low level of activity since then, with tiny bubbles forming on the surface.  This could be outgassing or maybe even the result of malo-lactic fermentation (MLF).  There is a lot of malic acid in apples, so MLF would not be surprising.  Today, I decided it was high time to rack it and perform a taste test.

I siphoned the wine into a clean carboy and added two crushed Campden tablets.  During the siphoning, I dispensed a small amount into a glass.  After stirring the wine to remove sulfur dioxide, measuring the specific gravity, and installing an air lock, I sat down with my notebook, pen, and glass of apple wine.

This is the best wine I have made to date.  The bouquet was of obviously of apple, but there was a hint of pear.  The taste was simply delicious and mild.  I was surprised at how much body it had, given that the ingredients were so simple.  There was hint of butter, which suggests that there may have been some MLF.  The cinnamon flavour was very mild, and in the background.  I only really noticed it at the end.  It confers a subtle amount of spicy 'heat' to the wine.  The acidity was just right.  I tasted it at room temperature, and I suspect it would be even nicer when chilled.

Tasting and the taking of notes.

For me, as a scientist and chemist, it is a joy to sit down with a new wine I have never tasted, and taste it carefully and slowly, with the intent to observe as much as I can.   A certain oenophile colleague of mine once pointed out how satisfying it is to try to describe what you see, smell, and taste.  Wine tasting is a lot more fun when you really slow down and pay attention to the complex mix of aromas and flavours that you experience in your nose and mouth.  A wine tasting wheel is a great help for this.

(As the wine isn't quite finished yet, this may be premature, but thanks to +Bob Perkins and +Pete Bottiglier for some of the tips you shared that I followed with this apple wine.  To your health!)
  

Valpolicella Racking, Stabilizing, and Degassing

Today, I racked, stabilized, and degassed the Valpolicella wine.  The kit instructions are to do this at day 14, but this is day 19.  I let the wine sit an extra five days because the fermentation was not quite complete at day 14.


After the usual sterilization of equipment, I transferred the wine to a clean carboy via autosiphon, without incident.  During this 'racking' step, I took a sample for a tasting.  Well, well, this is nice stuff.  This wine is dry and gentle.  There are woody and nutty tones with a hint of almond.  The tannins are noticeable at the end.  I have hopes for a very nice table wine that will pair well with pasta dishes.

Tasting.  Note-taking is important when it comes to stuff like this.

The specific gravity was 0.990.  From the starting point, this gives approximately 16% alcohol.  Yes, it's pretty dry.


The next step is the addition of potassium metabisulfite, which is provided with the kit.  Out of curiosity, I used my little portable balance to measure the mass of K₂S₂O₅.  The mass of K₂S₂O₅ was 4.4 g.  For comparison, I weighed a Campden tablet.  It was 0.6 g.  The recommended use of Campden tablets is 1 tablet per gallon of wine.  This is a 23 L kit, which is about 6 gallons.  6 gallons x 0.6 g per gallon = 3.6 g worth of Campden tablets.  So, this amount isn't too far off.

When you add the K₂S₂O₅ to the wine, SO₂ gas is formed (see picture).    The chemistry of this step is quite straightforward, and one of these days I'm going to write a blog post about it.

SO₂ bubbles.  You can get rid of the excess gas by stirring vigorously.

After the K₂S₂O₅, I added potassium sorbate and then a small packet of kieselsohl.  Tomorrow, I complete the addition of clarification agents, and then I wait three weeks until bottling.

Rhubarb Wine: Interim Satisfaction

Twelve days ago, I started the rhubarb wine.  I've been out of town for half of that time.  Today, I got around to checking on the progress.  When I opened the lid on the plastic bucket and looked at the surface, I could tell that fermentation was on the tail end.  There just wasn't a lot of "activity" in terms of bubbles.  I quickly sterilized a 3 gallon carboy and my auto-siphon and got to work racking the wine into a carboy.

Some observations:

1. Specific gravity = 1.012.  The initial s.g. was 1.097.  Therefore, the approximate alcohol content at this point is somewhere between 13.0 and 13.5 %.  (It's getting close to being done!)
2. The colour!  There is a nice peachy pink colour now.  I thought the colour had been totally  bleached by the campden tablets, but there might be something else going on.
3. The taste!  (Naturally, I tested it!)  There was no tartness at all, just a mild rhubarb flavour, along with a gentle grape taste from the concentrate that I added.  This has the potential to be a very nice dessert wine.

Front: Rhubarb wine, with some colour.  

Back: Mead, just prior to adding kieselsohl.

Mead v.1 has been sitting in a carboy for about 12 days as well, and there was a nice build up of lees at the bottom.  I racked it into another carboy and then added the kieselsol, which is step 1 of the finings.  And, I sampled the mead too.  It's getting better!  The taste has mellowed out a little and I think it will be really nice when it is chilled.

Mead at 6 weeks

For the last two weeks, the fermentation rate has been falling slowly.  Two days ago, I made the decision to stop the fermentation.  There was a nice layer of lees at the bottom of the carboy.  The bubble rate was down to 2 per minute.  I reckon that the fermentation probably would have continued for a week longer.  It was the specific gravity that tilted the decision to stop.  The initial specific gravity was 1.120, and it had fallen to 1.019.  Yes, with that final specific gravity, there is probably a small amount of fermentable sugars remaining.  However, from the hydrometer scale, the difference between starting and final specific gravities corresponds to an alcohol content of approximately 15%.  I felt that this was more than strong enough.  If there's a little sugar left, so be it.  It will taste sweeter.

So, I siphoned the mead into a sterilized secondary fermenter, and then added 1 tsp. of potassium metabisulfite and 3/4 tsp. of potassium sorbate, with lots of stirring in between.  Two days later, I haven't noticed any activity, and there is a nice layer of lees that has already settled out.

(1) Mead immediately after racking to the secondary.

After racking the mead, there was a small volume remaining in the primary and in the siphon hose.  So, I sampled it.  It was better than the junk I was served at that barbecue many years ago.  However, the unprocessed mead I tasted had some carbon dioxide in it, which made the taste sharp.  That will hopefully disappear with time.

 (2) Sediment two days after racking.

My plan is to let this sit for the next week or so, and then add the finings to make this beverage crystal clear, and ready for bottling!