IPA: the hot maturation experiment

In any modern account of the history of India Pale Ale, you’ll generally find a declaration that the casks of well-hopped beer sent out to India by ship via the Cape of Good Hope in the late 18th century matured and developed quickly in a way that the same beer kept at home in Britain did not. It was this accelerated maturation in a short time (three to four months or so) caused by travelling through the warm waters and hot climate of the central Atlantic and the Indian Ocean as the sailing ships twice crossed the equator that gave IPA the character that was so much appreciated by expatriate Britons in Bombay, Madras and Calcutta, supposedly. But is this actually true?

You’ll be pushed to find contemporary (that is, 18th and 19th century) confirmation of the “hot maturation” theory for IPA’s popularity in India. Contemporary writers talked about the enthusiasm with which IPA was consumed in the Indian heat, but never seemed to mention whether it was altered to the good on its way east.

Certainly “hot maturation” can’t be the cause for any popularity for IPA back in Britain, since if the beer did go through any accelerated changes on the voyage to the sub-continent, this couldn’t be happening to the beer stored in chilly cellars back home. Are current writers on beer guilty of assumptionism (otherwise known as “you’re making this up”), the crime of assuming without evidence that situation A must surely have brought about result B – that beer on board a sailing ship travelling through the tropics must surely have matured quickly?

For the defence, there is irrefutable evidence that wine certainly undergoes accelerated maturation when heated over months: this is precisely what happens in the making of Madeira. And how did the style of wine known as Madeira originate? Why, by casks of wine being bought on the island of Madeira, in the Atlantic, by the officers of sailing ships on their way to India from Europe. When it arrived in India, having been heated to temperatures of 40C (104F) or more for months in the holds of the wooden ships as they travelled under the baking sun, the Madeiran wine had acquired a new, fuller, deeper, rounder flavour.

After the wine makers back on Madeira discovered what had happened to their product on its journey east, and how it was more popular (and could be sold for a higher price) because of the changes brought about by hot maturation, they artificially recreated at home the conditions on board the India-bound ships. By heating their wines in tanks surrounded by pipes full of steam, keeping the contents of the tanks at 40C for months, the Madeiran wine makers were able to produce vintages that had undergone the same changes as the wine that had been at sea for 12 or 16 weeks under the sun.

Subsequent scientific studies have shown that for every 10C (18°F) increase in temperature, the ageing rate of wine doubles in the case of “low energy barrier” reactions and leaps an amazing eight times in the case of “high energy barrier” reactions. In other words, at 43C, compared to a cellar temperature of 13C (55F), some ageing reactions are happening eight times faster, and others a staggering 448 times faster. A wine spending three months at 43C, therefore, will have some of the characteristics of a wine that has spent two years in a cellar, and some of the characteristics of a wine that has spent 112 years in a cellar. Not all of those reactions will produce good results of course: the Madeirans were lucky that their wine evolved very well under hot maturation conditions.

But does the same thing actually happen with beer? Pete Brown wrote a best-selling book, published last year, in which he took a cask of Burton-brewed IPA to India by ship. He decided that, yes, the ship-borne beer had aged better and matured more than the same brew kept at home. But while I’m not knocking his huge achievement in organising the trip (and getting an excellent, highly readable book out of it), Pete himself never actually drank ship-borne IPA alongside stay-at-home IPA.

Earlier this year I decided I had the opportunity to conduct an experiment myself to test the “hot maturation” theory. Take two 75cl bottles of Meantime Brewery’s fine naturally conditioned IPA, 7.5 per cent abv, made in Greenwich, with East Kent Golding hops like the original IPAs. Leave one sitting in a cool cupboard in West London. Take the other by aircraft to the Middle East and place it, wrapped in a thick black plastic bag, outside on a shaded Abu Dhabi balcony for three months. Turn the bottle over occasionally to stir up the yeast inside and try to reproduce the sometimes violent rocking that casks of ship-borne IPA must have suffered on their journey from Britain to the sub-continent. In Abu Dhabi the beer would undergo temperatures that rose as high as 45C (113F), and seldom, if at all, dropped below 26C (79F) even at night. Fly the bottle back to London, open it alongside its non-traveller companion and contrast and compare.

I was lucky to have a professional brewer to help me do the contrasting and comparing: Steve Wright, top man in the mashing and pitching department at Hopback Brewery in Salisbury. He’s an old friend of a couple of very old friends of mine, and Steve and I were both invited to a barbecue our mutual pals were holding. I took along the two bottles of Meantime IPA so that he could give his expert take on the experiment.

The result was a relief, because I’ve been repeating the “hot maturation” meme myself when writing about IPA, with the growing fear that it might not actually have any reality. But the two bottles, stay-at-home IPA and three months in the Gulf heat IPA, were unmistakably different, the beer that had made a 7,000-mile round trip instantly recognisable. The bottle that had been in the heat certainly wasn’t noticeably oxidised, skunked or suffering from any other fault, Steve and I agreed, and it was very drinkable. More than this, the IPA that had stood on the Tropic of Cancer being gently baked was deeper, rounder than the same beer that had been kept in conditions no hotter than a chilly English Spring. With the hot-matured IPA the Goldings “Seville orange” was even more marmalade-y, the malt more rotund, more caramelly. The stay-at-home IPA was silver trumpets, with everything higher, brighter; the well-travelled, “maderised” version was golden trombones, a baritone to its brother’s tenor.

Which one was better? I liked them both very much, and I wished I had taken more bottles with me, and kept more at home, to make more side-by-side comparisons. If the stay-at-home beer just had a fetlock ahead of the “hot matured” beer, this was probably, I think, because we were drinking something that had not been designed to undergo a “maderisation” process: I’m sure a beer could be made to thrive even more when subject to hot maturation than Meantime’s IPA did.

Surprisingly, this is an experiment that seems not to have been done very much: Dr John Harrison of the Durden Park Beer Club, the British home-brew group that specialises in recreating old beer recipes, kept a well-hopped IPA in a cask in his shed over an English summer at least once, and we tasted the results at the seminar the British Guild of Beer Writers held on IPA at the old Whitbread brewery in London in 1994. But an English summer won’t reach the temperatures even a Gulf spring will, and the changes to the beer will be nothing like as pronounced. I suggest that if you want to try this one at home, you’ll have to be able to keep your beer at or above 40C for extended periods, and not let it drop below 26C at any time. That means, for professional brewers, a brewery somewhere in or near the tropics where casks can be stored in hot shade, or a heated storeroom, or a set of Madeira-style tanks warmed up by steam pipes or their equivalent.

For any brewer wanting to supply a particularly “authentic” form of IPA, however, I’d suggest “hot maturation” for three months is just the gimmick to put you ahead of your rivals. Your customers will certainly be able to taste the difference.

34 thoughts on “IPA: the hot maturation experiment

  1. Fascinating stuff, Pete Brown mentions that respected modern IPAs (carbonated & non-heat-treated hop-fests) would taste little like the originals, due in part to the lack of the long hot sea journey & them being served flat.

    I’m curious – would the temp down in the ship’s hold (assuming that’s where the casks were kept?) have been quite as warm as your Saudi balcony?

    I’m sure Pete B. & Alistair H. & the Meantimers would be very interested in this.

  2. Wow, that’s fascinating and very entertaining reading! Instantly, I wanted to send away some good IPAs to warmer climates by boat to test this myself. Would it be good enough to take a few bottles for a ride in my car during the summer vacation? 😉

  3. Glad it worked!

    For me the clue came while touring a Madeira winery on the island – it’s clear the conditions do something to the drink, and while Madeira is different from beer, its story and the alleged differences the journey makes to flavour were just too similar to be coincidence.

    And while I didn’t taste the ship-aged version side by side with the ‘green’ version (we attempted to, but as far as I know the green, unaged cask we flew to India is still lost in customs somewhere), I did the next best thing. Melissa Cole made tasting notes on an unmatured cask of the same beer while I was opening the ship one in India, and allowing for the fact that our palates might be different, if you read our tasting notes side by side they do point to hot ageing having had the effect we think it did.

    In terms of it being recorded historically, I’m not sure any brewer ever formally studied the process, but contemporary accounts again provide leading clues if not a full analysis. Ads in the Calcutta Gazette in December 1828 refer to Hodgson’s Allsopp’s and Bass’ beers “of different ages, some all perfection, others approaching it”. An ad for Hodgson’s in May 1824 refers to beer in Hogsheads “ripe for immediate use” and beer that has been bottled “not for immediate use”. That word “ripe” is commonly used to describe newly arrived beer. Sure, this only tells us it had to be aged – not that the sea voyage provided a specific kind of ageing – but the famous testers who evaluated the beer when it arrived in Calcutta not only decided whether the beer was of straightforward good enough quality; they judged whether the beer had fully ripened or not. References to the length of the journey, and unrecorded factors such as the conditions on the journey, clearly meant there was an element of unpredictability between departure from England and arrival in India.

    And then there are the repeated references to the beer “approaching a condition like wine”, scattered across the nineteenth century by brewers and IPA fans. I’d always thought of this as mere hyperbole, the best comparison you can use for a beer you really like. But my beer in India had taken on wine characteristics – a hint of sour acidity that, like the oxidisation that occurred in Madeira and probably beer, could be an off flavour but instead adds to a beer if it’s already got the right strength and complexity. Some of the Indians I gave it to insisted that it was wine, that I was trying to trick them by claiming it was beer!

    My theory on how it works, as someone who is not a brewer but has done the journey? Firstly, if you left beer in hot conditions in stasis, it would go stale. The fact that the liquid is in constant, gentle motion means the whole container is getting a gentle oxidisation that produces a different result. Secondly, residual yeast (they tried to filter it all out but didn’t have the techniques to get 100% filtration) goes a bit barmy in hot temperatures, producing fleeting hints of unpredictable characteristics, but not in enough quantities to turn the beer sour.

    Mike, you raise a good question, which I can answer. Most accounts of the IPA journey talk about how the ship’s hold would be the coolest part of the ship. This makes intuitive sense if you think about the hot sun on deck and the cool shade below. But having been below decks in a ship near the equator, I discovered it’s actually the hottest part! You’re below the waterline, and the water is heated to about 30 degrees C. This warm water surrounds the dead, stale air below decks, which heats up to higher temperatures than this, and that’s why I think the beer was ‘slow cooked’ in a very gentle, long type of pasteurisation, which is where that oxidised flavour comes from.

    A proper brewer may tell me I’m talking bullshit, but that’s my process of deduction!

  4. This lovely paragraph:

    “With the hot-matured IPA the Goldings “Seville orange” was even more marmalade-y, the malt more rotund, more caramelly. The stay-at-home IPA was silver trumpets, with everything higher, brighter; the well-travelled, “maderised” version was golden trombones, a baritone to its brother’s tenor”

    beautifully describes my observations of the behaviour IPAs. The “silver trumpets” description seems to be what I describe as “shouty”.

    I remember 3 or 4 yrs ago Sierra Nevada’s all-English IPA started coming to the UK. It didn’t find much favour. Most reviews were underwhelming. But I had a hunch – “this beer needs six months at room temperature”. I consumed 1/2 the 6-pack young, and the other 1/2 after six months living-room temperature composting (the word they use round these parts for “maturing”). The difference was remarkable. It was just as you described: Maderised, tangerine-y, bigger mouthfeel, better integrated hop character. It was a joy.

    I also experimented with Sierra Nevada Celebration, a beer which, when young, I find unbearably “shouty” and almost undrinkable. I can thoroughly recommend a composting of over 2 years after which it is almost ready!

  5. Thank you very much for your comments, gentlemen, and in particular Pete: I’ve no doubt what you and Melissa were finding was indeed a genuine difference between the two beers, but I did want to try the experiment myself, as close as is possible using a bottle-conditioned beer rather than a cask. Pelle, there’s a Norwegian akvavit (sp?) distiller who sends some of his product to Indonesia and back in casks to make “Linie” (“Line”) akvavit (so-called because it’s crossed the “line”, or equator, on its journey – perhaps our can persuade him to include some IPA in casks on the next journey … Mike, it was the UAE, not Saudi: I’d have been in jail for bringing alcohol into Saudi Arabia.

  6. That is very interesting. I remember many years buying imported beer in Florida (25 years ago or more), in a time when beer came in much more slowly than today. Some was bottle-conditioned, some not, some pale ale, some not. When you got an old sample, which was quite frequently, the beer had a “baked” taste to it. Didn’t matter if it was filtered or not. I attributed this to long storage in warehouses indifferently (if at all) cooled and leisurely ship rides before that. I found all this beer undrinkable, I could never abide that taste. It was indeed a type of maderization, which suits the eponymous wine but rarely does much for beer IMO. Like all of you I am fascinated to know what that IPA tasted like in India way back when. Some accounts suggest a lot of it was sour and turbid. Yet we all know the praise bestowed by many on the best productions of the Trent valley and London. The very high hops rates of the time possibly made the difference, that plus high attenuation rates perhaps made for a different final product, than, say, I consumed on the balconies of art deco hotels in Miami Beach all those years ago.

    When it comes to beer, I stand with the comment of an early Michigan micro-brewer, reported in an early issue of All About Beer magazine. He was brewing English style beers. He said he liked the beer best fresh off the line. I have never found reason to question that except maybe for a handful of specialties including some strong stout. That is my taste of course, and it is trite to say that taste varies. Rarely did I quarrel with the judgement of Micheal Jackson but still when he lauded some Belgian specialties at 4-5 years of age I could never get it, they always seemed stale to me.

    Where does this leave the famous Somerset vatted ales and other stock beers of olde England? I think they were fairly acid and that is why they disappeared.


  7. First: great posting!

    Martyn: it’s spelled “akevitt”, and you are absolutely right about the line version. It’s produced by Arcus (which used to be part of the government alcohol monopoly), and they ship the akevitt to Australia and back. They make two kinds: Løitens Linje og Lysholms Linje.

    As to whether you can induce them to include IPA on the next trip, well, you’d have to explain what it is first.

  8. (apologies for my Geographical dumbness, Martyn – I meant to go back & check I was talking about the right place – serves me right for taking the Mick out of you over on Pete’s blog the other week!)

    So from what Pete says there’s a real difference in temps throughout different parts of the journey – it would be interesting if we knew what these temps & times were & if someone could replicate them with a cask or few of IPA.

    As to the “motion in the ocean” I remember hearing that Adnams would store some casks of their excellent strong Old Ale, Tally Ho, some for a year or even two (it’s a great beer & so complex after that amount of maturation) – I heard that rather than simply leave the casks alone for this maturation, instead they used to roll them from one end of the cellar to the other (where they would bash into the wall leaving a dent).

    Obviously this is different again to ‘vat aged’ beers (e.g. Belgian ales & the 5X beer in GK’s Strong Suffolk) & AFAIK also different from most land-lubbing barrel-aged beers from the US, UK etc.

  9. Rolling the barrels also was common for some running beers, to rouse the yeast to ensure a good secondary. Perhaps it was done to ensure ditto in some stored beers too, it sounds like it was.

    But secondary fermentation continues apace even in stationary vats, there can be no doubt about it, many accounts from the 1800’s state that e.g., porter became fine and dry through ongoing attenuation. (I suppose it would happen faster if you rolled the barrels around).

    What makes me wonder about rocking and barrels in ships is that exploding barrels precisely is not what was wanted, which an active secondary, especially an uncontrolled one, could achieve. And so some accounts testify to shipping the beers flat. Maybe the flatness, rocking and amount of residual yeast were studied to ensure a good result at the other end. There must have been a lot of failures though, judging by the accounts of dumping bad beer in Indian harbours.

    The more I think about it, the more I feel that the stupendous hop levels of historical IPA explains the best results they did get. The beers were ripe on arrival because the hop quality diminished with the trip (just as it does with any long storage). So much hop was used to begin with though that the beer probably didn’t go too sour. But it must have been oxidized to a point.

    I think a good experiment would be to brew a pale ale with 6-7 lbs hops per barrel, attenuate high, and then send it over on a ship. It might be undrinkable at the beginning due to the very high hop levels, but round out with the trip. Still though, I think it would have the baked taste I don’t like.


    1. Wow. Everytime I have a good idea, it seems that the brewing community jump on it before me. I’m testing this hot maturing theory, and if the results are good enough, I plan to do a hot-matured-madeira-style-IPA in my brewery ( Brasserie artisanale Albion, in Québec) not open yet, but soon! I really think it will be something that the brewers will try in the future. But maybe no chance of being the first, with such clevers writers!
      Thanks Pete and Martyn! 🙂

  10. What a fascinating article. One has to wonder how much influence ingredients have on the “ripening” process.

    More specifically, I just read a thread on RateBeer.com that discusses the merits of crystal malt. It seems that these days many brewers (in the US at least) use this specialty malt in just about every beer style.

    There are some that believe that beers using lots of crystal malts develop a nasty (i.e. wet cardboard) oxidized flavor quite quickly.

    In addition, I wonder if some hop varieties are better at providing consistent flavor over time than others. Many of the new American hop varieties provide extremely pungent flavors and aromas when fresh. However, give that Double IPA brewed with Simcoe and Amarillo hops 6 months and it’s a mere shadow of it’s former self. Would the same beer brewed with Goldings and Hallertau hold up better?

    In my opinion, these two factors are the main reason why you hear beer nerds cry when their favorite double dry hopped double IPA has been sitting on store shelves for 2 months prior to sale. As a result, they believe that ALL beer is best when consumed immediately after fermentation.

    What ingredients would one use to create a beer purposely designed for aging? For example, how is it that Ballantine brewed an IPA that was aged for 1 year prior to release and folks today go bonkers when Russian River’s Pliny The Elder is more than 2 weeks old? Maybe it’s just public taste?

  11. MikeMcG, back in the early 1990s Zymurgy magazine did just such a study on seawater temperatures for the journey from Britain to India via the Cape, I recall. But as Pete points out, the water temperature isn’t necessarily going to be the same as the temperature inthe hold.

  12. Good stuff I have often wondering about the effect temperature had on the maturation process. It flies in the face of the common theory we were always taught that low temperatures over extended periods of time is the only way to go.

  13. I’ve had a bottle of Meantime IPA sat in my beer cupboard for some time as I’m also interested in seeing how it matures. It looks like I should have stuck it in the airing cupboard though!

  14. I have an 18 gallon cask of the IPA that Pete came to brew with me a year ago it was in the brew house next to the heat dump fan of a cooling unit for about 6 months, I plan to bottle this soon. I also have a 9 gallon cask of the same brew that has been in the cold store since racking nearly a year ago.
    I’m looking forward to trying them side by side.
    btw the hop additions for this brew were 750g target & 750g chinook at the start of boil with another 500g of each after 30 minutes, then 45 minutes later 1kg of target followed by 1kg of chinook and boil off.

  15. In the mid-1800’s Britannica Encyclopedia entry on brewing, whose author was Thomas Thomson, author of the text Brewing & Distillation (1849, co-written with practical brewer William Stewart), it is advised that to avoid acidity for pale ale sent to India, attenuate it to 90%, hop at the rate of 6 pounds per barrel, and ferment the beer slowly at a cool temperature.

    We know that 100% pale malt was used for pale ale then, so I’d use that, not crystal or any kind of colouring malt.

    I think it would be interesting to taste a beer made exactly this way and sent by boat to India. According to the entry (easy to find by a Google search), this kind of beer should not become acid. Now, whether it acquired Madeira-like notes that would have been prized at the other end is hard to say. I think some must have become oxidized in this way. It is a taste I think I wouldn’t like, but only further testing can add to the knowledge gained in this area (the experiment you reported, Martyn, and Pete Brown’s odyssey recounted in his excellent book). To these I’d add Atlantic IPA brewed by Brew Dog. I haven’t had a chance to taste that as yet. I believe it was not sent to India but traveled a fair bit on the Atlantic as the name suggests, and still it would be interesting to try it. It used I understand English varieties for hopping, and I think that is important. Interesting as many of the American IPAs are, I don’t think their taste would be close to the true IPA of the Thomson era and earlier since their hop qualities generally reflect the piney/grapefruity/gooseberry-like West Coast style.


  16. That’s great experiment! It pushed me to do the same with my batch of IPA I brewed at home a month ago using only pale malt and EKG with IBU more than 140.
    I was going to mature it just at home temperature (about 24C here in Russia), but after reading your post I will put some bottles to a balcony, where the temperature often breaches 45C mark.
    Will do it today and taste it somewhere in Autumn (or even Winter).

  17. […] Originally Posted by Saccharomyces At least one source I have read says that most likely the first historical IPAs brewed at Burton on Trent would have been 1.050 OG, and would have been 100+ IBUs since they were hopped at a level equivalent to 1-2 pounds per 5 gallons! Such a beer would have needed to age for quite awhile to even be drinkable, especially considering they didn't do any middle boil additions back then (half was added at the start of the boil, and the other half would have been added as dry hops.. talk about bitter!). Well what created the IPA as a style was that the beer seemed to mature much more rapidly than normal on the sea voyage to India, with the bitterness rounding out and mellowing in a fraction of the time it would have taken in a cellar; see Zythophile's most recent post. […]

  18. Meant to say, your book rocks. Read it once, hugely entertaining and informative. So much so that its on my list of books to go on holiday with next week. Just wish i could stop trying to clear the beer ring off the cover!

  19. *blush* Thanks, Joe – have a good holiday. If you – or anyone else who liked Amber Gold and Black – feels like making a ‘reader comment’ on Amazon, that would be very nice. (If you didn’t like the book, though, just keep your thoughts to yourself …)

        1. I vaguely recall reading that bottles of beer shipped east were stored upright – I can see that greater surface area exposed to air might incresse oxidation, but I think the effect over three months might be minimal.

  20. Our Stone 14th Anniversary Emperial IPA was brewed with 100% White Malt and 100% British hops, primarily a blend of Goldings and Target. It was definitely inspired by the recipes we saw from IPA’s brewed in the 1800’s, and from the information we got from Pete B. and Martyn (and others) while we were in England this past winter, although was not meant to be an exact re-creation.
    I’m willing to part with some of my supply if anyone wants to test the theory of aging during the ocean voyage! We have some beer aging in barrels right now.

    1. Quick question for you Mitch:

      Do you feel that the strong earthy character of Stone 14th that seems to be polarizing beer enthusiasts is a result of the salts or hops used in this recipe? (or maybe both?) I’ve seen a number of people who didn’t like the beer blaming the use of boadicea hops.

      For what it’s worth, I thought it was pretty delicious. A bit too much to have more than a glass at one time, but certainly enjoyable in an almost savory kind of way.

      The beer almost resembled a double strong version of a small IPA I brewed at home recently using unfiltered San Diego water. In that recipe I too used 100% base malt (95% Maris Otter, 5% Briess 6-row), a little bit of gypsum, and First Gold and Willamette hops.

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