The ingredients present during the cooking cycle have very definite effects on the swelling characteristics of the starch and the finished viscosity of the paste. Acids disrupt hydrogen bonding to bring about more rapid swelling of the granule. Soluble solids interfere by tying up the water necessary for hydration. Fats and proteins tend to coat starch which delays granule hydration and lowers rate of viscosity development.
The pH of the medium is very important in determining the proper starch selection. An unmodified starch will peak earlier and break down faster at a pH of 2.5 than it will at a pH of 4.0 (Fig. 12).
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