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Bean Properties

RS 2.06 Storage and Ageing

All coffee deteriorates as it ages. There is — as yet — no packaging or storage technique that can entirely prevent beans from fading.

The oxidation of carbohydrates, lipids, and proteins is primarily responsible for coffee’s deterioration as it ages (Abreu et al 2019). Oxidation and other chemical reactions break down these important flavour precursors, causing coffee to ‘fade’ and lose some of its flavour intensity.

Oxidation can also create off flavours in the bean, such as the rancid flavours created when lipids are oxidised. Rancid flavours are strongly influenced by the amounts and kinds of fatty acids present in the coffee, as well as how it is stored (Caporaso et al 2019). Proper storage methods that protect green beans from oxygen and excess moisture can prevent the development of off flavours — but do not prevent coffee flavour from fading over time (Selmar et al 2008).

Green coffee is traditionally stored in jute sacks, which offer virtually no protection from oxygen and humidity in the air

Coffee loses flavour compounds during storage, and the levels of antioxidants and caffeine also decrease. Researchers in Poland, in collaboration with Krzysztof Barabosz from Hard Beans, conducted a study into coffee storage methods and found that after 12 months of storage, caffeine levels decrease by around 40% (Zarebska et al 2022).

Different coffees fade at different rates. For example, Zarebska et al compared two similar-quality coffees from Guatemala, stored in identical conditions, and found that the dry-processed coffee faded less quickly than the washed coffee (Zarebska et al 2022).

The main factors that determine how much flavour a coffee loses during storage are the storage temperature and the moisture content of the bean. High temperatures increase the rate of reactions, such as the Maillard reactions, that take place during storage,