Sesame Unveiled: Unraveling the Secrets of Nature’s Tiny Treasure Trove

This is a genus of about fifteen species of annuals originating from Africa and tropical Asia, with simple or palmately divided leaves and white, pink, red or purple flowers that are tubular and 2-lipped. Sesamum belongs to the family Pedaliceae. The fruits are oblong capsules that naturally split open when dry to release their numerous small seeds. One notable species (Sesamum orientale) is the crop plant sesame, cultivated mainly for its seeds which are used to flavor bread, cakes and biscuits, and also serve as the source of sesame oil. The whole seed is widely used extensively in Middle East and Asia cuisines. A prominent example of its use is tahini, a nut-like cream made from ground sesame seeds that finds frequent application in Lebanese food.

The top leading sesame producers in the world include China, Myanmar, India followed by Japan. Approximately 70 % of the sesame seeds in the world are processed to obtain oil and meal. The major sesame oil producers in the world are China, United States, India followed by Indonesia. Remarkably, the cultivation of sesame for its oil was the earliest practice among oilseeds.

Sesamum orientale

It is also known as Sesamum indicum with the common name known as sesame. It is well recognized as “queen of oilseeds”, it stands out as one of the highest-yielding and non-perennial oil plants, which ranks second to olive oil. A key player in the realm of oilseed crops on a global scale. Sesame oil boasts a delightful golden yellow color with a pleasant flavor and is considered an essential edible oil and a main source of energy. This erect annual reaches a height of about 30 inches with dark green lance-shaped leaves and axillary pink or white tubular flowers.

Sesame exhibits mixed pollination plant that is capable of both self-pollinate and cross-pollination via insects. Following successful pollination, the sesame produces a pear-shaped, overripe and small flatted capsule that contains about 50 to 100 seeds will develop. The optimal time for seed harvesting is in the fall, before they are completely dried out and scattered. The seeds are typically around 3 to 4 millimeter long, ovate and flattened which are around 2 millimeter width and 1 millimeter thickness.

The collective weight of hundreds of sesame seeds ranges from 2 to 3.5 gram Commonly, the prevailing color of the most traded sesame species is creamish white. Other common colors are yellowish-brown, brown, golden-yellow, reddish, gray, tan, red, white and black. Sesame seeds contain three primary components, namely cotyledons, endosperm and testa. Notably, cotyledons contain a large significant concentration of oil drops. Higher oil contents are found in white seeds with the testa than in the dark or black seeds.

Cultivation

Sesame is an annual shrub that thrives in tropical zones. It holds utmost economic importance, particularly grown by small farmers in developing nations. These plants necessitate a warm climate to facilitate seed maturation. They thrive best in sandy and well-drained soil with hot weather and moderate rainfall. A growing season of 90 to 120 days of hot weather is imperative for their development. They do best in moderately fertile soil in a sunny position.

Sesame predominantly exhibits self-pollinating crops. It can be propagated from seed sowing in spring with a maturation period of about four months for full seed ripening. The maturation period ranges from 80 to 180 days, where mature stems are cut and hung upside down to facilitate the release of ripe seeds onto collecting mats. Alternatively, mechanical harvesting methods can be employed to harvest the seeds.

The productivity of the sesame has several major constraints including varietal adaptation, capsule shattering and seed loss, uneven maturity, the impacts of both biotic and abiotic stresses, agricultural activities as well as inadequate pre- and post-harvest infrastructure. Commonly, the abiotic loss is due to drought, waterlogging, salinity and frost.

It is found that field pests could yield a loss of 25 % in sesame and the major insect pests are gall midge (Asphondylia sesame), seed bug (Elasmolomus sordidus) and webworm (Antigastra catalaunalis). Seed bug is the pest that could bring 50 % yield loss at field and storage. Commonly, bacterial infection like blight (Xanthomons campestris pv. sesame) and fungal infection such as charcoal rot (Macrophomina phaseolina), stem anthracnose (Colletotrichum spp.), powdery mildew (Erysiphe cichoracearum), Fusarium wilt (Fusarium oxysporum f. sp. sesame), root rot (Rhizoctonia solani) and viruses (phyllody,  Orosius albicinctus) are widely observed in sesame cultivation.

Presently, sesame remains a low-yield crop, primarily attributed to its constrained genetic yield potential and vulnerability to both biotic and abiotic stresses. There is a demand to develop stress-tolerant and high-yielding varieties to sustain the global market.

Nutraceutical values

Sesame seed contains about 40 to 50 % oil, 20 to 15 % protein, 20 to 25 % carbohydrate and 5 to 6 % ash. It consists of unsaturated fatty acids where the fatty acids composition is 14 % saturated, 39 % mono-unsaturated and 46 % poly-unsaturated fatty acids. Because of its nutritional composition and being a good source of protein, it has become one of the main sources of edible oil. Sesame oil is highly stable and rarely turns rancid in hot climates (due to its high antioxidant property). Dietary fiber, protein, vitamin B1 and minerals such as iron, phosphorous, calcium, copper as well as zinc are abundantly present in the sesame seed.

Sesame seeds are widely used in food industry. They add a nutty taste and a delicate, almost invisible crunch to many Asian dishes. Sesame seeds hold global importance and can be used to make cakes, paste, flour, oil, and other confectioneries due to their high roasted flavor, nutrients, proteins and high oil contents. Moreover, sesame contains amino acids such as methionine, lysine and tryptophan found in sesame proteins. Sesame seeds are also used in micro-atomized protein foods for weaning babies. White sesame seeds are sprinkled over bread and are commonly used in cakes. Sesame paste and starch are the key ingredients to make special sesame tofu known as Goma dofu in Japan.

The protein of the sesame can be extracted as a supplement that contains α-globulin and β-globulin. One of the applications is the sesame meal, which comprises crushed seeds without oil. Sesame meal has a composition of approximately 7.92 % moisture, along with fat, protein, fiber, ash and carbohydrate.

Sesame is a highly nutritional seed oil-yielding crop. Mechanical pressing is used in sesame oil extraction. Various oils with different flavors and tastes have been introduced to fulfil the demand of the people. Sesame oil is used in various forms of popular medicine as a topical preparation. For instance, it is used to treat a variety of inflammatory skin disorders or leg ulcers in traditional Chinese medicine.

Sesame has medical uses on cholesterol and blood pressure regulation as well as neurological role. Additionally, it is attributed with analgesic, antioxidant, antibacterial, anticancer, anti-inflammatory and antioxidant properties among others. Some research has proved that sesame is effective against Parkinson’s disease. Then, sesame powder is also used to control amenorrhea, dysmenorrhea, ulcers, and hemorrhagic acne.

Sesame oil is utilized as a solvent, oleaginous vehicle for drugs, skin softener and used in the manufacture of margarine and soap. The demand for vegetable oils is rising with the increasing world population. The oil is mainly used in cooking, salad preparation and for making margarine. However, sesame oil is mildly laxative, emollient and demulcent.

Sesame has been utilized as an oleaginous seed for thousands of years due to its high lipid content. Sesame oil has been applied in the pharmaceutical and cosmetics industries. Typically, sesame oil can be used as moisturizing oils, ointments, hand products, creams, lotions, lip balms, soaps, shampoos as well as cosmetics for application to the eye area. The oil has been used for wound healing for thousands of years due to it has antibacterial properties against common skin issues caused by Staphylococcus and Streptococcus bacteria. Other than that, sesame oil is used for post-exposure to sunburn and protection from the damage by chlorine in swimming pool water.

Furthermore, sesame serves as a great source for biodiesel production. The declining petroleum resources and their increasing demand are of great concern for the past two decades. Sesame oil is a viable alternative to diesel fuel. However, its usage in engines is limited due to low instability (as biodiesel), high viscosity and triglyceride-like properties.

Sesame allergy

The prevalence of sesame allergy in the general global population is unknown. Sesame allergy commonly develops in childhood or adolescence. There are two types of sesame allergy, which are immediate-type and albeit extremely rare-delayed-type allergic reactions. Sesame oil also contains several potential contact allergens. Sesamolin and sesamin have been identified as the main triggers of contact allergic reactions to sesame-containing external agents, although sesamin has been proven to aid in protecting the liver from oxidative damage.

Skin prick tests can be carried out with commercially available aqueous sesame allergen skin prick test solutions to diagnose immunoglobulin (IgE)-mediated sesame allergy. In the case of known skin barrier disorders, food-based external agents should be avoided as a precaution, not only due to the possibility of immediate-type reactions but also because of the risk of delayed-type contact allergic sensitization.

Further reading:

Bedigian, D. (Ed.). (2010). Sesame: the genus Sesamum. CRC press.

Gangur, V., Kelly, C., & Navuluri, L. (2005). Sesame allergy: a growing food allergy of global proportions?. Annals of Allergy, Asthma & Immunology95(1), 4-11.

Gauthaman, K., & Saleem, T. M. (2009). Nutraceutical value of sesame oil. Pharmacognosy Reviews3(6), 264.

Oboulbiga, E. B., Douamba, Z., Compaoré-Sérémé, D., Semporé, J. N., Dabo, R., Semde, Z., … & Dicko, M. H. (2023). Physicochemical, potential nutritional, antioxidant and health properties of sesame seed oil: a review. Frontiers in Nutrition10, 1127926.

Ölmez, Y. A., & Sevilmiş, D. (2021). Importance of oilseed crop sesame (Sesamum indicum L.): A review. Muş Alparslan University Journal of Agriculture and Nature1(2), 86-97.

Patel, A., & Bahna, S. L. (2016). Hypersensitivities to sesame and other common edible seeds. Allergy71(10), 1405-1413.

Vittori Gouveia, L. D. A., Cardoso, C. A., De Oliveira, G. M. M., Rosa, G., & Moreira, A. S. B. (2016). Effects of the intake of sesame seeds (Sesamum indicum L.) and derivatives on oxidative stress: A systematic review. Journal of medicinal food19(4), 337-345.

Wei, P., Zhao, F., Wang, Z., Wang, Q., Chai, X., Hou, G., & Meng, Q. (2022). Sesame (sesamum indicum l.): A comprehensive review of nutritional value, phytochemical composition, health benefits, development of food, and industrial applications. Nutrients14(19), 4079.

Yadav, R., Kalia, S., Rangan, P., Pradheep, K., Rao, G. P., Kaur, V., … & Siddique, K. H. (2022). Current research trends and prospects for yield and quality improvement in sesame, an important oilseed crop. Frontiers in Plant Science13, 863521.

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