I received a great question from Tom Bruce this week. He took two coffees camping: “the first, a lighter roast, did not mix well with Baileys and the result was an unappetizing curdled mess. The second, a darker roast, resulted in a beautiful mix with no curdling. What do you think may been the cause of the curdling?”

Milk (or in this case the cream of Bailey’s) is a colloid mixture of fat and proteins suspended in a water based solution. Appetizing description, right? The proteins, particularly casein, repel each other to create milk’s uniform texture and cloudy white colour. Lowering the pH, by say adding lemon juice, upsets the balance and the proteins lump together in curds. In rotten milk, bacteria feeds off of the lactose, creating lactic acid. As it builds up, chunks form and the taste grows increasingly sour.

So, can the acids preserved by roasting light curdle milk? Potentially: the coffee grounds could increase acidity and drop the pH enough to foster unintentional yogurt. A more likely candidate is water. Given coffee is 99% water, slightly high levels of acidity will easily tip that scale. However, the most likely factor in this curdle mystery is temperature! Very hot temperatures will instantly coagulate the casein in milk, hence you have a cup with curds but none of the sour flavours of spoiled milk.

Curdled milk is interesting as it speaks to our often absentminded relationship with food and drink. We only pay attention to food when it is broken. Spoiled food forces our attention towards the cup or plate. Seems like a perfect cue for: Heidegger! I know, I know…

In Being and Time, Heidegger analyzes our relationship to ‘equipment’ or those tools in the world that enable us to cook, or to chop wood, or to brush our teeth. He points out how familiarity – honed through experience – allow us to lose ourselves in most tasks. The carpenter does not pay attention to the shape or texture of a hammer because their focus is the ongoing task of building.

However, what happens when the hammer breaks? Heidegger, writes “only a hitch in workings” of a hammer will generate “emotion and provoke thought”. We deliberately pay attention to the equipment itself. We take the hammer in-hand and deliberate on its construction, wear, and design; consider the way it pounds or pulls nails and seek out how and why it failed. This oscillation from disengagement towards engagement is important, as it requires ontological thought; in less obtuse terms, its one of the short windows in our daily life, when we think about living in the world. This is getting fairly abstract so back to the Baileys…

Olfactory blindness‘ is the tendency for our minds to drift away from flavour as we eat. As Charles Spense outlines in Gastrophysics, “we mostly do not pay attention to what we taste” because “our brains just do a quality check to ensure that there is nothing wrong”. If “it tastes pretty much as we expected (or predicted)”, we tune out. Like the carpenter and the hammer, we lose sight of the direct elements in-hand or, in this case, mouth. To repeat a line from above: we only pay attention to food when it is broken.

To see the real value of coffee, we should approach every cup like it is curdled. I am not calling for custard-forward cups, but am suggesting we leverage our sensory appreciation to cure our ‘olfactory blindness’. Like the craftsman engaging with the often-ignored characteristics of the hammer, we link taste notes to the mechanisms that create them. Not simply chocolate or fruit but their driving forces: the impacts of soil and rain, the influence of labour and picking, the effect of processing infrastructure, or the force of a farm’s institutional memory.

Allow me to end with Virginia Woolf‘s “Sketches of the Past”. She describes “seeing through the surface to the depths” in what she labels ‘moments of being’. An intensity that breaks through the ‘wool’ of everyday life. In the same way we gasp at curdled milk, we can take glee in the cup and use it to explore the layered depths reaching back to origin. We can initiate a conversation that moves from the sensory to the obstacles and obstructions that perpetuate inequality and unjust power relations in the chain. We actually see the hammer with its contoured wood, forged metal, and history of wear.

I always love Tom’s questions because he is so engaged in the process (plus I get to learn about things like milk pH in answering them). As Woolf states, in endlessly seeking out moments of being, we will “live most fully in the present“. And there is truly nothing curdled or sour in that.


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