Curing
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CURING
The ancient art of curing is the most important step in the development of flavour and/or fragrance within the bean. It is a multi-stage process – the stages of which range from minutes to months. Vanillin is stored as Gluco-vanillin and is the converted by the bean's own enzymes to vanillin as the bean is cured.
Blanching
Today, traditional vanilla curing processes differ considerably from one region to the other. The most common method is the Bourbon-type vanilla curing process, which starts with the immersion of the green vanilla beans in hot water (63 degrees Celsius) for 3-5 minutes. This is typically done in old barrels heated over a wood fire. Temperature control is handled by an experienced craftsman dipping a thermometer or even his finger into the water.
Sweating
The hot but still green beans are then tipped into large, insulated wooden boxes and covered with woollen blankets to prevent heat loss over the following two to three days. During this so-called 'sweating' procedure, the temperature drops to roughly 40 degrees Celsius and the beans lose their green colour, as the chlorophyll and several plant enzymes are eliminated. The beans turn brown, become supple and the flavour-forming enzymatic and non-enzymatic processes commence.
Drying
After sweating, the beans are sun-dried in the traditional way by spreading them out on tables or supports on the ground for several hours a day. Between sessions, the beans are re-wrapped in blankets and stored indoors to achieve the correct moisture balance by allowing the sweating process to continue. Depending on the amount of sunshine and rainfall, sun-drying is typically completed after about two weeks. If necessary, the beans are left to dry in the shade for some time, until the water content of the beans is below 20-25%. Some vanilla producers also use drying ovens to accelerate the drying process and reduce the weather dependence. After sun-drying, the beans are slow-dried indoors for about four to six weeks on wooden drying racks in airy warehouses.
Conditioning
The vanilla beans are then packed into boxes for conditioning, which continues for several months after the drying process. During this conditioning phase, the final rich, well-balanced vanilla flavour profile develops, which provides the sensory impact of up to 150-200 different flavour compounds.
Sorting and classification
During the conditioning phase, the cured vanilla beans are manually sorted and classified by length, shape and colour. Whilst length and shape (split, unsplit, cut, not-cut) are the criteria that determine final use, the colour differences are the sensory quality criteria. Black beans have the best flavour profile, red beans originating from unripe green beans are inferior in quality, and the latter are more susceptible to mould contamination during conditioning and storage. After curing, the vanilla beans are examined by hand, divided into split and unsplit, and then sorted into five commercial grades. Beans of the first three grades (extra, first and second) are sold as such to customers; third- and fourth-grade beans are used in manufacturing extracts. All the grades are described below:
- Extra – whole, unsplit, fine, fatty, oily pods. Uniform dark brown colour, no galls/warts, delicate flavour, high moisture content
- First – same as 'extra' except the pods are not quite as fatty
- Second – smaller pods, as few galls, good flavour, moisture content
- Third – thin, hard, twisted pods, slightly reddish colour, numerous blemishes
- Fourth (ordinary) – dry pods of a reddish colour, numerous blemished, ordinary flavour
- Inferior – pods that do not fall into any of the above categories
In addition to shape and colour, the following quality criteria for vanilla and the resultant extracts must be considered:
Vanillin content: Vanillin is considered the principle compound in vanilla beans and extracts. It contributes significantly to the overall flavour profile. The importance of vanillin differs from one application to another. The vanillin content is influenced by the region in which the plant is grown, as well as by the curing process.
Aroma and taste: Some less expensive beans, particularly those of Indonesian origin, can have smoky notes which may emerge as an odour in the finished product. A good-quality vanilla extract has a clean, rich flavour with some woody notes.
Alcohol content: In the United States, the law specifies a minimum 35% alcohol by volume for vanilla extracts.
High-quality beans are long, fleshy, supple, very dark brown to black in colour, somewhat oily, strongly aromatic and free from scars and blemishes. They contain 30-40% moisture content. Low-quality beans are hard, dry, thin, brown or reddish-brown in colour and have a poor aroma. They contain about 10% moisture content.
