Influence of Water Activity and System Mobility on Peroxidase Activity in Maltodextrin Solutions |
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Authors: | Lilia Neri Paola Pittia Gianni Bertolo Danila Torreggiani Giampiero Sacchetti |
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Institution: | (1) Department of Food Science, University of Teramo, Via C.R. Lerici 1 Mosciano S. Angelo, 64023 Teramo, Italy;(2) CRA, Via Giacomo Venezian 26, 20133 Milan, Italy; |
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Abstract: | Maltodextrins influenced the enzymatic activity in aqueous solutions by affecting the water activity (aw) and mobility as described by viscosity and T’g. In diluted solutions, viscosity being equal, (1) maltodextrin with dextrose
equivalents (DE) of 33 was more effective than glucose in limiting horseradish peroxidase (HRP) activity; (2) an increase
in the maltodextrin chain length from DE 33 to DE 8.7 did not further limited enzymatic activity; (3) the maltodextrin with
the highest chain length (DE 2.5) determined the highest enzyme inhibition. In general, the increase of molecular weight negatively
affected the HRP activity by increasing the viscosity and T’g (decreasing molecular mobility) but it positively affected the
aw and, in some cases, this compensated the HRP activity inhibition. In concentrated solutions (apparent viscosity ≈ 40 mPa s)
the HRP activity decreased with the increase of the maltodextrin molecular weight, and it showed a dependence on T’g which
could be described by a William, Landel and Ferry (WLF)-type equation. On the contrary, in the solution added with the maltodextrin
with the highest chain length (DE 2.5) the HRP activity was much higher than that predicted by the WLF-type equation. The
maltodextrin with DE 2.5 contains intact starch fragments and in water forms a suspension. In such a discontinuous system,
the viscosity in the vicinity of the protein is lower than the bulk viscosity, and thus, the enzyme activity is higher than
expected. Moreover, since T’g is a property of the soluble phase, it does not explain the mobility in discontinuous systems. |
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