Curing Vanilla
Pick a vanilla pod from the vine and smell it. Nothing. It is a long, green, slightly waxy fruit, faintly grassy, with no more perfume than a green bean. The aroma that every baker recognizes does not exist yet; it is manufactured over the following six months by the farmer, in a process of controlled dying, sweating and drying that is as skilled as anything a cheesemaker or a tea master does. Our history of vanilla covers the flower and the boy who learned to pollinate it; this is what happens after the pod comes off the vine.
Why a cure is needed
The green pod contains vanillin, the main aroma compound, but locked up as a glucoside, bound to a sugar molecule and odorless. It also contains the enzyme that can cut that bond, kept apart from the vanillin in separate cells. Curing is the art of killing the pod so the cells break down, letting the enzyme meet the glucoside and release free vanillin, and then drying the pod slowly enough that this and hundreds of related reactions run to completion without the pod rotting. Rush it and the bean is thin and one-dimensional; do it well and the bean smells of vanilla and also of dried fruit, rum, smoke, flowers and leather, the hundreds of compounds that imitation vanilla lacks.
Harvest
The pods are picked one at a time, by hand, about nine months after the flower was pollinated, when the tip begins to yellow but before the pod splits. Picked too early, the bean will be short on aroma; too late, it splits and loses value. On Madagascar's northeast coast, where most of the world's vanilla grows, the harvest runs from about June to August, and pods are sorted on the day by size and ripeness before the cure begins.
Killing
The pod is killed to stop it living and start it curing. The Bourbon method, developed on Réunion and used across Madagascar, plunges the green pods into water at about 63 to 65°C for two to three minutes, wrapped in cloth or baskets. Mexico traditionally kills by wilting in the sun or in ovens; some growers use freezing or scratching. The scald is the gentlest and most controllable, and it is the step that makes Bourbon vanilla taste the way it does.
Sweating
Straight from the hot water, the pods are wrapped in thick wool blankets and packed into wooden boxes, where they stay hot and humid for a day or two. This is where the enzymes go to work; the pods turn from green to brown within the first day as the cells collapse and the vanillin is released. The smell of a curing shed at this stage is the first moment the fruit smells of vanilla, and farmers describe it as the moment the crop becomes real.
Sunning and sweating, repeated
For the next two to four weeks the pods live a daily cycle. Each morning they are spread on dark blankets or racks in the sun for a few hours, until they are hot to the touch; each afternoon they are gathered, wrapped again in the blankets and put back in the boxes to sweat overnight. The sun drives off water and the heat continues the chemistry; the sweat keeps the pods supple and the reactions going. The pods darken, shrink, and become flexible and glossy. A curer judges each day's exposure by the weather and the feel of the pods, and a wet week can ruin a harvest. This is the labor that the price of a bean pays for: every pod handled twice a day for a month by someone who knows what a good one feels like.
Slow drying
Once the pods have lost most of their moisture they are moved to racks in the shade, indoors or under a roof, for a month or more of slow air drying. The aim is a bean at roughly a quarter to a third moisture: dry enough to keep, moist enough to stay pliable and oily. Too dry and the bean is brittle and loses aroma; too wet and it molds. Farmers bend pods around a finger to check; a well-cured bean wraps without cracking.
Conditioning
The final stage is rest. The beans are bundled, wrapped in waxed paper and packed into closed wooden or tin boxes for two or three months, during which the aroma continues to develop and deepen and the beans exchange moisture until the batch is even. Some develop a fine white frost of vanillin crystals on the surface, givre, prized as a sign of a high-vanillin cure. Only after conditioning are the beans graded, by length, moisture, suppleness and appearance, and sold. From flower to finished bean is a year and a half; from green pod to jar is about six months of that, almost all of it by hand.
Reading a cured bean
A good bean is dark brown to black, glossy, supple enough to bend and tie in a knot, oily to the touch and heavy for its size, with a strong, complex, sweet aroma when the packaging is opened. Grade A or gourmet beans are long, plump and moist, meant for splitting and scraping into a custard or a caramel. Grade B or extract beans are drier, shorter, sometimes split, less pretty and just as fragrant, and they are the better buy for making extract or vanilla sugar. A brittle, dull, thin bean was dried too fast or stored too long. Beans keep for a year or more in an airtight container in a cool dark place, never the refrigerator, where they harden.
Why it matters in the kitchen
The cure is why real vanilla tastes of more than vanillin, and why a bean, a paste and a good extract each taste of the origin: Madagascar's is rich and creamy, Mexico's spicier and darker, Tahiti's floral and fruity, differences that come from the plant but also from the curing traditions of each place. Split a bean, scrape the seeds into the cream, drop the pod in too, and afterward rinse and dry the pod and bury it in sugar. Six months of someone's twice-daily attention should not go in the compost. The beans and extracts on our baking shelf are at 263 Josephine Street in Cherry Creek, Denver, and ship nationwide from theambrosianpantry.com, and our spice harvest piece sets vanilla beside the other spices that are made, not merely picked.
