Understanding the Structure and Properties of Yam Starch–Lauric Acid Complexes: Effect of Plasma Pretreatment Times

This study investigated the effect of plasma pretreatment of yam starch (YS) for different times (0, 1, 3, 5, and 7 min) on the formation and properties of yam starch–lauric acid (LA) complexes. The CI value of YS1 (plasma treatment for 1 min)–LA was highest due to the increased amylose content in plasma-treated YS. XRD results revealed that the A + V type crystalline structure was formed. YS1–LA gave the highest relative crystallinity of V-type crystal (5.5%). However, the relative crystallinity of the A-type crystal increased gradually, and the highest value was provided by YS7–LA (8.3%). FTIR and Raman results indicated that as plasma pretreatment times increased, short-range molecular order gradually increased. DSC analysis displayed the melting of retrograded starch in YS and the YS–LA complexes, respectively. For the retrogradation peak, the highest Δ H (3.11 J/g) was exhibited in YS7–LA, while for the complex peak, the highest Δ H (3.30 J/g) was exhibited in YS1–LA. Digestive test showed that with plasma pretreatment times increased, in vitro digestibility gradually decreased, and YS7–LA gave the highest SDS and RS contents. In a word, short-term plasma pretreatment was beneficial for the formation of the YS–LA complexes, while long-term plasma pretreatment was conducive to the retrogradation of starch, which are of significant guiding value for the optimization of starch modification.