Effect of pre‐swelling and freezing/thawing cycles on the structure of molecular, morphological, and functional properties of potato starch.

This study aimed to investigate the effect of pre‐swelling at 55°C for 1 hr followed by freezing‐thawing cycles (PFTCs), and freezing‐thawing cycles (FTCs) in the starch granules to improve the freeze‐thaw stability and evaluate its impact on the molecular, morphological, and functional properties of potato starch (PS). FTCs at 1 cycle and 7 cycles were applied for both treated PS. Microscopical structure, thermal, molecular, and functional properties (i.e., swelling power, solubility, shear viscosity, and gel strength) were comprehensively analyzed. In terms of granule structures, treated PS by FTC showed a slightly affected on the surface of starch granules, while treating PS by PFTC showed an affected in the form of small cracks and holes in the outer surface of starch granules. The gelatinization enthalpy (∆Hgel) values decreased in the treated PS compared with the native. Thus, decreasing was systemically increased with the number of applied cycles from 1‐ to 7‐cycle. The viscosity of treated PS decreased systematically with molecular degradation or the physical modification, with remarkable reduction, particularly at a higher shear rate (150°C). Treated PS by FTC showed a clear difference (p ≤.05) in gel values compared with the native at disintegration temperature 115°C. Finally, the degradation of the molecular properties showed significant differences between the native and treated PS either by the FTC or PFTC in molecular weight of starch and amylose without debranching and after debranching by pullulanase enzyme. Practical applications: Freezing is one of the standard preservation methods used for ready‐to‐eat products. When this type of food's exposed to more freeze‐thaw cycles, the phase separation will be increased due to the increase in retrogradation of amylopectin. To avoid such changes during frozen storage, native potato starch (PS) was modified using both pre‐swelling followed by freezing‐thawing cycles (PFTCs) and freezing‐thawing cycles (FTCs) at 1‐ and 7‐cycle to enhance starch properties, such as swelling power, solubility, shear viscosity, and gel strength. The findings of this study might add to the theoretical understanding of modified PS and act as a guideline for modified starch manufacturing. [ABSTRACT FROM AUTHOR]