New Research Explains Structure, Taste of Kopi Luwak Coffee

When a Kopi Luwak coffee bean, the world’s most expensive coffee, comes out the other end of a large cat after it’s been eaten by the animal – called a civet or Luwak – the micro-structural properties of the beans are altered, according to new research by a University of Guelph scientist published in Food Research International.

They’re harder, more brittle and darker in colour than the same type of bean that hasn’t been eaten and digested by the three- to 10-pound tree-climbing animal found in Ethiopia and Indonesia. “The changes in the beans show that during transit through the civet’s GI track, various digestive biochemicals are actually penetrating the outer coffee cherry and reaching the actual bean surface, where a chemical colour change takes place,” said Massimo Marcone, author of “Composition and properties of Indonesian palm civet coffee (Kopi Luwak) and Ethiopian civet coffee.” Marcone is an adjunct professor in the Department of Food Science.

Marcone travelled to Ethiopia and Indonesia in 2003 to collect the rare coffee beans that cost $600 a pound. “During the night, the civet uses its eyesight and smell to seek out and eat only the ripest coffee cherries,” he said. “The coffee cherry fruit is completely digested by the Luwak, but the beans are excreted in their feces.”

The internal fermentation by digestive enzymes adds a unique flavour to the beans, which Marcone said has been described as “earthy, musty, syrupy, smooth and rich with jungle and chocolate undertones.”

Since people are paying $50 for each cup of Kopi Luwak, he wanted to determine whether or not they are actually getting a different kind of coffee. In addition to the differences in size, colour and hardness of the bean, he found that the lack of protein in the bean results in its superior taste.

“The civet beans are lower in total protein, indicating that during digestion, proteins are being broken down and are also leached out of the bean,” said Marcone. “Since proteins are what make coffee bitter during the roasting process, the lower levels of proteins decrease the bitterness of Kopi Luwak coffee.”

In the coffee industry, wet processed or fermented coffees are known to have superior flavour to dry-processed coffee, he said. “When coffee cherries are processed through the digestive track, they actually undergo a type of wet processing due to acidification in the stomach and fermentation due to the natural intestinal microflora. Lactic acid bacteria are preferred in wet processing systems. Lactic acid bacteria happen to be major colonizing bacteria in the civet’s digestive track.” The unique Kopi Luwak flavour could be due to the type of wet process the beans undergo in the animal’s digestive tracks, he said.

Although certified blinded human tasters could find little difference in the overall flavour and aroma of the beans, an electronic nose machine could detect that the aroma of the civet coffee beans is also affected.

So it tastes good, but is the coffee, having travelled trough an animal’s digestive track, safe to drink? Marcone found that although civet coffee beans are significantly more contaminated than regular beans, the civet beans on the market are actually quite clean. “Civet beans are typically extensively washed under running water after collection, which dislodges bacteria,” he said.

Marcone has also studied more common foods that have been processed through a living creature’s digestive track, including honey, edible birds’ nests and argan oil.

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