An innovative approach for significantly increasing enzyme resistant starch type 3 content in high amylose starches by using extrusion cooking

In this study effects of extrusion cooking on enzyme resistant starch (RS) formation in high amylose corn starches (Hylon V and VII) and the functional properties of RS preparations were investigated. Native starches were extruded at 50, 60, 70% feed moisture contents, at constant screw speed (100 rpm) and barrel temperature (140 °C). Among these samples, the highest RS contents were observed at 60% feed moisture. Therefore, feed moisture in the second and third extrusion cycles was set at 60%. There were significant increases in RS contents of both Hylon V and Hylon VII after the second extrusion cycle (p < 0.05). After the third extrusion, the RS levels reached to 40.0 and 45.1% for Hylon V and Hylon VII, respectively. Substantial loss of birefringence in these samples indicated that the increases in RS were mainly due to RS3 formation. The RS samples produced by extrusion did not have high emulsion capacity, but the ones produced from Hylon VII had high emulsion stability. Although, decreases in L* and increases in b* values of extruded samples were significant as compared to respective native starches, the changes were not substantial. Therefore, their incorporation is not expected to cause major changes in the colour of end-products.     

Structure and enzymatic resistivity of debranched high temperature–pressure treated high-amylose corn starch

High-amylose corn starch (HACS) was treated with high temperature–pressure (HTP) treatment and pullulanase debranching. It was found that 24 h storage was favorable for resistant starch (RS) formation. Structure (granular morphology, fractal structure, lamellar structure, crystalline structure, weight-average molecular weight) and properties (swelling power, solubility, enzymatic resistivity) were evaluated for native starch and the samples with 24 h storage. By modification, the surface became loose and rough fragmented and the birefringence crosses disappeared. All samples displayed a B + V crystalline structure. The scattering objects of native starch at the higher scale level were more compact than those of modified starches, and the latter displayed a mass fractal structure which became more compact as debranching increased. The native starch contained RS2 and RS5, while the modified samples included RS3 and RS5. The higher amount of V-type crystals and the starch chains with smaller molecular weight could lead to form more RS. Interestingly, a surface fractal structure with D_s2 was measured for the modified starches, leading to more RS, since some active sites of starch molecules were masked by the ordered-aggregations of molecular chains in the scattering objects. Furthermore, the more compact scattering objects with D_m1 contributed to forming more RS.     

Physicochemical properties and amylopectin fine structures of A- and B-type granules of waxy and normal soft wheat starch

This work fractionated waxy and normal wheat starches into highly purified A- and B-type granule fractions, which were representative of native granule populations within parent native wheat starches, to accurately assess starch characteristics and properties of the two granule types. Wheat starch A- and B-type granules possessed different morphologies, granule specific surface area measurements, compositions, relative crystallinities, amylopectin branch chain distributions, and physical properties (swelling, gelatinization, and pasting behaviors). Within a genotype, total and apparent amylose contents were greater for A-type granules, while lipid-complexed amylose and phospholipid contents were greater for B-type granules. B-type (relative to A-type) granules within a given genotype possessed a greater abundance of short amylopectin branch chains (DP_n < 13) and a lesser proportion of intermediate (DP_n 13–33) and long (DP_n > 33) branch chains, contributing to their lower relative crystallinities. Variation in amylose and phospholipid characteristics appeared to account for observed differences in swelling, gelatinization, and pasting properties between waxy and normal wheat starch fractions of a common granule type. However, starch granule swelling and gelatinization property differences between A- and B-type granules within a given genotype were most consistently explained by their differential amylopectin chain-length distributions.     

Effects of starch composition and type of non-solvent on the formation of starch nanoparticles and improvement of curcumin stability in aqueous media

In this study, we evaluated the effects of amylopectin/amylose ratio and non-solvent type on starch nanoparticle formation including the average particle size, polydispersity index, size distribution, and nanoparticle morphology using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The most uniform particles were obtained from normal corn starch with ethanol. The average particle size was 98.8 ± 1.8 nm using DLS while combination of size distribution study and SEM images showed that particle size ranged between 60 and 90 nm. A bimodal distribution was observed with two defined groups of nanoparticles when waxy corn starch (Amioca) was nanoparticulated with ethanol. SEM images of freeze dried samples and DLS size distribution curves of fresh samples showed that high amylose starch including Hylon V and Hylon VII gave uniform, spherical and small nanoparticles in the size range of 20–60 and 15–50 nm, respectively. The smallest nanoparticles were fabricated by precipitation with methanol, followed by ethanol and the largest nanoparticles were formed using acetone. Re-dispersion of nanoparticles was good when nanoparticles were fabricated using ethanol and acetone especially for Amioca, whereas redispersion of samples in aqueous PBS solution, precipitated using methanol was difficult especially in the case of Hylon VII. Stability of curcumin in the presence of 1 mg/ml native starch nanoparticles was much higher (83.7 ± 3.1%) than curcumin in phosphate buffered saline at pH 7.0 (5.5 ± 1.5%) over 10 days at ambient temperature. Interaction between iodine-potassium iodide solution and starch nanoparticles showed that the helical structures of amylose and amylopectin molecules remain in the nanoparticles and curcumin may interact with these helical structures giving it the stability which is not observed in water.     

In VitroDigestion of Wheat Microstructure with Xylanase and Cellulase fromTrichoderma reesei

Resistant starch (RS), producedin vitroby hydrolysis of retrograded pea starch gels and amylose gels by porcine pancreaticalpha-amylase, was characterised by X-ray diffraction, size exclusion chromatography and methylation analysis. These techniques showed that RSin vitroconsisted of semi-crystalline, mostly linear material that was present in two main molecular size subfractions (DP_n>100 andDP_n20–30) with a third, minor subfraction (DP_n≤5). The extent of retrogradation of amylose was found to be of primary importance in determining the RS content of starch. Analysis ofin vivoRS, recovered during an ileostomy study, produced results that were similar to those obtained from RSin vitro. Anin vitromodel for the structure of resistant starch is proposed.     

Physicochemical Studies on Resistant StarchIn VitroandIn Vivo

Resistant starch (RS), producedin vitroby hydrolysis of retrograded pea starch gels and amylose gels by porcine pancreaticalpha-amylase, was characterised by X-ray diffraction, size exclusion chromatography and methylation analysis. These techniques showed that RSin vitroconsisted of semi-crystalline, mostly linear material that was present in two main molecular size subfractions (DP_n>100 andDP_n20–30) with a third, minor subfraction (DP_n≤5). The extent of retrogradation of amylose was found to be of primary importance in determining the RS content of starch. Analysis ofin vivoRS, recovered during an ileostomy study, produced results that were similar to those obtained from RSin vitro. Anin vitromodel for the structure of resistant starch is proposed.     

Molecular Structure of a Low-Amylopectin Starch and Other High-Amylose Maize Starches

The molecular structure of two commercially available high-amylose maize starches, HYLON® V starch and HYLON® VII starch, and of a newly developed low-amylopectin starch (LAPS) was examined. These high-amylose starches give three apparent fractions as determined by gel-permeation chromatography: a high-molecular weight (mol.wt) amylopectin fraction, a low-mol.wt amylose fraction, and an intermediate-mol.wt fraction which contains both linear and branched components. The low-mol.wt amylose fraction increases from 9·4% in HYLON V starch to 17·7% in HYLON VII starch and 26·5% in LAPS, whereas the high-mol.wt amylopectin fraction decreases from 31·1% in HYLON V starch to 13·8% in HYLON VII starch and 2·5% in LAPS. The percentage of linear components in HYLON V starch, HYLON VII starch, and LAPS are 42, 54, and 80%, respectively. High-amylose starches have a large proportion of long chains in their branched fractions compared to waxy-maize and normal-maize starch. Both HYLON VII starch and the LAPS give B plus V-type X-ray diffraction patterns, but the LAPS has even a higher gelatinization temperature, lower swelling power in hot water, and is more resistant to acid digestion. With the lack of amylopectin, amylose accounts for at least part of the double helical structure in the LAPS granules.     

Amylolysis of wheat starches. I. Digestion kinetics of starches with varying functional properties

The susceptibility of wheat (Triticum aestivum L.) starches to hydrolysis by pancreatic α-amylase in vitro was investigated using a series of 35 starches with slightly enriched amylose content within a narrow range (36–43%), but widely differing functional properties. After 2 h of incubation with α-amylase, native starch granules were digested to different extents, but there were no differences between any of the starches once they were gelatinized. Cooling the starch for 72 h at 4 °C after cooking reduced the susceptibility of all of the starches to enzymic digestion by a similar extent, whereas addition of monopalmitin decreased the digestibility of the starches that contained amylose, but did not affect the digestibility of waxy starches that were also included in the study. Amylopectin chain length distribution of partly digested starch granules displayed increased proportion of short and medium chains and decreased proportion of long chains in comparison to native granules. Separated large (A) and small (B) starch granules from three of the starches differed significantly in their susceptibility to in-vitro digestion. A predictive model of the susceptibility of starch in the different forms was developed from the physico-chemical and functional properties of the starches.     

Impact of continuous or cycle high hydrostatic pressure on the ultrastructure and digestibility of rice starch granules

The effects of continuous or 2-cycle high hydrostatic pressure (HHP) treatments (200 and 600 MPa) on the microstructure and digestibility of rice starches were investigated. The morphological and structural changes were characterized using polarized light microscopy, scanning electron microscopy, atomic force microscopy, X-ray scattering and ¹³C CP/MAS NMR, and the starch digestibility was examined by in vitro hydrolysis. Results showed that HHP at 600 MPa significantly alters the microstructure and lowers the resistant starch (RS) compared with HHP at 200 MPa. Under the same pressure level, the two 15-min cycle treatment induced more structural disruption, gelatinization, disappearance of surface protrusion, and lower RS of rice starches than that of the continuous HHP treatment (30 min). Based on the results on RS, the two 15-min cycle HHP treatment at 200 MPa could be beneficial for improving the functionality of the rice starch.     

Retrogradation of waxy and normal corn starch gels by temperature cycling

Gelatinized waxy and normal corn starches at various concentrations (20–50%) in water were stored under temperature cycles of 4°C and 30°C (each for 1 day) up to 7 cycles or at a constant temperature of 4°C for 14 days to investigate the effects of temperature cycling on the retrogradation of both starches. Compared to starches stored only at 4°C, both starches stored under the 4/30°C temperature cycles exhibited smaller melting enthalpy for retrogradation (ΔH_r), higher onset temperature (T_o), and lower melting temperature range (T_r) regardless of the starch concentration tested. Fewer crystallites might be formed under the temperature cycles compared to the isothermal storage, but the crystallites formed under temperature cycling appeared more homogeneous than those under the isothermal storage. The effect of starch content on the retrogradation was greater when the starch gels were stored under cycled temperatures. The reduction in ΔH_r and the increase in conclusion temperature (T_c) by retrogradation under 4/30°C temperature cycles became more apparent when the starch concentration was lower (20 or 30%). Degree of retrogradation based on melting enthalpy was greater in normal corn starch than in waxy corn starch when starch content was low.     

Properties of maize starch modified by ball milling in ethanol medium and low field NMR determination of the water molecular mobility in their gels

Ethanol as moisturizing agent and ball-milling treatment, has been combined in order to determine their impacts on the improvement of the properties of physically modified maize (Zea mays) starch granules. The content of ethanol has been set respecting a ratio of starch to ethanol varying from 1:0 to 1:3 (w:v), and the ball-milling time varied between 0 and 72 h. We observed that the increase of the amylose content varied in a more effective way with increase of the milling time (p < 0.05) than with the variation of the starch to ethanol ratios. As expected, modified starches were more transparent, more soluble, less crystalline, and presented damaged structures. In all cases, the starch granule sizes were better distributed at ratios of starch to ethanol of 1:0 and 1:3 (w:v) respectively. In addition, the impact of the combination of these treatments on the mobility of water molecules in starch gels characterized by the transverse relaxation time (T₂), as well as the abundance of protons (¹H T₂) in each populations were determined by low field NMR. Mobility of water molecules within starch gels increased at high temperature. Nonetheless, the proton population at T₂ > 10 ms (characterized by T₂₂) for the modified starch (starch/ethanol, 1:3 w:v) was fundamental in the different water concentrations, and accounts for 70 to 90% of total protons, at temperatures >60 °C.     

Understanding how the cooking methods affected structures and digestibility of native and heat-moisture treated rice starches

In this study, the impact of different thermal methods (cooking and steaming treatment) on the structural variations of native and heat-moisture treated (HMT) rice starches and their effect on starch digestibility were investigated. As expected, HMT induced the disruption for starch semi-crystalline lamellae, crystallites, and helical structures. After thermal processing, varied destructions were obtained for lamellar, crystalline and helical structures of native and HMT-treated rice starches, especially under cooking treatment. And these structural alterations may improve the RDS fraction of rice starches and decrease their SDS and RS fractions. Particularly, steamed starches displayed higher enzyme resistance than their cooked counterpart, which may be attributed to the limited destruction of starch hierarchical structure during steaming process. And the aboved transformations demonstrated that water accessibility during thermal processing played a key role in starch structure and digestibility. Furthermore, HMT-treated starch still remained more crystallites and helices after thermal processing, thus resulting in slower digestibility. This work may be beneficial for encouraging the utilization of HMT-treated starch in food processing and obtaining gelatinized starch-foods with special nutritional functions.     

Investigation of the high-amylose maize starch gelatinization behaviours in glycerol-water systems

The effect of glycerol on gelatinization behaviours of high-amylose maize starch was evaluated by confocal laser scanning microscopy (CLSM), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), texture analyzer (TPA) and rheometer. Gelatinization of the high-amylose maize starches with glycerol content of 10% (w/w) began at 95.4 °C (T_o), peaked at 110.3 °C (T_p), and completed at 118.9 °C (T_c). The birefringence began to disappear at around 100 °C and finished at 120 °C which corresponded well to the onset and conclusion temperatures obtained by DSC. The high-amylose maize starch granules maintained original morphological structure at 100 °C and swelled to a great degree at 110 °C. The high-amylose maize starch paste formed at 100 °C showed the lowest hardness (39.92 g), while at 120 and 130 °C, showed the highest hardness (610.89 g and 635.43 g, respectively). It should be noted that in going from 100 °C to 110 °C there is a significant increase in the viscosity of the slurry solution. The identical apparent viscosity was observed when the shear rate exceed 100 s⁻¹, resulting from the high-amylose maize starch granules were completely gelatinized at 120 °C, which was consistent with DSC analysis.     

Microwave irradiation differentially affect the physicochemical properties of waxy and non-waxy hull-less barley starch

Waxy and non-waxy hull-less barley kernels and their isolated starches were irradiated under different microwave conditions (power 640, 720, and 800 W, time 60, 120 and 180 s). Changes in physicochemical properties were studied to investigate the effects of microwave irradiation (MWI) on in-kernel starches and isolated starches. For in-kernel starch, microwave reduced the ratio of 1047/1022 cm⁻¹ wavelengths, gelatinization enthalpy (ΔH_g) and relative crystallinity (RC), indicating that microwave of starch within the cells disrupted the crystalline regions. For isolated starch, microwave decreased the ratio of 1047/1022 cm⁻¹ wavelengths but increased ΔH_g of isolated starch, indicating that microwaving resulted in disruption of amorphous structure and an increase in the amount of remaining double helix structure. Moreover, viscosities of in-kernel starches decreased as microwave power and time increased, but this was not observed in isolated starches. Microwave treatment induced an enhancement of gelatinization temperature for non-waxy starches (NWS) but decreased in waxy starches (WS). Microwave had a greater effect for swelling power and solubility on in-kernel MWI-WS than MWI-WS, whereas the reverse results were found between in-kernel MWI-NWS and MWI-NWS. The results indicated that amylose plays a profound role in the properties of isolated and in-kernel starches during microwaving.     

Comparison of structural features of reconstituted doughs affected by starches from different cereals and other botanical sources

Starch, as the main component of flour products, determines the physicochemical properties of dough. This work investigated the relationship of the physical properties of seven types of starches from various cereals with the structural features of reconstituted dough. Results of mixing and tensile properties analysis and scanning electron microscopy displayed that rice reconstituted flour exhibited maximum water absorption; pea reconstituted flour had higher dough stability; sweet potato dough had higher tensile resistance; highland barley dough had the greatest extensibility. Moisture distribution analysis revealed that various model dough showed remarkably different water distribution, which was distributed at T₂₁ (0.07–0.11 ms), T₂₂ (0.8–2.66 ms) and T₂₃ (10.0–20.82 ms). Correlation analysis indicated that large starch granules associated with good dough stability; amylose content of starch positively affected tensile resistance of dough; crystallinity of starch showed negative effects on water absorption; starch with higher crystallinity associated with greater dough stability.     

Hydrolysis of granular corn starch with controlled pore size

Native corn (Zea mays L.) starch granules were hydrolyzed using glucoamylase at 50 °C for 1–8 h. The degree of hydrolysis over time was analyzed by the concentration of glucose released into solution. The pore sizes of hydrolyzed starch granules increased gradually with the degree of hydrolysis, as evidenced by scanning electron micrographs. It was deduced that every pore on the surface of granules was formed by hydrolysis of one enzyme molecule, so the size of pores distributed on the surface of starch granules was almost homogeneous for the same hydrolysis time. The specific surface area (S_BET), porosity, adsorptive capacity and mean pore radius of porous starch granules were determined to analyze the effect of digestion time on granule properties.     

Gluten free rice cookies with resistant starch ingredients from modified waxy rice starches: Nutritional aspects and textural characteristics

Experimental gluten-free (GF) rice cookies were formulated with 100% rice flour (CTR) or by substituting 50% of rice flour with native waxy rice starch (WRS) or with three different resistant starch (RS) ingredients obtained from debranched, annealed or acid and heat-moisture treated WRS (RS_a, RS_b and RS_c, respectively). Chemical composition, in vitro starch digestibility and physical and textural characteristics were carried out. Among cookies, RS_a-cookies had the highest total dietary fibre content, the lowest rapidly digestible starch and the highest RS contents. All the three RS preparations have proved effective in increasing the proportion that tested as RS with respect to native WRS. However, the estimated RS loss for each applied RS ingredients caused by the baking process followed the order of RS_a < RS_c < RS_b. Last, the lowest vitro glycaemic index value was measured for RS_a-cookies. Among cookies, differences in colour and hardness were reported. The partial replacement of commercial rice flour with RS_a could contribute to formulate GF cookies with higher dietary fibre content and likely slowly digestible starch properties more than equivalent amounts of RS_b and RS_c.     

Characterization of starches of proso,foxtail, barnyard,kodo, and little millets

Scanning electron microscope (SEM) pictures of small millet starch granules showed more large polygonal and few small spherical or polygonal granules. The granules of small millets resembled those of rice starch granules. The size of the starch granules ranged from 0.8–10 m. The size of the granules was larger in barnyard millet and smaller in proso millet. Several granules showed deep indentation caused by protein bodies. SEM of starch isolated from 24 hour-germinated kodo millet showed pitting or pinholes at some points due to the attack of amylases (preferentially on bigger granules). Brabender viscoamylograph studies on small millet starches revealed that the gelatinization temperatures ranged from 75.8 to 84.9 ^° C. Barnyard millet possessed lower amylograph viscosity, minimum breakdown, and relative breakdown values when compared to the other small millets.     

Chemical Composition,Mineral Profile,and Functional Properties of Canna (<Emphasis Type="Italic">Canna edulis</Emphasis>) and Arrowroot (<Emphasis Type="Italic">Maranta spp</Emphasis>.) Starches

The aim of the present study was to evaluate some chemical and mineral characteristics and functional and rheological properties of Canna and Arrowroot starches produced in the Venezuelan Andes. Canna starch showed a higher (P < 0.05) moisture, ash, and crude protein content than arrowroot starch, while crude fiber, crude fat, and amylose content of this starch were higher (P < 0.05). Starches of both rhizomes own phosphorus, sodium, potassium, magnesium, iron, calcium, and zinc in their composition. Phosphorus, sodium, and potassium are the higher in both starches. Water absorption, swelling power, and solubility values revealed weak bonding forces in Canna starch granules; this explained the lower gelatinization temperature and the substantial viscosity development of Canna starch during heating. Arrowroot starch showed a higher gelatinization temperature measure by DSC, than Canna starch and exhibited a lower value of ΔH. Both starches show negative syneresis. The apparent viscosity of Canna starch was higher (P < 0.05) than the Arrowroot starch values. The size (wide and large) of Canna starch granules was higher than arrowroot starch. From the previous results, it can be concluded that Canna and Arrowroot starches could become interesting alternatives for food developers, depending on their characteristics and functional properties.     

Flaking as a corn preparation technique for dry-grind ethanol production using raw starch hydrolysis

A 2³ full-factorial study was designed to study the effect of corn preparation methods (flaking and grinding) on dry-grind ethanol performance using raw starch hydrolysis (RSH) process. Moisture content (15, 22%), flaker roller gapsetting (0.508 mm, 1.016 mm), and grinding were studied. Fifteen hundred g of corn samples were cracked, roller pressed, and were either ground further or retained, along with control ground corn. A bimodal size distribution was observed for ground corn, regardless of flaking. Moisture at 22% resulted in bigger-sized flakes with d₅₀ between ∼1.3 and 1.8 mm, compared to ∼138–169 μm for ground corn. Not all ground corn resulted in higher ethanol concentration in fermentation beer; the ethanol levels in beer did not reflect the starch hydrolysis trend that favored ground corn. In a related study, the beer ethanol concentration did not show a clear trend with rollermill gapsetting while fermenting the flakes produced at 0.203, 0.305, 0.406, and 0.508 mm gapsettings. Generally, flakes from corn at 22% moisture resulted in higher ethanol content in beer. Rollermill flaking was found comparable to hammermill grinding for dry-grind corn ethanol via raw starch hydrolysis and yeast fermentation.