Micro-Kjeldahl Protein Determination in Moringa Leaves

Total protein (nitrogenous compounds content) was determined by the conventional micro-Kjeldahl method [57 ]. A sample of 0.3 g powder of Moringa leaves was weighed into a digestion flask. Ten mL sulfuric acid and 0.5 g digestion mixture (1:4 K₂SO₄:CuSO₄) were added. The sample was then incinerated, the digested sample was quantitatively transferred into the Markham micro-Kjeldahl with the least amount of ammonia-free distilled water, and then 20 mL of 50% NaOH solution was added. A strong current of steam was then passed and the ammonia was distilled into 10 mL of 2.5% boric acid. The ammonia was then titrated against HCl using a mixed indicator (0.4 methylene blue and 0.1 methyl red) until a faint red endpoint was obtained. After correction for the reagent blanks, the titration figures were converted into percentage protein using the following equation: $$Total crude protein\%=\frac{Read\times N of HCl\times 0.014\times Conversion Factor\times 100}{Sample weight}$$
The conversion factor for Moringa = 5.25.