Structural, nutritional and protein functional properties of trichilia emetica and trichilia dregeana seeds.
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Date
2022
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Abstract
Food and nutrition insecurity are prevalent in developing regions, especially in the
predominantly low-economic status of sub-Saharan Africa. Yet, several edible domesticated
and wild plants are grossly under-utilised as food sources. The woody plants Trichilia species
are indigenous to Africa and are also found in other developing countries. Although the oily
seeds of Trichilia species seem to have great potential for contributing towards the alleviation
of malnutrition in the developing regions, they are grossly under-utilised and there is a dearth
of scientific literature regarding their nutritional potential. To improve the utilisation of
Trichilia seeds on a commercial scale, it is vital to study their physical characteristics and the
nutritional and food-related (functional) physico-chemical properties of their components. In
this study, the structural and chemical composition of Trichilia emetica (T. emetica) and
Trichilia dregeana (T. dregeana) seeds, in addition to the nutritional and functional
properties of their proteins, were investigated and compared with the soybean.
The results of the seeds analysis showed that Trichilia seeds had difficulty sliding on surfaces
due to their oblate shape. Trichilia seeds showed lower sphericity (0.66) than soybean (0.99),
with higher bulk density (645.9 kg/m3 and 433.6 kg/m3, respectively) and lower true density
(875.8 kg/m3 and 950.4 kg/m3, respectively). The porosities for T. emetica and T. dregeana
were significantly lower (55.07% and 54.38%), with a higher geometric mean diameter (29.7
mm and 16.9 mm) than soybean. Trichilia species showed similar shapes, but different
localisation of the seeds‟ protein bodies when compared with soybean. Trichilia seeds‟
protein bodies were larger in size and more round in shape than those of the soybean.
The other investigations in this study determined the nutritional properties of the flour and
protein of T. emetica and T. dregeana seeds, and compared the chemical structure and
functional properties of protein in the Trichilia seeds with the soybean. The results showed
that T. emetica and T. dregeana seeds contained substantial protein (25.6% and 17.3%,
respectively) and high concentrations of fat (49% and 51.5%, respectively). Potassium,
calcium, iron and zinc were the major minerals in the Trichilia seeds. T. emetica and T.
dregeana protein had substantial concentrations of Phenylalanine, Leucine, Isoleucine,
Valine and Lysine and Methionine, which were comparable with those of the soybean. The
concentrations of essential amino acids in Trichilia seeds, similar to their concentrations in
soybean, were above the recommended Food and Agricultural Organisation standards for
adults. The proportion of essential amino acids to total amino acids of T. emetica and T.
dregeana seeds was similar to that of the soybean. The Trichilia spp protein had more β-
conformation than α-helices (21%) comparable with soybean protein. The protein
concentrates of T. emetica seed had higher Water holding Capacity, Foaming Capacity and
Foaming Stability with lower Oil holding Capacity and Emulsion activity Index when
compared with soybean and T. dregeana seeds.
The findings of the current study indicate that the physical and nutritional properties of T.
emetica and T. dregeana seeds and their protein properties had comparable properties to
existing commercial oilseeds. This could improve the utilisation of the seeds as
complementary foods and can cause an increase in the number of available food sources for
food and nutrition security, thereby improving the livelihoods of individuals. However, there
would be a need to modify the existing technologies for drying, milling, packaging and
transportation to accommodate the Trichilia seeds. Furthermore, the bioavailability of the
minerals and protein of the Trichilia seeds should be assessed.
Description
Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.