Abstract: Potato starch was microwave-treated respectively with the power of 2. 06 and 6. 63W/g,and the single and double-helical structures of native and microwave-treated starches and their digestibility were analyzed by means of DSC,XRD,¹³C CP/MAS NMR and in vitro digestion，so as to reveal the effects of the microwave treat- ment on the single and double-helical structures and digestibility of the potato starch as well as the relationship be- tween the single and double-helical structures and the digestibility.The results show that (1) as the microwave power increases,the contents of the single helix，the double helices,the gelatinization enthalpy and the relative crystallinity decrease,while the amorphous components increase; (2) the low-power (2. 06W/g) microwave has a small effect on the digestibility,while the high-power (6. 63W/g) microwave significantly decreases the content of the resistant starch and correspondingly increases the contents of the slowly-digestible starch and the rapidly-di- gestible starch; (3) the microwave treatment destroys the internal single and double-helical structures of the starch and thus decreases their contents，and the extent of the destruction gradually increases with the increase of the mi- crowave power; and (4) the reduction in the contents of the single and double-helical components causes the starch digestibility to change.In addition,the low-power microwave rarely decreases the contents of the single and double-helical components and thus hardly influences the starch digestibility,while the high-power microwave sig- nificantly decreases the contents of the single and double-helical components and thus results in a drastic change in the starch digestibility.

Key words: microwave, potato starch, single/double-helical structures, digestibility, crystallinity