conditioning of the beans. Killing The vegetative tissue of the vanilla pod is killed to stop the vegetative growth of the pods and disrupt the cells and tissue of the fruits, which initiates enzymatic reactions responsible for the aroma. The method of killing varies, but may be accomplished by heating in hot water, freezing, or scratching, or killing by heating in an oven or exposing the beans to direct sunlight. The different methods give different profiles of enzymatic activity. Testing has shown mechanical disruption of fruit tissues can cause curing processes, including the degeneration of glucovanillin to vanillin, so the reasoning goes that disrupting the tissues and cells of the fruit allow enzymes and enzyme substrates to interact. Hot-water killing may consist of dipping the pods in hot water () for three minutes, or at for 10 seconds. In scratch killing, fruits are scratched along their length. Frozen or quick-frozen fruits must be thawed again for the subsequent sweating stage. Tied in bundles and rolled in blankets, fruits may be placed in an oven at for 36 to 48 hours. Exposing the fruits to sunlight until they turn brown, a method originating in Mexico, was practiced by the Aztecs. Sweating Sweating is a hydrolytic and oxidative process. Traditionally, it consists of keeping fruits, for 7 to 10 days, densely stacked and insulated in wool or other cloth. This retains a temperature of and high humidity. Daily exposure to the sun may also be used, or dipping the fruits in hot water. The fruits are brown and have attained much of the characteristic vanilla flavor and aroma by the end of this process, but still retain a 60-70% moisture content by weight. Drying Reduction of the beans to 25–30% moisture by weight, to prevent rotting and to lock the aroma in the pods, is always achieved by some exposure of the beans to air, and usually (and traditionally) intermittent shade and sunlight. Fruits may be laid out in the sun during the mornings and returned to their boxes in the afternoons, or spread on a wooden rack in a room for three to four weeks, sometimes with periods of sun exposure. Drying is the most problematic of the curing stages; unevenness in the drying process can lead to the loss of vanillin content of some fruits by the time the others are cured. Conditioning Conditioning is performed by storing the pods