Scientists have found that bacteria plays an important role in making coffee taste great by fighting off other micro-organisms.
The key microorganisms for maximum flavour are Leuconostocs and lactobacilli but scientists say other species of microbes may also play a role.
These bacteria are the same ones that turn cabbage into sauerkraut and sourdough starters.
Bacteria multiply on the beans during fermentation as the coffee is often left for up to 24 hours to enhance the taste of the finished drink.
Professor Dr Luc De Vuyst, who conducted the study from Vrije University in Brussels, said: ‘A cup of coffee is the final product of a complex chain of operations: farming, post-harvest processing, roasting, and brewing.’
There are several types of post-harvest processes, with wet processing and dry processing being the most common.
Wet processing is the step that includes this fermentation phase and therefore where the bacteria thrive.
Professor De Vuyst added: ‘It is challenging to draw a causal link between the microbiota and the volatile compounds in the beans, those compounds that contribute to the coffee’s smell, since many of these compounds can be of microbial, endogenous bean metabolism, or chemical origin.
‘However, we did see an impact of the microbial communities, in particular the lactic acid bacteria.
‘They yielded fruity notes, and may have had a protective effect toward coffee quality during fermentation because of their acidification of the fermenting mass, providing a stable microbial environment and hence preventing growth of undesirable micro-organisms that often lead to off-flavours.
‘Furthermore, there is a build-up of the fermentation-related metabolites onto the coffee beans, which affects the quality of the green coffee beans and hence the sensory quality of the coffees brewed therefrom.’
Brewing the perfect of copy has been long investigated by scientists.
Previous studies have found the key to a perfect coffee lies in using hot water and not boiling water.
Using water at 70°C (158°F) is ideal as it does not burn the beans and ruin the taste.
Seven highly trained tasters from the Centre for Sensory Analysis and Consumer Behaviour at Kansas State University sipped various temperatures of coffee made from Arabica beans, Robusta beans or a combination of both.
The researchers also only used purified water to keep out any external tastes.
Panellists also breathed through a moistened warm, clean cloth between tastings to keep their nasal passages clear as to not obstruct the low scents and aromas from the hot beverage.