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CHANGES IN RHEOLOGICAL PROPERTIES OF HYDROXYPROPYL POTATO STARCH PASTES DURING FREEZE‐THAW TREATMENTS II. EFFECT OF MOLAR SUBSTITUTION AND CROSS‐LINKING
Author(s) -
KIM HAK RYANG,
ELIASSON ANNCHARLOTTE
Publication year - 1993
Publication title -
journal of texture studies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.593
H-Index - 54
eISSN - 1745-4603
pISSN - 0022-4901
DOI - 10.1111/j.1745-4603.1993.tb00044.x
Subject(s) - syneresis , differential scanning calorimetry , starch , rheology , materials science , dynamic mechanical analysis , rheometry , thermogravimetric analysis , chemical engineering , chemistry , composite material , food science , polymer , organic chemistry , thermodynamics , physics , engineering
The effects of molar substitution (M.S.) and cross‐linking on the freeze‐thaw stability of hydroxypropyl potato starch pastes were studied by following the changes in the rheological behaviour during heat treatment of the thawed starch pastes, and by determination of syneresis. In addition, differential scanning calorimetry (DSC) was used to investigate the thermal transition properties of the starch pastes that exhibited syneresis. With increasing M.S., the changes in both complex modulus (G*) and phase angle (δ) indicative of destabilization, and starch paste syneresis were delayed with regard to the number of freeze‐thaw cycles. When a starch paste showed a peak in G*, related to syneresis, it also showed a thermal transition peak in the DSC measurements. The enthalpy value decreased with increasing M.S., and it appeared to be related to the extent of syneresis and the magnitude of the peak in G*. Comparison of the rheological behaviour of hydroxypropyl potato starch pastes and hydroxypropyl and cross‐linked potato starch pastes, suggested that the former were gradually transformed into coarsely aggregated structures while the latter became diluted starch dispersions, due to shrinkage of swollen starch granules and their disruption.