The Essence of Sour

This post is in some ways a counterpoint to the post on sugar syrup being the essence of sweetness.  Here we’re going to talk about lime and especially lemon juice – the essence of sour.

But first we’re going to need to talk about our taste for Sour.  About what sourness is and what it means.

Sourness is a concept which is at once commonplace yet intangible.  Everyone understands what a sour taste is, yet struggles to explain it in words.  It is the acidic tang of lemon juice.  The sharpness of vinegar.  Or the tartness of fresh cranberries.

It is also the taste that some foods will acquire once they have gone rancid.

(Mostly) Sour Fruit

(Mostly) Sour Fruit

I suspect that this last part is why our taste buds evolved to include Sour as one of our five primary tastes.  As hunter gatherers it was important for us to be able to determine how sour a potential foodstuff was.  A little sour and we should be safe.  Very sour and we should avoid it – it’s probably rancid.

Back then the difference could be life and death.

Since, genetically speaking, our species hasn’t changed from those days these tastes remain the same now.  Even if the stakes for being wrong have changed dramatically.  In general a little sour is considered tolerable or even outright tasty.  Whereas very sour is nasty.

As always, within these general rules there is huge variance in the personal tastes of an individual.  For myself I like things slightly on the sour side of normal.  While my father is known for his sweet tooth.

Sourness in Cocktails

In cocktails we achieve sourness in two major ways: through the use of the juice of certain citrus fruits; and using other naturally tart fruits such as pineapples, kiwifruit or blackcurrants.

The use of tart fruit is typically recipe specific as each has a very distinct flavour.  True, the use of these fruits can somewhat counterbalance a sweetening agent but its effect is minor.  For example, muddling fresh apple in an Appletini balances the sweetness of an apple liqueur to give a clear, fresh tasting cocktail.

But what we really need is a sour equivalent to sugar syrup.  A highly concentrated, readily available sour liquid with a comparatively mild taste.  Something we can use on demand to balance the sweetness of our other cocktail ingredients.  For this we need to look to the juice of citrus fruits.

Sour juice

Sour juice

Orange juice isn’t much use in this regard.  As delicious as it is, it typically isn’t sour.  Grapefruit juice is better but also not ideal.  Though it is on the sour side it’s not that sour, and its taste is so distinct that it tends to dominate the drink’s flavour.  Hence its use is also recipe specific rather than generic.

So, by process of elimination, we are left with our winners:

Lemon and Lime Juice: the Essence of Sour

Nature has very thoughtfully provided us with an excellent solution to our needs.  Small, brightly coloured packages of concentrated sour juice which travel well and are surrounded by a skin rich in essential oils to keep the moisture sealed inside.



They even grow on trees.

Lemon and lime juice are rich in citric acid, one of many chemicals our taste buds register as Sour.  Though they also have their own flavour, this is comparatively mild compared to the sour punch they provide.  Hence they can be used in low enough quantities that their flavour doesn’t automatically overwhelm the other tastes in our cocktail.  Unlike grapefruit juice, for example.

Of course, like all natural products they will deteriorate over time.  Don’t expect a wrinkly old lime to be full of juice.  But their shelf life is much longer than for most other fruit typically used in cocktails.

Unlike various other more seasonal fruits, the most common varieties of lemons flower and fruit all year round.  They are comparatively cheap and travel well.  With modern transport systems this means that we can obtain ripe, standardized lemons in large quantities whenever we want them.

Mexican Elbow ready to squeeze

Mexican Elbow ready to squeeze

So it continues to baffle me why anyone would ever use a bottled lemon juice substitute.  Especially when they are so inferior to freshly squeezed juice.  I’ve said it before but it’s worth saying over and over.  There is no substitute for freshly squeezed lemon or lime juice.  This is one corner you cannot cut.

I do understand that people may think that squeezing the juice out of them is awkward and time consuming.  But there is an easy and practical solution to that: the Mexican Elbow.  With it you can squeeze the juice out of half a lemon in a couple of seconds.  When working at speed they are an essential piece of bar equipment.  When making a couple of drinks at home, you can live without them.

Lemon juice via a Mexican Elbow

Lemon juice via a Mexican Elbow

However, I should point out that what we in Western countries think of as lemons and limes is not the whole story.  Across the world there are a variety of species and variants of these citrus fruits.  Their appearance and the taste and sourness of their juice can vary quite widely.

A favourite of mine is the Limón de Pica, native to Chile and Peru.  It is the traditional souring agent in the Pisco Sour.  While it looks like a lime, its juice tastes like a mix of lemon and lime.  This has led to all sorts of confusion over time as westerners have tried to accurately categorize it.

The Balance of Sour

So now that we have become familiar with lemon and lime juice as the Essence of Sour, what do we do with them?

The answer is simple yet profound.

The flavours behind many different cocktails require a certain degree of sweetness or sourness to really come into their own.  To truly blossom in our taste buds.  This is visually represented by the Sweet vs Sour axis on my taste profile charts.

Lemon and lime juice, as the Essence of Sour, are major tools with which to achieve the exact balance you desire.  So is sugar syrup and other sweetening agents.


How much juice in half a lemon?

Typically we use lemon or lime juice to achieve two distinct aims:

The first is to cut back and mask the sweetness of a drink’s other components.  The Singapore Sling is a good example here.  With the inclusion of grenadine and three other liqueurs for their taste, the juice of 1/2 a lime is needed to prevent the drink becoming sickly sweet.  You don’t notice its presence, only its absence.

The second is when you actively want a drink to be sour.  This is usually when a recipe calls for the juice of a whole lemon and not just a half.   The quintessential example of this is the entire family of drinks known as the Sours.  From a Whisky Sour to an Amaretto Sour to my very own Sloe Sour Bitch.  I’ll be covering those in detail in due time.

So how do we actually achieve this?  In practical terms?  This is something which all new bartenders must learn for themselves.  A thousand words on the topic is no substitute for hands on experience.

So I have developed a series of experiments for new bartenders to play with to develop this understanding for themselves.  You’ll find some of these in the Balance of Sour post.  I strongly suggest you check that out next.