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

Apple Cider 2016

The last time I made cider (see post here), I was failed by EZ Cap bottles, which just didn't hold any pressure. This resulted in a batch of still cider. Still cider is fine, but I aspire to make carbonated, homemade cider. One of the reasons I wanted to make homemade beer was to get beer to carbonate in the bottles, using standard bottle caps. That worked out just fine (see Festa Brew "Continental Pilsner). So, it was time to revisit cider-making, and attempt natural carbonation in the bottles.

Tanya and I picked the apples off of our tree, and made the fatal decision that there were enough apples that we could simply cut them up by hand before pressing. That was crazy - the manual labour to cut up all of our apples up into eights (or smaller) was just too much. Next time, I'm going to obtain a fruit crusher like last time.

The pressing however, went fairly well, and we obtained approximately 4 gallons of apple juice. The specific gravity of the apple juice was 1.034, which was almost identical to juice from the last time we pressed apples. To this, I added 4 crushed Campden tablets, 2 tap. yeast energizer, and 1 tsp. of peptic enzyme. After 24 hours, I added a packet of Lalvin EC1118 yeast, by sprinkling it on the surface. Fermentation was well underway a day later.

Primary fermentation proceeded quickly. Four days after adding the yeast, the foam on the surface had collapsed and it was time to transfer to a carboy. The volume (4 gallons) created an opportunity for two separate batches. I siphoned the bulk of the cider to a 3 gallon carbon and placed an airlock on it. This batch is meant to be regular cider.

Spiced Cider

The remainder (which amounted to a little over 1/2 gallon) went into a 1 gallon jug which I topped up with distilled water to which I had added 1 cup of sugar. This was done to get the alcohol level up to where it should be. If I did not add any more sugar, this would have been a 1:2 dilution, and the cider would be very weak). I also added 1/4 tap of nutmeg and two cinnamon sticks for flavour. I sealed the jug with an airlock.

Regular cider (left), and spiced cider (right). Fine solids are settling out.

After four days in the carboy, fermentation of the regular cider was virtually complete, and the bulk of the fine solids had settled. It was time to add priming sugar and bottle! So, I siphoned the cider to a large pail, added 3/4 cup of dextrose, stirred thoroughly, and bottled it just like you would beer. The yield was 4 x 1 L bottles, and 22 x 330 mL beer bottles.

I bottled the spiced cider one day later, adding 1/4 cup of dextrose to the (approx.) 1 gallon of spiced cider. Yield was 10 x 355 mL bottles.

A taste test of the spiced cider revealed a beverage that tasted like Christmas. The nutmeg and cinnamon paired well with the apple and the little bit of sweetness from the priming sugar. It remains to be seen how the spices affect the taste when the cider is carbonated and dry. I can't wait!

According to the purple "Winemaker's Recipe Handbook", you should age the cider for three months!!! This seems like a long time. I might get impatient and open a bottle in a month or so, just to see how it's coming along.

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!)