Influence of corn starch type in the rheological properties of a white sauce after heating and freezing

The freeze/thaw and heating stability of white sauces prepared with two modified waxy corn starches (hydroxypropyl distarch phosphate and acetylated distarch adipate) and two native corn starches (waxy and normal) are compared.     

Rheology and functional properties of starches isolated from five improved rice varieties from West Africa

Starches were isolated from five improved rice varieties developed by West African Rice Development Agency (WARDA) namely FARO 32, FARO 51, FARO 52, FARO 54 and NERICA. Starch yield and amylose content varied between 73.77–70.02% and 22.88–24.48% respectively. Starches were polyhedral in appearances and within the size range 1.5–6.1 μm. The X-ray diffraction patterns of the starches show a peak centered on 2θ = 15.1°, a doublet on 17.1° and 18.1°, and another single peak at 23.12°. However, NERICA shows no doublet but a single peak at 2θ = 17.1° with a small shoulder. The peak viscosity of the starches ranged between 147.48 and 209.17 RVA corresponding to FARO 52 and NERICA respectively. A neat distinction is observed between the marked shear thinning of FARO 52 and the apparently plastic behavior of the other samples. Important differences appear in the low shear region where the viscosity increases in the following order: FARO 52 < FARO 54 < FARO 51 < FARO 32 < NERICA. The mechanical spectra exhibit similar profiles as the storage modulus (G′) prevails over the viscous component (G″) and is weakly dependent on the frequency. However, the storage modulus increases in the same order observed for low shear viscosity. The percentage retrogradation was between 61.9 and 86.6% and NERICA starch showed the least retrogradation indication. NERICA starch exhibited highest swelling and solubility, while the least was observed in FARO 52. Rheology and functional properties are dependent of amylose composition. This study provides knowledge for the utilization of starches isolated from improved rice varieties that would be relevant for both domestic and industrial applications.     

Structural properties of chemically modified Chinese yam starches and their films

Modified yam starch and dual-modified yam starch were produced with propylene oxide, sodium trimetaphosphate and sodium tripolyphosphate. Gelatinization temperature and final viscosity of native yam starch were 79.2 ± 0.4°C and 5702 ± 3 cP. Results showed that the molar substitution and degree of substitution were increased with the volume fraction of propylene oxide from 6–12%, the highest of molar substitution and degree of substitution were 0.0445 ± 0.0003 and 0.0065 ± 0.0006, the final viscosity and setback of dual-modified yam starch were also similar. However, the gelatinization parameters showed an inverse trend. Starch modified with a mixture of sodium trimetaphosphate and sodium tripolyphosphate had higher phosphorus content and increased viscosity compared to starch modified with sodium trimetaphosphate. The peak viscosity of starch modified with propylene oxide was higher than that of native yam starch and the highest was HP12. The granular surface of modified yam starch and dual-modified yam starch appeared significantly embossed and indented, while. Modified yam starch film treated with 12% propylene oxide showed a more homogeneous fractured surface. The tensile strength and elongation at break (E) of starch films were affected by crosslinking reagents and propylene oxide, respectively. The best transparence and E were demonstrated in starch film that was modified with 12% propylene oxide. However, the best tensile strength was demonstrated in starch film that was modified with 8% propylene oxide, sodium trimetaphosphate, and sodium tripolyphosphate. The final viscosity of HP6C1 and HP6C2 was 27 ± 7 and 45 ± 9 cP, which was too low to form film.     

Clean label starches as thickeners in white sauces. Shearing, heating and freeze/thaw stability

The linear viscoelastic properties and syneresis of freshly prepared and freeze/thawed white sauces prepared with different native starches (corn, waxy corn, potato and rice) at different shearing speeds were studied. Viscosity changes during processing were also measured using a starch pasting cell attached to a rheometer. The freeze/thaw cycle produced a significant increase in the viscous and elastic modulus and the appearance of syneresis in the corn and potato starch sauces, while the waxy corn and rice starch sauces were only slightly affected. Syneresis was significantly reduced upon subsequent heating. Greater shearing speed produced a significant decrease in viscoelasticity. Viscosity profiles revealed that the increase in shearing speed decreased the starch gelatinization temperature and swelling capacity and increased starch breakdown.     

Modification of imitation cheese structure and rheology using pre-gelatinised starches

The rheological properties and microstructure of imitation cheeses containing 3%, w/w, pre-gelatinised maize, waxy-maize, wheat, potato or rice starches were compared to a control (0%, w/w, starch). Dispersions of pre-gelatinised rice or waxy-maize starches with casein had the highest viscosities following heating at 80 °C compared to casein heated alone or in mixtures with the other starches. Imitation cheese products containing pre-gelatinised starches had larger fat globule size distributions (especially rice or waxy-maize starch) and less homogeneous background protein matrices than the control as evidenced by scanning electron microscopy, which indicated poorer fat emulsification. The resultant imitation cheeses were softer, less cohesive and had reduced melting properties compared to the control. During processing, the pre-gelatinised starch competed with the rennet casein for water and impaired the caseins hydration as evidenced visually by delayed emulsification of free oil. Differences in levels of amylose retrogradation may have been responsible for variances in functionality between starches of different origins.     

Thermal, microstructural and textural characterisation of gelatinised corn, cassava and yam starch blends

The functional properties of mixtures of maize, cassava and yam starches and their relationships with microstructural characteristics were investigated. Experiments were performed following the simplex‐centroid design with internal points and restrictions (upper limit) for yam starch proportion. The statistical model used (Scheffé canonical equation) was a powerful tool to predict the pastes behaviour within the limits of the experimental area. Polynomials with second level interactions were applied to obtain the surface response. Viscoelastic attributes of mixtures differed from those of individual starches. As shown by differential scanning calorimetry and microscopical observations, physical properties of the mixtures depended on the type of networks obtained. These networks varied upon yam, corn and cassava starch proportions as each one has a particular characteristic: gelatinisation temperature, granule size, swelling capacity and amylose/amylopectin ratio among others.     

两种大米淀粉及其磷酸酯淀粉理化特性的比较研究

对比分析2种大米(籼米和粳米)的全粉、淀粉和取代度均为0.068的磷酸酯淀粉的理化特性.粳米的全粉、淀粉和磷酸酯淀粉的膨胀力分别为7.5,10.7,21.6 g/g,分别高于籼米的全粉、淀粉和磷酸酯淀粉的膨胀力(5.8,8.9,17.4 g/g).2种大米淀粉经磷酸酯化后透光率增高,相应淀粉的透光率次之,全粉的透光率最低,籼米的全粉、淀粉和磷酸酯淀粉的透光率分别低于粳米的全粉、淀粉和磷酸酯淀粉的透光率.经快速黏度分析仪测定的糊化特性结果表明,淀粉或变性淀粉膨胀力高,其峰值黏度和崩解值也高,此外,蛋白质含量和直链淀粉含量也极大的影响了淀粉的糊化特性.使用动态流变仪测定的流变特性表明,在相同的温度下,籼米的全粉、淀粉和变性淀粉的储能模量(G')分别比粳米的全粉、淀粉和变性淀粉的储能模量(G')高,对于相同的大米品种,全粉的储能模量(G')最高,变性淀粉的储能模量(G')最低.     

Alteration of imitation cheese structure and melting behaviour with wheat starch

Imitation cheeses were manufactured with increasing levels (0–20%, w/w) of native wheat starch in partial or total replacement of rennet casein protein. With increased addition of native wheat starch up to 9% (w/w), irregular starch particles (sometimes horseshoe-shaped) became more numerous and disruptive of the protein structure. Differential scanning calorimetry showed the presence of a large endothermic peak at 42 °C, corresponding to the melting of the palm oil constituent, and a smaller second endotherm at 79–82 °C with the inclusion of starch at levels of up to 9% (w/w). This smaller endotherm was not present on heating imitation cheese containing 20% (w/w) starch, which had no meltability. Results indicated that the second smaller endotherm corresponded to a phase transition in the casein-continuous matrix facilitating flow behaviour in the imitation cheese network. At concentrations of 3–9% (w/w), wheat starch behaved like a filler material, with limited effects on the rheology of the casein matrix at temperatures below 50 °C, however its inclusion increased the processing time and reduced the meltability of the imitation cheese.     

Morphological and thermal characterization of native starches from Andean crops

We have characterized and compared the morphological and thermal properties exhibited by starches from different Andean crops. Starches were extracted from tubers, root, fruits, and other starch containing parts of different plants. Morphological characterization was carried out by means of light optical microscopy. Thermal analysis was performed by DSC. The morphological properties of starch granules as well as the gelatinization parameters vary considerably among plants sources. Feret's diameter of granule starches is related to the part of the plant from which starch is obtained corresponding the largest starch granules (≈42.5 µm) to tuber sources, whereas, smallest granules to root sources (≈8.9 µm). The specific enthalpies of gelatinization were in the range 9–18.7 J/g. An inverse correlation between specific enthalpies and specific surface area (SSA) for starch with water content of 75% indicates that starches with higher SSAs need less energy to complete the gelatinization process than those with lower SSAs. The results show that starches from Andean crops could be used as raw material for the production of new starch‐based thermoplastics.     

Macromolecular characteristics of ten yam (Dioscorea spp) starches

Starches from ten yam (Dioscorea) species were compared with those of maize, wheat, potato and cassava, and characterized by high‐performance size‐exclusion chromatography coupled with multiangle laser light scattering. Treatment with 95% (v/v) dimethylsulphoxide and microwave heating in a high‐pressure vessel led to complete dissolution of the starch samples. For yam starches, M?_w were between 1.88 × 10⁸ and 3.27 × 10⁸ g mol^?1 and R?_G were between 258 and 396 nm. The hydrodynamic coefficients of amylopectins were between 0.36 and 0.44, indicating that those of maizes and esculenta 5 and dumetorum yam species had particularly highly branched structures. Multidimensional analysis of the macromolecular characteristics of yam starches indicated three classes: dumetorum cultivar (Dioscorea dumetorum), esculenta 5 cultivar (Dioscorea esculenta) and the other eight yam starches, including cultivars of Dioscorea alata and Dioscorea cayenensis‐rotundata species. Some yam starches were also leached at 90 °C. The macromolecular characteristics of the leached fractions confirmed the previous typology. Copyright © 2003 Society of Chemical Industry     

Physico-chemical properties of potato starches

Starches were isolated and characterised from 10 potato cultivars grown under the same conditions (with a commercial starch for reference). The chemical composition revealed some differences amongst the starches with protein ranging from 0.30% to 0.34%, amylose 25.2% to 29.1% and phosphorus 52.6–66.2 mg 100 g⁻¹. High performance size-exclusion chromatography (HPSEC) fractionation of isoamylase debranched amylopectin showed that the amylopectin molecules were less branched and consisted of more B1, but less A-chains, than cereal starches. Gelatinisation onset (T_o), peak (T_p) and conclusion (T_c) temperatures of the native potato starches ranged from 58.7 to 62.5 °C, 62.5 to 66.1 °C and 68.7 to 72.3 °C, respectively, whilst the gelatinisation enthalpies ranged from 15.1 to 18.4 J g⁻¹. The gelatinisation temperatures of the starches increased in common with the amounts of short and intermediate sized amylopectin chains. The ¹³C magic angle spinning nuclear magnetic resonance (¹³C CP-MAS NMR) and wide angle X-ray diffraction (XRD) data (30.6% ± 0.22% crystallinity on average) showed little variance amongst the samples. Particle sizing results, however, revealed more variance (20.6–30.9 μm mean diameter). Overall, these data reveal the subtleties of cultivar specific variation against a background of constant environmental conditions.     

Improving effect of xanthan and locust bean gums on the freeze-thaw stability of white sauces made with different native starches

The effect of adding xanthan gum and locust bean gum at low concentrations (0.15% w/w) on the freeze/thaw stability of white sauces prepared with native starches from four different sources (corn, waxy corn, potato, and rice) was investigated. Linear viscoelastic properties were taken as structural indicators and these and syneresis as indicators of the freeze/thaw stability of the sauces. The pasting properties of the starch in the sauce system were also studied. Both hydrocolloids reduced the structural changes occurring after thawing, xanthan gum being more effective than locust bean gum. In corn and potato sauces, the most affected by the freeze/thaw cycle, the appearance of syneresis and the increase in viscoelastic functions were significantly reduced by both hydrocolloids. In general, the addition of hydrocolloids affected peak, hot peak and cold peak viscosities and reduced relative total setback. The results regarding the possible effects of hydrocolloid addition to white sauce systems are discussed in molecular terms.     

Effects of mucilage on the thermal and pasting properties of yam, taro, and sweet potato starches

This study investigates the effects of water-soluble mucilages (0, 2.5, and 5 g/100 g; w/w, dry basis) on the thermal and pasting properties of isolated starches from three root and tuber crops. The results show that yam tuber presents the greatest level of mucilage and also possess the largest amylose content of the three isolated starches. The addition of mucilage caused a remarkable increase in the temperature of gelatinization for the three tested starches due to the competition for water during starch gelatinization. Furthermore, adding mucilage increased the phase transition temperature range (Tc-To) of starches but decreased enthalpy (ΔH). However, although the pasting temperature increased with the addition of mucilage into tuber starches, it did not change that of taro starch. The peak viscosity of taro and sweet potato starches decreased significantly as their mucilages were added into each starch suspension system (p < 0.05). However, the addition of mucilage slightly increased the viscosity of yam starch. Furthermore, the addition of mucilage slightly increased the swelling power of yam and taro starches, but did not change that of sweet potato starch.     

Thermal and viscoelastic properties of starch gels from maize varieties

The aim of this work was to determine the thermal, functional and rheological properties of maize (Zea mays) starch isolated from seven varieties. Chemical analysis was undertaken in all starch samples. The gelatinization and retrogradation temperature at different storage times, as well as the enthalpy of the isolated starches, were determined using differential scanning calorimetry (DSC). Swelling and solubility were also measured in individual samples. Dynamic oscillatory tests (amplitude and frequency sweeps) were undertaken on starch samples with 10% (w/v) of total solids during a cycle of three stages (kinetics) of heating/cooling, using a strain‐controlled rheometer. The samples presented an amylose content which ranged from 22% to 29%, typical in normal starches, the lipid values were under 1%, while the protein contents were just over 1%. The calorimetric profile for the studied starches showed a peak temperature (gelatinization) over the temperature range from 72.5 to 75.7 °C and enthalpy values between 13.68 and 17.58 J g^?1. Four starches presented enthalpy values of the retrogradation transition that increased with the storage time, showing differences among the starches analysed. Maximum swelling and solubility were usually found at the second stage of the above‐mentioned cycle. The rheological profile showed that the gels formed during the first stage of the above‐mentioned kinetics presented the behaviour of weak viscoelastic gels with the storage or elastic modulus (G′) higher than the loss or viscous modulus (G″) over the applied strain and frequency ranges. All samples showed a more elastic character as the kinetics progressed. Starches isolated from diverse maize varieties showed differences in their characteristics studied, and might produce different functional properties in the products where they are used. Copyright © 2006 Society of Chemical Industry     

不同品种小麦淀粉提取及糊化粘度性质比较

采用实验室方法提取30种不同小麦籽粒淀粉;并用快速粘度分析仪(RVA)测定不同品种小麦淀粉糊化粘度性质,分析各粘度性质相关性及差异性。结果表明:普通小麦淀粉糊化粘度性质参数明显不同,粘度性质参数差异性显著,各参数间相关性极显著。     

微波辐射对木薯淀粉性质影响

研究微波辐射前后木薯淀粉物化性质变化,采用微波对30%水分含量木薯淀粉进行处理,结果表明,微波处理增强对应X–射线衍射峰强度,降低膨胀度、溶解度和冻融稳定性;木薯淀粉经处理后糊化起始温度升高、粘度降低,但其粘度曲线不改变。以上数据表明,在淀粉颗粒内无定形区和结晶区直链淀粉与直链淀粉、直链淀粉与支链淀粉发生交互作用,微波处理使淀粉分子发生一定程度降解。     

甘薯交联抗性淀粉热力学性质与消化性研究

根据膨胀度、糊化度及差示扫描量热仪(DSC)测得热力学参数,综合分析甘薯交联抗性淀粉和原淀粉热力学性质,并采用Jenkins提出In–vitro模型测定淀粉体外消化性。结果表明:在同一温度下,甘薯交联抗性淀粉膨胀度和糊化度均较原淀粉低,且交联剂用量越高,淀粉膨胀度和糊化度越小;DSC测试结果显示,甘薯交联抗性淀粉相转变温度To、Tp、Tc随交联剂用量增加而升高,Tc–To和△H均比原淀粉低。In–vitro消化模拟实验表明,甘薯交联抗性淀粉消化性比原淀粉低,并随交联剂含量增加,消化产物量减少,消化速度降低。