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

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.

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!)
  

Apple Cider, Apple Wine

As I write this, the room is nice and aromatic, full of the smell of apple.  It seems to me that fermentation enhances the richness of fruit aromas.  It's fantastic.

Here's what I did with all that pressed apple juice.

Apple Cider v.1

This cider is made from the apples from our own small apple tree in the back yard.  It is a Norkent variety that is hardy in our northerly climate.  The yield of apples was modest, and we only obtained about 1 gallon of juice.  I added one crushed Campden tablet to the juice.  Specific gravity of the juice was 1.035, so I added 1.5 cups of sugar, bringing s.g. to 1.050.

Once transferred to a 1 gallon jug, I added 1/4 tsp. of peptic enzyme and 1/4 tsp. of yeast nutrient, stirred.  I was perhaps a little bit too eager and went ahead and sprinkled about 1/3 of a packet of sparkling wine yeast on the surface.  From various recipes and instructions, it seems that peptic enzyme may work better prior to adding yeast and starting fermentation, but I don't see any scientific reason for why that would be the case.  Anyway, I went ahead and added the yeast and placed an airlock on the jug and waited for the magic to happen.

Cider fermentation

Apple Cider v.2

All the other apples that we obtained from generous friends produced in total about 4.5 gallons of juice.  This time, I more or less followed the instructions in the Winemaker's Recipe Handbook (the "purple book").

I added 4 Campden tablets, 1 tsp. of peptic enzyme, and 2 tsp. of yeast nutrient.  The specific gravity for this apple juice was the same as the first batch (1.035).  I added enough sugar to bring the density to 1.055.  I let the juice sit for 24 hours before transferring 3 gallons to a carboy and adding the yeast.


Apple Wine

There was a lot of leftover apple juice from the above cider batch, so I improvised a batch of apple wine.  I diluted the juice to just over 3 gallons, added sugar until the specific gravity was 1.090, and then added a packet of sparkling wine yeast.  That's all.  This batch is currently fermenting away in a plastic bucket with a loose fitting lid.

My plan is to add some spices to the wine when I transfer it to the secondary.  (Does anyone have suggestions on what to add?)

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 - An Inauspicious Beginning

The forced rhubarb thing actually works! As you can see in the picture below, the stalks are pale looking, and the leaves have very little green pigment. The forced rhubarb stalks themselves are very tender, and have none of that celery-like fiber that makes rhubarb so tough.  This is all good, but my  forced rhubarb was not a 100% success.  In places where the rhubarb had received a bit of light before I covered them up, or from imperfectly dark conditions, the rhubarb grew to an intermediate state.  It wasn't quite like the forced rhubarb in the picture below, but it wasn't like normal rhubarb either.

 

(1) Me and my forced rhubarb.

So, having collected all the rhubarb I could, I chopped it all into thin slices.  The result was 17 cups of chopped rhubarb.  I placed it in a big white plastic bucket and added 6 L of water and two crushed Campden tablets.  The Campden tablets are added to keep the bacteria at bay.

(2) Chopped rhubarb in water.

The next morning, I scurried off to the store to get some pectic enzyme.  Pectin is a carbohydrate in cell walls.  Pectic enzyme helps break it down and that, in turn, releases more of the sugars and flavors.  When I returned, and opened the lid on the bucket, I was very surprised.  Overnight, the red colour of the rhubarb had been bleached!

This was initially a mystery to me.  The bucket was rinsed well before use (i.e. perish the thought that there was any bleach leftover from sterilizing).  Campden tablets, however, contain potassium metabisulfite, which is a reducing bleach - something I just learned.  That means it bleaches colours by removing oxygen as opposed to adding oxygen (which is how household bleach and peroxide work).  So, for now, I'm going with the idea that the culprit was the small amount of metabisulfite in the Campden tablets.  It's going to be a "white rhubarb" wine.  At least it still smells like rhubarb!

(3) Bleached rhubarb

I added 1/2 tsp. of pectic enzyme and stirred the mixture occasionally for the next 36 hours.  At 48 hours, I removed the rhubarb from the water by straining.  Then, I added 1 L of white grape juice concentrate, and 14 cups of white sugar.  This was not some magic recipe: I simply kept adding sugar cup by cup until the specific gravity was between 1.095 and 1.100.  The final value was 1.097.

I added 3 tsp. of yeast nutrient and a packet of activated yeast.  And then I went to bed.  The fermentation is now underway in the bucket.  It smells good!