TOGETHER IN THE VAT: WHAT IS CO-FERMENTING AND WHY BOTHER?

Co-fermentation is one of the most quietly radical practices in winemaking. On paper, it’s simple: more than one grape variety, red and white or otherwise, is fermented in the same vessel at the same time. But behind that practice lies a long, layered history—one that spans necessity, tradition, rebellion, and, increasingly, a search for equilibrium in the vineyard.

Unlike blending, which happens after fermentation, co-fermentation asks the grapes to coexist from the beginning. It’s a marriage of variables—sugar levels, skins, acids, native yeasts, colors, textures, temperatures—that cannot be undone. The results are unpredictable, but when it works, the outcome can be greater than the sum of its parts. In fact, done by the right professional, it often is.

Historically, co-fermentation wasn’t always intentional. In older vineyards—especially in Portugal, the Rhône Valley, and parts of northern Italy—different grape varietals were grown haphazardly in the same plot. White and red vines might have been interplanted to stretch yields or add freshness, without much ceremony. Yet some of the world's most enduring wines—think Côte-Rôtie or Douro’s traditional palhetes—owe their distinctive character to these accidental, or at least intuitive, partnerships.

In more recent years, the practice has reemerged with the expansion of the natural winemaking movement. Co-fermentation offers winemakers a way to deepen complexity without manipulation. It can soften tannins, sharpen aromatics, stabilize color, or reflect the field’s diversity more honestly. In the hands of natural winemakers especially, it becomes a celebration of process over precision—a commitment to letting grapes speak for themselves, but collectively, rather than in isolation.

This month’s selection brings together three wines that are co-fermented in very different ways: one rooted in heritage, one born of experimental revival, and one pushing boundaries in a new-world setting. Each of them is a conversation in a bottle—between grapes, between traditions, between human intent and natural spontaneity.

REVIVING WHAT WAS ALMOST LOST

In the high-altitude plains of Mendoza, Argentina, wine production has flourished thanks to ideal conditions: intense sun during the day balanced by cool nighttime temperatures that slow ripening and preserve acidity, resulting in full ripeness without tipping into flab. Mountain conditions also shield crops from parasites, guaranteeing stable, consistent, and large-volume production. Over time, these conditions attracted large-scale viticulture and industrial production, with international demand focused largely on Malbec. But now, a handful of winemakers are looking backward—toward pre-industrial methods and the first Vitis vinifera that thrived here after their arrival from Europe.

Inmemorial is one of those projects. The founders, Norberto Páez and Sebastián Bisole, believe that before stainless steel and French oak, there were indigenous techniques and grapes that flourished with ancestral know-how. Their approach blends agrarian humility with an experimental edge. At its heart are the grapes brought by Spanish missionaries—adapted over centuries to the local terrain, then cast aside by modern commercial trends. Though its name references the past, Inmemorial is not only about nostalgia; it’s about reconnection: to genetic heritage, to forgotten methods, and to the kinds of wines that once flowed freely across the Andes—long before the market defined what “Mendoza” meant. But here, that reconnection is filtered through modern sensibility and craftsmanship. The result is a wine that couldn’t have been made anywhere else, or in any other time.

Featured August Amaro Wine Club Co-Fermented Wine: Inmemorial Viñedo Ancestral Amber Wine (2024)
VARIETALS: 30% Torrontés Riojano, 30% Pedro Ximénez, 40% Moscatel Rosado

In this wine, the winemakers co-ferment three uncommon grapes:
* Torrontés Riojano, a floral, perfumed grape with a citrus edge
* Pedro Ximénez, often sun-dried to make dessert wines, but used here in a dry, textural form
* Moscatel Rosado, a pink-skinned aromatic Muscat varietal with a reddish tint that contributes lift and hue.

norberto-paez-e-sebastian-bisole-enologos-e-socios-da-paso-a-paso-300x300.jpg

Norberto Páez and Sebastián Bisole

Norberto and Sebastián in their vineyards

Although previously referred to as “uncommon,” these three varietals were among the first grapes cultivated in the region in the 16th and 17th centuries, but were later eclipsed by French varietals like Malbec, Cabernet Sauvignon, and Chardonnay from the 20th century onwards.

Fermented together in a single vessel from the outset, these grapes produce a wine that resists classification. It’s not quite orange, not quite white, and not quite like anything else. What it is—unmistakably—is intentional. The wine spends a full 180 days on its skins, a maceration period that surpasses many red wines, let alone skin-contact whites. It is then aged in tank with lees stirring every 15 days, building body, texture, and a subtle oxidative edge.

This co-fermentation is a reclamation of South America’s early viticultural identity through the original European varietals planted in the region but expressed through the tools and confidence of 21st-century winemaking.

FOOD PAIRINGS: Carrot and chickpea tagine, grilled trout with herbs, roasted delicata squash, cumin-spiced lamb skewers, aged Manchego, walnut pesto over farro

DOING IT AS IT HAS BEEN DONE FOR CENTURIES

Quinta do Infantado was founded in 1816 on steep schist terraces in the Cima Corgo subregion of the Douro Valley, but has only been bottling wine on-site since 1979. The Roseira family were among the first in the Douro to reject the model of bulk grape selling and instead bottle their own wines, carving a path for small producers to show what the region could be beyond the farming of grapes to produce Port. Their work helped define a new future for the Douro.

What further distinguishes the estate is that despite their late start in winemaking, they chose to follow a regional tradition of co-fermentation. If we’re thinking of co-fermentation as an ancient idea reborn, Palhete is one of its oldest expressions—and Infantado, one of its most faithful stewards.

Still family-run: Alvaro Roseira is the winemaker

Quinta do Infantado’s vineyards are on steep schist terraces

Featured August Amaro Wine Club Co-fermented wine: Quinta do Infantado Douro Junior Palhete (2023)
VARIETALS: 75% native red varieties, 25% white varieties

The “Junior” Palhete revives a regional tradition of fermenting red and white grapes together to add levity to otherwise deeply structured, high-alcohol reds. This co-fermentation likely includes Touriga Franca, Tinta Roriz, and Touriga Nacional, blended with white varieties such as Rabigato, Gouveio, and Viosinho—all native to the Douro. The grapes are foot-treaded and fermented in open lagar tanks, relying on ambient yeasts and minimal intervention. The mix of berries and whole clusters macerated for about a week in a stainless steel tank, where the wine is also aged on its fine lees for 11 months, followed by a year in bottle. The wine is bottled unfiltered, with minimal sulfur—a true field expression. The objective was to create a wine with all its rustic texture intact in a region that is otherwise associated with high-alcohol polished wines.

FOOD PAIRINGS: Portuguese-style piri-piri chicken, grilled linguiça or other smoked sausages, grilled eggplant or roasted peppers with oregano and olive oil, hard sheep’s milk cheeses (e.g., Castelo Branco or Manchego), rustic olive tapenade with crusty bread

PUSHING THE FORM FORWARD

Anish Patel thought seriously about becoming joining a monastery.

Much of California’s winemaking history has followed familiar patterns: single varietals, controlled fermentations, and polished outcomes geared toward scale. That said, small-producer experimentation has always existed on the fringes, and those fringes have since expanded—nearly approaching the new norm. A new generation of winemakers—many informed by natural and low-intervention philosophies—are building wines by fermenting what comes in, trusting the vineyard, and letting instinct replace recipes.

Tinto Amorio, based in the Central Coast AVA (see There’s More to California than Napa and Sonoma for more on AVAs), is part of this growing movement. The estate was founded by Anish Patel, who reevaluated his life in his twenties after nearly dying in a car accident. He considered becoming a monk, but settled on starting a business that prioritized community, land preservation, and natural agricultural production.

He had previously lived in Spain, where he discovered minimal-intervention winemaking, and decided to bring that philosophy home. The estate works with vineyards that are sustainably farmed at minimum, and increasingly organic or biodynamic. In the cellar, they avoid over 60 additives commonly found in “conventional” wines—animal products, synthetic flavorings, and aggressive manipulations like pasteurization. The wines are native-fermented, low-sulfur, unfined, and often co-fermented—a style that favors reaction over correction.
With Monje, they apply this ethos to a seasonal skin-contact wine.

Featured August Amaro Wine Club Co-fermented wine: Tinto Amorio Monje Skin-Contact Orange Wine California (2023)
VARIETALS: 53% French Colombard, 32% Gewürztraminer, 10% Zinfandel, 5% Albariño

The wine began with three aromatic white grapes—French Colombard, Gewürztraminer, and Albariño—sourced from vineyards in Madera, Paso Robles, Potter Valley, and Lodi. These grapes underwent a 7-day skin fermentation with partial carbonic maceration. Once fermentation was underway, Zinfandel (10%) was added to the tank.

The wine aged on its lees for four months in a mix of French oak and stainless steel, then was coarse-filtered and bottled with less than 30 ppm of sulfur. The hand-waxed bottles reflect the ethos behind the name Monje—Spanish for “monk”—a nod to devotion without pretense, and to the contemplative spirit behind the project.

FOOD PAIRINGS: Grilled halloumi with herbs, lentil and roasted beet salad, duck confit tacos, shakshuka, za’atar-spiced eggplant, mushroom polenta with rosemary oil

Anish and his staff