The structural and digestive properties of indica rice starch-fatty acid complexes.

The structural and digestive properties of indica rice starch-fatty acid complexes and the effects of lipoxygenase on the structural and digestive properties of the complexes were examined in this study. The complexes were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy and Raman spectroscopy. The results showed that indica rice starch had the highest molecular chain order and the highest crystallinity, and the crystallization disappeared after gelatinization, and the formation of indica rice starch-fatty acid complexes promoted the transformation of starch crystal structure from A-type to V-type. Lipoxygenase reduced the regularity of starch molecular crystal structure in the complexes, while enzyme protein improved the order of starch molecular structure in the complexes. The regularity of starch crystal structure in the complexes could improve with the increase of composite temperature and the increase of fatty acid unsaturation. In vitro digestibility and in vitro digestion kinetics showed that the formation of indica rice starch-fatty acid complexes reduced the digestibility of indica rice starch to a certain extent. The RDS content of indica rice starch was 66.42 ± 0.39 %, and lipoxygenase reduced the reduction of rapidly digested starch content during complexes digestion, while enzyme protein increased the content of resistant starch.

Ingesting retrograded rice (Oryza sativa) starch relieves high-fat diet induced hyperlipidemia in mice by altering intestinal bacteria.

High-fat diet is a risk factor for many chronic diseases, whose symptoms are probably regulated by ingesting food ingredients such as resistant starch. For cooked rice stored in cold-chain, the starch component can retrograde to generate ordered structures (helices and crystallites) and become resistant. However, the role of retrograded starch in managing hyperlipidemia symptoms is insufficiently understood. Here, compared to the normal high-fat diet, ingesting retrograded starch reduced the triglyceride and low-density lipoprotein cholesterol levels of high-fat diet mice by 17.69% and 41.33%, respectively. This relieved hyperlipidemia could be linked to the changes in intestinal bacteria. Retrograded starch intervention increased the relative abundance of Bacteroides (2.30 times higher), which produces propionic acid (increased by 8.26%). Meanwhile, Bacteroides were positively correlated with butyric acid (increased by 98.4%) with strong anti-inflammatory functions. Hence, retrograded starch intervention may regulate the body's health by altering intestinal bacteria.

Microwave Cooking Enriches the Nanoscale and Short/Long-Range Orders of the Resulting indica Rice Starch Undergoing Storage.

The chain reorganization of cooked starch during storage plays an important role in the performance of starchy products such as rice foods. Here, different analytical techniques (such as small-angle X-ray scattering) were used to reveal how microwave cooking influences the chain assembly of cooked indica rice starch undergoing storage for 0, 24, or 48 h. While stored, more short-range double helices, long-range crystallites, and nanoscale orders emerged for the microwave-cooked starch than for its conventionally cooked counterpart. For instance, after storage for 24 h, the microwave-cooked starch contained 46.8% of double helices, while its conventionally cooked counterpart possessed 34.3% of double helices. This could be related to the fact that the microwave field caused high-frequency movements of polar groups such as hydroxyls, which strengthened the interactions between starch chains and water molecules and eventually their assembly into double helices, crystallites, and nanoscale orders. This work provides further insights into the chain reassembly of microwave-cooked starch undergoing storage, which is closely related to the quality attributes of starch-based products.

Physicochemical and structural properties of pregelatinized starch prepared by improved extrusion cooking technology.

Pregelatinized starch was made from indica rice starch using a so-called "improved extrusion cooking technology" (IECT) under 30%-70% moisture content. IECT-pregelatinized starch (IPS) had higher water solubility and water absorbability compared to native starch at low temperature. For pasting properties, the breakdown and setback viscosities of IPS were significantly (p<0.05) lower than native starch, suggesting improved gel stability and reduced short-term retrogradation. The rice starch granules lost their integrity in IPS, and formed a honeycomb-like structure with increased moisture content in the raw material. These properties can be explained in terms of molecular structural features, particularly the large reduction in the size of molecules, but without significant changes in the chain-length distributions of amylopectin component, and no significant change in amylose fraction. These results indicate that IECT is suitable for preparing IPS with desirable water solubility and gel stability properties.

Structure and digestion of hybrid Indica rice starch and its biosynthesis.

The fine structure (including contents, size and chains length distribution) of amylose and amylopectin of Hybrid Indica Rice starch have an impact on digestion properties of Indica Rice. Indica Rice starches with different amylose contents were chosen as model materials in this study. The amylose and amylopectin size were characterized using size-exclusion chromatography (SEC), the fine structure of amylopectin were studied by flurophore-assisted carbohydrate electrophoresis (FACE) and parameterized by amylopectin biosynthesis model to identify associations with starch digestibility. The digestograms of all starches fit first-order kinetics. All results show that the hybrid Indica rice starch with higher amylose content has a slower digestion rate. SEC results show that there is no obviously in chains length distribution (CLD) for amylopectin, but a significantly sharp difference in amylose. No difference in amylopectin was also observed from FACE result. The amylose starch controlled by GBSSI enzyme may be the key parameter to influence starch digestion.

Structure characterization and hypoglycemic effects of dual modified resistant starch from indica rice starch.

Hypoglycemic effects of indica rice resistant starch (IR-RS) were investigated. We prepared IR-RS using a method that combined physical modification and enzyme modification, and the RS content was 47.0%. Differential scanning calorimetry--thermal gravimetric analysis showed that IR-RS have higher enthalpy and less loss of mass than single modified RS, heat-moisture RS and native starch. Scanning electron microscopy revealed that IR-RS displayed more compact spatial structure. IR-RS products displayed a mixture of B-and V-type x-ray diffraction patterns and the cyrstallinity was 51.0%. IR-RS significantly affected body weight, blood glucose, organ indices and serum lipid levels. These results demonstrated that dual modification changed the structure of indica rice starch and affected its digestibility as well as the blood glucose levels of the diabetic mice who consumed it.

Particle-stabilizers modified from indica rice starches differing in amylose content.

Octenyl succinic anhydride (OSA) starches were prepared from four cultivars of native indica rice starches with amylose contents of 1.90%, 18.01%, 25.40% and 26.98% (w/w). The emulsion stability and microstructure of the oil-in-water Pickering emulsions (soybean oil/water, 1/2, v/v) stabilized by OSA starch particles were investigated. Results indicated that the average droplet sizes of the emulsions were in the range of 10-70 µm, depending on starch cultivars. During 100 days of storage, the emulsions made from OSA starches (degree of substitution: 0.0287-0.0294) were stable. Optical microscopy showed that starch particles were accumulated at the oil-water interface in the form of a densely packed layer, which prevented the flocculation and coalescence of oil droplets by a steric mechanism. Moreover, the emulsification of particle-stabilizers was positively correlated with degree of substitution (P<0.01) but had no obvious correlation with amylose content and pasting properties.

The effect of three gums on the retrogradation of indica rice starch.

Retrograded starch (RS(3)) was produced from indica rice starch with three kinds of gums (konjac glucomannan, KGM; carrageenan, CA, USA; and gellan, GA, USA) by autoclaving, respectively, and the effect of the gums on the retrogradation behavior of starch was estimated. The influences of polysaccharide concentration, sodium chloride concentration, autoclaving time, refrigerated time, and pH value on RS(3) formation were discussed. Except for sodium chloride's persistent restraint on RS(3), the others all forced RS(3) yields higher at first, but lowered it after the peak value. The influencing sequence of these impact factors was: sodium chloride concentration > polysaccharide concentration > autoclaving time > refrigerated time > pH value. The results also proved that in the three gums, KGM plays the most significant role in RS(3) changing. It was concluded that the incorporation of each of these three gums into starch, especially KGM, results in an increase or decrease of RS(3) under different conditions. This phenomenon could be taken into consideration when developing starchy food with appropriate amount of RS(3).