Formulating low glycaemic index rice flour to be used as a functional ingredient

Amylose and resistant starch (RS) content in rice flour were manipulated. The experiment was conducted using a full factorial design. Rice flour with average amylose content of 20 and RS content of 0.5 g/100 g dry sample was fortified with pure amylose from potato and high RS modified starch to reach the final amylose content of 30, 40 and 50 and RS content of 2, 4 and 6 g/100 g dry sample. The fortified rice flours were examined for their gelatinisation properties, in-vitro enzymatic starch digestion and gel textural properties. It was found that amylose and RS significantly affect all the fortified rice flour properties (p < 0.05). High amylose and RS improved starch digestion properties, reducing the rate of starch digestion and lowering the glycaemic index (GI) values. Amylose had a more pronounced effect on the fortified rice starch properties than RS. In this study, the fortified rice flour which contained amylose and RS of approximately 74 and 9 g/100 g dry sample respectively was used to produce rice noodles. The noodles exhibited low GI values (GI < 55). However, amylose and RS affected the textures of rice noodles providing low tensile strength and break distance (extensibility).     

小麦淀粉与面条质量关系的研究进展

小麦淀粉品质对白盐面条的质量（尤其是煮后的感官特性）有重要影响。直链与支链淀粉的含量及比例是影响面条质量的重要因素,是造成不同小麦品种淀粉糊化和膨胀特性及面条质量差异的物质基础。较低直链淀粉含量的小麦粉具有较好的糊化和膨胀特性,制作的面条煮制时吸水率高,烹调损失低,具有较高的感官评分。优质白盐面条的直链淀粉含量应在22%左右。峰值黏度、稀懈值、峰值时间是影响面条质量的重要糊化参数,这3项参数高的小麦粉适合制作优质面条。高膨胀势或膨胀体积的小麦粉制作的面条中等偏软,光滑且富有弹性,可以作为面条用小麦的重要选择标准。一般认为,直链淀粉含量较低、峰值黏度和稀懈值高、峰值时间长、膨胀势或膨胀体积高的小麦粉适合制作优质白盐面条。其中,直链淀粉含量、峰值黏度和膨胀势是优质面条小麦评价的关键品质性状。     

Effects of semidry flour milling on the quality attributes of rice flour and rice noodles in China

To investigate the effects of semidry-milling on the quality attributes of rice flour and rice noodles, the properties of rice flours and cooking properties of rice noodles prepared with wet-, dry- and semidry-milled rice flours were characterized. The level of starch damage of semidry-milled rice flour at 30% moisture was significantly decreased to the level of wet-milled rice flour (P < 0.05); the whiteness of dry-milled rice flour was decreased compared with wet-milled rice flour (P < 0.05), while that of semidry-milled rice flour was not; the wet- and semidry-milled rice flours showed similar morphology and water hydration properties; the dry milling method reduced significantly the hardness, chewiness, and resilience of rice noodles (P < 0.05) compared with wet-milling, but semidry-milling did not; the cooking qualities of rice noodles produced by semidry-milling were comparable to wet-milling. It indicated the semidry-milling at 30% moisture may provide the protective effects on the characteristics of rice flours, which could be used to produce similar qualities of rice noodles to the wet-milling.     

Characterization of sorghum grain and evaluation of sorghum flour in a Chinese egg noodle system

Sorghum is a gluten free grain that has potential to be used as an alternative to wheat flour for the Celiac Sprue market. There are thousands of sorghum lines that have not been characterized for grain, flour or end product quality. The objective of the research was to gain an understanding among grain sorghum quality factors and Chinese egg noodles quality. Four sorghum hybrids were characterized and evaluated for kernel characteristics, proximate analysis, flour composition and end product in a Chinese egg noodle system. Kernel size and weight affected the flour particle size and the amount of starch damage. Flour with fine particle size and high starch damage conferred noodles with high firmness and high tensile strength. Water uptake was highest for flour with smaller particle size (38 μm at 50% volume) and higher starch damage (6.14%). Cooking losses for all samples were below 10%. Starch of particle size <5 μm (C-type) contributed to firmer and higher tensile strength noodles. Water absorption was significantly affected by flour particle size, starch particle size and starch damage. Through control of sorghum grain and flour quality characteristics it is possible to manufacture a Chinese egg noodle with good physical attributes.     

Thermal and rheological properties of brown flour from Indica rice

The thermal, paste and rheological properties of brown flours from four Indica rice subspecies with different amylose content were examined using Differential scanning calorimetry (DSC), Brabender Viscometer and rheometer. Peak, final and setback viscosities (p < 0.05) increased with increasing amylose content from Brabender micro Visco-Amylo-Graph (MVA), but the phase transition temperatures of brown rice flour from DSC (p < 0.05) decreased with increasing amylose content. Rheological properties were determined by steady shear, small amplitude oscillatory shear (SAOS) and thixotropic experiments. SAOS results showed a gel-like viscoelastic behavior with G′ higher than G″. Steady-shear results showed that the brown rice flour exhibited a non-Newtonian shear-thinning behavior and the flow curves can be well described by the Herschel-Bulkley model. The upward-downward rheograms showed that brown rice flour gel, except IR-1, had a hysteresis loop, indicating a strong thixotropic behavior.     

Effect of hydrothermal treatment of rice flour on various rice noodles quality

The rice noodle industry in Thailand is facing problems regarding rice flour quality. This research aims to study the effects of hydrothermally modified rice flour on improving rice noodle quality. High-amylose rice flour (Chai Nat 1 variety) was modified using heat–moisture treatment (HMT) and annealing (ANN). Response surface methodology (RSM) with face-centered central composite design (FCCD) was applied to optimize the hydrothermal treatment condition. The effects of treatment conditions – moisture content; heating temperature and heating time on pasting; rheology; and textural properties of rice flour gel – were observed. A contour plot showed that all responses using HMT increased when moisture content and heating temperature increased. But heating time had no significant effect on response variables. ANN showed a lower response than HMT for all parameters. The optimum modified conditions were then matched with those of commercial flour for fresh, semi-dry and dry rice noodles; this showed no significant differences in texture or cooking quality (P≤0.05). The storage modulus (G′) after cooling of HMT (19,100 Pa) was much higher than that of ANN (5490 Pa). The differences in rheological properties of both treatments supported their proper uses to achieve various rice noodle qualities.     

Kinetics of starch digestion and functional properties of twin-screw extruded sorghum

The time-course of starch digestion in twin-screw extruded milled sorghum grain was investigated using an in-vitro procedure based on glucometry. The sorghum grains were hammer-milled, and extruded at three levels each of moisture and screw speed. Irrespective of the extrusion conditions, extruded and non-extruded milled sorghum grain exhibited monophasic digestograms, and the modified first-order kinetic and Peleg models adequately described the digestograms. Extrusion increased the rate of digestion by about ten times compared with non-extrudates. Starch gelatinisation varied in the extrudates, and microscopy revealed a mixture of raw, gelatinised and destructured starch and protein components in the extrudates. Starch digestion parameters significantly (p < 0.05) correlated with extruder response and various functional properties of the extrudates. Extrusion conditions for maximum starch gelatinisation in milled sorghum grain for fastest digestion as an efficient animal feed were interpolated, as well as the conditions for directly-expanded extrudates with potential for human food, where minimum starch digestion is desired.     

Functional characterization of extruded rice noodles with corn bran: Xanthophyll content and rheology

The rheological changes in rice noodles by the substitution of corn bran and the effect of temperature on the xanthophyll content (lutein and zeaxanthin) of the corn bran-rice flour noodles were evaluated. The use of corn bran increased the water holding capacity of rice flour at room temperature while the opposite results were observed after heating. The pasting parameters of rice flour-corn bran mixture were reduced with increasing levels of corn bran and the mixture paste exhibited more dominant liquid-like behavior. The noodles containing corn bran exhibited lower expansion ratio and softer textural properties. The levels of lutein and zeaxanthin in raw corn bran were 336.9 and 123.1 μg/100 g, respectively and were significantly reduced (P < 0.05) by heating. While lutein and zeaxanthin were not detected in the control noodles without corn bran, their levels in corn bran-incorporated noodles ranged from 56.2 to 137.3 μg/100 g and from 37.9 to 61.9 μg/100 g, respectively and were significantly reduced by 37.7–45.4% (P < 0.05) after cooking. Thus, the heat-labile characteristics of two xanthophylls were clearly observed. This study provides useful information on the processing performance and xanthophyll content of corn bran, possibly extending its use in a wider variety of foods.     

Preparation and characterization of gluten-free sheeted doughs and noodles with zein and rice flour containing different amylose contents

This study aimed to explore the feasibility of zein as a gluten alternative in preparing sheeted doughs with rice flours containing different amylose contents (12, 19, and 26%) that were successfully slit into noodle strands. Rice-zein mixtures with lower amylose contents exhibited lower pasting parameters and the high amylose paste samples possessed more elastic properties. Higher water absorption was observed in the low amylose rice-zein mixture whereas the use of zein were effective in increasing the stability of rice dough regardless of amylose content. In case of thermal conductivity, the noodle doughs prepared with high amylose rice-zein mixture had low thermal conductivity, probably implying a long cooking time. The structure of the rice-zein noodles had a tendency to become firmer with increasing levels of amylose by showing greater breaking stress and resistance to extension that could be correlated to reduced cooking loss.     

鲜湿米粉品质及其影响因素

米粉种类丰富,口感爽滑,质地柔韧,既可作为主食,又能当作早餐,深受广大消费者喜爱。因此,科学评价米粉品质、探究米粉品质影响因素始终受到研究者和企业的密切关注。本文综述了鲜湿米粉的分类与评价方法,从稻米品质、浸泡处理方式、磨粉工艺、辅料与食品添加剂、贮存保鲜方式等五个方面探讨了影响米粉品质的因素。目前,按成型工艺将鲜湿米粉分为切粉和榨粉。高直链淀粉含量品种做的米粉断条率和蒸煮损失率低,感官品质好,因此可将直链淀粉含量作为核心指标筛选出适宜作米粉的水稻品种。在调试出合适米水比的条件下,半干法研磨安全环保,对淀粉损伤较小,生产出的米粉品质与湿法研磨无显著差异。盐类或单甘脂等添加剂与保鲜方式结合使用,对鲜湿米粉保鲜效果更好。     

Effect of germination time on physicochemical properties of brown rice flour and starch from different rice cultivars

The present work was designed to obtain information on the effect of germination time on the selected physicochemical properties of brown rice flour and starch prepared from three different rice cultivars. Changes in total starch, amylose and amylopectin contents of flour, amylopectin/amylose ratio and molecular weight of starch, gelatinization, pasting, rheological, and morphological properties of flour and starch during 5 days of germination were investigated. Significant changes of pasting and rheological properties of brown rice flour were found during germination, but only small changes of these properties could be found in isolated starch. Scanning electron micrographs of flour showed that the continuous matrix structure of flour was highly destroyed after germination and scanning electron micrographs of isolated starch showed that after three days of germination, pits and holes were discovered on the surface of some starch granules. Germination had little effect on the average molecular weight of starch, but the polydispersity value in germinated brown rice (2–5 days germination) was higher than that in non-germinated brown rice. The changes observed in physicochemical properties of brown rice flour and starch after germination provided a crucial basis for understanding flour and starch modification mechanisms with potential applications for an industrial scale.     

Quality and antioxidant properties of instant noodles enhanced with common buckwheat flour

The objective of this study was to investigate the feasibility of incorporating common buckwheat (Fagopyrum esculentum Moench) into instant noodle formulations. Australian Soft (AS) and Baker's flours were used to evaluate the effects of varying buckwheat contents (0–40%) on noodle quality. The results of texture analysis indicate that noodles made using AS flour produced softer texture whereas there was minimal effect for Baker's flour when buckwheat was incorporated. The colour, measured by L* values, decreased with increased addition of buckwheat for both flours. Fat uptake for noodle samples made from AS flour was only marginally affected, but increased for Baker's flour, when higher levels of buckwheat flour were added. The antioxidant rutin was detected in noodles made from both wheat flours, generally increasing with % buckwheat flour added. These findings indicate that the incorporation of 20% buckwheat into the formulation can be used to enhance the quality of instant noodles.     

Modification of physicochemical properties and in vitro digestibility of wheat flour through superheated steam processing

Native and moistened wheat flours (moisture contents were 13.5 and 27.0%, respectively) were treated with superheated steam (SS) at different temperatures (140 and 170 °C) and times (1, 2 and 4 min). Their physicochemical and digestive properties were analyzed. For native flour, SS treatment altered the starch molecular structure and behavior slightly. While for moistened flour, crystalline degree, gelatinization enthalpy, amylose leaching (AML) and falling number significantly decreased, but thermal transition temperatures increased with the rise of treating severity. Clumping of starch granules, aggregation of proteins and formation of amylose-lipid complexes occurred in both native and moistened flours. Broader pasting temperature ranges and higher viscosities were found on SS-modified flours. Additionally, SS treatment on moistened flours increased resistant and slowly digestible starch contents. In general, SS treatment induced changes in starch molecular structure and reactions among flour components leading to more stable structures, thus affecting their pasting behavior, thermal properties and in vitro digestion.     

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.     

Investigation of amber durum wheat for production of yellow alkaline noodles

Samples of Canadian amber durum wheat varieties, of various protein content and a composite of export cargo samples, were milled to yield straight-grade and patent flours by reducing semolina and processed into yellow alkaline noodles (YAN). Samples of Canada Hard White Spring (CWHWS) and Canada Western Red Spring (CWRS) were included for comparative purposes. YAN from durum wheat displayed a colour advantage over CWRS and CWHWS YAN. The durum YAN displayed an approximate 9–20 unit greater b* (yellowness) value than CWRS and CWHWS at 2 and 24 h after preparation. This relates to greater yellow pigment and flavonoid contents in the durum flours. All durum wheat YAN exhibited excellent noodle brightness, which was retained over time due to lower levels of the enzymes polyphenol oxidase (PPO) and peroxidase (POD). Durum noodles displayed significantly fewer specks than CWRS and were comparable to CWHWS. Durum wheat YAN cooking quality was equal to or slightly superior to CWRS and CWHWS. Durum wheat flour refinement imparted no significant effects on cooked noodle texture (maximum cutting stress, recovery, resistance to compression). However, the various texture parameters improved with durum wheat protein content and gluten strength.     

The composition of floury and vitreous endosperm affects starch digestibility kinetics of the whole maize kernel

Maize grain starch is the major energy source in animal nutrition, and its high digestion and utilization largely depend on endosperm traits and the structure of the starch-lipoprotein matrix. The aim of this work was to determine floury and vitreous endosperm traits and its relation to starch digestibility rate. In total, kernels of 30 hybrids were manually dissected, and amylose, total zein and starch and non-starch lipids were determined in both vitreous and floury endosperm. Starch digestibility of the whole kernel was determined based on glucose released during a two-step in vitro pig model of enzymatic digestion, and starch digestibility rate was calculated according to the first-order kinetics. The vitreous endosperm of tested hybrids had higher contents of amylose (204.6 vs 190.4 g/kg), zein (63.2 vs 40.4 k/kg) and starch lipids (5.6 vs 4.9 g/kg), and lower content of non-starch lipids (7.3 vs 9.6 g/kg) than floury endosperm. Digestibility coefficients varied among hybrids, and starch digestibility rate varied from 0.73 to 1.63 1/h. Lipids in both vitreous and floury endosperm negatively correlated with the most of digestion coefficients, whereas zein correlated in vitreous and amylose in the floury endosperm (P < 0.05). Starch digestibility rate negatively correlated with all traits, except amylose content in vitreous endosperm. As a result, a linear regression model with four variables including contents of zein and starch lipids in vitreous and zein and amylose in floury endosperm can predict more than 65% variability of starch digestibility rate of tested hybrids.     

Impact of pre-germination on amylopectin molecular structures,crystallinity, and thermal properties of pre-germinated brown rice starches

Ungerminated brown rice (UGBR) and pre-germinated brown rice (PGBR) obtained from different pre-germination durations were studied to investigate the changes in total starch contents of flour, amylopectin molecular structures, crystallinity, and thermal properties of starches as affected by pre-germination. Each paddy of three rice cultivars with different amylose contents (RD6, waxy; KDML105, low amylose; and RD31, high amylose) was soaked in water at 30°C for 12 h and incubated over different periods until the three stages of embryonic growth length (EGL) were achieved. The total starch contents of three-stage PGBR flour from all rice cultivars decreased when pre-germination durations were increased. The three-stage PGBR starches from the three rice cultivars had lower weight-average molecular weight (Mw) and number-average molecular weight (Mn) than UGBR starches. All starches from the three rice cultivars displayed an A-type X-ray diffraction pattern (XRD). Isolated UGBR starch from RD6 had the highest (31.33%) relative crystallinity (RC), while RD31 showed the lowest RC (26.79%). The slight increases in the RC of three-stage PGBR starches from three rice cultivars were found after pre-germination. Isolated PGBR starches from the three rice cultivars had higher gelatinization temperatures and enthalpy, but lower retrogradation enthalpy and %retrogradation than UGBR starches.     

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.     

Effects of Early- and Late-Sowing on Starch Accumulation and Associated Enzyme Activities During Grain Filling Stage in Rice

The environmental temperature occurring during the grain filling stage is an important factoraffecting starch synthesis and accumulation in rice. We investigated starch accumulation, amylaseactivity and starch granule size distribution in two low-amylose japonica rice varieties, Nanjing 9108 andFujing 1606, grown in the field at different filling temperatures by manipulating sowing date. The two ricevarieties exhibited similar performances between two sowing dates. Total starch, amylose andamylopectin contents were lower at the early-filling stage of T1 treatment (Early-sowing) compared withthose at the same stage in T2 treatment (Late-sowing). In contrast, at the late-filling stage, when fieldtemperatures were generally decreasing, total starch and amylopectin contents in T1 were highercompared to those in T2. The ideal temperature for strong activity of ADP-glucose pyrophosphorylaseand soluble starch synthase was about 22℃. A higher temperature from the heading to maturity stagesin T1 increased the activities of starch branching enzyme and suppressed the activities of granule boundstarch synthetase and starch debranching enzyme. We found that rice produced larger-sized starchgranules under the T1 treatment. These results suggested that due to the early-sowing date, the hightemperature (30℃) occurring at the early-filling stage hindered starch synthesis and accumulation,however, the lower temperatures (22 ℃) at the late-filling stage allowed starch synthesis and accumulationto return to normal levels.     

Differences of Physicochemical Properties Between Chalky and Translucent Parts of Rice Grains

Rice grain chalkiness is an important characteristic, but the difference between chalky and translucent parts in grains is still unclear. Here, we investigated the differences of flour made from the chalky or translucent part of rice grains in three indica and three japonica rice varieties. The chalky flour had significantly lower amylose and protein contents and looser starch granule morphology, and starches in the chalky flour had higher relative crystallinity, higher short chain content but lower long chain content than those in the translucent flour. The water states, determined with nuclear magnetic resonance, differed between the chalky and translucent flour after soaking, cooking and retrograding, and the chalky flour had more bound and free water but less constructural water than the translucent flour. Mostly, the chalky flour had lower viscosity and shorter gel consistency, but higher onset temperature and gelatinization enthalpy than the translucent flour. The results indicated that starch granule morphology would be more indicative than other attributions on pasting and gelatinization properties of chalky and translucent parts of rice grains.