Characterization of Physical Properties of Flour and Starch Obtained from Gamma‐Irradiated White Rice

Physical and structural characteristics of rice flour and starch obtained from gamma‐irradiated white rice were determined. Pasting viscosities of the rice flour and starch, analyzed by using a Rapid Visco Analyser, decreased continuously with the increase in irradiation dosage. Differential scanning calorimetry showed that gelatinization onset, peak and conclusion temperatures of rice flour and starch changed slightly but the enthalpy change decreased significantly with increase of irradiation dosage. All irradiated starch displayed an A‐type X‐ray diffraction pattern like the native starch. Gel permeation chromatography showed that the blue value ratio of the first peak (amylopectin) to the second one (amylose) decreased with the increase of the irradiation dosage. The weight‐average molecular weight (M_w) and gyration radius (R_z) of amylopectin analyzed by using HPSEC‐MALLS‐RI (high‐performance size‐exclusion chromatography equipped with multiangle laser‐light scattering and refractive index detector) decreased gradually from 1.48×10⁹ (M_w) and 384.1 nm (R_z) of native rice starch to 2.36×10⁸ (M_w) and 236.8 nm of 9 kGy‐irradiated starch. The branch chain‐length distribution of amylopectins determined by HPAEC‐ENZ‐PAD (high‐performance anion‐exchange chromatography with amyloglucosidase post‐column on‐line reactor and pulsed amperometric detector) showed that gamma irradiation had no significant effect on the amylopectin branch chains with 13≤DP≤24 and 37≤DP, but produced more branch chains with 6≤DP≤12 when the irradiation dosage was less than 9 kGy. It might be deduced that gamma irradiation caused the breakage of the amylopectin chains at the amorphous regions, but had little effects on the crystalline regions of starch granules, especially at low dosage irradiation.     

Estimation of the Intrinsic Birefringence of the A,B and V Crystalline Forms of Amylose

Optical birefringence (Δn) for A, B, V_a, V_h amylose crystals were calculated by vector summation of bond polarizabilities. Orientation of the O‐H bond vectors in these amylose crystals is not well understood so results were given for a range of O‐H conformers. For B amylose, Δn was calculated to be 0.043‐0.058 for the Wu and Sarko crystal structure, while Δn = 0.0‐0.01 for the now widely accepted crystal structure of Imberty and Perez. This latter estimate is somewhat lower than experimental values of 0.031‐0.037 determined previously for highly oriented amylose films. Reasons for the discrepancy may include uncertainty in empirical polarizability parameters or neglect of contributions from amorphous components and water. Predicted values of Δn for A amylose were similar to B amylose while Δn for V amyloses were smaller (‐0.04‐0.0). These estimates of the intrinsic birefringence of amylose crystals should be helpful in estimating the degree of orientation for starch films/fibers and in better understanding the molecular origins of birefringence of oriented starch.     

Gelatinization and Pasting Properties of Waxy and Non‐waxy Rice Starches

Gelatinization and pasting properties of diverse rice types grown in two locations were examined by differential scanning calorimetry (DSC) and rotational rheometry, respectively. The data were compared to previously reported molecular starch properties for these samples: specifically, amylose content, starch molecular weight (M_w), and amylopectin side‐chain‐length distributions. Significant correlations were observed between amylose content, starch M_w, and the weight degree of polymerization of the long side chains of amylopectin F₁(DP_w) and many of the gelatinization and pasting properties measured. Higher amylose content corresponded with increased gelatinization onset (T_o) and peak temperatures (T_p), pasting onset and peak temperatures, and decreased peak and trough viscosity. Starch M_w correlated negatively with T_o, T_p, pasting onset, and peak temperature and positively with peak, trough, final, and breakdown viscosity. Amylopectin with DP_w 59‐78 of F₁(DP_w) correlated with increased T_o, T_p, pasting onset and peak temperature, and decreased peak, trough, final and breakdown viscosity. Pasting properties were also somewhat related to DP_w 21 of shorter side chains of amylopectin (F₂(DP_w)). Significant correlations between F₂(DP_w) and peak, final, and breakdown viscosity were observed (r = −0.447*, −0.391*, −0.388*, peak, final, and breakdown viscosity, respectively).     

Studying different dimensions of amylose–long chain fatty acid complexes: Molecular, nano and micro level characteristics

Recently amylose inclusion complexes, or V-amylose, have drawn much attention as a possible vehicle for the nanoencapsulation of unsaturated fatty acids. This study aimed to study three different structural strata of V-amylose, the molecular attributes using XRD, DSC and ¹³C CP/MAS NMR and the nanostructures using SAXS. Using these methods it was noted that decreased degree of fatty acid unsaturation induces the formation of more organized and well defined structures. Specifically, calculations based on SAXS data show that regardless of the crystallization temperature saturated SA yields the highest values for parameters like average crystalline lamellar thickness (φ = 0.26) and characteristic particle dimension (R_g = 9.6). SEM shows this trend extends even into the microscopic level. Overall, this study shows that in the case of long chain fatty acids, increased fatty acid unsaturation impairs the structure of amylose inclusion complexes.     

Comparison between Size Exclusion Chromatography and Micro‐Batch Analyses of Corn Starches in DMSO using Light Scattering Detector

The molecular structure of corn starches different in amylose content (waxy, normal, and high‐amylose) was analyzed in 90% dimethyl sulfoxide (DMSO) solution by refractive index (RI) and multi‐angle laser light scattering (MALLS) detectors. The starch sample solutions were measured either by medium‐pressure size exclusion chromatography (MPSEC) or by the micro‐batch mode. For waxy corn starch, the average molar mass (M_w) and radius of gyration (R_g) values were similar in both methods. However, for normal and high‐amylose corn starches, M_w measured by the micro‐batch mode was 2–4 times greater than that by the chromatographic method, although R_g values obtained from both methods were not very different. The M_w difference was the greater the higher the amylose content of starch.     

Effects of molecular characteristics of on konjac glucomannan glass transitions of potato amylose, amylopection and their mixtures

BACKGROUND: The purpose of this study was to explore further the functions of konjac glucomannan (KGM) in starch‐based foods. Experiments were carried out using the mixed amylose/amylopectin/KGM system as a model. High‐speed differential scanning calorimetry (hyper‐DSC) with the support of high‐performance size exclusion chromatography (HPSEC) equipped with multi‐angle laser light scattering (MALLS) and differential refractive index (RI), X‐ray diffractometry (XRD) and viscosimetry was used to investigate the effects of KGM on glass transition temperatures (T_gs) of mixtures with different amylose/amylopectin ratios. RESULTS: Hyper‐DSC results showed that the T_gs of amylose, amylopection and their mixtures decreased with increasing concentration of KGM. Based on the molecular characteristics of KGM, HPSEC‐MALLS‐RI, viscosimetry and XRD results showed that the molar masses of KGM ranged from 1.023 × 10⁶ to 1.329 × 10⁶ g mol^?1; the root mean square (RMS) radii were distributed from 110.5 to 129.6 nm, and M_w/M_n was 1.017. KGM was a linear molecule with random‐coil conformation in solution and the crystallinity was 0.00%. CONCLUSION: It is suggested that the addition of KGM has plasticizing effects on the structures of amylose and amylopectin, which can increase free volume and molecular movement of amylose and amylopectin chains, resulting in a decrease in their T_gs. Copyright © 2010 Society of Chemical Industry     

Photometrische Titration der Särkepolysaccharide mit Jod. II. Mitt. Hydrolyse mechano-chemisch abgebauter Amylose durch β-Amylase

Photometric Titration of Starch Polysaccharides by Iodine. Part 2: Hydrolysis of Mechano Chemically Degraded Amylose by β-Amylase. With photometric titration of amylose by means of iodine, the course of the graph depends on molecular weight distribution, average molecular size and concentration of polysaccharides. Respective data are: size of the linear part of the titration graph, total iodine concentration at half saturation of amylose by iodine, and maximum value of extinction. This new method is applied to examine β-amylolysis of natural amylose of various molecular size. High-molecular substrates are degraded according to a single-chain mechanism and amyloses having been swing-milled for more than 48 h are degraded by a multichain mechanism. The change in the effect of β-amylase occurs in the range between P_n 130 and 200, This change is to be contributed to differences in the molecular configuration of the substrate.     

Rice Starch Molecular Size and its Relationship with Amylose Content

The composition and starch molecular structure of eight rice varieties were studied. Waxy and non‐waxy (long‐, medium‐, and short‐grain) rice varieties from California and Texas were used. The amylose contents were measured using the Concanavalin A method and were found to be related to the type of rice: waxy ≈ 1.0%, short and medium grain 8.7–15.4%, and long grain 17.1–19.9%. The weight‐average molar masses (M_w) of the starches varied from 0.52 to 1.96×10⁸ g/mol. As would be expected, a higher M_w of rice starch correlated to lower amylose content. The range of M_w of amylopectin was 0.82 to 2.50 ×10⁸ g/mol, and there was also a negative correlation of amylopectin M_w with amylose content. Amylose M_w ranged from 2.20 to 8.31×10⁵ g/mol. After debranching the amylopectin with isoamylase, the weight‐average degree of polymerization (DP_w) for the long‐chain fraction correlated positively with a higher amylose content. California and Texas varieties were significantly different in their amylose content, starch M_w (short‐ and medium‐grain only), and amylopectin M_w (p < 0.05).     

Relationships Between Some Physicochemical Properties of Starches from Maize Cultivars Grown in East China

Granule size, amylose content, degree of crystallinity, thermal, pasting, and gel textural properties of starches separated from thirty seven maize cultivars grown in East China were studied with a laser particle size analyzer, spectrophotometer, X‐ray diffractometer, differential scanning calorimeter, Rapid Visco Analyser, and texture analyzer. Various correlations between the physicochemical properties were observed. The correlation coefficient between T_o and T_p, between T_o and T_c, and between T_p and T_c were 0.967, 0.879, and 0.941 (p<0.01), respectively. Amylose content was correlated negatively with T_c (r=‐0.640, p<0.01). Pasting temperature was positively correlated to T_p (r=0.738, p<0.01). Significantly positive correlations were observed between amylose content and final viscosity, between amylose content and setback (r=0.665 and 0.735, respectively, p<0.01) and between peak viscosity and breakdown (r=0.893, p<0.01). Trough viscosity was positively correlated to final viscosity and setback (r=0.851 and 0.704, respectively, p<0.01). Significant correlations existed between final viscosity and setback, and hardness (r=0.972 and 0.615, respectively, p<0.01). There was a significant interrelationship between setback and hardness (r=0.655, p<0.01).     

In vitro degradability of three forages: fermentation kinetics and gas production of NDF and neutral detergent‐soluble fraction of forages

The fermentation of the neutral detergent‐soluble (NDS) fraction of three forages (alfalfa hay, Italian ryegrass + oats hay and corn silage) was measured using a curve subtraction technique with in vitro gas production data from the whole forage (WF) and the isolated neutral detergent fibre (NDF). NDF disappearance and volatile fatty acid (VFA) production were determined. There was no significant difference between the VFA patterns from the whole forage and the isolated NDF. There were significant (P < 0.001) linear correlations between the volume of gas and moles of VFA produced and the mass of fibre digested in the NDF samples. Using the monophasic curve model, maximum gas production rates (R_M) for the whole forages and the isolated NDF and NDS fractions can be calculated. For all three forages we obtained R_M‐NDS > R_M‐WF > R_M‐NDF. Trends in the rates of gas and VFA production were similar in the whole forages. The NDF showed a high superimposition between substrate degradability and VFA production. Our experiment confirmed the curve subtraction technique as a simple method to obtain information on the size and digestion kinetics of the NDS fraction, which helps in understanding the nutritional significance of this important fraction of the forages studied. © 2001 Society of Chemical Industry     

Amylose content,molecular structure,physicochemical properties and in vitro digestibility of starches from different mung bean (Vigna radiata L.) cultivars

Physicochemical and in vitro digestibility characteristics of starches isolated from six cultivars of mung bean (Vigna radiata L.) were studied. Significant differences (p < 0.05) were observed between the cultivars with respect to amylose content (29.9–33.6%), relative crystallinity (29.0 to 31.7%), particle diameter (16.2–17.1 µm) and molecular weight of amylopectin (260–289 × 10⁶ g/mol). The scanning electron micrographs revealed the presence of large oval to small round shape granules with average particle diameter of 16.2–17.1 µm. The X‐ray diffraction pattern was of the C‐type. The enthalpies of gelatinization and retrogradation were 8.9–10.3 and 4.6–6.3 J/g, respectively. The amounts of slowly digesting and resistant starch of mung bean followed the order: PBM‐1 > SML‐32 > ML‐613 > SML‐134 > ML‐267 > ML‐5 and ML‐5 > ML‐267 > SML‐134 > ML‐613 > SML‐32 > PBM‐1, respectively. The six starches exhibited significant (p < 0.05) differences in their pasting parameters. Correlation analysis showed that amylose content, granule diameter and relative crystallinity values were important in determining thermal, pasting and in vitro digestibility of starches.     

Nutritionally Important Starch Fractions of Rice Cultivars Grown in Southern United States

Abstract: Dietary starches can be classified into 3 major fractions according to in vitro digestibility as rapidly digestible (RDS), slowly digestible (SDS), and resistant starch (RS). Literature indicates that SDS and/or RS have significant implications on human health, particularly glucose metabolism, diabetes management, colon cancer prevention, mental performance, and satiety. In this study, the nutritionally important starch fractions (RDS, SDS, and RS) in cooked rice were assayed in vitro, making use of 16 cultivars grown in 5 southern U.S. rice growing locations (Arkansas, Louisiana, Mississippi, Missouri, and Texas). RDS, SDS, and RS were 52.4% to 69.4%, 10.3% to 26.6%, and 1.2% to 9.0%, respectively, of cooked rice dry weight. Cultivar, location, and cultivar-by-location interaction contributed to the variations in RDS, SDS, and RS contents. Means pooled across locations indicated that SDS was higher for the Louisiana samples than those from Texas, whereas RS was higher for the Texas samples than those from Arkansas, Louisiana, and Mississippi. Some cultivars were identified to possess high levels of RS (for example, Bowman and Rondo) or SDS (for example, Dixiebelle and Tesanai-2) and were also stable across growing locations. Apparent amylose content correlated positively with RS (n = 80, r = 0.54, P ≤ 0.001), negatively with RDS (n = 80, r =−0.29, P ≤ 0.05), and insignificantly with SDS (n = 80, r = 0.21, P > 0.05). RS and SDS were not collinear (n = 80, r =−0.18, P > 0.05); it does not follow that a cultivar high in RS will also be high in SDS, and vice versa. The observed differences in RDS, SDS, and RS among the samples are indicative of wide genetic diversity in rice.     

Effects of feeding micronised flaxseed on yield and composition of milk from Holstein cows

Nine multiparous Holstein cows were used in three 3 × 3 Latin squares to investigate the effects of feeding unheated and micronised flaxseed on milk yield and milk fatty acid composition. Three diets were formulated to meet the nutrient requirement of dairy cows in early lactation: a control diet with no added flaxseed (NFS), an unheated flaxseed diet (UFS) and a micronised flaxseed diet (MFS). The level of flaxseed in UFS and MFS was 70 g kg^?1 of the diet dry matter (DM). Feeding flaxseed to dairy cows had no effect on DM intake or milk yield. However, energy‐corrected milk was higher (P < 0.05) for cows fed MFS than for those fed UFS or NFS. Supplemental flaxseed reduced (P < 0.05) the milk fat percentage without affecting the concentration of milk protein or milk lactose. However, the yield of milk components was not affected by feeding flaxseed. The concentrations of short‐chain (C_4:0 to C_12:0) and medium‐chain (C_14:0 to C_17:0) fatty acids were decreased (P < 0.05) while those of long‐chain fatty acids (C_18:0 to C_18:3) were increased (P < 0.05) in the milk of cows fed UFS and MFS compared with cows fed NSF. Feeding flaxseed to dairy cows can alter the milk fatty acid composition, but only minor effects on milk fatty acid composition can be expected by feeding micronised versus unheated flaxseed. Copyright © 2003 Society of Chemical Industry     

Dietary Trans Fats Enhance Doxorubicin‐Induced Cardiotoxicity in Mice

This study investigated the combined effects of trans fat diet (TFD) and doxorubicin upon cardiac oxidative, inflammatory, and coagulatory stress. TFD increased trans fatty acid deposit in heart (P < 0.05), and decreased protein C and antithrombin‐III activities in circulation (P < 0.05). TFD plus doxorubicin treatment elevated activities of plasminogen activator inhibitor‐1, lactate dehydrogenase, and creatine phosphokinase (P < 0.05). This combination also raised xanthine oxidase activity, and enhanced cardiac levels of reactive oxygen species, interleukin (IL)‐6, IL‐10, tumor necrosis factor‐alpha, and monocyte chemoattractant protein‐1 than TFD or doxorubicin treatment alone (P < 0.05). TFD alone increased cardiac nuclear factor kappa B (NF‐κB) activity (P < 0.05), but failed to affect expression of NF‐κB and mitogen‐activated protein kinase (MAPK) (P > 0.05). Doxorubicin treatment alone augmented cardiac activity, mRNA expression, and protein production of NF‐κB and MAPK (P < 0.05). TFD plus doxorubicin treatment further upregulated cardiac expression of NF‐κB p65, p‐p38, and p‐ERK1/2 (P < 0.05). These findings suggest that TFD exacerbates doxorubicin‐induced cardiotoxicity.     

Use of High-Performance Size-Exclusion Chromatography for Characterization of Amylose Isolated from Diverse Botanical Sources

Amyloses were isolated from diverse botanical sources (apple, mango, maize, and potato), and they were studied in their molecular characteristics (amylose content, molar mass, and molecular weight) using high-performance size-exclusion chromatography as a repetitive and faster protocol. The amylose purity ranged between 85.6–92.6 %, in agreement with the λ_max values (601–610 nm), showing that some impurities with molecules of higher molar mass (amylopectin) were present. The standard curve of pullulan showed a high regression coefficient (0.998) inside of the limits of molar mass of amylose. Chromatograms of amylose showed the presence of components of high molar mass with a principal peak that corresponds to amylose. Molar mass of amylose ranged between 1.2 and 8.5 × 10⁵ g/mol with polydispersity values between 1.3–4.1, indicating a narrow range of molar mass distribution of the amyloses analyzed. The high-performance size-exclusion chromatography coupled with a refractive index methodology used in this study may be considered simple and rapid for molecular studies of amylose.     

Lipid classes,fatty acid composition and triacylglycerol molecular species in the kernels of pumpkin (Cucurbita spp) seeds

The lipids extracted from the kernels of pumpkin (Cucurbita spp) seeds of three cultivars were classified by thin layer chromatography into six fractions: steryl esters (SEs, 0.5–1.2%), triacylglycerols (TAGs, 92.7–93.4%), free fatty acids (FFAs, 2.9–3.5%), sn‐1,3‐diacylglycerols (1,3‐DAGs, 0.4–0.9%), sn‐1,2‐diacylglycerols (1,2‐DAGs, 0.7–0.9%) and phospholipids (PLs, 1.5%). Fatty acids derivatised as methyl esters were analysed by gas chromatography with flame ionisation detection. Molecular species and fatty acid distributions of TAGs, isolated from the total lipids in the kernels, were analysed by a combination of argentation thin layer chromatography (TLC) and gas chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total chain length of fatty acid groups. With a few exceptions, SM₂ (5.8–20.1%), S₂D (8.8–11.2%), M₃ (6.7–24.8%), SMD (6.8–16.7%), M₂D (16.7–23.6%), SD₂ (4.6–15.1%) and MD₂ (4.9–18.6%) were the main TAG components. These results suggest that there are significant differences (P < 0.05) not only in fatty acid distributions of acyl lipids but also in molecular species of TAGs among the three cultivars. The differences in pumpkin cultivars could be appreciable, based on the distribution of molecular species in TAGs. However, pumpkin seed kernels could be utilised successfully as a source of edible oils for human consumption. Copyright © 2004 Society of Chemical Industry     

Effect of calcium and vitamin D2 fortification on quality characteristics of dahi

Two levels (500 and 600 ppm) of calcium (calcium phosphate and calcium citrate) along with vitamin D₂ (600 IU/L) were fortified in milk for dahi preparation. pH, water‐holding capacity and syneresis of fortified dahi were not affected significantly (P > 0.05). However, acetaldehyde content decreased and setting time increased upon fortification. Microbial count significantly (P < 0.05) decreased in calcium phosphate‐fortified dahi, whereas no difference was observed in calcium citrate‐fortified dahi. Firmness and viscosity decreased in calcium phosphate‐fortified dahi, whereas it increased in calcium citrate‐fortified dahi as compared to control. All dahi samples showed good sensory acceptability.     

Charakterisierung von Weizensorten durch SDS-Polyacrylamidgel-Elektrophorese (SDS-PAGE) und zweidimensionale Elektrophorese (2D-PAGE) der Glutenine

Zusammenfassung Vierundzwanzig Weizensorten wurden durch SDS-PAGE und 2D-PAGE in horizontalen, ultradünnen Gelsystemen mit Silberfärbung auf Glutenin-Untereinheiten analysiert. Das Auftreten der hochmolekularen Untereinheiten 2 (codiert auf Weizenchromosom Glu-1A) bzw. 3 und 10 (Glu-1D) sowie 5 und 9 (G1u1B) ist mit guten Backeigenschaften (A-Qualität) der Mehle korreliert. Zwischen den hochmolekularen Untereinheiten (Gruppe A, HMW-Untereinheiten,M _r = 90000–125000) und den niedermolukularen Gluteninen (Gruppe B, LMW-Untereinheiten;M _r = 43 500–56 000) tritt eine bisher wenig beachtete Gruppe mit mittleren Molekulargewichten (Gruppe AB, MMW-Untereinheiten;M _r = 56 500–80 000) auf, die ebenfalls sortenspezifische Unterschiede zeigt.In der zweidimensionalen Elektrophorese zeigt sich neben der ladungsbedingten Heterogenität der einzelnen Untereinheiten bei einigen Sorten eine weitere, anscheinend eigenständige Gruppe BC mit niederem Molekulargewicht (M _r = 40 500–43 500). Die Proteine dieser Gruppe besitzen, im Gegensatz zu den umgebenden basischen Gruppen B und C, deutlich niedrigere isoelektrische Punkte.

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Characterization of glutenins in wheat varieties by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional electrophoresis (2D-PAGE)

Summary Twenty-four wheat varieties were analysed for glutenin subunits by SDS polyacrylamide gel electrophoresis (PAGE) and two-dimensional (2D)-PAGE using horizontal ultrathin pore-gradient gels and silver staining. The following high-molecular-weight (HMW) subunits correlated well with good baking quality (Grade A varieties): 2 (coded in wheat chromosome Glu-1A), 3 and 10 (Glu-1D) and 5 and 9 (Glu-1 B). Some other grade A varieties showed the HMW subunits 2, 4, 8, and 11, which are typical for grade B and C varieties.Between the HMW subunits (group A subunits,M _r = 90000–125 000) and the low-molecular-weight (LMW) subunits (group B subunits,M _r = 43 500–56 000), the electropheretograms exhibited a group of sharp protein bands with intermediate molecular weights (MMW-subunits,M _r = 56 500–80 000). The pattern of this group, which has up to now been practically unnoticed, is also dependent on the wheat variety.In addition to the charge-dependent heterogeneity of the subunits, the 2D-electropheretograms of some varieties showed an additional protein group, denoted BC, which has a low molecular weight (M _r = 40 500–43 500). In contrast to the adjacent basic groups B and C, these BC proteins have significantly lower isoelectric points.

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Gefördert von der Arbeitsgemeinschaft Industrieller Forschungsvereinigungen (AIF) über den Forschungskreis der Ernährungsindustrie e. V.     

A transgressive brown rice mediates favourable glycaemic and insulin responses

BACKGROUND: We evaluated glycaemic response of a brown rice variant (BR) developed by cross‐breeding. Subjects (n = 9) consumed 50 g carbohydrate equivalents of BR, white rice (WR) and the polished brown rice (PR) in comparison to 50 g glucose reference (GLU) in a cross‐over design. Plasma glucose and insulin at 0, 15, 45, 60, 90, 120 and 180 min were measured and incremental area under the curve (IAUC) and indices for glucose (GI) and insulin (II) calculated. RESULTS: BR compared to PR or WR produced the lowest postprandial glycaemia (GI: 51 vs 79 vs 86) and insulinaemia (II: 39 vs 63 vs 68) irrespective of amylose content (19 vs 23 vs 26.5%). Only BR was significantly different from GLU for both plasma glucose (P = 0.012) and insulin (P = 0.013) as well as IAUC_glu (P = 0.045) and IAUC_ins (P = 0.031). Glycaemic and insulinaemic responses correlated positively (r = 0.550, P < 0.001). Linear trends for IAUC_glu and IAUC_ins indicated a greater secretion of insulin tied in with a greater glycaemic response for WR (r² = 0.848), moderate for PR (r² = 0.302) and weakest for BR (r² = 0.122). CONCLUSION: The brown rice variant had the lowest GI and II values but these advantages were lost with polishing. Copyright © 2011 Society of Chemical Industry     

Effect of Heat‐Moisture Treatment on Structural and Thermal Properties of Rice Starches Differing in Amylose Content

Starches from glutinous rice (1.4% amylose), Jasmine rice (15.0% amylose) and Chiang rice (20.2% amylose) were exposed to heat‐moisture treatment (HMT) at 100 °C for 16 h and at different moisture levels (18, 21, 24 and 27%). The effect of heat‐moisture treatment on structural and thermal properties of these three rice starches was investigated. The HMT did not change the size, shape and surface characteristics of rice starch granules. The A‐type crystalline pattern of rice starches remained unchanged after HMT. The relative crystallinity (RC) and the ratio of short‐range molecular order to amorphous (RSA) of heat‐moisture treated glutinous and Jasmine rice starches decreased with increasing moisture level of the treatments. In contrast, the RC of the treated Chiang rice starch remained practically unchanged. A peak of crystalline V‐amylose‐lipid complexes was clearly presented in all treated Chiang rice starches. The peak became progressively stronger with increasing moisture level of the treatment. Differential scanning calorimetry (DSC) of all treated rice starches showed a shift of the gelatinization temperature to higher values. Increasing moisture level of the treatments increased the onset gelatinization temperature (T_o) but decreased the gelatinization enthalpy (ΔH) of rice starches. A broad gelatinization temperature range (T_c‐T_o) with a biphasic endotherm was found for all treated Chiang rice starches and Jasmine rice starch after HMT₂₇ (HMT at 27% moisture level). Additionally the (T_c‐T_o) of treated Chiang rice starches increased linearly with increasing moisture level of the treatments.