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Fermentation - Spiritual Transformers!



Malaya 1948.  It’s 11:45 am and it’s scorching in the close to mid-day sun.  Coupling this with the humidity of the tropics only exacerbates the anxiety for Samy, a humble law-abiding street peddler squatting next to an open drain at the local wet market.  Hot and sweaty, Samy nervously springs ups ever so often to spot but hoping never to catch those deep-set eyes of the heavily bearded, six-foot-four Sikh mata-mata (police) who patrols that beat.


Samy has five bottles of neera left to sell and he’s getting increasingly desperate to cut a deal.  With each passing moment, the need to clear this remaining stash of what started at daybreak as a clear, delicious sweet nectar harvested from palm trees.


It’s just a few years after the war and hardly anyone is well off, but something was brewing - literally - and come 12 noon, should there be any remaining bottles left he would by law need to dispose of the contents as they would by then be legally classified as toddy, an alcoholic beverage.  Each day at high noon, should Samy have unsold stocks he must make an executive decision: ditch the toddy or run the risk of encountering the wrong end of the stick that Constable Singh fashionably wields.


Having missed the experiences of that exotic bye-gone era, I was determined to put some of a raconteur uncle’s tall tales to the test.  It’s now present-day West Malaysia - having passed several kampongs, I was taken to a makeshift eatery where I was told neera was being sold.  It came very chilled in a used 1.5 litre plastic mineral water bottle.  Time now 9:30 am, and as I had anticipated the neera was delectably tasty and sweet.


Having found what I had come for, I left for the comforts of a hotel’s lobby bar that I ran in Ipoh 30 minutes away.  I re-tasted the neera on arrival and as expected, it had developed a stronger flavoured palate, nevertheless it was still a tasty brew.  I stuck the bottle in the chiller and revisited it every half hour, noticing each time that the plastic bottle was bloating with a rush of gas escaping as I twisted the cap.  The nose was getting more pungent and the flavours increased in intensity and sharpness each time.


It was a little past mid-day when I declared an end to my experiment after not having enjoyed the last few tastings.  I left the remainder in the chiller, and being slightly light-headed by that time forgot about the bottle until I heard an unexpectedly loud popping sound from the direction of the chiller.  The plastic bottle cap had violently shot out taking much of the contents along with it whilst rearranging the other items in the chiller.  Wow! I thought, it would be great as a propellant for an amateur rocket!


I’m sure that cavemen all around the world must have had similar experiences and thus the chance discovery of alcoholic beverages and the associated mishaps must have been universal.  I’m also sure there must have been a partner bitching somewhere in the background.


So, let’s explore what had been taking place above.  Sugars which are primarily carbon based molecules or organic compounds react with bacteria and yeast which are prevalent in unsterile environments. This accounts for decomposition.  Under controlled conditions, yeast and to some extent bacteria can be manipulated to produce tasty and complex alcoholic beverages.  However, the influence of these micro-organisms must be carefully controlled as spoilage can easily result.


Yeast, a group of micro-organisms belonging to the fungi kingdom, consumes simple sugars in organic matter such as fruit juices or nectar to produce both carbon dioxide and ethanol in a process we term fermentation.  There are two noteworthy phases in the fermentation process that deserves mention.  First, yeast ferments in the presence of the existing oxygen dissolved in the liquid to reproduce, replicating itself up to 50 times.  This aerobic fermentation continues until most of the dissolved oxygen is consumed.  At the same time, carbon dioxide bubbles out to form a frothy layer which further restricts contact of external oxygen with the brew.  Other by-products of aerobic fermentation are higher molecular weight alcohols such as butanol and amyl alcohol.  Fusel oils, which are primarily amyl alcohol, contribute rich and robust flavours in spirits however they can also have an unpleasant thinner like smell and have been blamed for causing hangovers.  That’s debatable and the jury is still out!


The next phase is anaerobic fermentation which occurs in the absence of oxygen.  However following from the previous reproductive phase, this fermentation has the benefit of a higher population of yeast cells.   As in phase one, carbon dioxide is produced, but this time the good stuff ethanol or alcohol is the other “waste product”.  Hence anaerobic fermentation is also known as ethanol or alcoholic fermentation.  The flavours released at this stage are more fruity and floral.


Temperature certainly influences the rate of fermentation and for that reason, freshly harvested neera is always kept cold to slow down the transformation process.  If one were impatient and wanted a more rapid conversion of neera to toddy, leaving the beverage in a warmer area should do the job.  But be aware that the very process of fermentation produces heat which can affect active yeast at temperatures above 36°C.


Yeast exists practically everywhere, even on our bodies; hence natural fermentation commences as soon as simple sugars are exposed to yeast at room conditions.  In the case of toddy, natural or wild yeast is sufficient to trigger fermentation and the final outcome is usually variable on the environment and the time the brew is allowed to ferment.


Under controlled conditions of a whisky distillery, little is left to chance and strict procedures are followed.  Whole grains that make up the raw material used for whisky production are milled to a grist and then sparged with water to form a viscous mash in the mash-tun.  The mash is then drained and sent to the fermenter or backwash as a non-alcoholic sweet syrupy liquid called wort.  This transfer must be done expeditiously to minimize exposure to foreign matter and unwanted bacterial infection.  Next, inoculation or pitching the wort with yeast is carried out without delay.


Each distillery has its own peculiar fermentation regimes which contribute to its characteristic style of whisky.  New makes from short ferments of around 50 hours are nuttier and can be quite muscular, whilst ferments that go up to 120 hours are lighter with more floral and fruity notes.  In some distilleries, malolactic fermentation that convert sharper malic acid to softer lactic is encouraged through the use of wooden washbacks. The time when fermentation comes to its natural end depends on the level of inoculation, temperature, yeast strain used and the health of the yeast.


Fermentation usually ends when frothing in the washback subsides, indicating that carbon dioxide has ceased to be produced and sugars are therefore no longer being converted to ethanol.  There are instances when fermentation ends prematurely, at times owing to bacterial contamination and in other instances this results largely due to the lack of nutrients in the original wort.   Not much can be done when the wort turns bad or sour but in the latter case, supplements such as thiamin, nitrogen, phosphates, magnesium and zinc can revive a “stuck” ferment.  This intervention to resuscitate the wort is however not permitted by the Scotch Whisky Association’s regulations. 


When the wort has undergone its completed fermentation cycle, it is known as wash or beer with an alcoholic strength ranging from 7% to 9 % ABV.  This then becomes the charge or liquid substance that is fed into the stills for distillation and subsequently condensed as new make or raw distillate.


Wild yeast is not a single strain of yeast but rather a moniker for yeast indigenous or unique to a certain site.  If a “wild yeast” produces good flavours, it can be isolated and propagated for use by a winery or distillery.  The strains of yeast used in distilleries vary significantly and contribute to the character of the final bottled whisky.  Concoctions of different strains of yeast usually make up the recipe as some are early starters in the fermentation process but are killed off earlier as the alcohol strength builds up.  Another strain may kick off later, often working concurrently midway with the less robust strain until this earlier fermenting strain dies off.  The second strain carries the baton further ahead as it will have a higher tolerance to alcohol concentrations.


Yeast used in fermentation is primarily from the large classification of the Saccharomyces Cerevisiae family and can be purchased in various forms.  Liquid or fresh yeast that come in various concentrations require significant care against contamination and heat.  The dry form however is more durable and can be stored for more than a year in cool rooms. 


The production of whisky takes on an additional stage compared to Brandy or Rum.  Grape juice and molasses or sugar cane juice are readily fermentable when they come into contact with yeast.  However, in the case of whole grains which is the raw material component of whisky, fermentation is not spontaneous.  Even when milled, the grist is composed of complex sugars which cannot be easily fermented.  In the natural world, the process of malting or germination activates a layer in the grain that produces enzymes which converts unfermentable starches in the grain into simple sugars for food to grow the shoot and root in a seed.  The malt master tricks the grain into thinking that it’s going to be a plant by malting it hence releasing enzymes that convert starches in the grain to simple fermentable sugars.  The enzymes in malted barley are very efficient, so much so that other unmalted dry grains such as wheat, corn, rye and even barley may be added to the mash for saccharification or hydrolysis to convert stable starches to simple fermentable sugars.  It is noteworthy that for this reason, whisky was primarily made historically from malted barley, with blended and grain whiskies being later tweaks adopted in the whisky trade.


Conceivably, if Constable Singh had known how dynamic the transformation was for hapless Samy’s merchandise, he might have cut him a little slack, perhaps even setting his watch back a half hour or so.  They could have then both taken a short mid-day break and had a drink or two, and everyone’s happy!


Lewis Mitchell

Cask & Drams Magazine

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