The Fermentation Trail: A Day in the Mae On Valley

Fermentation is time used as an ingredient. It sits among the forces shaping dining in 2026 and 2027, according to MICHELIN inspectors, from house-made ferments prepared weeks ahead at Baan Tepa in Bangkok to slow processes that build depth without weight. In the Mae On valley the same idea runs through a landscape, not a menu.

Coffee ferments. Cacao ferments. In the north, tea ferments into miang. The vines at the Vineyard were planted in 2025, and wine is the ferment still to come. This trail follows all four across two sites, 1.5 kilometres apart, 30 minutes from Chiang Mai city centre.

One cast, four crops

The same small cast does the work in every cup and bar. Yeasts turn sugar into alcohol. Lactic acid bacteria soften the acidity. Acetic acid bacteria, which need air, finish the job where air is allowed in. The craft lies in deciding how much oxygen each of them gets, and for how long.

Coffee, cacao and tea each answer that question differently. Cacao ferments in a pile and needs air at the right moment. Miang ferments sealed away from it. Coffee does either, depending on the lot. The trail shows all three approaches in one day.

Morning: the Roastery

Start at the Roastery. Coffee begins as a cherry, and what happens to the cherry before roasting shapes the cup. In a washed process the beans ferment in water for two days, then dry in the sun. In a natural process they dry inside the fruit and take on its sugars.

Anaerobic processing goes a step further. Whole cherries or depulped seeds go into a sealed tank, where microbes feed on the sugars in the mucilage. The carbon dioxide they release pushes out the oxygen through a one-way valve. According to Seattle Coffee Gear, the ferment runs from 24 to 120 hours. An anaerobic natural keeps the fruit on the bean and leans towards rich fruit and strong fermentation character. An anaerobic washed lot shows more clarity. Tropical fruit such as pineapple, passion fruit and mango turns up often in the cup, and the lactic acidity is rounded rather than sharp.

The method known as carbonic maceration is a specific form of this, borrowed from winemaking. In the winery, whole bunches ferment in a tank filled with carbon dioxide, which draws flavour from the skins without their harsher tannins. In coffee, whole cherries are sealed in the tank and carbon dioxide is pumped in to drive out the oxygen. Barista Magazine notes that the tanks need one-way valves and that careful cupping is essential. Without that control, the same process produces astringency, dryness and bitterness.

The wider trade is moving this way. London roaster Climpson and Sons calls fermentation-forward coffees a 2026 coffee trend that looks set to stay, and names a mosto-fermented lot from northern Thailand among the two experimental coffees it roasted in 2025. The same piece says these coffees depend on infrastructure, scientific tools and training, which keeps them largely with established producers.

The north has a short history with coffee. Chiang Mai Citylife reports that Prince Bhisadej Rajani decided in 1972 to introduce Arabica to the northern mountains, and that by 1974 several strains were growing across hill stations. The best sites turned out to be places where opium had once grown. The same Citylife feature says the four northern provinces now grow more than 20,000 rai of coffee. Experiments with fermentation are a recent chapter in a story that is only five decades old.

The Roastery runs an experimental series built on carbonic maceration and yeast fermentation. Its signature coffees show the range. Strawberry Fields Forever comes from controlled fermentation and carries pink guava, wild strawberry and cedar pineapple. Drunken Sailor uses natural yeast processing before a light roast, with rum-raisin, dark chocolate and dried fruit in the cup. Tasting the two side by side makes the point of the whole trail: one crop, two decisions about microbes, two different drinks.

The Roastery offers guided tastings that compare roast levels, origins and brewing methods, and the roastery experience article walks through a visit. The Roll Bar bakery is on the same site.

Late morning: the chocolate lab

Every bar begins with fermentation. Freshly harvested cacao beans sit in a sweet white pulp, and the pulp does the first work. The sequence follows three phases, as described by the American Society for Microbiology in May 2026. In the first hours the pulp creates an anaerobic environment, rich in citric acid and short of oxygen. Yeasts consume the pulp sugars and produce ethanol. The ethanol shifts the community towards lactic acid bacteria, which convert the citric acid into lactic acid. Farmers then turn the beans every 24 to 48 hours. The air this lets in brings acetic acid bacteria, which oxidise the ethanol into acetic acid. Throughout, the microbes build the compounds that become chocolate flavour, among them pyrazines for roasted notes, aldehydes and esters for fruit.

The smell shifts from fruit towards vinegar as the pile heats. According to one craft chocolate maker, this runs for four to five days, and the beans turn from bitter purple to brown as flavour develops.

Thailand is a young cacao country. In 2017 Chiang Mai Citylife reported that Maejo University had bred a hardy, high-yielding hybrid called IM1, and that cacao pods in the north can be picked every two weeks across the year. The same 2017 Citylife report points out that most cacao grows within about 10 degrees of the equator, while Chiang Mai sits at 18 degrees north. Siamaya Chocolate CEO Neil Ransom told Kennedy's Confection in 2026 that Thailand has around one hundred craft chocolate makers and that fermentation and drying practices vary widely between farms. He also described a community enterprise in Lampang that ferments beans for small farmers across the north. The care taken at this step varies by farm and region, The Nation reports, and it shapes both the flavour and the price of the finished chocolate.

The chocolate lab turns single-origin Thai cacao into bean-to-bar chocolate through roasting, cracking, winnowing, grinding, conching and tempering. Each stage has a job. Roasting develops flavour and loosens the shell. Cracking and winnowing remove the husk. Grinding turns the nibs into liquid chocolate. Conching smooths the texture over hours. Tempering sets the crystals so the bar snaps and shines. Skugga's own account of Chiang Mai's cacao culture describes the process as three days of rhythm and rest. The result earns praise for its depth and complexity from Time Out Chiang Mai. The Chocolate Bar puts the lab's work on the counter.

Skugga's ceremonial cacao leaves the bean whole. The beans are ground whole and nothing is removed, so the drink tastes closer to the bean. Gatherings take place across the farm, the vineyard and the gardens.

Midday: the Tea Bar

Northern Thailand has its own ferment, and it is tea. Miang is fermented Assam tea leaf, chewed after meals for energy and as a palate cleanser. Chiang Mai Citylife reports that the tea has grown in Lanna for at least 500 years, and that its exact origin remains unclear. The village of Pa Miang in Lampang province takes its name from the forest tea gardens where the leaves grow in the shade of large trees. Each September the village holds a Tan Miang ceremony, offering fermented tea at the temple.

The method sits at the opposite end of the oxygen question from cacao. A laboratory study in Frontiers in Microbiology describes the steps. Young leaves are steamed for three hours, cooled on bamboo trays, wrapped in banana leaves and packed tightly so no air reaches them. Fermentation then runs in the dark at ambient temperature, from weeks up to months. Traditional producers ferment the leaves in bamboo baskets for anywhere from several days up to a year. Lactic acid bacteria dominate throughout, with Lactobacillus plantarum the leading species, and yeasts of the Candida genus take second place. Two routes exist. One begins with five to ten days of fungal growth in air, followed by a few days sealed. The other goes straight into the sealed ferment.

Chiang Mai University's miang research centre, founded in 2017, keeps stations in Mae Taeng, Doi Saket and Mae On, according to a 2022 report in Chiang Mai Citylife. The Mae On station is at Ban Mae Kam Pong. The centre had analysed 44 types of miang from 22 traditional producing locations. Its director, Dr Chartchai Khanongnuch, describes two broad styles. Eastern miang uses older leaves and tastes sour. Western miang uses younger leaves and leaves a bitter aftertaste. The valley sits inside a working research landscape for the oldest ferment in the region.

The Tea Bar on the Farm serves estate-grown teas from forest gardens on the same site, from delicate whites through to green. Cacao husk tea is brewed from the roasted shells of the chocolate lab. Guests blend their own from ingredients on the counter. A half-day tea and coffee workshop follows both crops from plant to cup. Miang reaches the markets of Lampang and Chiang Rai from villages such as Pa Miang, and the Tea Bar offers the other end of the tradition, tea at its freshest.

Lunch: The BBQ at Skugga

Lunch is a pause between ferments. The BBQ at Skugga serves grilled plates and sandwiches. The afternoon moves 1.5 kilometres to the Vineyard.

Afternoon: the Vineyard

The last stop is the one still to come. The vines at Skugga Estate Vineyard were planted in 2025, at 410 metres in the Mae On valley. No wine has been produced, and the wine programme is developing.

Vines behave differently in the tropics. Research from Brazil's agricultural research body Embrapa on tropical grape growing explains why. Without a cold winter the vine has no dormancy, so it keeps growing whenever water and nutrition allow. Pruning sets the rhythm instead, and a productive cycle runs 90 to 150 days. The same research favours higher ground in the tropics, where milder temperatures slow vine and fruit development, and where mild days and cool nights help build colour and aroma in the grape. Altitude is the quiet variable in this valley, and the young rows are where it will be tested.

Walk the rows and the trail makes its argument. Coffee, cacao and tea are ferments in motion. Wine is the one ahead. The slow wine article sets out the thinking behind the pace.

The Vineyard holds the estate gin and the Festival Hall. Fine dining runs across two rooms, Upstairs at The Vineyard and Downstairs at The Vineyard. Dinner there closes the day.

Planning the trail

Allow a full day. Stay a night with Skugga Villas and Suites and there is no drive back to the city. Workshops need booking ahead through the workshops page, so settle that first and plan the rest around it. Reserve the Vineyard restaurant ahead. Check opening days before you set out.

Ask one question at each stop: how long did this ferment run, and what would change it. The Roastery will answer in hours and tanks. The chocolate lab will answer in days and piles. The Tea Bar will answer in leaves and seasons. The answers explain the cup.

The fermentation trail: quick answers

What is a fermentation trail?

A route between producers where fermentation shapes what they make. In the Mae On valley it links coffee, chocolate and tea on the Farm with the young vines at the Vineyard.

What is carbonic maceration coffee?

Coffee processed by sealing whole cherries in a tank filled with carbon dioxide, a method borrowed from winemaking. The Roastery uses it in its experimental series.

How is anaerobic coffee different from carbonic maceration?

Anaerobic describes any ferment held without oxygen. Carbonic maceration is one form, in which whole cherries sit in a carbon dioxide environment, as whole grape bunches do in the winery.

How long does cacao fermentation take?

Craft makers describe four to five days. The pile is turned every 24 to 48 hours so that air reaches the beans at the right stage.

What is miang?

A fermented tea leaf from northern Thailand, eaten after meals. The leaves are steamed, packed away from air and left to ferment for days up to many months, depending on the producer.

Has Skugga produced wine?

Not yet. The vines were planted in 2025 and the wine programme is developing.

How far is the trail from Chiang Mai?

The estate is 30 minutes from Chiang Mai city centre. The Farm and the Vineyard are separate sites, 1.5 kilometres apart.