Cereals & Grains Association
Log In

Interaction of proanthocyanidins with partially gelatinized normal and waxy maize starch and impact on in-vitro starch digestibility
D. B. AMOAKO (1), J. M. Awika (1). (1) Texas A&M University, College Station, TX, U.S.A.

Proanthocyanidins (PA) from sorghum interact with amylose to increase resistant starch (RS) in fully gelatinized corn starch. However starch typically undergoes partial gelatinization in most starchy foods. This study investigated the effect of reacting sorghum PA with partially gelatinized maize starch on <i>in-vitro </i>digestibility. PA extract from high-tannin sorghum was incubated with normal and waxy maize starch, in 30% and 50% ethanol solutions at 70°C for 20 mins. Samples were then centrifuged and sediments oven dried at 40°C overnight. Non-tannin extract from white sorghum was used for comparison, and cellulose was used as a control. <i>In-vitro </i>digestibility (Rapidly digestible starch - RDS, Slowly digestible starch – SDS, RS), starch pasting properties and X-ray (WAX) diffraction pattern were determined. The amount of PA that interacted with starch (mg PA/g of starch) was higher in 30% ethanol treatments (5.94 – 6.47) than 50% (3.44 – 3.47); largely due to the greater degree of starch granule swelling in the 30% ethanol treatments. Normal starch treated with PA (in 30% ethanol) had higher SDS (27.4%) and RS (29.9%) compared to non-tannin treatment (SDS=10.2, RS=13.9) and cellulose control (SDS=9.09, RS= 15.75). This trend was also observed in waxy starch treatments. Normal starch treated in 30% ethanol also had higher SDS (27.4%) than waxy starch treatment (9.82%), a direct result of a less hindered interaction between linear amylose in normal starch with PA. Peak viscosities of PA starches were all significantly higher than controls, suggesting the formation of tougher gels due to PA-starch interaction. PA treatments incubated in 30% ethanol had higher pasting temperature and crystallinity (%) than controls, implicating the possible formation of new crystalline regions due to PA action. PA interact with maize starch to reduce <i>in-vitro </i>digestibility.

View Presentation