Composition, functional and nutritional quality of marama (Tylosema esculentum) storage root

Marama root is known to be the major source of nutrition for the first settlers (the Herero, Tswana and Khoisan people) of Sub-Sahara Africa, but it is not yet domesticated. The potential of Marama (Tylosema esculentum) root in food and nutrition security may pave way for the domestication of the plant in Sub-Saharan Africa. Marama storage roots collected from two locations, Omipanda and Okomumbonde in Namibia were analysed and compared to commercial potato and waxy potato tuber as well as sweet potato root. Fresh weight (FW) marama roots had mean water content, crude protein, fat, ash, and starch content of about 866, 24, 2, 22, and 56 g/kg root, respectively. Marama root showed higher total soluble solids (4.3°) compared to potato, waxy potato and sweet potato. The swelling index (3 g/g) and water absorption capacity (1.5 g/g) of marama root were close to those of sweet potato, but lower than those of the potato and waxy potato. The soluble and insoluble dietary fibre of marama root (4.8, and 15%, db, respectively) were higher than those of the commercial potatoes; and the in vitro- starch digestibility of marama root was close to those of potatoes. Marama root has potential as prebiotic and its food value is similar to sweet potato in functional properties and nutritional composition. The high soluble solids of marama root can enhance the energy density of complimentary food, but will require compositing with high protein legume flour. There is a prospect of a protein-energy dense composite flour from a blend of the bean and root.

Physicochemical properties of a new starch from ramie (Boehmeria nivea) root

A new starch was isolated from ramie root, and its physicochemical properties were investigated. Ramie dry root contained 45.9% starch. Starch had truncated, ellipsoidal, and spherical granule shapes with size from 7 to 30 μm and D[4,3] about 14.1 μm. Starch contained 38.9% apparent amylose content and 22.4% true amylose content, exhibited B-type crystallinity, and had 26.6% relative crystallinity, 0.82 ordered degree, and 9.2 nm lamellar thickness. Starch had 71.8 °C gelatinization peak temperature and 15.6 J/g gelatinization enthalpy, and exhibited 31.4 g/g swelling power and 17.1% water solubility at 95 °C. Starch had peak, hot, breakdown, final, and setback viscosities at 3048, 2768, 279, 4165, and 1397 mPa s, respectively, and showed peak time at 4.36 min and pasting temperature at 75.0 °C. The native, gelatinized, and retrograded starches contained 15.1%, 94.0%, and 86.5% rapidly digestible starch and 83.3%, 4.0%, and 10.7% resistant starch, respectively. Compared with potato and rice starches, ramie starch was somewhat similar to potato starch but significantly different from rice starch in starch component, crystalline structure, and functional properties. Therefore, ramie starch exhibited the potential to be used as a thickening agent, resistant-digesting food additive, and alternative to potato starch in food and nonfood industries.

Orphan Legumes Growing in Dry Environments: Marama Bean as a Case Study

Plants have developed morphological, physiological, biochemical, cellular, and molecular mechanisms to survive in drought-stricken environments with little or no water caused by below-average precipitation. In this mini-review, we highlight the characteristics that allows marama bean [Tylosema esculentum (Burchell) Schreiber], an example of an orphan legume native to arid regions of southwestern Southern Africa, to flourish under an inhospitable climate and dry soil conditions where no other agricultural crop competes in this agro-ecological zone. Orphan legumes are often better suited to withstand such harsh growth environments due to development of survival strategies using a combination of different traits and responses. Recent findings on questions on marama bean speciation, hybridization, population dynamics, and the evolutionary history of the bean and mechanisms by which the bean is able to extract and conserve water and nutrients from its environment as well as aspects of morphological and physiological adaptation will be reviewed. The importance of the soil microbiome and the genetic diversity in this species, and their interplay, as a reservoir for improvement will also be considered. In particular, the application of the newly established marama bean genome sequence will facilitate both the identification of important genes involved in the interaction with the soil microbiome and the identification of the diversity within the wild germplasm for genes involved drought tolerance. Since predicted future changes in climatic conditions, with less water availability for plant growth, will severely affect agricultural productivity, an understanding of the mechanisms of unique adaptations in marama bean to such conditions may also provide insights as to how to improve the performance of the major crops.