Saturday, 14 January 2017

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.


 

Monday, 2 January 2017

American Red Ale

Over the holiday break, I made a batch of beer from a kit. The "ReadyBrew" kit was manufactured by craft brewer Paddock Wood Brewing, Saskatoon (Hey, that's almost local for me!). According to the manager of the store where I bought it, Paddock Wood Brewing prepares fifty 23 L kits from every batch of their own beer. That's kind of cool!

The "kit" consisted of a boxed bag of 23 L of wort. That's all. (But, frankly, I didn't mind because nothing says 'serious' like a kit consisting of only one raw material. "You need to select your own yeast, buddy.")

A couple of days before Christmas, I started the fermentation. Within a day, there was quite an accumulation of foam - enough to push the lid off the bucket:

Uh oh!

While I didn't bother to take a picture of what happened next, I can assure readers that the foam created quite a mess, especially when it dried out. Fortunately, I put the entire primary fermentation bucket in a large plastic tub, which contained the mess. The excessive foam production did not last very long. Another day, and the foam had collapsed to a manageable level.

On Christmas Day, I took a few minutes to transfer the beer from into a sterilized carboy, and installed an airlock. And, today, January 2, 2017, I added priming sugar and bottled. I'm really looking forward to enjoying a bottle in a couple of weeks.

Happy New Year!

Tuesday, 8 November 2016

Fermentation Kinetics

Since I "re-started" the fermentation in the mead about three weeks ago, I have kept an eye on the fermentation rate. It seems to be going as one would expect: after the large increase in bubble rate over the first 2-3 days, the bubble rate has been decreasing slowly. As a chemist, in this sort of situation, I can't keep myself from taking measurements and recording them in a table. For many years, in all sorts of chemistry experiments, I measured and modeled chemical kinetics (i.e. the study of the rate of reactions). Here's what I found about the mead fermentation.

Method: Measure the number of airlock bubbles per minute, noting the time and date. Calculate the logarithm of bubble rate, and make a plot of this against time.


This is what is known as a "first order plot". It shows that the rate does not decrease linearly, but that the rate of decrease slows down with time. This is typical of reactions in which the rate depends on how much of the starting material, or reactant, is present. In the case of fermentation, the reactant is sugar. As sugar is consumed by the yeast, the rate of fermentation will obviously decrease. However, the decrease in rate is not linear - the "deceleration" slows down over time. In this type of reaction, when you make a graph of the logarithm of the rate vs. time, you get a straight line. That's what happened here.

Fermentation kinetics are actually a lot more complicated, especially at the beginning of the fermentation process, when yeast populations are growing, and the fermentation rate is accelerating. In this case, fermentation is almost complete and the yeast population is no longer growing. There are lots of yeast cells present, and the rate is only limited by the amount of sugar remaining. The result is "first order kinetics".

One day, I would like to try measuring the fermentation rate from start to finish, but it gets complicated. Measuring airlock bubble rate would be a pain during primary fermentation, when the rate is quite high. The other way you can measure the rate is by looking at alcohol content. The problem with alcohol content is that the measurement is in situ, requiring the insertion of a wine thief and hydrometer into the must. This increases the likelihood of introducing oxygen or microbes into the must.
  


Saturday, 15 October 2016

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.

Sunday, 9 October 2016

Prohibition, Temperance, and Pseudoscience

This post deviates a from my normal blog topic (making alcoholic beverages). Why is prohibition important? Well, Alberta still has legislative and regulatory "quirks" that are holdovers from the days of prohibition in Alberta. For example, in home winemaking, there is no legal way for a wine kit supply store in Alberta to provide customers with a clean, physical space inside the store in which to make wine, store it as it ferments, and bottle the wine when it's ready. These services are popular in other provinces, but are not allowed in Alberta, because such a service goes beyond "home winemaking". Governments in Alberta are liberalizing the liquor laws, but there is a long way to go. An interesting documentary account of the history of beer in Alberta, including the impact of prohibition, can be found at: Aleberta

Some time ago, I was surfing through the photo collection of the Provincial Archives of Alberta, and came across a bunch of old "Temperance posters". These posters were published by "The Dominion Scientific Temperance Committee", which, I gather, was an arm of the Women's Christian Temperance Union back in the days of prohibition. Some of these posters are quite amusing:

Provincial Archives of Alberta, Object number PR1974.0001.0400a.0001
Provincial Archives of Alberta, Object number PR1974.0001.0400a.0006
It is not clear to me what phagocytosis (the white blood cell "swallowing and digesting" germs) has  to do with alcohol consumption. Clearly, the idea was to scare people away from consuming alcohol, and, I suppose, get them to drink water instead.

The next poster piqued my interest because it touches on some chemistry.

Provincial Archives of Alberta, Object number PR1974.0001.0400a.0002
The poster argues that the nutritional value of grape juice is much greater than that of wine, but the numbers don't make a lot of sense. The only number that looks correct is the 20% "food value" of grape juice. That number roughly corresponds to the percentage (by mass) of sugar in grape juice. However, the percentages of water, alcohol, and "food value" in wine do not make sense.

1) The water content of wine is a lot higher than 78%. Water is a by-product of the fermentation of sugar. So, during fermentation, sugar decreases, and the proportion of water and alcohol increase.

2) The poster gives 17.5% alcohol for wine. Is this 17.5% by mass or 17.5% by volume? On wine, beer, and liquor labels, alcohol content is usually listed as a percent by volume. 17.5% would be on the high end of percent volume for wine. This poster, however, seems to be using mass percentages. The mass percentage should be a lot lower, because the density of pure ethanol is less than that of water. So, there is something funny going on.

3) The food value of wine is listed as 4.5%. Sure, wine contains residual sugars and other organic components that have nutritional value, but this number appears to have simply come from subtraction: 100 - (78 + 17.5) = 4.5. But, as the percentages of water and alcohol are suspect, so is the 4.5% value.

4) The poster implies that alcohol has zero food value, which is incorrect! The caloric content of foods and beverages can be determined through calorimetry: In the good old days, a scientist would combust a sample of food in a sealed chamber and measure the amount of heat produced. Calorimetry is a lot of work, so nowadays, the caloric content of foods is determined indirectly using the "Atwater system" (Scientific American has an article on this, here). Basically, this involves adding up reference caloric values for different components of the food or beverage in question. The reference caloric value of carbohydrates (including sugar) is 4 kcal/g (1 kcal = 1 food Calorie). The reference value for alcohol is... wait for it... 7 kcal/g! (Yes, on the basis of mass, alcohol has more food Calories than sugar.) So, the poster is WRONG.

The web site Compound Interest has a lot of neat infographics about various familiar substances. Take a look at their infographic on red wine. Their numbers make a lot more sense (86% water, 12% alcohol, 2% other organic compounds).

By the way, the "food value" of a 5 oz. glass wine is around 125 Calories, which is equivalent to 25 jelly beans. The glass of wine is arguably the healthier option of the two!

These temperance posters were published ca. 1912. Are these scientific mistakes forgivable, given that they were made over 100 years ago? Not really. Even in 1912, physics and chemistry were sufficiently advanced that mass and volume compositions were well understood and measured reliably. And, calorimetry was already an established experimental technique in the field of thermodynamics, which had its heyday in the age of steam engines. What's going on here is the twisting of information to support a particular agenda. It's pseudoscience!




Friday, 16 September 2016

Peach Melomel

For a couple of years, I have followed home winemaking posts about small batches of melomels. A melomel is simply a mead amended with some kind of fruit. You can use any kind of fruit you want. The resulting mead will have a mix of honey and fruit flavours.

I had some good honey leftover from the most recent batch of mead, and we had some fresh fruit from British Columbia, including some very juicy, perhaps even overripe, peaches. This presented an opportunity to try making a peach melomel, which struck me as a potentially nice combination.

Here's the recipe I used:

- 10 L of filtered water
- 3 campden tablets
- 2 tsp yeast nutrient
- 1 tsp peptic enzyme
- approximately 3 kg honey
- 1 cup of sugar*
- 11 pitted peaches, sliced
- packet of Lalvin EC1118 yeast

*Sugar was needed because the dissolved honey only gave s.g. = 1.078. The sugar brought up the s.g. to 1.086.

After mixing up all the ingredients except fruit and yeast in my primary fermentation bucket, I put the peaches in a nylon straining bag, tied it off, and squeezed the peach juices into the must. The amount of peach juice was surprising. I put the whole bag of strained peaches into the must and let it sit for 36 hours. After removing the bag, I sprinkled yeast on the surface. A few hours later, fermentation was going strong.

Fermentation "head" on the peach melomel
After six days of primary fermentation, the 'head' had collapsed, and s.g. = 1.024. I transferred to a sterilized 3 gallon carboy for secondary fermentation.


Peach Melomel in Secondary.
Unfortunately, these pics don't really show the subtle peachy colour of this melomel. I'm looking forward to seeing how the colour turns out after it's aged, clarified, and bottled.

Thursday, 25 August 2016

Beeswax?

Back to the mead...

Four weeks ago, I racked the mead into a carboy, to allow secondary fermentation to proceed, which it did. Fermentation was more or less over a couple of weeks ago Tonight, I decided it was time to rack the mead into a clean carboy so the mead can bulk-age, lose CO2, and clear up.

During secondary fermentation, there was a small froth on the surface, which isn't a big deal. However, as fermentation slowed down, a fine, beige solid remained on the surface of the mead, and along the inside, top surface of the glass, under the neck. The solid never dissolved.

Beeswax?

After racking, I managed to swipe my finger into the dirty, empty carbon, and get some of this material. It was granular, hard, but seemed a bit 'gummy', like paraffin wax. Question for honey and mead people: Is this beeswax?

This particular honey is not heavily processed. I used 2-3 kg of honey, so it wouldn't be a surprise if there was a small amount of beeswax in there.

Sadly, before I could measure specific gravity, I dropped my hydrometer on the floor. So, I cannot estimate alcohol content of the mead right now.

The mead sure tasted good, though. I was surprised by the sweetness. Fermentation was OVER. There shouldn't be any residual sugar in there. It could be that there are other sugars (e.g. pentoses or something like that) that the yeast did not touch. This deserves some research. Question for honey people: what types of sugar are present in honey?