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.     

Thermal properties of new varieties of yam starches

Starches isolated from yam varieties of Dioscorea alata and Dioscorea cayenensis‐rotundata species were prepared at different time–temperature conditions and characterised by DSC, amperometric iodine titration, light microscopy and rheology and compared to native and chemical modified tapioca starches. The observation by light microscopy showed different morphologies of the granules when heated above 100°C and the tendency for disintegration decreased in the order native tapioca starch > yam starch > modified tapioca starch. Differences between yam and tapioca starches were also revealed by DSC. Yam starch enthalpy is higher than tapioca starch, but the peak temperature is low. However, the significant differences between yam and the other tested starches were found in terms of their rheological behaviour. The viscosity of yam starch was very stable at high temperatures on the viscograph. With this property, yam starch can be used as thickening and gelling agent in food.     

Effect of gelatinisation on slowly digestible starch and resistant starch of heat-moisture treated and chemically modified canna starches

The effects of gelatinisation on slowly digestible (SDS) and resistant starch (RS) of native and modified canna starches were investigated. Starch slurries (10% w/w) were gelatinised at 100 °C for 5, 10, 20 and 40 min using a rapid visco analyzer (RVA). Significant change in the degree of gelatinisation (DG) values of all starch samples was observed during the initial 10 min of gelatinisation; after that the DG values increased gradually with gelatinisation time. The RS contents in all gelatinised starches decreased with increasing gelatinisation time, while the SDS values fluctuated. Chemical modification affected DG values as well as RS/SDS contents. The RS contents in 10% (w/w) acetylated, hydroxypropylated, octenyl succinylated and cross-linked canna starches gelatinised at 100 °C for 40 min were 26.6%, 32.0%, 45.3% and 19.8%, respectively, which were higher than that of the native starch (12.4%). Canna starch modified by crosslinking had the highest SDS content when gelatinised for 20-40 min. Modification of canna starch by heat-moisture treatment resulted in a lower content of RS for all treated samples. However, the Vt-HMT25 (canna starch containing moisture content of 25% during heat treatment) when gelatinised for 5-20 min contained a higher amount of SDS, compared to unmodified starch. The most effective modification method for RS and SDS formation was octenyl succinylation, where the sum of RS and SDS approached that of Novelose260.     

3种栗属坚果淀粉的结构及其理化特性

以我国南北方种植的3种栗属坚果(板栗、锥栗和日本栗)为原料提取淀粉,通过扫描电镜(SEM)、X射线衍射仪(XRD)、差示扫描量热仪(DSC)、快速黏度仪(RVA)等仪器和方法,研究14个品种淀粉的颗粒结构和理化特性的差异,并对其进行相关性分析。结果表明:栗属坚果的直链淀粉含量差异显著,淀粉颗粒形态较为复杂,颗粒表面光滑完整;淀粉均属于C型晶体,结晶度为20.43%～25.63%,淀粉的冻融稳定性好。不同品种淀粉的颗粒结构和理化特性之间存在多种相关性,说明直链淀粉含量和结晶结构影响淀粉的理化性质。     

The effect of long‐term alkali treatment on the molecular characteristics of native and extruded starches at 35°C

In this study the molecular characteristics of native and extruded starches of wheat, corn, and potato were observed under long‐term alkali treatment (0.5 M NaOH, 7 days, 35°C). The molar mass distribution of samples determined by means of calibrated semi‐analytical size exclusion chromatography (SEC) showed different profiles (double and single peak distribution) depending on the dissolution status of the starch polysaccharides with simultaneous loss of supermolecular structures because of disintegration of the aggregates. The molecular range was between 4 × 103 and 2 × 106 g/mol and their calculated average molar masses were M_w = 1.7 × 105–4.1 × 105 and M_n = 2.5 × 104–1.1 × 105 g/mol. The reduction value and the value of intrinsic viscosity were additional indicators for the dissolving status of starch polysaccharides as well as for the stability of starch molecules in alkaline solution.     

普通玉米杂交种间淀粉的糊化热力学性质的分析

采用湿磨法在实验室条件下提取了31种玉米杂交种(普通玉米杂交种29种、糯玉米和高直链玉米杂交种各1种)淀粉,并采用差示扫描量热仪(DSC)分折了玉米杂交种淀粉的糊化热力学性质。结果表明:普通玉米杂交种淀粉的热焓值(ΔH)介于糯玉米和高直链玉米杂交种淀粉之间,且具有最低的起始糊化温度(To)、峰值糊化温度(Tp)、终止糊化温度(Tc)。普通玉米杂交种淀粉间峰值糊化温度(Tp)与起始糊化温度(To)和热焓值(ΔH)相关性达到极显著水平;根据热焓值(ΔH)的大小对供试的普通玉米杂交种进行分类。     

变性淀粉特性及其在食品工业中应用

该文介绍变性淀粉分类、应用特性和几种常用变性淀粉在食品工业中应用,并指出变性淀粉发展方向。     

天然的,物理和化学改性的面包果淀粉的功能特性

淀粉从面包果中分离出来,它通过氧化、乙酰化、热湿处理和退火作用而深度改性。研究了天然和改性淀粉的功能特性,近似分析表明,通过退火、氧化和乙酰化作用改性的淀粉比天然淀粉有较高的湿度,而通过热湿作用改性的淀粉有较低的湿度。除了天然淀粉和退火淀粉有相同的天然纤维含量(042％)之外,其它改性淀粉的天然纤维含量均降低。通过改性之后,蛋白质和脂肪含量也降低了。乙酰化、氧化和热处理作用提高了天然淀粉的膨胀力。     

几种小红栲变性淀粉的糊化与回生特性

研究了几种小红栲变性淀粉的糊特性、糊化特性和回生特性。结果表明,较之原淀粉（或微孔淀粉）,交联淀粉（或交联微孔淀粉）糊的结构强度明显增强,其抗老化性、抗剪切性、抗酸性和冻融稳定性均有较大提高;小红栲原淀粉、微孔淀粉、交联淀粉和交联微孔淀粉的吸收热焓依次增高,而糊化温度依次增高的顺序则为微孔淀粉、原淀粉、交联微孔淀粉和交联淀粉;糊化后原淀粉、微孔淀粉、交联淀粉和交联微孔淀粉的回生难度依次增加,用Avrami方程能较好地模拟各种小红栲淀粉糊中回生晶体的生长行为。     

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.     

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.     

Isolation and characterization of the flour and starch of plantain bananas (Musa paradisiaca)

Plantain bananas of the variety “Terra” (Musa paradisiaca) may have industrial value due to their high starch content. In this research, the flour and starch of such unripe fruit were isolated and their chemical, physicochemical, and structural characteristics were determined. Banana flour and starch had a dry basis yield of 50.6 and 28.5%, and an average granule size of 31.7 and 47.3 µm, respectively. Both raw materials revealed a C‐type pattern and high gelatinization temperatures. The peak viscosity was greater for flour (378.0 RVU) than for starch (252.6 RVU), although the final viscosity was lower. At temperatures above 65°C, the swelling power of banana flour was lower than that of starch, while the solubility of flour was greater than that of starch at all temperatures. Furthermore, the presence of other components in banana flour influenced its physicochemical properties. In general, the flour and starch processed from unripe bananas have numerous possible uses as ingredients in food systems and for other industrial purposes.     

Properties of enzyme modified corn, rice and tapioca starches

Corn, rice and tapioca starches were partially hydrolyzed by treating the starch dispersions with heat stable α-amylase. Dextrose equivalent (DE) of 8–12 was achieved by hydrolyzing the starch samples (10–20% w/v) for 30 min at 90 ± 2 °C. Scanning electron micrographs showed that starch granules had broken down to smaller particles. High performance liquid chromatography with refractive index detection indicated that oligosaccharides with broad molecular weight distributions are present in the reaction products. Hydrolyzed starch dispersions were analyzed for their rheological properties. The storage modulus values (G′) for 20% solid containing slurries were 7373 and 1470 Pa for untreated and enzyme treated samples, respectively, indicating a marked decrease in solid properties due to enzyme action. The complex viscosities (η^*) for native corn starch and hydrolyzed corn starch were 8243 and 1637 Pas, respectively, which indicate that the enzyme treatment decreases the overall resistance of the sample to flow such that the product can spread easily. Further 13C CP/MAS NMR and FTIR studies revealed the loss of ordered structures in the enzyme modified starches. Free flowing fat substitute in the form of fine powder was prepared by spray drying the hydrolyzed starch slurry.     

Functional and dynamic rheological properties of acetylated starches from two cultivars of cassava

The starches derived from two different cultivars of cassava were modified with acetic anhydride. The increase in swelling power and solubility of the cassava starch (CS) pastes treated with different acetic anhydride concentration could be attributed to easier hydration, resulting from reduction of interaction between starch chains due to the substitution. The transition temperatures (T_o, T_p and T_c) and enthalpy of gelatinisation (ΔH) of acetylated CS, were determined. The values were lower than those of native starches. Rheological properties of CS pastes (5% w/w) as a function of the degree of substitution were evaluated in dynamic shear force measurements. Magnitude of storage modulus (G′), loss modulus (G′′) and complex viscosity (Eta*) of acetylated CS pastes were determined also. Dynamic moduli (G′, G′′ and Eta*) values of acetylated sweet cultivar pastes were generally higher than those of native starch whereas the acetylated samples of the bitter cultivar were lower than those of native starch. The magnitudes of G′ were greater than those of G′′ and Eta* at all frequencies (ω). The fact that all the tan δ (ratio G′′/G′) values (0.7–0.48 and 0.25–0.44) were less than one is an indication that the samples are more elastic than viscous. The acetylated starches could find promising industrial uses in food products like Lemon curd and Mayonnaise and other non‐food applications.