olsonetal2016moringaproteinminerals.pdf |
We surveyed protein (really total nitrogen) plus Ca, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, S, and Zn. Because of the variation within species and statistical groupings of species, it is often not strictly possible to say that X species is always the highest or lowest for a given nutrient. This is why we use the wording throughout the paper that “X species tended” to fall in groups with high or low levels of a given nutrient. This is not equivocation, it’s just correct wording given what the statistics say. Even given the uncertainty inherent in all scientific processes, our sampling allowed us to say many important things about the distribution of nutrients across the genus.
The most striking thing was that there was no one best species for all nutrients. But all around, Moringa oleifera still seems like the best nutritional bet. It had the highest protein levels, though M. concanensis, M. stenopetala, the M. concanensis X oleifera hybrid, and M. longituba also had very high protein levels. Leaf toughness, as measured by a variable called leaf mass per unit area (leaflet weight divided by leaflet area) strongly and negatively predicted protein content. This means that the tougher leaves, with their thicker and sturdier cell walls, have less room inside cells for protein and thus less protein per unit leaf area. Moringa oleifera, with its soft, almost filmy leaflets, is packed with protein. Other highlights included M. ruspoliana, with its very tough leaflets and low protein content, having by far the highest calcium content across the genus.
The strong negative relationships between some variables probably mean that breeding the perfect moringa is impossible. The leaf toughness-protein content relationship I just mentioned is a case in point. It would be nice to breed moringas with larger leaflets (making plucking the leaflets off of the woody rachises for eating a lot easier) and maximal protein content. Alas, given that large leaflets seem to require more celluose-lignin support tissue and therefore less intracellular space for protein, large leaflets inevitably seem doomed to having lower protein content. Mind you, this is still the genus Moringa we’re talking about, and even the worst species have around 15% protein by weight, which is still quite acceptable for a vegetable. Other negative relationships we recovered were between protein and calcium; potassium and magnesium; and various others. These suggest that simultaneous maximization of these nutrients might not be possible.
With each species being highest in at least one nutrient (except M. hildebrandtii), the study shows the value of surveying across a maximal range of genetic diversity. Finding the best of the best will require sustained studies across species as well as within the old standard Moringa oleifera.