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The post-harvest handling of coffee significantly influences its distinctive flavor profile. Traditional coffee processing techniques include dry, wet, and semi-dry methods. Additionally, the use of enzymes to enhance fermentation during coffee processing has been explored. Specialty coffee, particularly digested coffee, undergoes a unique fermentation process within the gastrointestinal tract. This approach has elevated its status as one of the most premium and exotic coffee varieties globally, boosting its market appeal. Some specialty coffees are processed through the digestive systems of specific animals.

Animal-Fermented Specialty Coffees

Kopi Luwak Coffee

In Indonesia, "Kopi" means coffee, and "Luwak" refers to the Asian palm civet (Paradoxurus hermaphroditus), a nocturnal mammal native to parts of Asia. This civet consumes coffee cherries, producing the renowned Kopi Luwak. Originating from coffee plantations during Dutch colonial times in 1945, Kopi Luwak became highly sought after, with local workers receiving compensation for collecting these unique beans. Due to its rarity, civet coffee production remains limited, with only 250–500 kilograms of wild civet coffee harvested annually. Prices range from $35–$80 per cup, while the beans themselves sell for $100–$600 per pound.

Civet coffee is regarded as one of the most luxurious and scarce varieties, with an annual production estimated at 127 kilograms. Its price can reach $200–$400 per kilogram. Kopi Luwak is widely available in global markets, including Europe, the United States, Japan, Taiwan, and South Korea.

Kopi Luwak Production Process

Palm civets instinctively select ripe coffee cherries by climbing coffee trees. During digestion, the coffee fruit’s pericarp is broken down, leaving the intact beans to be excreted. This natural fermentation process takes approximately 12 hours. The beans are then collected, thoroughly cleaned, and dried under controlled conditions to ensure quality.

Physical Characteristics

The feces of civets contain semi-solid excretions covered by a mucus layer. The appearance of the feces varies based on the animal's diet, including differences in form, color, and texture. Kopi Luwak beans are typically darker and exhibit a reddish hue compared to regular coffee beans.

Chemical Composition

The fermentation process inside the civet’s digestive system reduces the caffeine content in both Robusta and Arabica Luwak coffees. It also imparts a unique aroma to the beans. While roasting minimally affects caffeine levels, it alters the lipid content compared to standard coffee. Kopi Luwak beans contain higher levels of Valine, L-Glutamine, Aspartic acid, and Glutamic acid, which contribute to the coffee's body, balance, acidity, and fragrance. Proteolysis during digestion leads to lower protein content, resulting in shorter peptides and amino acids that reduce bitterness in Kopi Luwak coffee.

Ivory coffee (Elephant Dung Coffee)

Process of Ivory Coffee Production (Elephant Dung Coffee)

Ivory coffee is derived from Arabica coffee beans that have passed through the digestive system of the Asian elephant (Elephas maximus). During digestion, the coffee cherries ferment inside the elephant's alimentary canal for a duration of 12 to 70 hours, alongside other consumed food items. The beans are then retrieved from the feces and undergo a series of steps, including washing, drying, hulling, and sorting, to produce high-quality green coffee beans.

Chemical Composition of Ivory Coffee

Four distinct chemical markers have been identified in ivory coffee: 3-methyl-1-butanol, 2-methyl-1-butanol, 3-penten-2-one, and 2-furfurylfuran. These compounds are critical for ensuring authenticity and maintaining quality standards. Ivory coffee also boasts a higher Total Phenol Content (TPC) compared to conventionally processed coffee. Its tannin levels and antioxidant activity are significantly enhanced due to the bio-processing within the elephant's digestive tract.

Jacu Coffee

Jacu coffee, a unique specialty from Brazil, is made from coffee beans processed by the Jacu bird (Penelope spp.), a frugivorous bird native to the Atlantic rainforest. These birds consume sweet coffee cherries rich in sugar content, which are then excreted with the seeds intact. Although typically forest dwellers, Jacu birds forage in open fields as well. This coffee is highly esteemed, particularly in Espirito Santo State, and ranks among the most expensive specialty coffees in the region.

 Monkey Parchment Coffee

Monkey Parchment Coffee, sometimes referred to as monkey spit coffee, is a less-explored specialty variety originating in India and Taiwan. Monkeys consume ripe coffee cherries, stripping the pulp and either spitting out or excreting the seeds. In some cases, they are fed cherries alongside other foods such as bananas, leafy greens, sweet lime, and nuts. The monkeys often suck out the pulp juice and retain the seeds briefly in their mouths before spitting them out. This unique processing imparts a superior flavor profile to the coffee compared to regular beans.

Role of Gut Microbes in Specialty Coffee Processing

Lactic acid bacteria present in the gastrointestinal tracts of animals play a key role in the fermentation of specialty coffees. These microbes have enzymes that break down proteins and pectins, yielding amino acids and simple sugars that influence the coffee’s taste during roasting. Additionally, some microbes, such as Methylobacterium populi, Klebsiella quasipneumoniae, and Raoultella ornithinolytica, are capable of degrading caffeine.                                                                                                                                                                              

References: 

Raveendran A, Murthy PS. New trends in specialty coffees - "the digested coffees". Crit Rev Food Sci Nutr. 2022;62(17):4622-4628. doi: 10.1080/10408398.2021.1877111. Epub 2021 Jan 28. PMID: 33506696.