Sesame

Sesame seeds are a source of vitamin B6, protein, iron, and calcium. The seeds are often added to breads, bagels, and crackers and lend a nutty flavor. The seeds also can be made into tahini, a Middle Eastern paste. Prior to use, sesame seeds must be processed. The raw stalks and flowers of the plant are harvested from the fields and then brought most often to a commercial plant for processing. If an individual is patient, it is possible to hull or husk the seeds and then process into oil or paste. The commercial method of processing sesame seeds is far more efficient.

Sudan, Pakistan, Nigeria, Ethiopia, Tanzania, Thailand etc. There is a substantial export market, with the European Countries, Japan and certain Gulf countries being the bulk buyers. Sesame seeds have a thin shell or husk which needs to be removed and this process is known as dehulling. The weight of hull is about 17% of total weight of sesame seed. The hull contains a great deal of oxalic acid and indigestive fiber. Oxalic acid can reduce biological utilization ratio of Ca in Food and influence taste.

After dehulling, oxalic acid can reduce from 3% to 0.25% in sesame seeds, which improve the protein digestibility greatly. So, dehulling of sesame seeds is the precondition of enlarging application of sesame in food field. Hulled sesame seeds are softer and tastier than unhulled seeds. Sesame seeds are also an excellent source of unsaturated fatty acids and phytosterols.

Processing

Wet Dehulling Process

Wet Dehulling Process is compared with dry dehulling process. Dry dehulling process is that dry the sesame seeds after cleaning at a certain level, which can dehydrate the moisture in hull quickly and be brittle. Then use clash dehulling method, the hulls are peeled from sesame seeds. The dry process is short in technology line, little investment in equipment but low at dehulling rate; easily get yellow or brown even burnt at high temperature. So, for commodity use, dry method is not commonly used in processing sesame seeds, generally, only for little quantity self-use in some foodstuff factories.

A wet dehulling process has been developed for easy removal of the husk from the sesame seed. The process of dehulling consists of preliminary cleaning and grinding, hot lye treatment, removal of the skin and pigments, thorough washing and drying. The dehulled seed is expelled to get high grade oil.
The cake is further expelled to recover the residual oil and protein-rich meal. The protein-rich sesame cake flour finds multiple uses in protein fornication of food preparations. The dehulled sesame seeds and flour offer good potential for both domestic and export markets.

A process has also been developed for washing of white sesame seeds to produce confectionery grade product. Brilliant white seeds are produced, which is known as hulled sesame seeds.

Process Flow for Complete Hulled Sesame Plant

• Soaking: The purpose of soaking is that make hull of sesame seeds sopped up water to expand for peeling off from seeds. The project use lye, soaking raw sesame seeds in a certain temperature, which improve the speed of infiltration ratio of water into hull, shorten the soaking time greatly to 30-40 minutes from original 7-8 hours. The produce periods is shortened. At the same time, lye weakens pigments in hull for the whiteness of sesame seeds.
• Dehulling: The project use vertical huller to make sesame seeds in relative movement. By soft friction between sesame seeds, the hull is removed.
• Separating: It is the key process in sesame seeds production, affecting final yield of finished product. Generally, put the mixture of hulls and seeds into water tank, by different buoyancy of hulls and seeds, fish out the hulls by hand. But it is not thorough method by buoyancy. So the project uses separation theory by different geometrical sizes of hulls and seeds. Namely, use best soaking technology to soften hulls, increase crush rate of hulls but do not influence intact rate of seeds when hulling, then use hulls smaller than seeds, taking away the hulls with water flow in subsidence-type automatic separator. The seeds are captured. The separation of hulls and seeds successes. The technology save labor and product yield next to theoretical value.
• Drying: The process use single chamber fluid bed drier. The sesame seeds float in hot air flow and polish by friction between seeds, which decrease sticky hull rate and improve the smoothness of finished product. It avoid the disadvantage of yellow, unpolished, high sticky hull rate etc. in normal fluid bed drier