Effect of non-starch polysaccharides on the in vitro digestibility and rheological properties of rice starch gel

The starch digestibility and rheological properties of gels were evaluated in the presence of three non-starch polysaccharides (agar, xanthan gum and konjac glucomannan) with rice starch. Each polysaccharide was added to 30% (w/w) rice starch suspension at defined concentrations and starch gels were prepared. The extent of starch gel digestibility was determined by an in vitro method and rheological properties by a dynamic oscillatory test and a compression test. The added polysaccharides suppressed starch hydrolysis in the gels compared with the control, and a concentration dependency of this suppressive effect was observed. Adding agar and xanthan gum increased the storage shear modulus (G′) of starch gels, while adding konjac glucomannan decreased G′ values. The results indicate that the suppressive effect of non-starch polysaccharides on starch digestibility appears to be not only due to the rigidity of the gel, but also the interaction between starch and non-starch polysaccharides.     

Functional properties of water-soluble non-starch polysaccharides from rice and ragi: Effect on dough characteristics and baking quality

Water-soluble non-starch polysaccharides (NSP) were isolated from native and malted rice and ragi. The effects of addition of water-soluble NSP on dough rheological characteristics and baking quality were investigated. Water-soluble NSP had low relative viscosity and showed no gelling activity despite considerable amount of ferulic acid (∼492.5-528.0 μg/g). However, they were found to stabilize protein foams against thermal disruption. Addition of water-soluble NSP (0.25 and 0.50%) to wheat flour resulted in increased water absorption and decreased dough development time. However, prolonged mixing resulted in slightly lower dough stability. Increase in dough extensibility and improvement in starch pasting characteristics were observed upon the addition of water-soluble NSP. Significant increase in loaf volume and softness of the bread was also observed. Water-soluble NSP both from malted rice and ragi had higher effect compared to the native one. Results showed that water-soluble NSP can be added to various low-fiber food preparations with positive dough functionality.     

Endogenous rice endosperm hemicellulose slows in vitro starch digestibility

Hemicellulose, the primary non-starch polysaccharide originating from cell walls of rice endosperm, greatly influences the digestibility of starch in food matrix. Three rice varieties differing in total dietary fibre content were treated with hemicellulose and in vitro starch digestion with α-amylase was conducted. Removing the hemicellulase significantly promoted starch digestion, and the magnitude of the impact was dependent on rice variety. The impact was more pronounced in variety cw high in apparent amylose and total dietary fibre content, while was negligible on the japonica rice Nipponbare. Endogenous hemicellulose slowed in vitro starch digestibility in rice by interacting with amylose and amylopectin, particularly with the long chain amylopectins, inherent existing and during the cooking process. Non-starch polysaccharides, including hemicellulose, can be tailored in rice to modify the digestible carbohydrate content; however, more research is required to fully understand the interactions between non-starch polysaccharides and starch and their influences on grain quality.     

Physicochemical properties of hull-less barley fibre-rich fractions varying in particle size and their potential as functional ingredients in two-layer flat bread

The performance of barley fibre-rich fractions (FRF), as high dietary fibre ingredients, in two-layer flat bread was investigated. In addition, the effects of particle size reduction by pin milling on functional properties of FRF were studied. FRF enriched in non-starch polysaccharides (β-glucans and arabinoxylans) were obtained by roller milling of hull-less barley. Pin milling (PM) of FRF significantly reduced their particle size, slightly increased the solubility of β-glucans and arabinoxylans, and increased the viscosity of water slurries containing FRF. The addition of 20% of barley FRF to wheat flour significantly increased dough water absorption and weakened the dough properties, as indicated by farinograph mixing curves, but the FRF-enriched doughs exhibited good handling characteristics at the dividing and sheeting stages. The appearance, diameter, layer separation, crumb, and aroma of the FRF-enriched flat breads were comparable to that of the control. The PM of FRF did not significantly affect the dough handling or the quality characteristics of flat breads. The addition of 20% of barley FRF to wheat flour flat bread provided substantial health benefits by significantly increasing the total and soluble dietary fibre contents and by decreasing starch digestibility.     

Rheological properties of gluten-free bread formulations

In this study, the rheological properties of rice bread dough containing different gums with or without emulsifiers were determined. In addition, the quality of rice breads (volume, firmness and sensory analysis) was evaluated. Different gums (xanthan gum, guar gum, locust bean gum (LBG), hydroxyl propyl methyl cellulose (HPMC), pectin, xanthan–guar, and xanthan–LBG blend) and emulsifiers (Purawave^™ and DATEM) were used to find the best formulation for gluten-free breads. Rice dough and wheat dough containing no gum and emulsifier were used as control formulations. The rice dough containing different gums with or without emulsifiers at 25 °C showed shear-thinning behavior with a flow behavior index (n) ranging from 0.33–0.68 (except pectin containing samples) and consistency index (K) ranging from 2.75–61.7 Pa sⁿ. The highest elastic (G′) and loss (G″) module were obtained for rice dough samples containing xanthan gum, xanthan–guar and xanthan–LBG blend with DATEM. When Purawave^™ was used as an emulsifier, dough samples had relatively smaller consistency index and viscoelastic moduli values compared to DATEM. The viscoelastic parameters of rice dough were found to be related to bread firmness. Addition of DATEM improved bread quality in terms of specific volume and sensory values.     

大豆多糖对大米淀粉糊化及凝胶特性的影响

以大米淀粉为材料,研究了大豆多糖对淀粉糊化及凝胶特性的作用.通过布拉班德黏度计,DSC差示量热扫描和质构仪等分析手段,研究分别添加相当于淀粉干基质量分数1.0%、2.5%、5.0%的大豆多糖的影响.结果表明,大豆多糖能有效降低大米淀粉黏度,改善其凝胶品质,且添加量越大,效果越明显,对淀粉基食品的改良有重大意义.     

Functional Characteristics of the Mucilaginous Polysaccharides Derived from Cowpea (Vigna sinensis), Black Gram (Phaseolus mungo) and Linseed (Linum usitatissimum)

The cowpea polysaccharides had the maximum viscosity at around pH 6 and it decreased with increase in temperature but increased with increase in concentration. Both black gram and cowpea polysaccharides stabilized against thermal disruption the foam formed by the surface active proteins. Black gram starch and the mucilage together showed greater foam stability, probably due to enhanced viscosity caused by synergistic interactions between these polysaccharides. Gelatinization temperature as well as the peak and set back viscosities of wheat starch were considerably decreased by adding either the black gram or the linseed polysaccharide. In farinograph experiments the black gram polysaccharide exhibited a strengthening effect on wheat flour dough, whereas the linseed polysaccharide resulted only in an increased water absorption. Extensographic data indicated increased resistance and decreased extensibility of wheat flour dough by the addition of black gram and linseed polysaccharides.     

Influence of non-starch polysaccharides on the in vitro digestibility and viscosity of starch suspensions

The effects of adding non-starch polysaccharides (xanthan gum, guar gum, konjac glucomannan, and pectin) on the starch digestibility and viscosity of raw starch suspensions in a mixed system were determined. Each type of polysaccharide was added to high-amylose corn starch suspensions at defined concentrations. High-amylose rice starch suspensions mixed with xanthan and guar gum were prepared for comparison. The extent of starch digestibility was determined by an in vitro method, and the glucose diffusibility from the dialysis tube in the presence of polysaccharides was measured. The added polysaccharides were observed to decrease the starch digestibility in a mixed system. When compared at the same concentration, xanthan gum showed the most pronounced suppressive effect on starch digestibility and glucose diffusibility from the dialysis tube. The addition of polysaccharides increased the viscosity of the starch suspension. Significant relations were found between the extent of starch digestibility and the apparent viscosity at low shear rate.     

Rheological Properties and Bread Quality of Wheat and Rice Starch Composite Flours

Rice starch was added to wheat flour to form different rice composite flours. The rheological characteristics of different mixtures showed a decrease in the farinograph absorption and an increase in mechanical tolerance index when rice starch was added at 40% level. Dough stability, development time, arrival time and over-all farinograph profile scores were decreased. Extensograph data showed an increase in dough deadness and a drop in dough extensibility. Although dough rheology data indicated that the addition of rice starch weakened the dough, bread of acceptable quality was obtained when rice starch was added at 25% level. This should be of interest for development countries where rice is a native crop.     

The effects of extruded black rice flour on rheological and structural properties of wheat-based dough and bread quality

Addition of raw black rice flour leads to deficient processability on bread making quality. One of the effective methods to modify the functional properties of black rice flour (BRF) composite dough is to extrude black rice flour (EBRF) before incorporation. This study investigated and compared the effect of BRF and EBRF addition level of 10%–50% on the rheology, microstructure of dough and bread quality. The rheological properties of composite dough were recorded by Mixolab, stress relaxation and tensile test. The substitution of EBRF presented higher water absorption but lower development time, protein weakening, starch gelatinization, starch gel stability and starch retrogradation than wheat flour dough. Both the BRF and EBRF dough presented solid-like behaviour, while the EBRF dough showed more viscous, higher resistance and extensibility than BRF dough. The dough microstructure of dough was observed by SEM, and a more compact structure of EBRF dough could be seen than BRF dough. The incorporation of EBRF in bread quality presented higher specific volume, lower bake loss and firmness than BRF bread. These findings indicated the potential utilisation value of extruded black rice flour in bread making.     

Effect of starch and non-starch components on water migration,microstructure, starch retrogradation and texture of flat rice noodles made from different rice varieties

Effects of starch and non-starch components on rice noodle quality, water migration during rehydration, texture, microstructure and starch retrogradation of dried rice flour and rice starch noodles made from five rice varieties with similar high amylose contents were examined. Rice noodle qualities depended mainly on starch properties and to a lesser extent on the presence of non-starch components. Elongation of rice flour noodles was lower than rice starch noodles due to the presence of non-starch components that interrupted the starch network. Non-starch components reduced cooking loss of flour noodles in some varieties. Water migration in rice flour noodles with a looser microstructure was faster than in rice starch noodles. Nuclear magnetic resonance imaging revealed different water migration speeds in rice flour noodles among varieties, related to noodle microstructure and retrogradation properties. For production of good quality rice noodles, manufacturers should consider not only amylose content but also non-starch components.     

Effects of plasma-activated water and heat moisture treatment on the properties of wheat flour and dough

Plasma-activated water (PAW) production and use is an emerging technology for enhancing product safety, extending shelf-life and quality retention, and promoting sustainable processing. At present, it has generated considerable attention for applications to starch and flour modification. This work presents an innovative approach to wheat flour (WF) modification using PAW and heat-moisture treatment (HMT), and compares this approach with distilled water (DW) treatment. As expected, PAW and HMT promoted flour granule clustering, increasing particle size. These treatments accelerated molecular interactions between wheat starch and non-starch components (e.g. proteins and lipids), which eventually increased resistant starch (RS) content. Addition of modified flour (30 g) to WF positively affected its rheological properties, and closely bound water content of the dough. The gluten protein network structure in the dough suffered varying degrees of damage. In conclusion, our results showed that PAW and HMT may provide a novel beneficial method for modifying wheat flour during food processing to obtain viscoelastic wheat flour products with nutritional functions.     

Retrogradation Kinetics of Eight Starches

Retrogradation rate and extent were determined by differential scanning calorimetry and rheology measurements on 40% dry matter gels made from pea, modified waxy maize, rice, waxy rice, wheat, manioc, potato and microwaved irradiated potato starches. As a result, each starch retrogrades differently, depending also on the measurement technique. Nevertheless, potato and pea starches seem to be the most sensitive and the waxy and modified waxy types are the least sensitive to retrogradation.     

Characteristics of Imitation Cheese Containing Native Starches

ABSTRACT Imitation cheeses containing 3% native maize, waxy‐maize, wheat, potato or rice starch were manufactured and the microstructure, meltability, texture and dynamic rheology of these products were compared to a control (0% starch). Fat globules in starch‐containing products (except potato) were smaller than in the control as evidenced by electron microscopy. All starches reduced meltability and cohesiveness of the imitation cheeses. Hardness was increased by wheat, potato or maize starch but reduced by waxy‐maize or rice starch. Starches significantly reduced tan 8 peaks compared to the control with potato starch having the greatest effect. Rice starch appears to have the most potential as a partial casein substitute in imitation cheese.     

Effects of Soy Protein on Physical and Rheological Properties of Wheat Starch

It is necessary to understand the interaction phenomena between proteins and polysaccharides for the development of starch‐based products with better physical and sensory properties. A simplified model system was chosen to study the influence of soy protein on physical and rheological properties of wheat starch and the possible interactions between them. Thermal and pasting behaviors of the slurries and texture properties, water retention capacity and ultra structure of soy protein‐wheat starch gels were analyzed. While soy protein isolate increased the viscosity of starch suspension during and after heating, gels with soy protein presented a weaker structure than wheat starch gels. Results suggested association between leached out material and swollen granule surface of starch with soy protein. Scanning electron microscopy reflected these changes in the gel ultrastructure.     

辐照糙米储藏过程中淀粉脂和非淀粉脂组成及变化

目的：研究低剂量60Co-γ辐照对储藏糙米的淀粉脂和非淀粉脂的粗脂肪含量和脂肪酸组成的影响,为辐照糙米储藏提供数据支持和理论依据。方法：晚粳米收获后进行60Co-γ辐照,设0.2、0.5、1.0 kGy和2.0 kGy 4 个不同的辐照剂量水平,之后恒温（15±0.5）℃储藏12 个月,每3 个月进行一次品质测量。结果：辐照糙米在储藏12 个月的过程中,非淀粉脂含量变化不显著（P＞0.05）,淀粉脂含量在储藏过程中持续下降,储藏12 个月后,淀粉脂含量显著降低（P＜0.05）。在储藏过程中,非淀粉脂和淀粉脂的各个脂肪酸组成的含量表现出不同的增加或减少趋势。在同一时期,辐照糙米和未辐照糙米的粗脂肪（淀粉脂和非淀粉脂）含量没有显著差异（P＞0.05）,说明辐照不会影响粗脂肪含量,辐照对各糙米的脂肪酸组成没有显著的影响。结论：低剂量的辐照处理不会改变储藏过程糙米的脂类组成,储藏对糙米的淀粉脂和非淀粉脂有不同的影响。     

Analysis of Cereal Starches by High-Performance Size Exclusion Chromatography

Starch has unique physicochemical characteristics among carbohydrates. Two important characteristics of starch are amylose/amylopectin ratio and molecular weight. The objective of this study was to develop a simple, one-step, and accurate method for the determination of amylose/amylopectin ratio and weight-averaged molecular weights of starch in whole meal cereal samples. This method would allow for the simultaneous measurement of these important properties without the time-consuming step of large-scale starch extraction. Starch from spring wheat, barley, oat, rye, buckwheat, rice, durum wheat, and corn was precipitated with ethanol and solubilized with potassium hydroxide and urea before analysis by a high-performance size exclusion chromatography (HPSEC) system with a refractive index detector. To verify peak identity, fractions were collected and then gas chromatography analysis of soluble starch and beta-glucan assays was performed. All HPSEC fractions contained only glucose and no beta-glucan was detected, indicating that there was no contamination from non-starch polysaccharides. Weight-averaged molecular weights were calculated using a series of gel permeation chromatography grade dextrans. The method described in this study can be used to determine amylose/amylopectin ratio and weight-averaged molecular weight of cereal starches using as low as 25 mg whole meal samples without large-scale starch extraction.     

Effect of polysaccharides with different ionic charge on the rheological,microstructural and textural properties of acid milk gels

The effects of addition of polysaccharides with different ionic charge on rheology, microstructure, texture and water holding capacity (WHC) of acid milk gels were studied and compared to that of gelatin addition. Similar to gelatin, starch (neutral) and xanthan gum (anionic) did not prevent milk gelation in the first 30 min of the acidification stage, even at high concentrations, and the typical casein network in acid milk gels could still be seen from electron micrographs; gelling and melting of these hydrocolloids were observed during the cooling and heating stages at specific concentrations. On the other hand, two neutral polysaccharides, guar gum (≥ 0.05%) and locust bean gum [LBG] (≥ 0.1%) inhibited milk gelation from the beginning of the acidification stage; the microstructure of the gel was modified greatly and no gelling/melting was observed during the cooling or heating stages. Another anionic polysaccharide, carrageenan, induced earlier milk gelation at low concentration (≤ 0.05%), but inhibited gelation entirely at high concentration (0.2%); inflections at ~ 27 °C and 21 °C were also observed during the cooling and heating stages at 0.05% concentration. The gel microstructure was not changed greatly, but showed smaller particle size at a carrageenan concentration of 0.05% than control sample. None of the polysaccharides showed as much improvement in WHC of the milk gels as gelatin did. Hence, xanthan and starch were found to be closer to gelatin in their effect on acid milk gels compared to guar gum, LBG and carrageenan.     

Glycosidases and glycanases of wheat flour doughs

Wheat flour contains hydrolytic enzymes capable of reducing dramatically the viscosity of the aqueous solution obtained by high-speed centrifugation of dough. Indirect evidence suggests this reduction in viscosity is largely due to the hydrolysis of glycosidic linkages in the non-starch polysaccharides. Soluble proteins and starch contribute less to the viscosity of this dough liquor than do the flour gums. The glycanases in flour relatively rapidly hydrolyse the galactomannan, guaran and carboxymethylcellulose. Flour also contains a wide range of enzymes capable of hydrolysing nitrophenyl α- and β-glucosides, α- and β-galactosides, α- and β-mannosides, α-arabinoside, β-fucoside and β-xyloside. Both the glycanases and the glycosidases show pH optima within the range 4-6 which covers the range normally encountered in dough.     

Utilization of rice starch with gums in Asian starch noodle preparation as substitute for sweet potato starch

Starch noodles were produced using a medium grain rice starch in the presence of various gums, and physical properties of the noodles were compared with sweet potato starch noodle. Pasting viscosity of the rice starch was lower than that of sweet potato starch (830 vs. 1,618 cp as peak viscosity). The peak viscosity, however, was increased by the addition of gums (0.1% based on dispersion), and especially xanthan was the most effective in increasing the peak viscosity (1,478 cp). The cooking loss for the rice starch noodles (1.5 mg/mL), greater than that for the sweet potato starch noodle (0.2 mg/mL), was effectively reduced to 0.8 and 0.9 mg/mL, respectively, by the addition of locust bean gum (LBG) and curdlan. The addition of LBG or gellen gum also increased the hardness of the rice noodles. Aging (extended retrogradation) the noodles was effective in reducing the cooking loss and improving the textural properties of the rice starch noodles. The combination of the gum addition (like LBG) and aging of the rice starch noodle might be useful for utilizing rice starch as a substitute for sweet potato starch in Asian noodle preparation.