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The taste of the Amazon

Wolfgang Stuppy
9 November 2012

This month Kew's Seed Morphologist, Wolfgang Stuppy, brings us a post about his recent adventures in the Amazon. Now safely back in the Millennium Seed Bank, he can share with us news of Cupuaçu; the taste of the Amazon!

I am a bit behind with my blog this month, having only just returned from a trip to Manaus (Brazil) where I taught one of my courses on the structural diversity of fruits and seeds. However, while there I encountered another pretty amazing fruit which is worth devoting a blog post to. 


Wolfgang Stuppy with Amazonian fruits
The Amazon is a great place to discover new exotic fruits... and the Tarzan way-of-life (image Wolfgang Stuppy)

When travelling to such far-flung places, one of my passions is to try all the available exotic fruits, most of which I have at least heard about before. However, when I got to Manaus for the first time, I was almost shocked to find I had never heard of cupuaçu (pronounced ‘coo poo asoo’) before. Everyone told me this is the most famous and original fruit of the Amazon basin. In fact, it is considered by both locals and non-local connoisseurs to be the ‘taste of the Amazon’ and in March 2008 it was even declared the national fruit of Brazil. Sure enough, I was burning to try this mysteriously delicious fruit and find out what it actually ‘is’, from a botanical point of view.

 

Theobroma grandiflorum fruit
The fruit of a cupuaçu (Theobroma grandiflorum) growing in the Amazon (image Wolfgang Stuppy) 

What’s chocolate got to do with it?

I was surprised to learn that cupuaçu (Theobroma grandiflorum) is a very close relative of cocoa (Theobroma cacao), the main ingredient in chocolate. Both plant species are indigenous trees of the Amazon rainforest and native tribes have used their fruits as a food source for centuries, if not millennia. The cupuaçu’s shared ancestry with cacao is clearly reflected in their very similar flowers and fruits, although at a height of just up to eight metres, cocoa is dwarfed by its cousin the cupuaçu, which can grow up to twenty metres tall. Incidentally, the flowers of cupuaçu are also much larger and more heavily built than those of cocoa.

 

Theobroma grandiflorum and T.cacao flowers

Left: flower of cupuacu (Theobroma grandiflorum); right: flowers of cocoa (Theobroma cacao) - (image Wolfgang Stuppy) 

These very interesting-looking flowers give rise to large pods with a thick and tough brown (cupuaçu) or yellow to orange (cocoa) rind. Although similar in length (15-35 cm), the fruits of cupuaçu are more plump (up to 16 cm in diameter) and weigh up to 2 kg whereas cocoa pods are more slender and weigh only around 500 g. Inside their hard shell the fruits contain a white or yellowish juicy lump which consists of numerous large seeds covered in soft, fleshy seed coats (similar to the ice cream bean I have blogged about previously). 

 

Theobroma cacao fruits and fleshy seeds
Fruits of cocoa (Theobroma cacao) on the tree (left) and cut in half (right), revealing the fleshy seeds, one of which has already started germinating (image Wolfgang Stuppy) 

What most chocolate eaters won’t know

Chocolate owes its heavenly taste to cocoa butter extracted from the fermented seeds (‘cocoa beans’) of Theobroma cacao. Unbeknown to most people outside South America, the seeds of Theobroma grandiflorum yield a fat very similar to cocoa butter that is also used to make a type of chocolate called ‘cupulate’. Another fact that most chocolate eaters are unaware of is that the soft seed-coat-derived pulp surrounding fresh ‘cocoa beans' is also edible and it tastes delicious, just like the pulp of cupuaçu. However, neither of the two tastes even remotely of chocolate. Disappointing as you may find this - wait until you read about the flavours these fruits yield as they unfold on our palates.

Coca beans in Mexico
Dried cocoa ‘beans’ on display in a market stall in Mexico City

Strange flavours

The pulp of cocoa pods has a fresh, sweet and sour taste that has variously been described as reminiscent of apple, lychee, mangosteen, banana, rambutan or soursop. This sounds pretty exciting, but to me cupuaçu has a far more exotic and unusual smell and taste. In fact, it doesn’t taste like anything else so it is really hard to explain its aroma, but I will try. The cupuaçu’s rich, voluminous flavour is sweet, sour and slightly tart at the same time, with a very pleasant but heavy, fruity component reminiscent of a mix of pear, banana and pineapple. On top of all this, almost like a blanket, lies a rather strong hint of something bizarre, almost artificial, that to me tastes like a mix of aniseed and wintergreen or perhaps the resinous aroma of mango skin. In short, it simply tastes like cupuaçu! Some people claim that cupuaçu also has a hint of chocolate but this seems more of a fantasy inspired by its close relationship to cacao. 

Amazonian superfood

The fresh pulp of cupuaçu is either eaten raw or turned into refreshing drinks, ice cream, pastries, candies, jams etc. Because of its high levels of antioxidants (with anti-ageing effects!) cupuaçu has been touted by some as the next Amazonian ‘superfood’ after the fruits of the açai palm (Euterpe oleracea, Arecaceae) and guaraná (i.e. the seeds of Paulinia cupana, Sapindaceae), both also from the Amazon region. The latter two have already caused some recent ‘health-food excitement’ in North America and Europe. 

 

Guarana seeds and Paullinia pinnata fruits
Left: seeds of guarana (Paullinia cupana) for sale at a market in Manaus. Right: fruits of Paullinia pinnata which look very similar to those of guarana (image Wolfgang Stuppy)

 Some natural history ...

As exciting as the unusual flavours of tropical fruits are, far more exciting is to find out why these fruits have evolved these flavours in the first place. Soft and fleshy tissues in fruits are usually there to attract fruit-eating animals which, in exchange for food, help with seed dispersal. Co-adaptation to a certain group of dispersers is reflected in a distinct set (‘syndrome’) of fruit characteristics.

For example, the yellow- to orange-coloured fruits of Theobroma cacao are protected by a thick, tough rind that is typical of primate-dispersed fruits. In order to open the fruits to get to the sweet pulp, an animal must have a certain strength and dexterity, such as that of monkeys. Although monkeys avoid swallowing the soft, bitter-tasting seeds, they still disperse them. They remove the cohesive lump of up to fifty fleshy seeds from the cocoa pods, and then take their bounty to a safe place in the canopy where they nibble off the luscious pulp.



Monkeys of the amazon: Saguinus imperator subgrisescens

After birds and bats, primates like these Emperor tamarin monkeys (Saguinus imperator subgrisecens) from the Amazon basin are among the most important seed dispersers in rainforests (image Wolfgang Stuppy)

The story isn’t quite that simple with the harder and much heavier fruits of Theobroma grandiflorum. There is no doubt the fruits are adapted to be dispersed by a certain type of animal, albeit one with a very big mouth and perhaps a taste for the extraordinary. However, when trying to match the cupuaçu’s suite of functional traits against present-day dispersers in the Amazon rainforest, there is nothing that really fits.

The available animals are either too small to handle the heavy, hard-shelled fruit, or stuff like this is simply not part of their diet. The fascinating truth is that the cupuaçu’s texture, size, colour, taste and odour indicate that it is a typical ‘megafauna fruit’, adapted to be dispersed by the huge beasts that inhabited the Americas until the end of the last ice age, between 10,000-15,000 years ago. Among them were giant ground sloths, mastodons and gomphotheres (four-tusked elephant-like creatures). Like many other fruits in the Amazon rainforest, the cupuaçu really is a typical gomphothere fruit!

 

anachronistic fruits of the Amazon

Top: horse cassia (Cassia grandis; Leguminosae; the white bar); left: tagua palm (Phytelephas macrocarpa; Arecaceae); middle: stinking toe (Hymenaea courbaril, Leguminosae); right: genipap (Genipa americana, Rubiaceae) (Image Wolfgang Stuppy)

Some more Amazonian megafauna fruits that used to be on the menu of the big beasts of the last ice age. Note the dull colours - large mammals are colour-blind!

For a more detailed explanation of the megafauna dispersal syndrome see my earlier blog about the Texas Mountain Laurel. To readers who have a special interest in fruits that are adapted for dispersal by extinct animals (‘anachronistic fruits’) I recommend the excellent paper by Guimarães et al (2008) which also discusses the cupuaçu. 

Oh, one last thing....

Because of its low melting point, the fat (‘butter’) extracted from the seeds of both cupuaçu and cocoa is also used as a base for suppositories.

- Wolfgang - 

 


 

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Comments

14 August 2013
Comment: 
Hi Julia, About how to become a Seed Morphologist: Be mad enough to do a PhD on 'The Systematic Morphology and Anatomy of the biovulate Euphorbiaceae' (a group now divided between Phyllanthaceae and Picrodendraceae) and be lucky enough that the world created a Millennium Seed Bank just at the right time!
11 August 2013
Comment: 
Random question, how does one become a Seed Morphologist? Thanks.
27 April 2013
Comment: 
The downside of the wonderfully diverse and exciting world of botany is discovering yet another plant I am unlikely to ever see or taste! Thanks for sharing :)
17 April 2013
Comment: 
This is a reply to my dear friend ‘FM’ from Singapore. Very good question as to how anachronistic plants have managed to continue to exist until today despite having lost their co-adapted seed dispersers. The reasons are: A long generation time (they're trees!); limited and fortuitous dispersal by pulp thieves; seed predators and surface water movements facilitating haphazard limited dispersal; as well as usefulness to humans - these are all reasons that allowed extreme anachronists their reduced but continued existence. This is the short answer. I have written a lot more about this subject in my book ‘Fruit – Edible, Inedible, Incredible’, if you are interested (hint, hint!).
13 April 2013
Comment: 
Hi Wolf, I have a question. If the huge beasts had died 10-15 thousand years ago, why haven't the plant, fruit or seed adapted itself to the animals around today? Or have they? I'm sorry I may have overlooked this info in your article.
12 March 2013
Comment: 
Hi Marianne, thanks for your comment. We'll contact you directly to take this forward.
8 March 2013
Comment: 
I have just returned from the Amazon but in Ecuador (as an eco tourist) It was thrilling but although a Biology teacher, I m not an expert. Also went to the Galapagos and looking at your maps I see that Galapagos does not feature. They were very concerned about damage caused to plant species by El Nino a few years ago. I told our guide about the Millennium Seed Bank and I would be interested in passing on the name of a contact either at Kew or Wakehurst Place who could be involved with the scientists working there. Could you advise me please? I live locally (Tunbridge Wells) and am a supporter of the millennium Seed bank. " Friend of Kew"

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