Jay-lin Jane

Effects of amylopectin branch chain length and amylose content on the gelatinization and pasting properties of starch

ABSTRACT Structures and properties of starches isolated from different botanical sources were investigated. Apparent and absolute amylose contents of starches were determined by measuring the iodine affinity of defatted whole starch and of fractionated and purified amylopectin. Branch chain-length distributions of amylopectins were analyzed quantitatively using a high-performance anion-exchange chromatography system equipped with a postcolumn enzyme reactor and a pulsed amperometric detector. Thermal and pasting properties were measured using differential scanning calorimetry and a rapid viscoanalyzer, respectively. Absolute amylose contents of most of the starches studied were lower than their apparent amylose contents. This difference correlated with the number of very long branch chains of amylopectin. Studies of amylopectin structures showed that each starch had a distinct branch chain-length distribution profile. Average degrees of polymerization (dp) of amylopectin branch chain length ranged from 18...

Branch-structure difference in starches of A- and B-type X-ray patterns revealed by their Naegeli dextrins☆

Abstract Naegeli dextrins and debranched Naegeli dextrins were prepared from native starches that display A- and B-type X-ray diffraction patterns. In comparison with their debranched counterparts, Naegeli dextrins prepared from the A-type starches consistently possessed substantially more singly branched molecules than those prepared from the B-type starches. The results indicated that the A-type starches had branch points scattered in both amorphous and crystalline regions. The branch linkages present in the crystalline region might be protected during the exhaustive acid hydrolysis. The B-type starch had most branch points clustered in the amorphous region, making them more susceptible to the acid hydrolysis. These models are consistent with the previously reported amylopectin structures that the A-type starch has more short A-chains (dp 6–12) than the B-type starch. The short A-chain is likely attached to a B-chain with the branch linkage located in the crystalline region. The branch linkages present in the crystalline region and the short double helices derived from the short A-chains provide the ‘weak points’, which are more susceptible to enzymatic hydrolysis and to generate pinholes and pits to the A-type starches. Banana starch, a C-type starch resistant to enzymatic hydrolysis, produced Naegeli dextrins with substantially less singly branched chains than the A-type starches. Naegeli dextrins prepared from starches that display A-, B-, and C-type X-ray patterns have different structures. The structures of the Naegeli dextrins indicate that the A-type starch amylopectin has a scattered branch structure and the B-type has a clustered branch structure.

Characterization of SSIIIa-Deficient Mutants of Rice: The Function of SSIIIa and Pleiotropic Effects by SSIIIa Deficiency in the Rice Endosperm

Starch synthase IIIa (SSIIIa)-deficient rice (Oryza sativa) mutants were generated using retrotransposon insertion and chemical mutagenesis. The lowest migrating SS activity bands on glycogen-containing native polyacrylamide gel, which were identified to be those for SSIIIa, were completely absent in these mutants, indicating that they are SSIIIa null mutants. The amylopectin B2 to B4 chains with degree of polymerization (DP) ≥ 30 and the Mr of amylopectin in the mutant were reduced to about 60% and 70% of the wild-type values, respectively, suggesting that SSIIIa plays an important part in the elongation of amylopectin B2 to B4 chains. Chains with DP 6 to 9 and DP 16 to 19 decreased while chains with DP 10 to 15 and DP 20 to 25 increased in the mutants amylopectin. These changes in the SSIIIa mutants are almost opposite images of those of SSI-deficient rice mutant and were caused by 1.3- to 1.7-fold increase of the amount of SSI in the mutants endosperm. Furthermore, the amylose content and the extralong chains (DP ≥ 500) of amylopectin were increased by 1.3- and 12-fold, respectively. These changes in the composition in the mutants starch were caused by 1.4- to 1.7-fold increase in amounts of granules-bound starch synthase (GBSSI). The starch granules of the mutants were smaller with round shape, and were less crystalline. Thus, deficiency in SSIIIa, the second major SS isozyme in developing rice endosperm affected the structure of amylopectin, amylase content, and physicochemical properties of starch granules in two ways: directly by the SSIIIa deficiency itself and indirectly by the enhancement of both SSI and GBSSI gene transcripts.

Resistant Starch: Promise for Improving Human Health

Ongoing research to develop digestion-resistant starch for human health promotion integrates the disciplines of starch chemistry, agronomy, analytical chemistry, food science, nutrition, pathology, and microbiology. The objectives of this research include identifying components of starch structure that confer digestion resistance, developing novel plants and starches, and modifying foods to incorporate these starches. Furthermore, recent and ongoing studies address the impact of digestion-resistant starches on the prevention and control of chronic human diseases, including diabetes, colon cancer, and obesity. This review provides a transdisciplinary overview of this field, including a description of types of resistant starches; factors in plants that affect digestion resistance; methods for starch analysis; challenges in developing food products with resistant starches; mammalian intestinal and gut bacterial metabolism; potential effects on gut microbiota; and impacts and mechanisms for the prevention and control of colon cancer, diabetes, and obesity. Although this has been an active area of research and considerable progress has been made, many questions regarding how to best use digestion-resistant starches in human diets for disease prevention must be answered before the full potential of resistant starches can be realized.

Internal structure of the potato starch granule revealed by chemical gelatinization

Abstract Potato starch was separated into four different size groups. The starch of a uniform granular size with diameters between 30 and 52 μm was chemically gelatinized at the periphery of the granules with aqueous calcium chloride (4 m) at 23°C. Chemically gelatinized starch at the periphery was mechanically removed from the granule by using a blender. The gelatinized starch and the remaining granular starch were subjected to iodine titration, gel permeation chromatography, amylopectin branch-chain-length, and phosphorus analyses. The results showed that amylose was more concentrated at the periphery than at the core of the granule. Amylose at the core had larger molecular size than that at the periphery. Amylopectin at the core had longer long B-chains than that at the periphery. Starch phosphate esters were more concentrated at the core than at the periphery.

Chapter 6 – Structural Features of Starch Granules II

Publisher Summary Starch granules are commonly found in seeds, roots, tubers, stems, and leaves. Grain seeds, such as maize kernels, contain up to 75% starch on a dry starch basis. The stored starch granules can be converted by enzymes (amylases) to glucose, and the glucose is utilized to generate energy during germination or whenever energy is needed. Starch granules are densely packed with semicrystalline structures and have a density of about 1.5 g/cm3. Because of this stable semicrystalline structure, starch granules are not soluble in water at room temperature. In the granular form, starch can be isolated easily by gravity sedimentation, centrifugation, and filtration, and can be subjected to various chemical, physical, and enzymatic modifications with subsequent washing and processing. There are two major starch polymers: amylopectin and amylose, each having different properties. Biosynthesis of starch granules takes place primarily in the amyloplast. Minor components found in starch granules include polymers of sizes and with properties intermediate between those of amylose and amylopectin, starch lipids, monostarch phosphate ester groups, and proteins, particularly granule-bound starch synthase. Some minor components, especially phospholipids, free fatty acids, and phosphate ester groups, although at low concentrations, can drastically affect the properties of starch pastes and gels. An understanding of the internal organization of starch granules is crucial for scientists and engineers to optimize reaction conditions for chemical, physical, and enzymatic modifications.

Characterization of a Novel Resistant-Starch and Its Effects on Postprandial Plasma-Glucose and Insulin Responses

ABSTRACT Objectives of this study were to understand the physicochemical properties of a novel resistant starch (RS) made by complexing high-amylose maize starch VII (HA7) with palmitic acid (PA), and its effects on reducing postprandial plasma-glucose and insulin responses. The HA7 starch was heat-treated and debranched using isoamylase (ISO) to enhance the starch-lipid complex formation. The RS content of the HA7 starch debranched with ISO and complexed with PA (HA7+ISO+PA) was 52.7% determined using AOAC Method 991.43 for dietary fiber, which was greater than that of the HA7 control (35.4%). The increase in the RS content of the HA7+ISO+PA sample was attributed to the formation of retrograded debranched-starch and starch-lipid complex. The postprandial plasma-glucose and insulin responses of 20 male human-subjects after ingesting bread made from 60% (dry basis) HA7+ISO+PA were reduced to 55 and 43%, respectively, when compared with those after ingesting control white bread (as 100%) containing the same...

Effects of lipids on enzymatic hydrolysis and physical properties of starch

This study aimed to understand effects of lipids, including corn oil (CO), soy lecithin (SL), palmitic acid (PA), stearic acid (SA), oleic acid (OA), and linoleic acid (LA), on the enzymatic hydrolysis and physical properties of normal corn (NCS), tapioca (TPS), waxy corn (WCS), and high-amylose corn (HA7) starch, and to elucidate mechanisms of interactions between the starches and lipids. After cooking with the lipids (10%, w/w, dsb), NCS, TPS, and HA7 showed significant decreases in enzymatic hydrolysis, and their DSC thermograms displayed amylose-lipid-complex dissociation peaks except with the CO. (13)C NMR spectra of amylodextrin with CO showed downfield changes in the chemical shifts of carbons 1 and 4 of the anhydroglucose unit, indicating helical complex formation. Generally, free fatty acids (FFAs) reduced, but SL increased the peak viscosities of starches. FFAs and SL decreased, but CO increased the gel strength of NCS. These lipids displayed little impacts on the enzymatic hydrolysis and physical properties of WCS because it lacked amylose.

Structural and functional characteristics of selected soft wheat starches

ABSTRACT Starches from eight soft wheat samples (two parent lines and six offspring) were isolated; relationships between their structures and properties were examined. Branch chain-length distributions of amylopectins were determined by using high-performance anion exchange chromatography equipped with an amyloglucosidase reactor and a pulsed amperometric detector (HPAEC-ENZ-PAD). Results showed that the average chain length of the eight samples varied at DP 25.6–26.9. Starch samples of lines 02, 60, 63, 95, and 114 consisted of amylopectins with more long chains (DP ≥ 37) and longer average chain length (DP 26.2–26.9) than that of other samples. These starch samples of longer branch chain length displayed higher gelatinization temperatures (55.3–56.5°C) than that of other samples (54.4–54.9°C) and higher peak viscosity (110–131 RVU) and lower pasting temperature (86.3–87.6°C) than others (83–100 RVU and 88.2–88.9°C, respectively). The Mw of amylopectins, determined by using high-performance size exclusi...

MAIZE STARCH FINE STRUCTURES AFFECTED BY EAR DEVELOPMENTAL TEMPERATURE

Abstract Growing temperature is known to affect the grain yield and quality of maize. Two genetically unrelated normal dent maize inbreds, ICI63 and ICI92, with different heterotic backgrounds were grown in a greenhouse with the ears wrapped in temperature control devices set at 25 and 35 °C during the grain-filling period. Grain yield, kernel weight, and kernel density were less for ears at 35 °C than for those at 25 °C. The extent of the loss, however, varied with the variety: 13.1 and 37.9% kernel weight loss and 8.47 and 10.08% density loss for ICI63 and ICI92, respectively. The starch granular shape of ICI63 became more oval-shaped, but there was no shape change for ICI92. As developmental temperature increased, starch granule size decreased and gelatinization temperature increased. With increasing developmental temperature, the true amylose content of ICI63, determined by iodine affinity, decreased 2.39% and that for ICI92 decreased 2.20%; amylose molecular size of both varieties also decreased. Size exclusion chromatography and high-performance anion-exchange chromatography revealed an increased medium branch-chain fraction and decreased long and short branch-chain fractions for ICI63 amylopectin, whereas ICI92 amylopectin had increased long and medium branch-chain fractions and a decreased short branch-chain fraction, when the ear developed at 35 °C.