Acid-producing mechanisms in minced leaves

Abstract

The drift of pH towards the acid side observed when minced tobacco leaves are neutralized with alkali is mainly due to the enzymic demethylation of pectin when the pH is raised above that of the normal sap. Metabolic production of CO2 also produces some drift. The liberation of methanol is more rapid in milled than in minced leaf fibre, and at pH 8 than at pH 6, in the presence or absence of sap. Heating to 100[degree] prevents the pH drift but a small amt. of methanol is liberated at pH 8 by non-enzymic demethylation. The pectase is ex-tracted from the fibre at pH 8 but not at pH 6. Minced leaves of some Cucurbitaceae have a spontaneous alkaline drift when washed, which permits demethylation without the addition of alkali.