Tracking Sugar Content of a Cider and Kettle Sours: Mr Wizard

Q: Last November I purchased my usual 20 gallons (75.7 L) of cider from an orchard here in Michigan. In one 5-gallon (19-L) batch I added 80 ounces (2.27 kg) of clover honey and two types of yeast — English Cider yeast and champagne yeast. Eight months later I took a gravity reading and it was 0.995.

If the FG of your cider/cyser is less than 1.000, does that mean that it doesn’t have any sugars left in it? I’m trying to change up my diet and I want to significantly reduce my sugar intake. Most commercial ciders are high in sugars (20-35+ grams per 12 Fluid ounce/354 ML serving). I’m thinking about degassing one, warming to 65 °F (18 °C) and then taking a gravity reading just so that I can compare the gravity to the sugar content. Any thoughts would be appreciated.
Terry Lowry
Lake Orion, Michigan

A: Most homemade ciders, unless specially handled, ferment out completely and contain very little residual sugars. This is because apple juice mainly contains fermentable sugars (fructose, sucrose, and glucose), and smaller amounts of non-digestible carbohydrate (e.g., pectin), organic acids, especially malic acid, amino acids, and minerals. This is very different from wort that contains a significant amount of dextrins; while dextrins are not fermentable by yeast, they are digestible by humans and contribute carbohydrate calories to beer. It is the lack of non-fermentable sugars that make dry ciders attractive to carbohydrate watchers.

Sweet commercial ciders are different in this regard because they do contain residual sugars. This can be accomplished by arresting fermentation with the addition of sulfite or sorbate, or by pasteurization. It is tempting to stop fermentation through chilling, but this usually does not work and the cider continues fermenting to completion. Other cidermakers allow their cider to fully ferment, stabilize with sulfite or sorbate, and then add sugar or fresh juice; this practice is called back-sweetening.

Measuring the specific gravity of fermented cider, beer, or wine does not provide enough information, even when the specific gravity is less than 1.000, to know if there is residual sugar because there are more than two parts to these solutions. The rule of thumb used by winemakers is to be cautious about bottling wines with a specific gravity greater than ~0.995 because there may be residual sugars that will re-ferment in the bottle. There are colorimetric tests, like the now discontinued Clinitest® urine test kit, that provide more accuracy than hydrometers. For your purpose, however, it is reasonable to consider ciders with final gravities less than 1.000 to be dry and to contain very little, if any, residual, digestible carbohydrates.

I specifically mentioned the Clinitest® test kit because there are many references in the home winemaking literature about this specific kit. There is a replacement kit on the market called the AimTab®. Although these test kits are designed to measure reducing sugars, such as glucose, lactose, fructose, galactose, and pentoses, that may be excreted in urine, a particular concern related to diabetes, the kits are also very handy to run tests on wine and cider. If you are interested in learning more about this method, there is quite a lot of information out on the web.

Dry ciders are becoming more popular as farmhouse cider operations are taking hold throughout apple-producing parts of the U.S. Many of the ciders being produced by the newer operations are more traditional in their approach where arrested fermentation, back-sweetening, and pasteurization methods are less common. The use of bacteria that convert malic acid to lactic acid, in a process known to winemakers as malolactic fermentation or MLF, such as Oenococcus oeni (formerly Leuconostoc oenos) and some Lactobacilli, other yeasts, like Brettanomyces, and barrel-aging in both wine and Bourbon barrels, is adding a whole new dimension to ciders. The dry ciders you want to make are really ideal for these aged types that oftentimes are more similar to white wines than most of the ciders that are served in pubs.

Q: I have started to see more sour beers in my local beer stores. When did these become so popular? I am interested in the different methods used to produce sour beers, especially those used by craft brewers who are canning and bottling sours in 12 ounce bottles and selling these beers for pretty normal prices. I really want to brew some of these beers at home and want to know where to begin!
Aaron Rupp
Atlanta, Georgia

A: It took a while for brewers outside of the small sour brewing centers of Belgium and Germany to produce excellent sours because so much of the science and practice of sour beer brewing was closely guarded ~30 years ago when brewers from other parts of the brewing world began dabbling with sour beer. Jean-Xavier Guinard’s Lambic (Brewer’s Publications, 1990) was really ahead of its time because there were very few US homebrewers, let alone U.S microbreweries, that were experimenting with sour beers in 1990.

In retrospect, it is pretty amazing that JX, as he was known by his colleagues at UC-Davis, was actually brewing sour beers in the UC-Davis brewing lab while completing his Ph.D. because Dr. Michael Lewis was not a big fan of contaminated beer. I remember having a conversation with Dr. Lewis sometime in 1992. We were sitting in his office when the phone rang. I could only hear one side of the conversation, but the topic was clear; a well-known microbrewery was interested in brewing Berliner Weisse. Dr. Lewis repeatedly asked the brewmaster on the other end of the line “why do you want to [mess] up your brewery by bringing Lactobacilli into your cellar?” I don’t know if Dr. Lewis’ continual protests influenced this brewer, but the brewery never produced a Berliner Weisse. But in the brewing lab, a small collection of JX’s lambics remained in storage for the occasional tasting. I don’t know if those beers were as excellent as I remember them being, but they seemed like the real deal at the time. It was like JX transported the magic from Belgium to Davis using that clichéd blend of art and science.

The early sours to hit the US microbrewing scene were brewed in the Belgian tradition. New Belgium launched La Folie in 1997, Tomme Arthur was brewing sours at Pizza Port in Solano Beach, California in the late 90s, Vinnie Cilurzo was busy up in Santa Rosa, California in the early 2000s and Tim Schwartz was brewing some great sours in Austin, Texas at the Bitter End in the late 90s and early 2000s. Today there are breweries in nearly every state with sour barrel programs. Although many of these beers are produced in less than a year, sour barrel programs require a substantial investment in beer, wood, and space. There is also a higher level of risk with these beers and many breweries simply steer clear of sours that develop in the cellar.

I am not sure when US brewers began producing any real volume of Berliner Weisse-type beers, and their Gose-inspired cousins, but it was really only after the early Belgian styles were garnering attention in the beer world. Indeed, some of the brewers playing with sour barrels were also playing around with bacteria in the brewhouse. Although traditional Berliner Weisse is fermented with a mixed culture of yeast and bacteria, and bottled with the same, modern interpretations can be produced in the brewhouse to keep their fermenters clean of bugs.

With the growth of this market segment, the supplies required to produce these beers has also grown. The various bacteria and yeast used to brew these beers have gone from obscure and guarded to readily available from brewing yeast suppliers. Most of the cultures used to sour beer in barrels are mixed, whereas the bacteria used for kettle sours tend to be single strains, or a mixture of Lactobacillus species. Some brewers use yogurt as the source for bacteria, but this can be hit or miss.

The most common methods use the brewhouse to produce sterile, very lightly hopped wort. Start with a normal boil or by holding wort at near-boiling temperatures for 20-30 minutes, effectively pasteurizing the wort. Next use a wort cooler to temper the wort into the 95-122 °F (35-50 °C) range, hit it with carbon dioxide to strip oxygen from the wort and to try to maintain an anaerobic environment. Then add the bacterial culture to get the party started. Most kettle sours only require about 48 hours for the wort to sour, and the progress of souring is usually monitored by pH or titratable acidity (TA). When the process is complete, the sour wort is boiled, cooled, aerated, and pitched with yeast. The beauty of this method is that it keeps the bugs out of the cellar, and only adds a couple of days to the normal brewing process. Since this technique is easiest carried out in the brew kettle, it does have the disadvantage of tying up the kettle and greatly reducing brewhouse utilization. Many breweries have worked around this dilemma by adding sour wort tanks to their brewhouses.

If you are new to kettle sours, do yourself a favor and simply buy a pitchable culture. Growing these bacteria is a bit different from growing yeast because the acid production can suppress cell growth. If you want to propagate your own cultures, consider using a carbonate buffer in the propagation media to keep the pH in check. Milk the Funk has some great practical advice on their website regarding techniques to best grow these bugs.

While the kettle sour method produces very clean, and sometimes very sour beers, the beers are often criticized by lovers of Belgian sours for being one-dimensional. This is where fruits, herbs, spices, and other beers enter the equation. If you have a great sour base, use it like vinegar in your kitchen and blend with other ingredients. These ingredients can be added at any step of the process depending on what makes the most sense. And this is how many of the new generation sours are being produced and are key to their success.

Although some folks really like things that are simply sour, most like sour foods and beverages that are balanced by sweet, salty, or hot ingredients. This is where blending can transform one-dimensional kettle sours into a wide array of new and interesting flavor combinations. Sweetness can come in the form of a neutral beer, like a wheat beer, to smooth out acidity and add a little body and texture to beers that can come across as very dry and thin. Fruit juices add sweetness, fruitiness, and aromas. Fruit essences, such as citrus peel oil, can be used to add top notes. Herbs and spices can also be used to add aroma and complex flavors. And the judicious use of salt and heat may be fun to bring into the mix for certain flavor combinations. These sorts of methods are being used to produce some of the new generation kettle sours that are popping up on the shelves with price tags that are more in-line with IPA. I hope this helps you ease your foot into the sour end of the pool!

Mr. Wizard’s musings from the 2017 MBAA Annual Convention in Atlanta, Georgia (Oct. 11–14, 2017)

I annually attend several brewing meetings and every so often I see or hear something that really gets me thinking. And I like to write about these topics to give fellow brewers something to noodle on. A few years ago, back in 2012, Dr. Tom Shellhammer from Oregon State University gave a presentation at the Craft Brewers Conference in San Diego, California about differences in the analytical methods used to measure hop bitterness that was very intriguing. Shellhammer explained how beer bitterness measured with the International Bitterness Unit method (iso-octane extraction, and absorbance at 275 nm) is typically higher, especially with late-hopped and dry-hopped beers, than iso-alpha-acids (IAA) reported by the high performance liquid chromatography (HPLC) method. There was a presentation given this year related to a similar topic that again perked my ears.

Andreas Gahr, from the St. Johann Research Brewery, gave a presentation based on work performed by the German Hop Growers Cooperative (HVG) titled “What Are Auxiliary Bitter Compounds?” Andreas presented this paper on behalf of a group that included himself and Drs. Adrian Forster and Florian Schüll from HVG in Wolznach. What follows is a summary of his presentation along with some take-home points about hopping.

Andreas established that there are compounds in beer that are measured by the IBU method that do not show up with the HPLC method used to measure IAA (this makes sense because the HPLC is specific for IAA, and the IBU method is not). This is the same topic that Tom Shellhammer covered at the 2012 CBC in San Diego. Andreas used the term “alternate bitter compounds”, or ABCs, as the difference between the HPLC IAA value and the IBU. For example, a beer with 20 IBUs and 17 IAA has 3 of these ABC units. A convenient way of comparing these differences is with the IBU:IAA ratio. When IBU=IAA, there are no ABCs and the IBU:IAA ratio is 1.0. When a beer has 20 IBUs and 17 IAA, the ratio is 1.18.

The point of this discussion is not the development of a new number, but an understanding of the discrepancy in these two values. These ABCs include deoxyhumulones, xanthohumol, iso-xanthohumol, humulinones (alpha acid derivatives), hulupones and hulupinic acid (beta acid derivatives), traces of beta acids, and alpha acids. All of these compounds are bitter, but are not typically considered significant sources of bitterness in beer. But brewers are changing the way beers are hopped, so the rules of the past are being changed by current brewing techniques.

Andreas cited the work of Hofmann, Haseleu and Dresel, and established that ABC bitterness is generally perceived as positive and mild. Although the compounds that contribute to ABC are usually below flavor threshold values, their effect on beer flavor may be additive and synergistic in nature. This is especially relevant when beer has higher levels of ABCs, as is the case with many new generation beers with very high hopping rates at the late-boil and/or post-boil stages.

Beers brewed using iso-alpha-acid extracts (common on the international scene) and/or high alpha hops for bittering, and no aroma hop additions contain very little to no ABCs, whereas beers brewed using multiple hop additions in the brewhouse and dry hopping can have an IBU:IAA ratio approaching 2, or about 50% ABC. Gahr presented a plot of IBU:IAA ratio versus the total of alpha acids, hulupones, and humulinones that showed a significant, positive correlation between the two measures. This correlation was used to validate the use of IBU:IAA ratio as an indicator of ABC’s concentration.

Aside from the numerical debate that can follow such differences, especially among brewers who like to brag about hop bitterness, the real question is how do these ABCs influence beer flavor and the quality of bitterness. This was the focus of Gahr’s presentation, and here are the major points.

1. Not all hop varieties have the same composition, and it seems that German landrace varieties (these are hops that developed by selection within a region and largely comprised of the so-called noble varieties) produce beers with higher IBU:IAA ratios compared to high alpha and newer generation aroma hops.

2. Bitterness quality scores were higher in beers with higher IBU:IAA ratios (2005, German Central Marketing Association for Agricultural Products study).

3. Gahr, Forster, and Schüll found significant correlation between IBU:IAA ratio and hop beta acid:alpha acid ratio (β/α). This correlation is of practical significance because it allows brewers to select hops that may have a positive influence on the IBU:IAA ratio. Gahr showed the following β/α ratios for German hops:
• β/α ratios of high alpha varieties = 0.3 to 0.5
• β/α ratios of Hüll aroma varieties = 0.7 to 1.0
• β/α ratios of German landrace varieties and
Saphire = 1.3 to 2.4

4. Sensory data from two sensory trials examining the hedonic response to low alcohol (<3.5% ABV) and alcohol-reduced beer (<1.2% ABV) also showed a clear positive correlation between sensory score and IBU:IAA ratio (in other words, ABCs improve sensory scores).

The take home points offered to brewers were pretty direct:

• Use other hop varieties if you currently exclusively use high alpha hops.
• Use plenty of aroma hops and landrace hops (β/α ratio > 0.7).
• Limit hop boil time by adding hops later in the boil; this increases the IBU:IAA ratio because ABCs dissolve quickly, whereas alpha takes time to isomerize.
• Use multiple aroma additions.
• Dry hop more.

This topic needs further exploration, using other hop varieties from other hop regions of the world, to determine if these metrics are robust. But the suggestions are aligned with what many brewers have empirically determined. One thing of note is most hop varieties have a fairly low and consistent beta acid content in the 3-5% range, so high alpha hops almost always have a low β/α ratio. This means most new American hops, do not fare well using this metric. Anecdotally, there are some old-school brewers who swear by using aroma hops for bittering purposes, and Andreas Gahr’s presentation implicitly gives credence to this thought.

Issue: January-February 2018