Original article: The influence of pH and digestion with commercial enzymes on calcium adsorption in casabe

• Published in: International journal of food science & technology 2006-11, Vol.41 (9), p.991-996
• Main Authors: Navas, Petra Beatriz, Carrasquero-Duran, Armando
• Format: Article
• Language: English
• Subjects: Manihot esculenta
• ISSN: 0950-5423; 1365-2621
• DOI: 10.1111/j.1365-2621.2006.01055.x

The Ca super(2+) binding capacity of a sample of casabe made from cassava (Manihot esculenta) was evaluated by using adsorption isotherms after a digestion process with commercial enzymes. It was found that enzymatic treatment increased the ability of vegetable material to retain calcium and to release endogenous mineral ions as a consequence of possible modifications to the carbohydrate matrix. Untreated casabe did not release mineral ions. pH also influenced the retention of Ca super(2+): at pH 4.5 release was the main process but adsorption increases with alkalinity up to pH 8.5. The Ca concentrations at which neither adsorption nor release occurred [Ca super(2+)] sub(e) were as follows: 5.2 mm (pH 4.5), 3.5 mm (pH 7.1), and 0.63 mm (pH 8.5). The pH effect was explained by an increase in the density of negatively charged functional groups produced by ionization reactions at pH below the point of zero net charge (pH sub(o)) which was evaluated by using the Gouy-Chapman double layer model. Values of pH sub(o) were 6.4 for raw material and 4.1 after digestion with enzymes. In both cases, the density of positively charged sites below pH sub(o) was much higher that the density of negatively charged sites above pH sub(o).