Effect of multiple freezing and thawing on the surface and functional properties of granular potato starch

Influence of multiple freezing and thawing on the porosity of potato starch granules was determined with a nitrogen sorption method. As a consequence of the processing, the granule specific surface area and the size of granule pores significantly increased, whereas the true (helium) density of the granules noticeably decreased. The effect depended on freezing conditions and the moisture content in starch. The most pronounced result was achieved on gradual freezing of ambient native granular starch containing 13% (w/w) water. In that case, after 10 freezing/thawing cycles, specific surface area of granules increased from initial 0.36 to 1.64 m2/g. Single deep freezing in liquid nitrogen of oven-dried starch (8% w/w of moisture) in water suspension resulted in the increase of the granule initial total pore volume and the mean pore diameter by five and almost three times, respectively. The processing notably influenced wetting ability and α-amylase digestibility of the granules. The obtained data could be helpful in evaluation of storage stability of potato starch-based foodstuffs. Due to its modified physical properties, granular potato starch subjected to multiple freezing and thawing could be suitable for new applications in food technology or pharmacology.