Debranched unacetylated and acetylated potato starches with two degrees of substitution, 0.041 (low) and 0.078 (high), combined with or without β-amylase hydrolysis were prepared to form soluble and insoluble complexes with stearic acid. The effects of modifications on the complexation, thermal properties, and X-ray patterns of soluble and insoluble complexes were investigated. Acetylation decreased the recovery of insoluble complexes but increased that of soluble complexes. Low acetylated, β-amylase-treated starch had a significantly increased amount of complexed stearic acid (123.1 mg/g) for insoluble complexes; high acetylated, β-amylase-treated starch had the highest complexed stearic acid (61.2 mg/g) for the soluble complexes. The melting temperature of the complexes decreased with acetylation. All β-amylase-treated acetylated complexes displayed the V-type diffraction pattern with peaks at 2θ = 7.4°, 12.9°, and 20°. These results suggest that starch can be modified by acetylation, debranching, and/or β-amylase to produce significant quantities of soluble starch-stearic acid complexes.

Cereal Chem. 93(1):39-46Germinated brown rice is popular in Asia for its increased g-aminobutyric acid (GABA) content and sweeter and softer texture compared with conventional brown rice. However, most studies investigated germinated rice properties on medium-grain or aromatic rice. The objective of this study was to compare differences between a medium-grain (Jupiter) and a long-grain (Wells) rice under similar germination conditions on their milling, physicochemical, and textural properties over the course of germination. Rough rice was soaked in water at 25°C for 12 h and then incubated at 30-34°C for four germination durations. Wells had a higher breakage percentage and a greater weight decrease than Jupiter during germination. Wells had a significantly lower GABA content before germination and at the first two germination durations than Jupiter, but the GABA content in Wells significantly increased at the third germination duration to become significantly higher than that of Jupiter. There were no significant changes in gelatinization temperatures and pasting properties of germinated rice from both cultivars at different germination durations. The cooked rice hardness from Wells decreased at the longest germination duration, whereas Jupiter showed a more significant decrease in cooked rice stickiness from germination. The results demonstrate that the impacts of germination on physical, chemical, and textural properties of rice were affected by grain type and germination

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The solubility of starch-inclusion complexes affects the digestibility and bioavailability of the included molecules. Acetylation with two degrees of substitution, 0.041 (low) and 0.091 (high), combined without or with a β-amylase treatment was employed to improve the yield and solubility of the inclusion complex between debranched potato starch and oleic acid. Both soluble and insoluble complexes were recovered and analyzed for their degree of acetylation, complexation yields, molecular size distributions, X-ray diffraction patterns, and thermal properties. Acetylation significantly increased the amount of recovered soluble complexes as well as the complexed oleic acid in both soluble and insoluble complexes. High-acetylated debranched-only starch complexed the highest amount of oleic acid (38.0 mg/g) in the soluble complexes; low-acetylated starch with or without the β-amylase treatment resulted in the highest complexed oleic acid in the insoluble complexes (37.6-42.9 mg/g). All acetylated starches displayed the V-type X-ray pattern, and the melting temperature generally decreased with acetylation. The results indicate that starch acetylation with or without the β-amylase treatment can improve the formation and solubility of the starch-oleic acid complex.

Linear starch forms inclusion complexes with hydrophobic compounds, and the complexation is affected by many factors, such as the degree of polymerization (DP) of linear starch. Enzymatic modification of starch may create more linear starch with favorable DPs that could enhance starch‐inclusion complexation. Starches from different botanical sources, including potato, common corn, and high amylose corn starch (Hylon VII, ∼70% amylose), were modified enzymatically using isoamylase alone or combined with β‐amylase prior to complexing with stearic acid, and the resultant modified starches and their complexes were characterized. Debranching significantly increased iodine affinity (IA) of potato and common corn starch, but had no effect on Hylon VII; the additional β‐amylase treatment further increased IA of potato and common corn starches, but decreased IA of Hylon VII. The highest amount of complexed stearic acid as measured by gas chromatography was formed by the debranched and β‐amylase‐treated potato starch. All the starch complexes displayed a mixture of the B‐ and V‐type X‐ray diffraction patterns, with the debranched and β‐amylase‐treated starch complexes exhibiting more of the V‐type pattern. These results indicate that an additional β‐amylase treatment significantly increased complexation between starch and stearic acid for debranched potato and common corn starches, but debranching alone was sufficient to increase Hylon VII and stearic acid complexation under the present experimental conditions.

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The objective of this human study was to investigate the effect of a novel parboiled brown rice product on blood glucose levels. We hypothesized that the prepared‐parboiled brown rice product caused lower blood glucose responses than the control glucose solution. Using a randomized crossover design, 14 healthy male participants were divided among 3 cohorts (4–5 subjects per cohort) and consumed both treatments with a one‐week washout period. After consuming the rice product, subjects showed significantly lower blood glucose response at 15, 30, 45, 60, 75, and 90 minutes in comparison with the control glucose solution (P<0.05). Subsequently, the incremental AUCs (Area Under the Curve) of blood glucose were also significantly lower with the novel rice product (3795±602 mg·(−15~180 min)/dL) than the control glucose solution (5880±658 mg·(−15~180 min)/dL) (P<0.05). In addition, the incremental AUCs of plasma insulin response reduced significantly to 37–40% when subjects ingested the rice product comparing with the glucose solution (P<0.05). Results suggest the novel brown rice product would assist in managing blood glucose levels for individuals suffering from diabetes. Funding provided by Arkansas Biosciences Institute is greatly appreciated.