Study on multiscale structures and digestibility of cassava starch and medium-chain fatty acids complexes using molecular simulation techniques

Effect of complexation of three medium-chain fatty acids (octanoic, decylic and lauric acid, OA, DA and LA, respectively) on structural characteristics, physicochemical properties and digestion behaviors of cassava starch (CS) was investigated. Current study indicated that LA was more easily to combine with CS (complex index 88.9%), followed by DA (80.9%), which was also consistent with their corresponding complexed lipids content. Following the investigation of morphology, short-range ordered structure, helical structure, crystalline/amorphous region and fractal dimension of the various complexes, all cassava starch-fatty acids complexes (CS-FAs) were characterized with a flaked morphology rather than a round morphology in native starch (control CS). X-ray diffraction demonstrated that all CS-FAs had a V-type crystalline structure, and nuclear magnetic resonance spectroscopy confirmed that the complexes made from different fatty acids displayed similar V6 or V7 type polymorphs. Interestingly, small-angle X-ray scattering analysis revealed that α value became greater following increased carbon chain length of fatty acids, indicating the formation of a more ordered fractal structure in the aggregates. Changes in rheological parameters G' and G'' indicated that starch complexed with fatty acids was more likely to form a gel network, but difference among three CS-FAs complexes was significant, which might be contributed to their corresponding hydrophobicity and hydrophilicity raised from individual fatty acids. Importantly, digestion indicated that CS-LA complexes had the lowest hydrolysis degree, followed by the greatest RS content, indicating the importance of chain length of fatty acids for manipulating the fine structure and functionality of the complexes.

Effects of Stir-Frying and Heat-Moisture Treatment on the Physicochemical Quality of Glutinous Rice Flour for Making Taopian, a Traditional Chinese Pastry

Taopian is a traditional Chinese pastry made from cooked glutinous rice flour. The effects of heat-moisture treatment (110 °C, 4 h; moisture contents 12-36%, w/w) on the preparation of cooked glutinous rice flour and taopian made from it were compared with the traditional method of stir-frying (180 °C, 30 s). The color of heat-moisture-treated (HMT) flours was darker. HMT flours exhibited a larger mean particle size (89.5-124 μm) and a greater relative crystallinity of starch (23.08-42.92%) and mass fractal dimension (1.77-2.28). The flours exhibited water activity in the range of 0.589-0.631. Although the oil-binding capacity of HMT flours was largely comparable to that of stir-fried flours, HMT flours exhibited a lower water absorption index. Accordingly, the taopian produced with HMT flours exhibited a lower brightness, accompanied by a stronger reddening and yellowing. In addition, more firmly bound water was observed in the taopian produced with HMT flour. The taopian made with HMT flour with a moisture content of 24% exhibited moderate hardness, adhesiveness and cohesiveness and received the highest score for overall acceptability (6.80). These results may be helpful to improve the quality of taopian by applying heat-moisture treatment in the preparation of cooked glutinous rice flour.

The Effect of Different Milling Methods on the Physicochemical and In Vitro Digestibility of Rice Flour

Preparation methods have been found to affect the physical and chemical properties of rice. This study prepared Guichao rice flour with wet, dry, semi-dry, and jet milling techniques. Differences in the particle size distribution of rice flour were investigated in order to assess their impact on pasting, thermal, gel, starch digestibility, and crystalline structure using an X-ray diffractometer (XRD) and a Rapid Visco Analyzer (RVA) across in vitro digestibility experiments. The results showed that semi-dry-milled rice flour (SRF) and wet-milled rice flour (WRF) were similar in damaged starch content, crystalline structure, and gelatinization temperature. However, compared with dry-milled rice flour (DRF) and jet-milled rice flour (JRF), SRF had less damaged starch, a higher absorption enthalpy value, and a higher gelatinization temperature. For starch digestibility, the extended glycemic index (eGI) values of WRF (85.30) and SRF (89.97) were significantly lower than those of DRF (94.47) and JRF (99.27). In general, the physicochemical properties and starch digestibility of WRF and SRF were better than those of DRF and JRF. SRF retained the advantages of WRF while avoiding the high energy consumption, high water consumption, and microbial contamination disadvantages of WRF and was able to produce better rice flour-associated products.

Physicochemical properties of A- and B-type granules isolated from waxy and normal hull-less barley starch

Large A-type and small B-type starch granules separated from waxy and normal hull-less barley starches were investigated for their physicochemical properties. Hull-less barley starch granules were covered by a membrane composed mainly of phospholipids. Channels of waxy A- and B-type granules were rich in proteins and phospholipids. Compared with A-type starch, B-type starch exhibited higher specific surface area, volume and average diameter of mesopores. Waxy A-type granules exhibited the higher peak, breakdown, final and setback viscosity than did B-type granules, while normal A-type granules showed the lower peak, breakdown, final viscosity and the higher setback viscosity than did B-type granules. B-type starch gels with lower storage modulus exhibited a less elastic gel network structure and retrograded more slowly. Moreover, in vitro hydrolysis of starch showed that the B-type granules exhibited a higher hydrolysis extent and rate than the A-type granules in the first stage, which was consistent with higher initial α-amylase binding ability of B-type granules. The study showed that the A-type and B-type starch separated from waxy and normal hull-less barley exhibited very different physicochemical properties.

Soybean lecithin-stabilized oil-in-water (O/W) emulsions increase the stability and in vitro bioaccessibility of bioactive nutrients

This study was proposed to investigate the possibility of co-delivering essential oils and lipophilic nutrients via lecithin stabilized emulsions. Emulsions with different droplet sizes (62.5-105 nm), zeta potentials (-33.7 to -58.6 mV), and PdI values (0.155-0.275) were successfully prepared. Incorporation of curcumin into emulsions significantly improved its water solubility (1700-fold), thermal and photochemical stability. The droplet size of curcumin-loaded emulsions did not change over 30 days of storage at 4 °C. Gastrointestinal tract (GIT) digestion caused significant changes in the droplet size and interfacial properties of curcumin-loaded emulsions. The bioaccessibility of encapsulated curcumin was 4.79-10.6-fold higher than that of free molecule. This is mainly attributed to the different solubility of curcumin in essential oils, which also showed different bioaccessibility. The findings suggested that emulsions can be novel carriers for co-delivering essential oils and lipophilic nutrients with increased stability and bioaccessibility.

Sonication increases the porosity of uncooked rice kernels affording softer textural properties, loss of intrinsic nutrients and increased uptake capacity during fortification

This work investigates the effect of sonication on brown and milled rice grains of both waxy and non-waxy varieties. We report herein the microstructural analysis of uncooked rice kernels under sonication and its effect on the textural properties. X-ray computed tomography results showed the formation of microporous surfaces and the creation of cracks and fissures. Sonication increased the % porosity of the rice samples allowing for easy penetration of water during the cooking process and promotes softer texture. Moreover, the effect of sonication in brown rice resulted to the decrease in endogenous iron and phosphorus contents but increased its capacity for iron uptake through fortification when sonicated rice is soaked in the mineral solution.