Monthly Archives: September 2013

Double Brewday: Imperial IPA and Ginger-Lemon Mead

Today we brewed up one batch of beer and one of mead. This is the first time I try making mead, i.e. honey wine, and I must say that the pre-fermentation must was tasting promising! The beer is an Imperial IPA (though more in IPA territory, as the efficiency was slightly lower than predicted) inspired by The Alchemist’s Heady Topper. We used a malt bill consisting of Pearl malt, Carahell and Wheat malt, supplemented with some cane sugar during the boil to further dry out the beer. We hopped it with enormous amounts of Amarillo, Apollo (first time using it, smelling awesome!), Centennial, Columbus and Simcoe. Oh, and we also used 15 ml of Hop Extract for bittering (theoretical IBU yield of around 120). After fermentation we will throw in even more hops for dry-hopping. The beer will be fermented with Conan, which I harvested from a can in the beginning of this year and has been on an agar plate since. The starter was smelling very peachy and fruity, so it should bring some nice tones to the game. Can’t wait to try it out! The brewday went quite well, but we ended up with 22 liters of 1.065 wort instead of 20 liters of 1.072 wort, so the beer will have slightly lower ABV than intended.

[beerxml recipe=http://beer.suregork.com/wp-content/uploads/2013/09/heady_topper.xml metric=true cache=-1]

For the mead we used a simple recipe of 10 liters of water, 3.2 kg of honey (various sorts), 0.5 kg of brown sugar, 100 g ginger, 2 lemons and one small pack of raisins. We allowed the water to come to boil, and we added in 3 g of yeast nutrient, the raisins, the sugar and the ginger. After a couple of minutes we added in the lemons and the honey, and allowed it to cool. We then pitched some white wine yeast and placed to ferment at 18C. The OG was 1.095, which will result in 10-14% ABV depending on when the yeast decides to quit. I wouldn’t mind a slightly sweet mead. Can’t wait to try it in a couple of weeks/months. During the day we also had time to keg and bottle our recent Black Rye IPA, which was tasting quite promising. There was quite alot of suspended yeast still, but otherwise the flavor was bitter, lightly roasted and hoppy. Gravity had fallen to 1.015, giving an ABV of 6.4%. Should be a really nice beer for the cold autumn evenings.

[beerxml recipe=http://beer.suregork.com/wp-content/uploads/2013/09/mead.xml metric=true cache=-1]

The Perfect IPA?

Having just come home from our old apartment (where I did some last minute cleaning, before we have to hand it over to the new tenants), tired and exhausted, I decided I should reward myself with a beer. I take a quick look into my new dedicated beer fridge (which I will soon integrate into a bar counter; will probably make a post once I get it finished), and see a bottle of Firestone Walker’s Union Jack. The beer is bottled in the end of June, so it should be fresh (at least from a Finnish point-of-view). I pour up the beer, and the room already fills with citrusy and floral hop aroma. A beautiful beer. Strong hop aroma. Tones from C-hops, Amarillo and Simcoe. The flavor is perfectly balanced. A relatively light maltiness, combines with loads of citrus and resin from the hops, and ends in a lingering bitterness. The beer feels so smooth. Is this the perfect IPA? I think so.

Homebrew: Tasting a 15-month old Imperial IPA

In June 2012 I brewed up an Imperial IPA that was loaded with 500 grams of hops in a 20 liter batch. I never made a ‘proper’ review or tasting notes of the beer, but published some short ones right after the beer was kegged and bottled. Overall I was quite happy with the beer, as it featured a strong bitterness, loads of hop aroma (especially when fresh), some nice resiny hop flavors, and a slightly sweet maltiness to balance it all up. The beer was a little grassy and ‘raw’ though, and when we are brewing an IIPA next week (recipe will follow soon), we will replace some of the hops with hop extract to hopefully reduce the amount of grassiness in the end product. Anyways, I found a couple of bottles of this homebrewed IIPA (at least I think it is, as the bottles have no labels or text, just a golden bottle cap) stored away in a closet (we are currently moving, and have been cleaning and packing up everything). I though it would be interesting to try how this one has held up. The general consensus is that IPAs should be drank fresh, and I mostly concur with this statement, however some of the sweeter IIPAs can get really nice with some age in my opinion. This doesn’t mean that I purposely age (I)IPAs, but if I find a bottle that has been forgotten in the fridge/closet for several months I still tend to enjoy them. Hop aroma, flavor and bitterness tend to fade with age, while malty sweetness tends to strengthen. This beer has been stored in quite poor conditions, as the temperature of our old apartment has been quite high (especially during the summers), so my expectations are not that high. Anyways, lets see how it tastes! Oh, and sorry about the picture below. Since we’ve just moved, I’m trying to find a new setting for taking beer pictures. The table and wall combination here results in pictures slightly red-tinted and almost with a desaturated look. Will have to experiment a little.

  • Brewery: Sly Cat Brewery
  • Country: Finland
  • Style: Imperial India Pale Ale
  • ABV: 7.7 %
  • Size: 500 ml
  • Bought from: –
  • Not on Beer Advocate
  • Not on RateBeer

[easyreview title=”Sly Cat CatnIPA – Imperial IPA” cat1title=”Appearance” cat1detail=”The beer pours with a really murky orange-amber color, and a slight oily off-white head is formed that collapses rather quickly. The beer was crystal clear when I looked through the bottle when I found it in the closet, but 24 hours in the fridge resulted in lots of chill haze that didn’t have time to settle. Very heavily dry-hopped beers tend to have some dry-hop haze, so I guess it suits the style. It could look prettier though, but I’ve never cared that much about appearance. The appearance is similar to what I remember it fresh.” cat1rating=”3.5″ cat2title=”Smell” cat2detail=”The aroma is fairly sweet, with quite a large malt presence (caramel). There are hop tones left though, despite the 15-month age, and they are mostly floral and perfumey, with some citrus and resin in the background. Quite a nice aroma actually, but it steers more towards the American Barleywine category than the Imperial IPA category. A lot of hop aroma has been lost, but was is left is still a nice combination of sweet caramel and floral hop tones. Reminds me of many IIPAs I’ve consumed ‘old’ (e.g. Port Brewings 3rd Anniversary Ale and Alesmith’s Yulesmith Summer).” cat2rating=”4″ cat3title=”Taste” cat3detail=”The flavour is similar to the aroma, with an initial impact of caramelly sweetness, quickly followed by a mellow resiny hoppiness. These combine quite well, and also give off a Barleywine vibe. The finish is semi-sweet, moderately bitter, and features some warming alcohol, which strengthen this impression. Overall the flavors are not bad, but quite different to when the beer was fresh. The beer has changed alot during 15 months, but change in this case isn’t bad, as the beer has turned into a nice Barleywine. The dank, earthy and fruity hop flavors have definitely mellowed, and left are only the resiny and floral tones (myrcene- and linalool-derived perhaps?). What really makes me happy is that there are no signs of infection or other off-flavors, suggesting that my sanitary practices are good. I really like this, but if I tasted this blind I wouldn’t guess it was an IIPA, rather a Barleywine or American Strong Ale.” cat3rating=”4″ cat4title=”Mouthfeel” cat4detail=”The beer has a medium-full body and a medium-low carbonation level. Not a thrist-quencher for the heat, but really fits nicely as a slow-sipper a rainy autumn day like today.” cat4rating=”3.5″ summary=”Overall, this beer has aged poorly as a IIPA, but quite nicely as an American Barleywine. The huge hoppiness that was present in the fresh beer has faded, but left is a nice caramelly maltiness together with a mellow floral and resiny hoppiness. We will be brewing a new IIPA next week, and this time I will tweak the recipe for a slightly drier finish. This time around I will try to drink them all while they are still fresh. “]

Homebrew: Black Rye IPA Brewday

On Monday we brewed the Black Rye IPA mentioned a couple of posts back. This was our first brewday testing out our new mash tun and hop spider. The mash went quite smoothly, and the flow rate of the wort during the mash (recirculation) was much higher than in our previous setup, allowing for more precise temperature control. I also think we managed to squeeze out a couple of extra litres of wort from the tun. Mashing didn’t go perfectly though, as after the mash we first noticed that our pre-boil gravity was much lower than that predicted by Beersmith (@65% efficiency): 1.051 vs 1.065. The second problem, was that the weight of the false bottom and grain had made some marks in the bottom of inner bucket, which I assume had softened up a bit because of the warm temperatures. The false bottom is kept above the bottom of the bucket with 5 screws, and I think we need to distribute the weight some more to prevent further ‘damage’ in the future. The boil went smoothly, and the hop spider managed to keep the hop pellets contained. After the boil we recirculated the hot wort for 10 minutes through the hop spider to catch as much trub as possible. Pumping into the fermentation vessel went smoothly, and we ended up with 24 liters of 1.065 wort (= 65% efficiency), instead of the intended 20 liters of 1.078 wort (calculated with 65% efficiency). So in the end, the low pre-boil gravity was a result of using too high of a mash volume. A quick glance at the BeerSmith settings, and I realized that I had setup the mash tun loss as 8 liters. I lowered this to 4 liters, which should hopefully result in us hitting the correct gravities in the future. I don’t really mind the lower gravity, since now the ABV will be lowered from around 8.3% to 6.3%, resulting in a more drinkable beer. Anyways, the wort tasted really nice with lots of hoppy bitterness and some light roasted tones. The pre-boil sample tasted really chocolately, which I assume is from the Chocolate Rye, which is known for its milk chocolate flavours. We pitched one pouch of US-05 and one of S-04 when the wort had hit 17 degrees C, and placed the fermenter in our fermentation chamber set at 17.5 degrees C. The next day there was already lots of activity in the airlock, and I’m hoping the beer turns out great!

Diacetyl in beer (Part II): Diacetyl formation and wort amino acids

This is the second part of my mini-essay on diacetyl formation during beer fermentation. You can find the first part here. Most of the text is based on my recently published review on diacetyl in brewery fermentations, so have a look at it as well and please cite the review rather than the text in this blog.

So what kinds of fermentation conditions favour the formation of diacetyl? We ended the previous part by stating that fermentation conditions favouring rapid yeast growth can give rise to increased diacetyl production if wort free amino nitrogen content is insufficient. Why is this then? Since diacetyl is directly linked to the valine biosynthesis pathway, the concentration of valine inside the yeast cell will affect the amount of diacetyl generated during fermentation. It has been shown that valine strongly inhibits the acetohydroxyacid synthase (AHAS) enzyme, responsible for catalysing the formation of α-acetolactate from pyruvate (see the second Figure in the previous part) (25, 26). Hence, the more valine present in the yeast cells, the less α-acetolactate will be synthesized, as the catalysing enzyme is inhibited, and consequently less diacetyl will be formed as well. Studies have shown varying data on the inhibitory effects of other branched-chain amino acids on AHAS. Both Barton and Slaughter (26) and Magee and de Robichon-Szulmajster (25) observed that leucine inhibited the AHAS enzyme’s activity, though not as much as valine. No inhibitory effect was observed with isoleucine. Pang and Duggleby (27) observed the opposite on the other hand, i.e. that isoleucine had a slight inhibitory effect and leucine had no inhibitory effect on AHAS activity.

Nakatani et al. (28) studied the effect of supplementing valine and isoleucine to wort on the production of diacetyl and found that increased wort valine concentrations significantly reduced the amount of diacetyl produced during fermentation. In fermentation trials with lager yeast involving wort of differing original gravities, free amino nitrogen and valine content, Petersen et al. (29) observed that low concentrations of valine in the wort resulted in the formation of double-peak diacetyl profiles (most likely as a result of valine depletion toward the end of fermentation), while high concentrations of valine in the wort resulted in single-peak diacetyl profiles with a lower maximum diacetyl level compared to the worts with low valine concentrations. The results show that the valine concentrations of the wort influence the amount of diacetyl formed, but the trials performed in the study varied in specific gravity and free amino nitrogen, meaning that no definite conclusions regarding the relationship between wort valine concentration and diacetyl concentration can be drawn. Cyr et al. (30) observed in trials with two different lager yeast strains, that diacetyl concentrations in the fermenting wort were constant or decreased when valine uptake increased, while diacetyl concentrations increased when valine uptake decreased or was null. Krogerus and Gibson (31) showed that direct supplementation of wort with valine (100 – 300 ppm) and consequently greater uptake of valine by yeast cells resulted in less diacetyl being formed during fermentation. Other fermentation parameters such as fermentation rate and yeast growth were unaffected (31).

The general free amino nitrogen (FAN) content of the wort may also affect the valine uptake rate and consequently diacetyl production. Krogerus and Gibson (31) reported that when FAN levels were lowered the diacetyl production was also lowered presumably due to faster absorption of preferred amino acids, resulting in an earlier and greater demand for valine and its increased uptake due to less competition for permease interactions. Increasing background levels of initial wort amino acids (while keeping valine concentration constant) resulted in a greater production of diacetyl. This increased production was influenced by which amino acids were increased. Preferred amino acids, i.e. those taken up faster than valine, caused greater diacetyl formation in the first stage of fermentation, while increasing the concentrations of non-preferred amino acids influenced diacetyl levels later in the fermentation and therefore had a greater influence on the diacetyl levels in green beer (31). Pugh et al. (32) also observed that the maximum diacetyl concentration during fermentation decreased as the initial FAN content was increased from 122 to 144 ppm, after which it again increased as the initial FAN content was increased from 144 via 168 to 216 ppm. Verbelen (33) reports a lower diacetyl production rate and simultaneously increased valine uptake rate and BAP2 expression level in lager yeast for fermentations of 18° Plato worts containing adjuncts (FAN contents of around 150-210 ppm) compared to 18° Plato all-malt wort (FAN content around 300 ppm). Nakatani et al. (28) on the other hand report a negative correlation between the initial wort FAN content and the maximum VDK concentration observed during fermentation. These conflicting results are presumably due to differences in valine uptake. At high FAN levels the yeast cell utilizes the preferred amino acids and less valine is taken up as a result (resulting in higher α-acetolactate production), while at very low FAN levels many amino acids will be entirely removed from the system and yeast growth is affected. If valine is depleted in this fashion then the demand for anabolic valine synthesis is increased and the α-acetolactate level increases as a result. It would appear from the values available in the literature that a FAN level of approx. 150 ppm is optimum for low diacetyl production, however this value will vary depending on individual fermentation and process conditions. Lei et al. (34) also observed that the amount of valine absorbed during fermentation decreased when FAN content was increased from 264 ppm to 384, 398 and 433 ppm by adding protease enzymes during mashing, despite the increased in total valine concentration.

Barton & Slaughter (26) investigated the effect of adding individual amino acids and ammonium chloride in excess to wort on the VDK concentration and AHAS activity during fermentation, and found that alanine and ammonium chloride significantly lowered both the amount of diacetyl formed and the AHAS activity, suggesting they have an inhibiting effect on the enzyme. Valine and leucine also showed an inhibiting effect on AHAS (their effect on diacetyl concentration was not studied). The results suggest that alanine, ammonium chloride and possibly leucine could be used in excess together with valine in wort, to minimize the formation of diacetyl during fermentation, and that AHAS activity is vital for the control of diacetyl formation. Dasari and Kölling (35) observed elevated diacetyl production in petite mutants of S. cerevisiae, as a result of cytosolic localization of the AHAS enzyme, suggesting that accumulation of AHAS in the cytosol could result in increased diacetyl production, possibly as a result of increased secretion of α-acetolactate from the cell.

In this part we focused primarily on the theory of how wort amino acids affect diacetyl formation, and in the next part we will continue looking at how other fermentation conditions affect diacetyl formation and some methods brewers can use for reducing the amount of diacetyl formed during fermentation.

References:

  • (25) Magee, P., de Robichon-Szulmajster, H., (1968) The regulation of isoleucine-valine biosynthesis in Saccharomyces cerevisiae – 3. properties and regulation of the activity of acetohydroxyacid synthetase. Eur. J. Biochem. 3, 507-511.
  • (26) Barton, S., Slaughter, J., (1992) Amino acids and vicinal diketone concentrations during fermentation. Tech. Q.  Master Brew. Assoc. Am. 29, 60-63.
  • (27) Pang, S., Duggleby, R., (2001) Regulation of yeast acetohydroxyacid synthase by valine and ATP. Biochem. J. 357, 749-757.
  • (28) Nakatani, K., Takahashi, T., Nagami, K., Kumada, J., (1984) Kinetic study of vicinal diketones in brewing, II: theoretical aspect for the formation of total vicinal diketones. Tech. Q.  Master Brew. Assoc. Am. 21, 175-183.
  • (29) Petersen, E., Margaritis, A., Stewart, R., Pilkington, P., Mensour, N., (2004) The effects of wort valine concentration on the total diacetyl profile and levels late in batch fermentations with brewing yeast Saccharomyces carlsbergensis. J. Am. Soc. Brew. Chem. 62, 131-139.
  • (30) Cyr, N., Blanchette, M., Price, S., Sheppard, J., (2007) Vicinal diketone production and amino acid uptake by two active dry lager yeasts during beer fermentation. J. Am. Soc. Brew. Chem. 65, 138-144.
  • (31) Krogerus, K., Gibson, B.R., (2013) Influence of valine and other amino acids on total diacetyl and 2,3-pentanedione levels during fermentation of brewer’s wort. Appl. Microbiol. Biotechnol. 97, 6919-6930.
  • (32) Pugh, T., Maurer, J., Pringle, A., (1997) The impact of wort nitrogen limitation on yeast fermentation performance and diacetyl. Tech. Q.  Master Brew. Assoc. Am. 34, 185-189.
  • (33) Verbelen, P., (2009) Feasability of high cell density fermentations – for the accelerated production of beer. Ph.D. thesis. Katholieke Universiteit Leuven.
  • (34) Lei, H., Zheng, L., Wang, C., Zhao, H., Zhao, M., (2013) Effects of worts treated with proteases on the assimilation of free amino acids and fermentation performance of lager yeast. Int. J. Food Microbiol. 161, 76-83.
  • (35) Dasari, S., Kölling, R., (2011) Cytosolic localization of acetohydroxyacid synthase Ilv2 and its impact on diacetyl formation during beer fermentation. Appl. Environ. Microbiol. 77, 727-731.