Sesame is one of the oldest cultivated oilseed crops in the world. Harvesting presents a unique challenge because traditional varieties are dehiscent, meaning the seed capsules naturally burst open upon drying. This characteristic necessitates a specific, multi-step process for harvesting and processing to maximize yield and ensure seed quality. Following a structured approach from the field to storage allows growers to capture the full value of this nutrient-rich crop.
Recognizing Harvest Maturity
The timing for harvesting sesame is precise and relies heavily on visual cues of the plant’s progressive maturation. Sesame plants develop from the bottom upward; the lowest seed capsules ripen first while upper ones may still be green. A grower knows the plant is ready for cutting when the lower leaves begin to yellow, dry, and drop from the stalk.
This leaf drop reveals that the lowest seed capsules have fully matured and started to turn from green to a distinct yellow or brown color. Plants are typically ready for harvest between 90 and 130 days after planting, depending on the variety and local climate. Harvesting at this stage prevents significant seed loss from the lowest pods shattering while allowing the upper pods to finish maturing during curing.
Cutting the Stalks and Initial Curing
Because sesame capsules tend to open and scatter seeds immediately upon drying, the entire plant must be cut before the capsules are fully dry. The stalks should be cut close to the ground, usually about 10 centimeters above the soil line, using a sharp tool like a sickle or knife. Care must be taken not to shake the stalks, which could prematurely release seeds from the already-dried lower pods.
After cutting, the stalks are immediately gathered into small bundles, often called sheaves, and tied securely. These bundles are stacked upright, traditionally on bamboo racks or in a field, allowing them to dry fully and uniformly. The curing process involves hanging the bundles upside down in a protected, dry location, such as a barn or shed, for seven to fourteen days.
This inverted hanging position uses gravity to keep the seeds inside the pods as the remaining capsules dry and open. To collect the seeds that inevitably fall out during this phase, a clean tarp or plastic sheet must be spread beneath the hanging bundles. This collection step minimizes seed loss and prevents contamination from soil and debris.
Seed Extraction and Cleaning
Once the stalks are fully dry and brittle, the process of seed extraction, known as threshing, can begin. Threshing involves physically separating the seeds from the dried capsules and plant material. The simplest method involves gently shaking, tapping, or beating the inverted bundles over the collection tarp or a designated clean surface.
The physical impact causes the open capsules to release the mature seeds onto the clean surface below. This action also releases light plant debris, broken capsule walls, and dust, resulting in a mixture of seeds and chaff. The harvested seeds must then be cleaned to remove this unwanted material through a process called winnowing.
Winnowing separates the lighter chaff from the heavier seeds using air movement. This is done by slowly pouring the seed mixture from one container to another while exposed to a natural breeze or a controlled fan. The lighter debris is carried away by the air current, while the dense, clean seeds fall straight down.
This cleaning process should be repeated several times to ensure the final product is free of dirt, stones, and plant material.
Storage and Preservation of Sesame Seeds
After cleaning, the seeds must be dried further to a low moisture content, ideally below 10%, before storage to prevent mold. Sesame seeds possess a high oil content, making them susceptible to rancidity when exposed to heat, light, or air. Storing the seeds in an airtight container, such as a glass jar, protects them from moisture and oxygen exposure.
The best location for long-term storage is a cool, dark, and dry place, like a pantry, where they remain fresh for approximately six months. For extended preservation, the seeds can be stored in the refrigerator or freezer. This significantly slows the oxidation of the oils. When stored in an airtight, freezer-safe container, sesame seeds can maintain their quality for a year or longer.