The second introduction of vanilla occurred in 1850 (Costantin and Bois, 1915). French Polynesia received new plants from Paris, sent by Admiral Bonard. There were many V. planifolia plants coming from the botanical garden of Paris and many V. pompona plants from the Antillas (Florence and Guérin, 1996). These two species are still found in French Polynesia. But they are not really cultivated. The weather conditions do not always allow V. planifolia to flower. In addition, V. pompona is only considered as an ornamental plant in French Polynesia.
The third introduction of vanilla plant was by Major Pierre, in 1874, who brought new vanilla plants from Mexico (Costantin and Bois, 1915; Florence and Guérin, 1996). These plants were described as the best vanilla species from Mexico and Bourbon, with broader, thicker, and more round leaves than the vanillas cultivated in French Polynesia, which possess pointed and lanceolate leaves. According to these descriptions, it seems that this third introduction did also correspond to V. planifolia.
According to morphological and historical comparisons, many hypotheses on the origin of Tahitian vanilla were elaborated. According to Portères (1951), the morphology suggests that V. tahitensis was a clonal population resulting from segregations of natural crossings between V. fragrans (Salisbury) Ames (syn. V. planifolia Andrews) and V. pompona Schiede, which was probably already a hybrid of Vanilla odorata Presl. Portères (1953) suggests that this initial hybridization could have occurred in French Guiana or in Reunion Island between V. fragrans and a complex species (V. pompona–V. odorata). However, according to Florence and Guerin, V. tahitensis does not show any intermediate traits that a hybrid between V. planifolia and V. pompona should exhibit. These authors consider V. tahitensis as synonymous of V. planifolia. They do see it as a segregation issued from a small number of introductions. The segregants have brought some variations resulting in traits specifying the Polynesian form.
At present, the origin of Tahitian vanilla is still unknown; nevertheless, morphological diversity exists among the vines encountered in French Polynesia. The most cultivated vanilla vines in French Polynesia are Tahiti and Haapape. The cultivar Haapape was first mentioned in 1914 (Bouriquet and Hibon, 1950). According to C. Henry (1924), Haapape seems to be an inbred of Tiarei, which was described in 1900 (Costantin and Bois, 1915). The cultivar Tiarei was reported as a case of gigantism (Henry, 1924). Comparing the morphological characters, color, and flavor of the beans, the Tiarei form cannot be the result of a cross between a Tahitian vanilla and a vine originating from Mexico. According to Bouriquet and Hibon (1950), the Tiarei cultivar is issued from a somatic mutation or is a spontaneous hybrid of V. planifolia and a Tahitian form.
Biology of the Tahitian Vanilla
Vanilla is mainly propagated by stem cuttings. Seed germination is difficult because it requests a symbiotic fungus: Rhizoctonia. Flowering necessitates approximately 18 months. However, this delay varies with the size of the vine. Cuttings of 20 nodes can flower within less than one year after plantation.
Flowering is induced by a decrease in the temperature (18–19°C) and by drier and sunnier weather during the fresh season. Two flowering periods often occur in a year: the main one is between July and September and another is possible in December–January. The ends of the hanging stems will then dry and 1–3 inflores-cences from 10 to 15 flowers will appear. The flower opens at dawn and fades during the evening. On a single inflorescence only 1–2 flowers open each day.
There is no pollinating insect in French Polynesia and thus pollination, or “ marriage,” is hand-made early in the morning, to prevent pollen becoming too dry to adhere to the stigmata. The marriage is performed according to a common procedure developed in Reunion Island by Edmond Albius (Bouriquet, 1954, see also Chapter 17).
The bean is ripe after nine months. Green until then, the bean starts to yellow and then browns, starting from the heel. This indicates that the bean can be collected and cured.
Curing Process
Thanks to original sensory and physical properties having been retained, the Tahitian vanilla has a unique flavor. In French Polynesia, Tahitian vanilla is nowadays considered as a bona fide source of cultural identity demonstrating the know-how of growers and curers. Polynesians developed a specific curing process based on harvesting pods when fully mature and flavorful, followed by a natural browning enabling the development of the aroma.
For most vanillas cultivated worldwide, notably V. planifolia, ripeness involves dehiscence of the beans. To avoid this phenomenon, clusters of beans are harvested before fully mature; and then ripeness is stopped by a treatment at high temperature. Tahitian vanilla beans rarely develop split ends and they are harvested when fully ripe, with complete aroma potential (Figure 13.1). Natural browning is achieved and allows a complete conversion of glycosylated aroma compounds into corresponding aglycones responsible for the vanilla flavor.
FIGURE 13.1 Mature beans of Tahitian cultivar Haapape, still green or turning brown.
Traditional Polynesian curing involves water loss to concentrate the flavor and to enable a good conservation of the beans. In the course of the curing process, many biochemical reactions (enzymatic and nonenzymatic like oxidative reactions) occur in the vanilla pods, which result in the development of the flavor (Odoux et al., 2006, for more details see Chapters 11 and 12); such biochemical reactions are poorly studied in Tahitian vanilla.
Tahitian curing consists of three main steps that necessitate being very patient and meticulous (Larcher, 1989; Ranadive, 1994):
1. Shade browning After harvest, mature vanilla beans are exposed in the shade until uniform browning and initiation of sweet-scented flavor are attained. Then, they are washed and dried.
2. Sun drying Beans are exposed to sunshine for a few hours a day for several weeks. Their water content drops from 80% to the final moisture content desired (50–55%). When they are exposed to warm temperatures or the sun; water evaporates. Then, while still warm, beans are wrapped in cotton sheets called “faraoiti” and kept in wooden cases overnight to ensure water loss by sweating. The beans become flexible and glossy as their epidermis is increasingly covered with oil. They are massaged one by one, when necessary, to spread and homogenize the seeds lengthwise.
3. Air drying (refining) Beans are finally dried in the shade to homogenize batches and stabilize water content, enabling optimal shelf life.
The curing process allows the development of Tahitian vanilla flavor. The beans become sweet-smelling and rich anise flavored. Their physical properties are also intensified as they show a very attractive oily texture and appearance. The lipid components are involved both in these properties and aroma development because they restrict aroma loss from occurring during the process.