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The influence of pH and digestion with commercial enzymes on calcium adsorption in casabe
Author(s) -
Navas Petra Beatriz,
CarrasqueroDurán Armando
Publication year - 2006
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.2006.01055.x
Subject(s) - chemistry , adsorption , alkalinity , calcium , digestion (alchemy) , point of zero charge , enzyme , inorganic chemistry , chromatography , nuclear chemistry , biochemistry , organic chemistry
Summary The Ca 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 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 2+ ] e were as follows: 5.2 m m (pH 4.5), 3.5 m m (pH 7.1), and 0.63 m m (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 o ) which was evaluated by using the Gouy–Chapman double layer model. Values of pH 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 o was much higher that the density of negatively charged sites above pH o .