Hierarchical Structure, Gelatinization, and Digestion Characteristics of Starch from Longan (Dimocarpus longan Lour.) Seeds.

Starch was isolated from longan seeds of three widely distributed cultivars (Chuliang, Shixia, and Caopu) in China. Comparisons of the multi-level structure of the starch of longan seeds among various cultivars were made, and the relations between these structural and property characteristics are discussed. The isolated starch, accounting for 44.9⁻49.5% (w/w) in longan seeds, had an oval or an irregular polygonal shape with a smooth surface. Their chain-length distributions (CLDs) varied with longan cultivar; Chuliang showed a larger proportion of longer amylopectin chains with a degree of polymerization (DP) 30~100. This is attributed to the slightly higher relative crystallinity of Chuliang longan seed starch. Apparent differences were also detected in amylose structure. Caopu showed a higher amylose content than Chuliang and Shixia, resulting in its lower gelatinization temperatures and enthalpy change. All longan seed starch had a typical A-type crystal structure with relative crystallinity ranging 28.6⁻28.9%. For raw starch, Caopu showed the lowest digestion rate, followed by Chuliang; Shixia showed the highest. This is because Caopu had the highest amylose content. Chuliang had a more intact structure than Shixia, as suggested by its higher crystallinity, although they had similar amylose content. After being fully gelatinized, all starch showed a similar digestion process, indicating that the digestibility of gelatinized starch does not differ with starch source or structure.

Enhanced stability and controlled release of menthol using a ß-cyclodextrin metal-organic framework.

Menthol inclusion complexes (ICs) have addressed a range of opportunities in food applications due to their volatile resistance. However, previous protocols used for their synthesis give low yields and high industrial application costs. In the present investigation, metal-organic frameworks based on ß-cyclodextrin (ß-CD-MOF) have been prepared for the molecular encapsulation of menthol. Menthol/ß-CD-MOF-IC was synthesized under the optimized parameters, after which release behavior was studied. In this optimized manner, a higher menthol capacity was obtained in which the menthol content and encapsulation efficiency were 27.1 and 30.6%, respectively. Compared with menthol/ß-CD-IC, menthol/ß-CD-MOF-IC is resistant to high temperature, but sensitive to moisture. In a simulated oral release experiment, the rate of menthol release from different samples followed the order of: pure menthol > ß-CD > ß-CD-MOF, which can be attributed to two mechanisms: non-specific binding and site preference. We propose that ß-CD-MOF can be used as a promising delivery system for aroma compounds.

Encapsulation of menthol into cyclodextrin metal-organic frameworks: Preparation, structure characterization and evaluation of complexing capacity.

Cyclodextrin (CD)-metal-organic frameworks (MOFs) are developed as a new type of food-acceptable multi-porous material, which shows a great potential for controlled volatile compound release. This study aimed to synthesize CD-MOFs from potassium nitrate, crystallized with α-cyclodextrin (α-CD), ß-CD or γ-CD, and their complex capacities were further evaluated using menthol encapsulation. Compared with CD, all the CD-MOFs had highly ordered crystal structures and more regular shapes. ß-CD-MOF showed better thermal stability, with an initial thermal degradation temperature of 253 °C, higher than the other two CD-MOFs. The CD-MOFs were used for menthol encapsulation and the resulting menthol concentration within the inclusion complexes (ICs) was determined. The menthol concentration in ICs followed the order: ß-CD-MOF > ß-CD > Î³-CD-MOF > Î³-CD > α-CD ≥ α-CD-MOF. The menthol content and encapsulation efficiency of ß-CD-MOF were 21.76% (w/w) and 22.54% (w/w) respectively, significantly higher than those of other reported solid materials, such as amylose, CD and V-type starch.