Kitchen Project #162: An Introduction to Tropical Fruit

with Louis Thompson

Hello, and welcome to today’s edition of Kitchen Projects.

Today you will be taken on a journey into the world of tropical fruit by Louis Thompson, pastry chef at Spring. If you read his piece on finding the perfect peach in London last summer, you’ll know he’s the ideal guide. I’m marvelled by his words & the visuals within and very excited for you to dive in with him.

Over on KP+, Louis has shared a recipe for passionfruit custard creams, an ode to the his native australian yo-yos and a celebration of these bright, delicious fruits. Click here for the recipe.

What’s KP+? Well, it’s the level-up version of this newsletter. By joining KP+, you will support the writing and research that goes into the newsletter (including the commissioning - and fair payment - of all the writers), join a growing community, access extra content (inc., the entire archive) and more. Subscribing is easy and only costs £6 per month or £50 for the whole year. Why not give it a go? Come and join the gang!

Love,
Nicola

An Introduction to Tropical Fruit

by Louis Thompson

Did you know a majority of the fruits we eat in England come from just one family? Plums, peaches, apricots, cherries, quinces, apples, pears, strawberries, raspberries, and blackberries all belong to the Rose family. As a chef who is primarily guided by the seasons, I’ve dedicated myself to fruit, though really only a very small subset. Peaches and pears are fantastic attractions, but if you never branch out from there it’s easy to quickly find yourself in a repetitive fruit cycle. There is a striking lack of diversity in the fruit we eat, talk, and hear about considering the bounty and diversity of nature’s gifts: there has to be more than winter citrus, spring berries, and summer stone fruit.

At this time of year, our fields and grocers are particularly barren. Rhubarb and citrus are holding down the fort, though the end of their seasons is approaching, and little else will show up between them and distant June strawberries. Living in London, it is now that I and many other chefs feel able to indulge in the capitalist megalopolis of it all (as a treat), looking further afield to the tropics to fulfil my fruity needs and wants. Since there’s not a lot growing locally, and we’re importing our blood oranges anyway, it’s the perfect opportunity to try new things.

While tropical fruit certainly has its seasons, deep in the temperate zone in England we can’t count on any local biodynamic pedigree specimens. Tropical regions have different seasons entirely - broadly categorised as wet and dry seasons (this will change vastly depending where you go - some places articulate six different seasons to characterise the difference in rainfall and temperature). Furthermore, in their native habitats many tropical fruits will bloom year-round, making them an ideal candidate to import during our time of need.

Owing to their origins in places of abundant sun or water (or both) tropical fruit has a reputation for being particularly sweet, flavourful, and/or juicy - there is more plant food for it to do plant things with. Having learned to cook in London, it was easy to be swept up in a eurocentric approach to ingredient-led cooking which reifies the four seasons we’re all familiar with. When I thought about my home in Australia, there was a sense of missed opportunity to practise the same philosophy of ingredient-led cooking with nearer, dearer, and more unique fruits.

On a recent trip home to Australia I took the opportunity to fully dive into this curiosity the only way I know how: with ice cream. I’ve done a few ice cream experiments before, with berries and citrus, turning a family of fruits into a suite of ice cream flavours to better discern their character and flavours. The intense flavour experience of ice cream combined with the opportunity to get hands on with the fruit and see how it behaves is the perfect learning environment to give myself a tropical primer.

I’ve long believed that if you want to know what something tastes like, turn it into ice cream. Scientifically speaking, the Food Quality and Preference Journal tells us “Ice cream is a highly complex food matrix, containing proteins, fat, sugars, air, minerals, etc. and countless interfaces between the different constituents. During consumption it undergoes phase changes from solid to liquid. This … provides an important matrix for investigating dynamic flavour intensity”. In simpler terms, it is the slow and controlled release of flavour directly on the palette; flavour is taste plus aroma, and since ice cream is frozen, volatile aromatic compounds (‘flavonoids’) are inert until they are on your tongue, where they effectively ‘bloom’. Kitty Travers, owner of La Grotta Ices and London’s doyenne of fruity ice cream who has been described as making ice cream that is “metaphysically slippery” (where transforming fruit into ice cream makes it somehow more itself), adds that you are literally painting the flavour on your tongue, with little other textural distraction for a pure flavour experience. As someone who is more enthusiastic than experienced in the domain of exotic fruit ice cream, I spoke to Kitty to gain better insight into the project. She echoed the other worldly appeal of the tropics, describing “mind-altering flavour” that awaited me.

On approaching unfamiliar fruit, Kitty offered the following: “If I were more technically-minded i’d use a computer program to work out the fibre, the protein (if any) and the sugar content in the fruit, then that way I’d know the quantity of fat, water, dairy, eggs and sugar et cetera that I then need to add to achieve the perfect texture. But I’m a bit old-fashioned, and aim to do do the same thing by tasting and smelling instead”

Kitty reminds us that food is both a science and an art, something easily forgotten in the notoriously technical realm of ice cream. They say knowledge is knowing a tomato is a fruit, wisdom is not putting it in a fruit salad. With that in mind, I prefer to be guided by flavour above fat-sugar-protein matrices; If my ice cream is less creamy and more icy, so be it. People love granita, icy poles, and slushies, so why reject those characteristics now if it means superlative flavour and purer expression of the fruit itself?

For this project, I chose ten different fruits to work with: Kiwi, Dragonfruit, Papaya, Passionfruit, Cantelope, Pineapple, Guava, Banana, Lychee, Rambutan, and Soursop. Depending on the flavour, texture, and character of fruit I used anywhere between 10-60% dairy to fruit juice/puree. I prepared a large batch of creme anglaise (custard) and blended it to taste with each fruit. In most cases, fruit was processed by blending and passing raw to preserve maximum fresh, lively, complex flavour. Puree was then combined with custard, and seasoned with sugar and lime juice to taste to produce something in between ice cream and sorbet. When a fruit puree had less body and more intense flavour, more custard was used, where less custard was used for fruits with delicate flavour and/or already rich texture.

The Results

Soursop

Ratio: 75% soursop, 25% custard

One of the more peculiar fruits on this list, its reputation preceded it. Belonging to the same family as custard apples, sweetsop, and cherimoya Jane Grigson was so enthused that in 1982 she proclaimed “all three will be more familiar to our children, I am sure”. The flesh of the fruit is usually spooned out and eaten raw, or can be sieved to make a natural custard. As for the flavour, well, it does what it says on the tin: it tasted like a sour apple flavoured custard. For the purpose of ice cream making, I gave the flesh a quick blitz to break it up and strained out the seeds. The texture was exactly like a pouring custard.

Among friends who tasted, this was a popular favourite for the complexity and novelty of its flavour. Beyond its notes of apple and custard, it had a sort of sour funk. It reminded one friend of Vietnamese dipping sauce which had sweet, sour, salty, funky notes.

Application: I would take Grigson’s advice and use it to make a ready custard, which can be zhushed up with a dash of cream, sugar and lime. Try it poured over an apple crumble!

Lychee/Rambutan

Ratio used: 50% lychee/rambutan juice, 50% custard

Members of the soapberry family Lychees and Rambutan have an almost indistinguishably similar flavour; I would liken them to peaches and nectarines in this regard. After peeling away their readily removed dragon-like skin, the fruit inside has a semi-translucent juicy white flesh which readily separates from a single inner seed. With their taut skin and juiciness, they are almost blister-like in texture. They are absolutely delicious to eat fresh and raw with a balance of sweetness, sourness, juiciness and floral aroma.

When used for ice cream, they were blended and strained to produce an exceptionally flavourful juice. It was a crowd favourite. The liquid nature of the fruit resulted in an extremely light and refreshing ice cream, with superb flavour payoff. This was one of my favourites. What became apparent in ice cream form is the slight ‘funk’ of the fruit. This was a fantastic ice cream and I highly recommend using lychee juice in your cooking.

Application: Granita or jelly would be particularly amazing refreshing desserts.

Banana

Ratio: 50% banana, 50% custard

I used ladyfinger bananas, a smaller, sweeter, and denser relative of the standard Cavendish bananas most commonly found in supermarkets. I used very ripe bananas and puréed them with custard.

This had perhaps the richest texture and most complex flavour. Ladyfingers, like many non-cavendish bananas tend to be denser and more starchy (which down the line means more sugar and flavour esters), making for a thick custard and dense ice cream. Banana is already deliciously creamy so adding dairy enhances this quality - it is also so richly flavoured that combining it with dairy helped to open the flavours and let them sing - much like adding water to whiskey It hardly needed to be said, but never overlook the humble banana and if you come across a new variety, take it!

Application: Embrace any banana cream dessert - I’m now dying to make a banana cream pie or cheesecake with banana as part of the custard, not a separate element.

Guava

Ratio: 40% guava, 50% custard, 10% poaching liquor

This was my waterloo. While guava is not commonly found on fruit stands in this part of the world, guava products like jam and cordial are relatively easy to find in shops like Sainsbury’s. It is very popular, and famed for its intense aroma likened to fig and peaches. Sadly, due to a lack of good timing and knowledge I was using guavas which were underripe and out of season. Your best bet is in late summer, searching with your nose. Go for fruit that has some blemishes and imperfection - picture perfect and it’s probably underripe.

For ice cream, I poached them in a 2:1 (water:sugar) syrup until tender (in my case ~10 minutes. Most sources would suggest 3-5 minutes for ripe guava) and puréed them. If you are lucky enough to have properly ripe guava that is soft enough to puree without cooking, then skip this step. Their texture is variously described as granular and woolly depending on how ripe or cooked it is. I used a healthy glug of their poaching liquor to loosen and season the custard base.

While I wasn’t happy that I had properly expressed the fruit through cream with its insipid colour and grainy texture, I was shocked at the amount of flavour these guavas delivered despite their second-rate state. The takeaway here is that guavas are capable of delivering serious flavour, even if not at their best. If you happen to come across some a) use them! b) let them ripen for a few days until they are super smelly. You may also come across feijoas, which resemble a smaller more oblong guava. They also go by pineapple guava and are like smaller, special supercharged versions. Don’t pass them up!

Application: Apart from ice cream, I would do nothing more than lightly poach and serve with whipped cream.

Cantaloupe

Ratio: 40% melon, 60% custard

Cantaloupe was my chosen representative from the melon family. Compared to watermelon, its sweeter more perfumed flavour and richer texture were more appealing to cook with. While it is certainly not the most exotic fruit on this list, its application in ice cream was revelatory. Not typically thought of as a fruit to cook with, balancing its sweet juiciness with the gentle embrace of cream produced a superlatively refreshing ice cream.

Application: For the love of all that is good, put cream with your melon! If you don’t have an ice cream machine but are inclined to make semifreddo, that is a fantastic application. Alternatively, simply purée ripe melon, add a squeeze of lime and a dash of sugar, and add to whipping cream - 15% by weight is a good guideline. There you have the easiest wow-factor cake topper for a simple summertime picnic sponge.

Pineapple

Ratio: 67% pineapple juice, 33% custard

I was lucky enough to get my hands on a beautifully ripe and fragrant pineapple, and its clarity of flavour was exceptional both out of hand and in ice cream. This was an instance where it feels like nothing is lost, but rather enhanced with the addition of cream and eggs. Cutting it open will test your knife skills - cut away the skin generously to remove all nubbins (If you are just juicing you need not worry about nubbins since they’ll be strained out), slice into quarters and cut out the tough inner core.

Application: If you come across a pineapple that is golden, with a healthy green stem, and above all fragrant: buy it. The pungency of flavour makes it easy to apply anywhere. I’m particularly attracted to the idea of a pineapple galette a la Natasha Pickowicz

Passionfruit

Ratio: 33% passionfruit juice, 67% custard

Using passionfruit to flavour things is much like lemon: it’s as easy as it gets. With over fifty flavour volatiles, it is one of the single most strongly flavoured fruits, its pulp acting like a ready-to-go flavour extract. You can simply cut them open and push the pulp through a sieve, or if you’re processing a large amount loosen everything up with a quick blitz for easier passing.

The main challenge is managing a tart flavour without overwhelming it with sugar. My advice is to simply let the passionfruit be sour. We are used to sweet passionfruit flavoured drinks et al. but when using the fresh fruit, season with sugar to amplify rather than manipulate its flavour.

If there is any fruit on this list you should use to venture into the tropics, let it be passionfruit. They are more commonly grown in Europe, and even have a second season this time of year. Go get it!

Application: You can add it to almost anything - cake batter, custards, or even as a garnish akin to a squeeze of lemon or lime.

Passionfruit Custard Creams on KP+

Papaya

Ratio: 80% papaya, 20% custard

This was a fruit I was particularly interested to get my hands on. Often described as unpalatable and with a funky smell sometimes likened to… vomit, conventional wisdom says that the plentiful addition of lime provides the necessary balance to bring its flavour into harmony. I did not find this to be the case - the papaya I ate was pleasantly sweet and with just a breath of bitterness. I would liken it to mango and peaches in its soft creamy fruitiness, with the slightest savoury edge

Application: Papaya purée was pleasantly thick and creamy, and required little seasoning to make its flavour sing. Eat fresh slices with dollops of cream or lighten a papaya puree with a small amount of whipped cream for an exotic pastry filling/topper - this time using just 15% cream to papaya. Lime spiked rhum-baba with papaya cream anyone?

Dragonfruit

Ratio: 90% dragonfruit, 10% custard

One of the more strikingly, beautifully bizarre fruits on this list. I haven’t forgotten the days of early iPhones where a dragonfruit was a holy grail on the game Fruit Ninja. It seems to most perfectly typify the exotic beauty and appeal of tropical fruit. Botanically related as a cactus and similar in texture to a prickly pear it has very watery, not exceptionally sweet flesh. It is most like its more familiar water-loving fruit, watermelon. When blended and strained it produced a thin juice, so I opted to add back in its fibrous pulp and seeds to increase both body and flavour. Dragonfruit probably had the lowest flavour payoff on this list.

Application: Eat it fresh with a dollop of cream and some lime and sugar sprinkled over for a light and simple dessert or snack. It might not electrify your taste buds, but it certainly will your and your friends’ eyeballs. And I sincerely believe that’s just as good a reason to buy and eat it - eating is a multisensory experience after all.

Kiwi

Ratio: 45% Kiwi, 55% custard

This was a standout for me, perhaps my favourite. I absolutely adore kiwi and lament its relegation to mediocre supermarket fruit salads. For this I used standard green kiwis, though golden kiwis are becoming increasingly common and with their sweet, reliable flavour they prove their worth at the fruit stand.

Application: This is another fruit with a strong flavour payoff. The tartness of the kiwi seemed more apparent in this distilled form, so it’s an attractive element in baking projects which call for balance against sweetness and richness. The classic Australian pavlova is after all commonly served with slices of Kiwi. Alternatively I think it would make a fabulous curd - just be wary that you may not get the same thick set without citric acid.

Conclusion and Findings

As initially suspected, it is clear that these fruits are not as alien as they may seem. Anatomical differences proved superficial if relevant at all: where papaya resembled peach and dragonfruit watermelon, oddities like guava and lychees were more than manageable to approach using basic technique and common sense and if nothing else, a quick google.

What struck me most were differences in pure flavour: many of these fruits had more complicated flavour profiles than the standard sweet/acidic balance we anticipate in most fruits. In particular, papaya, lychee, rambutan, and soursop possessed savoury qualities in their own ways.

An English friend of mine, unfamiliar with lychees, was adamant that they didn’t like ice cream made from their juice as to them it tasted like baby sick. I have even heard some extremely discerning chefs say they detect a note of bile in passionfruit. Problematic vomit comparisons aside, it seems clear that these fruits possess far more diverse flavour notes than we are used to in our humble Rose family, and appreciating this complexity is a matter of familiarity.

My only general theory about tropical fruit is that coming from regions defined by abundant heat, sun, and rain, they have the ability to produce in equivalent abundance sugars and water, making for sweet, flavourful, juicy fruit. There is something to be said about cultivation and context though - why is it that more complex, even savoury qualities only seem apparent in fruits from further away?.

Fruits such as strawberries and peaches have been aggressively cultivated for hundreds of years. For a long time, a perfect, sweet specimen of fruit was an invaluable prize - cheap commercial sugarcane is only a relatively recent luxury. The strawberry for example arrived in France from Chile in the 18th century and was domesticated for hundreds of years as a royal project before we arrived at the sweet, familiar gem we have now.

While I can’t trace the botanical lineage of all these fruits, what is apparent is that the idea of fruit primarily as a sweet treat is… constructed. There are many regions of the world where mango is enjoyed with salt, chilli, and lime. Or green papaya enjoyed with a sauce comprising sweet, sour, salty, spicy, and fishy notes. Native Australian fruits like the ooray plum are commonly described as intensely sour and even salty, owing to the arid ground they grow in. I mean look at the ubiquitous umami appeal of tomatoes!

There was no single flavour profile which characterised the fruit I tested; the only recurring theme was complexity and novelty. Stepping out of the rose family of fruits, it is clear that fruit can be more than what we think it is and ultimately fruit is what we make of it, ice cream or otherwise. Next time you’re at the fruit stand and see something strange and unfamiliar, let your piqued interest become curiosity, not caution and embrace some mind-altering flavours.

---

You can keep up with Louis’ recipe development, special creative commissions and work at Spring via instagram @_louisthompson