When we think about coffeewe are spontaneous to distinguish between that traditionalprepared with the mocha or the machine, and that instantwhich melts into hot water. But the biggest difference between the two lies in the solubility: In fact, the instant coffee is soluble in water, while the ground one does not.
If we tried to add hot water to the ground coffee, we would immediately notice that there dust remains suspendedand the drink would become impossible to drink. Instant coffee, however, It melts completely in the watercreating a ready -to -drink solution, without residues.
How do you get soluble coffee? Liophilization
But then in instant coffee, particular substances are added to make it soluble? You will probably have thought of yes, but in reality it is not so: the process – employed by companies like Nestlé, with its Nescafé brand – is entirely and solely physical, and it is the process of liophilisation.
The procedure begins with the roasting and grinding of coffee beans, exactly as it happens to obtain traditional coffee. Then the coffee is extracted with the water, as happens with a mocha: it is then obtained of liquid coffee. At this point, liophilization comes into play: Liquid coffee is first frozen at -40 ° C in a special freezer. Then, this frozen coffee is transferred to a dryer Where, through emptiness (low pressure), water passes from solid state to gaseous state without going through the liquid state. This phenomenon is called sublimationwhich is the same that we observe when we open the freezer and we see a sort of “smoke”: it is the ice that becomes steam. Thanks to this process, all the water contained in the coffee is removed, leaving a product completely dry which is then ground and packaged.
But then do the properties of instant coffee change with liophilization?
At this point, you are probably wondering if this process does not alter the organoleptic properties of coffee. Well, here too the answer is negative, because taking place at low temperatures, freezement allows keep color, flavor, perfume and aromas unchanged of coffee.
In this regard, the packaging: The aluminum film used for packaging, in fact, is designed to preserve aromas and prevent oxygen and humidity from altering the properties of the product. The next time you prepare an instant coffee, therefore, think of the wonders of the physics behind it.
