Poster Topical Area: Dietary Bioactive Components
Location: Hall D
Poster Board Number: 321
Objectives: Characterized structural, functional and digestibility changes in maize amylopectin and potato starch resulting from complexations with phenolics.
Methods: Caffeic acid, ferulic acid or gallic acid was complexed with maize amylopectin (MA) and potato starch (PS), respectively. Phenolic contents of native starch and starch-complexes were determined by LC-MS. Rheological properties were determined by rapid visco analyzer and differential scanning calorimetry. Rapidly digestible starch, slowly digestible starch (SDS) and resistant starch (RS) contents were measured in the presence and absence of phenolics complexations. In addition, FTIR, NMR and iodine binding techniques were used to explore molecular mechanisms underlying the rheological and digestibility changes.
Results: Complexation increased phenolic content of both native starches. Complexed phenolics decreased thermal stability of native MA (70.6 ± 0.18 ℃) and PS (64.7 ± 0.14 ℃) by reducing melting temperatures to 69.2-69.4 and 58.6-58.8 ℃, respectively. Significantly reduction of swelling factors were observed for both MA (30.4 ± 3.1 vs. 21.4-25.1) and PS (40.9 ± 4.2 vs. 22.0-26.1, p < 0.05). Peak viscosity, hot paste viscosity and cool paste viscosity of starch-phenolics complexes were at 2-30 times lower than those of native starches and uncomplexed starch-phenolics mixtures. More interestingly, complexed phenolics appeared to have additional inhibitory effects on starch digestion with evidence on the modest increase in SDS contents for MA and RS contents for PS, when compared to the matching starch-phenolics mixtures. These alterations were tentatively attributed to disruptions of starch crystallinity and α (1,4) glycosidic linkage, as reductions in short-range orders of starch granules and 1H (1,4) signals were discovered by FTIR and NMR respectively.
Conclusions: Phenolics complexation could serve as an important factor in modulating rheological properties and digestibility of starch. While complexation appears to lead to structural alterations that thermally destabilize starch granules and reduces viscosity of gelatinized MA and PS, these changes may modestly delay starch digestion in vivo.
North Carolina State University
Kannapolis, North Carolina