Plantain and banana starches: granule structural characteristics explain the differences in their starch degradation patterns

Different banana cultivars were used to investigate the influences of starch granule structure and hydrolases on degradation. The highest degrees of starch degradation were observed in dessert bananas during ripening. Scanning electron microscopy images revealed smooth granule surface in the green stage in all cultivars, except for Mysore. The small and round granules were preferentially degraded in all of the cultivars. Terra demonstrated a higher degree of crystallinity and a short amylopectin chain length distribution, resulting in high starch content in the ripe stage. Amylose content and the crystallinity index were more strongly correlated than the distribution of amylopectin branch chain lengths in banana starches. α- and β-amylase activities were found in both forms, soluble in the pulp and associated with the starch granule. Starch-phosphorylase was not found in Mysore. On the basis of the profile of α-amylase in vitro digestion and the structural characteristics, it could be concluded that the starch of plantains has an arrangement of granules more resistant to enzymes than the starch of dessert bananas.     

Isolation and partial characterization of banana starches.

Two varieties of banana green fruit growing in Guerrero, Mexico, were used for starch isolation. Chemical analysis and physicochemical and functional properties were studied in these starches. The "macho" variety presented higher starch yield than "criollo". In general, chemical compositions in both starches were similar, except in ash content, where the "criollo" variety showed a lower value than "macho". The results of freeze-thaw stability suggested that banana starches cannot be used in frozen products. Both starches presented similar water retention capacity values that increased when temperature increased. Solubility profiles showed that at low temperature "criollo" had lower solubility than "macho", but at higher temperature an inverse behavior was evident; also the solubility increased when temperature increased. Behavior similar to that for solubility was obtained in the swelling test. The banana starch studies indicate the "macho" and "criollo" varieties have different starch structures as evidenced by viscosity.     

Morphological, structural, thermal, and rheological characteristics of starches separated from apples of different cultivars

The starches were separated from unripe apples of five cultivars (Criterion, Ruspippum, Red Spur, Skyline Supreme, and Granny Smith) and evaluated using scanning electron microscopy (SEM), gel permeation chromatography (GPC), X-ray diffraction, differential scanning calorimetry (DSC), and dynamic viscoelasticity. SEM showed the presence of round granules as well as granules that had been partially degraded, probably by amylases. The starch granules in different apple starches ranged between 4.1 and 12.0 mum. Debranching of starch with isoamylase and subsequent fractionation of debranched materials by GPC revealed the presence of an apparent amylose, an intermediate fraction (mixture of amylose and amylopectin), long side chains of amylopectin, and short side chains of amylopectin in the range of 28-35.2, 3.6-4.4, 20-21.3, and 39.9-47.1%, respectively. The swelling power of starches ranged between 14.4 and 21.3 g/g. X-ray diffraction of apple starches showed a mixture of A- and B-type patterns. All apple starches showed peak intensities lower than that observed for normal corn and potato starch, indicating the lower crystallinity. The transition temperatures (onset temperature, T(o); peak temperature, T(p); and conclusion temperature, T(c)) and enthalpy of gelatinization (deltaH(gel)) determined using DSC ranged between 54.7 and 56.2 degrees C, between 57.1 and 59.1 degrees C, between 60.2 and 63.5 degrees C, and between 3.3 and 4.2 J/g, respectively. The viscoelastic properties of starch from different cultivars measured during heating and cooling using a rheometer differed significantly. Red Spur and Criterion starches with larger granule size showed higher G' and G' ' values, whereas those containing smaller size and amylolytically degraded granules showed lower G' and G' '.     

Physicochemical and digestibility properties of double-modified banana ( Musa paradisiaca L.) starches

Banana starch was chemically modified using single (esterification or cross-linking) and dual modification (esterification-cross-linking and cross-linking-esterification), with the objective to increase the slowly digestible starch (SDS) and resistant starch (RS) concentrations. Physicochemical properties and in vitro digestibility were analyzed. The degree of substitution of the esterified samples ranged from 0.006 to 0.020. The X-ray diffraction pattern of the modified samples did not show change; however, an increase in crystallinity level was determined (from 23.79 to 32.76%). The ungelatinized samples had low rapidly digestible starch (RDS) (4.23-9.19%), whereas the modified starches showed an increase in SDS (from 10.79 to 16.79%) and had high RS content (74.07-85.07%). In the cooked samples, the esterified starch increased the SDS content (21.32%), followed by cross-linked starch (15.13%). Dual modified starch (cross-linked-esterified) had the lowest SDS content, but the highest RS amount. The esterified and cross-linked-esterified samples had higher peak viscosity than cross-linked and esterified-cross-linked. This characteristic is due to the fact that in dual modification, the groups introduced in the first modification are replaced by the functional group of the second modification. Temperature and enthalpy of gelatinization decreased in modified starches (from 75.37 to 74.02 °C and from 10.42 to 8.68 J/g, respectively), compared with their unmodified starch (76.15 °C and 11.05 J/g). Cross-linked-esterified starch showed the lowest enthalpy of gelatinization (8.68 J/g). Retrogradation temperature decreased in modified starches compared with unmodified (59.04-57.47 °C), but no significant differences were found among the modified samples.     

水肥耦合对芒果光合特性和产量及水肥利用的影响

为探明干热区芒果高效生产的水肥耦合模式。以4a生芒果树(贵妃芒)为研究对象,采用4因素3水平正交试验设计,共9个处理。试验4因素为3个生育期施肥量(花芽分化期:F_Ⅰ、开花期:F_Ⅱ、果实膨大期:F_Ⅳ)和灌水水平。3个施肥水平分别为高肥(F_(75))、中肥(F_(50))和低肥(F_(25)),3个灌溉水平分别为充分灌溉(F_Ⅰ)、轻度亏水灌溉(DI_M)和重度亏水灌溉(DI_S)。分析芒果冠层结构、光合特性、产量及水肥利用效率对水肥调控的响应规律。结果表明,与充分灌溉相比,重度亏水显著减少叶面积指数、净光合速率(15:00除外)、蒸腾速率、气孔导度和羧化效率(P0.05)。在果实膨大期施肥之后,T8处理(F_ⅠF_(Ⅰ50)F_(Ⅱ25)F_(Ⅳ75))叶面积指数和蒸腾速率最大;T6处理(DI_MF_(Ⅰ75)F_(Ⅱ25)F_(Ⅳ50))11:00的净光合速率和羧化效率均高于其余处理;此外,大多轻度亏水灌溉下11:00的叶片瞬时水分利用效率显著大于充分灌溉(P0.05)。在全生育期定量施肥条件下,增加芒果花芽分化期和果实膨大期肥料占比,充分灌溉能提高产量和肥料利用效率,而轻度亏水灌溉能提高灌溉水分利用效率。T8处理的产量(14 480.46 kg/hm~2)和肥料偏生产力(96.54 kg/kg)最大,T6处理的灌溉水分利用效率(6.67kg/m~3)最高。由极差分析可知综合影响产量和水肥利用的各因素依次为:灌溉水平、开花期施肥、果实膨大期施肥和花芽分化期施肥。综合评分法表明,水肥耦合的最优模式为轻度亏水灌溉、花芽分化期高肥、开花期低肥和果实膨大期中肥组合(DI_MF_(Ⅰ75)F_(Ⅱ25)F_(Ⅳ50))。该研究结果可为干热区芒果水肥管理提供科学依据。     

Relationships among the composition and physicochemical properties of starches with the characteristics of their films

The physical, molecular, and functional properties of corn, cassava, and yam starches were related to the film properties of these starches. Corn, cassava, and yam starches contained 25%, 19%, and 30% amylose, respectively. Amylose from yam starch showed the smallest molecular weight among the starches and amylopectin from corn starch the smallest molecular weight. Cassava starch presented a higher amylopectin content, and its gels and films were less strong, more transparent, and more flexible than corn and yam films. Plasticized films of the three starches were more flexible, with a higher strain and lower stress at break when the glycerol content increased. Unplasticized films were brittle and had water vapor permeability values ranging from 6.75 x 10(-10) to 8.33 x 10(-10) g m(-1) s(-1) Pa(-1). These values decreased when the glycerol content reached 20 g/100 g of starch because a more compact structure was formed. Then, at a glycerol content of 40 g/100 g of starch, the WVP increased because the film matrixes became less dense.     

Physicochemical and structural properties of maize and potato starches as a function of granule size

Chemical composition, molecular structure and organization, and thermal and pasting properties of maize and potato starches fractionated on the basis of granule size were investigated to understand heterogeneity within granule populations. For both starches, lipid, protein, and mineral contents decreased and apparent amylose contents increased with granule size. Fully branched (whole) and debranched molecular size distributions in maize starch fractions were invariant with granule size. Higher amylose contents and amylopectin hydrodynamic sizes were found for larger potato starch granules, although debranched molecular size distributions did not vary. Larger granules had higher degrees of crystallinity and greater amounts of double and single helical structures. Systematic differences in pasting and thermal properties were observed with granule size. Results suggest that branch length distributions in both amylose and amylopectin fractions are under tighter biosynthetic control in potato starch than either molecular size or amylose/amylopectin ratio, whereas all three parameters are controlled during the biosynthesis of maize starch.     

Determination of the degree of succinylation in diverse modified starches by raman spectroscopy

A method using Raman spectroscopy was recently developed for the determination of the degree of substitution of succinate in waxy maize starch. In this paper it is demonstrated that the method can be generalized to a wide range of starches of different amylose contents and botanical origins. Raman calibration sets were used to form regression equations for five types of succinylated starches, that is, waxy, regular, and two high-amylose maize samples (47 and 66% amylose, respectively) and wheat. The derived calibration curves can be used to find the degree of substitution in samples with unknown levels of succinylation. The Raman calibration lines had linear correlation coefficients of 0.995 or better and enable the fast and nondestructive determination of the degree of substitution of succinate for different types of starches with minimal sample preparation. Also discussed is the potential utility of Raman spectroscopy to simultaneously determine the degree of substitution of succinate and amylose content, using previously determined calibration curves developed for the amylose content of maize starches.     

芒果采收车机械臂运动特性分析及试验

为提高芒果采收车机械化采摘的适应性,该研究采用多体动力学理论方法对其机械臂的运动特性进行分析。首先,结合芒果生长和农艺特征及采摘机械臂几何构型与向量特性,运用D-H法建立了机械臂运动学模型以探索其运动特性,并进行末端执行器运动轨迹规划。轨迹规划结果表明末端执行器运动平稳,满足芒果采摘运动要求。进一步地,利用拉格朗日法构建了机械臂的动力学模型,对其进行了正逆动力学仿真验证,以深入了解机械臂的关节运动特性。动力学分析结果表明,在恒力矩工况下,伸缩装置和摆动装置的运动呈现一定的周期性,摆动装置、旋转装置角加速度和伸缩装置加速度均约在1.25、2.3、4.15 s达到阶段峰值;在仅做摆动周期运动的情况下,旋转装置、摆动装置所受驱动力矩均近似呈周期性变化,峰值分别为72.5与52 N·mm,且在一个运动周期内,均有两个极大值点。对机械臂结构进行仿真模态计算和模态试验,结果表明前六阶固有频率误差在5%以内,验证了芒果采收车机械臂多体动力学仿真建模的准确性。研究结果可为保证有效实现机械臂的采摘效果及提高其可靠性与稳定性提供依据。     

钾钙镁营养对香蕉生长和叶片生理特性的影响

在田间试验条件下,研究了不同钾钙镁营养条件下香蕉生长和叶片生理特性的变化。结果表明,适量增施K、Ca及Mg肥有利于香蕉植株的生长发育,有利于为香蕉果实的生长发育提供良好的物质基础。且能有效促进叶片叶绿素的合成,提高叶片净光合速率,从而有效提高叶片光合作用能力。适量增施K、Mg肥能降低叶片抗氧化酶活性及膜脂过氧化强度,从而有效延缓叶片衰老。在广东高州市香蕉主产区,钾钙镁适宜用量为K2O 990、Mg 37.5、Ca 90.0 kg/hm2。     

Influence of lipid extraction process on the rheological characteristics, swelling power, and granule size of rice starches in excess water

The influence of the lipid extraction process on both macroscopic and microscopic characteristics of nonwaxy rice starch gelatinization in excess water was examined. Surface lipids extraction did not change the thermodynamics of starch gelatinization but lead to a significant reduction (33%) in the enthalpy of starch-lipid complex melting at high temperature, resulting in less viscous dispersions. Internal lipid extraction using hot aqueous alcoholic solutions resulted in an irreversible increase in starch granule diameter (50% increase in D[4,3]) and a dramatic change in cooking characteristics of the starch. Instead of the bimodal swelling observed for native nonwaxy rice starch, only one broad transition in swelling, solubility, granule size, and viscosity was observed in the case of the totally defatted starch. While the total removal of lipids resulted in a slight increase in starch swelling at intermediate temperatures, the harshness of the process caused irreparable changes leading to notably lower swelling at high temperatures.     

巴西蕉的营养特性及钾镁肥配施技术研究

钾、镁肥配施是香蕉施肥的重要措施之一。研究巴西蕉(Musa.AAA.Giant.Cavendish.cv.Baxi)的营养特性及钾镁肥配施对其生长影响的田间试验结果表明,假茎与叶片是养分累积的最主要部位;在整个生育期,叶片Mg／K比波动最大。为获得60t／hm2的高产,巴西蕉需要吸收N.275.3.kg、P24.6.kg、K900.0.kg、Ca.151.2.kg、Mg.73.2.kg、S.23.9kg、Fe.2091.7g、Mn.2910.6g、B.228.6.g和Zn.435.6.g。在土壤镁素丰富及Mg／K比为6.87和香蕉大量施钾条件下,施镁肥对巴西蕉的叶片营养、植株长势、蕉果农艺性状、品质及产量没有明显影响,因此,在此条件下可不必配施镁肥。     

香蕉秸秆与牲畜粪便固体联合厌氧发酵产沼气的特性

为了探讨香蕉秸秆与牲畜粪便的组合对固体厌氧发酵产沼气特性的影响,该文在20%的固体质量分数和中温(35±1)℃条件下,分别开展了不同质量分数的牛粪或猪粪与香蕉秸秆的联合厌氧发酵产气性能的比较研究。结果表明,与香蕉秸秆单独厌氧消化相比较,分别组合质量分数为75%的牛粪和猪粪,沼气累积产量可提高1.3～2.0倍。虽然组合猪粪或牛粪皆可改善底物厌氧消化产气性能,促进产气量的提高,但二者对改善底物的厌氧产气特性的影响不同,组合猪粪可以显著增强产气效率。对于猪粪与香蕉秸秆的组合底物,当猪粪的质量分数为50%时,甲烷产率和累积甲烷产量达到最高值,分别为191 mL/g和12.7 L,较牛粪与香蕉秸秆的组合底物分别提高了69%和92%。而沼气产率和累积沼气产量最高值出现在猪粪的质量分数为75%时,较牛粪与香蕉秸秆的组合底物分别提高了18%和32%,达到365 mL/g和23.9 L。此外,2种牲畜粪便的组合亦可显著增强底物中纤维素和半纤维素降解,它们的降解率相较于香蕉秸秆单独厌氧消化最高可提高1.2和3.6倍。该文研究结果可为香蕉秸秆和牲畜粪便固体厌氧产沼气工程提供参考。     

香蕉纤维酶解脱胶工艺及脱胶纤维性能

香蕉纤维的开发利用是香蕉茎秆资源综合利用的有效突破口。该研究以中国主栽品种巴西蕉香蕉茎秆纤维为研究对象,采用俐迪链霉菌对其进行生物脱胶,研究其产酶和脱胶的条件并对脱胶后纤维的结构和理化性质进行分析。研究结果表明:俐迪链霉菌在果胶和半纤维素筛选培养基中观察到明显的水解圈,具有水解果胶和半纤维素的能力;以残胶率和果胶酶活性为指标,筛选出产酶和脱胶的条件为:pH值5.0、NH4NO34 g/L、麸皮10 g、接种量9 mL,在此条件下菌体产酶活力为75μg/(mL·min),香蕉纤维残胶率4.80%,纤维得率为59.48%;扫描电镜(scanning electron microscope,SEM)结果显示脱胶后纤维的直径和表面结构发生了改变;脱胶后纤维的强力从345.37 cN降至273.37 cN,纤维的细度由18.55 tex增加至8.91 tex;纤维中的纤维素含量增加,半纤维素、木质素和果胶等非纤维素成分明显减少,致使脱胶后的纤维素热稳定性和结晶度都明显增加,这一结果与SEM、X射线衍射(X-ray diffraction,XRD)和傅立叶红外光谱(Fourier transform infrared spectroscopy,FTIR)分析结果一致;表明该菌株在香蕉纤维脱胶方面具有一定的应用前景。     

Molecular degradation rate of rice and corn starches during acid-methanol treatment and its relation to the molecular structure of starch

The degradation rates of rice and corn starches with different contents of amylose treated in methanol containing 0.36% HCl at 25 degrees C for 1-15 days were evaluated by monitoring the weight average degree of polymerization of starch. A two-stage degradation pattern during acid-methanol treatment was found for the starches studied, which were the slow (first) and the rapid (second) degradation stages. Waxy starches showed a shorter time period of the first stage than that of nonwaxy starch. Rice starch showed a shorter time period of the first stage and a higher degradation rate of the second stage than the counterpart corn starch with similar amylose content. Despite the botanic source and amylose content of starch, the degradation rate of starch in the second stage significantly (p < 0.05) correlated to the S/L ratio (r = -0.886) and polydispersity (r = 0.859) of amylopectin branch chains of native starch.     

Chemical, molecular, and structural characterization of alkali extractable nonstarch polysaccharides from Job's tears

The polished Job's tears ( Coix lachryma-jobi L.) seeds, dark and white husk types, were sequentially extracted by hot water (75 degrees C) and 0.5 M NaOH solution. Nonstarch polysaccharides were not found in the water extract but were present in the alkali extract. The major components of the alkali extract from both Job's tears were protein, ash, and nonstarch polysaccharides, mainly arabinoxylans. The high arabinose to xylose ratio of 1.25 and 1.24 indicated a highly substituted structure. The average molecular weight (MW) of arabinoxylans of the dark and white husk types were 741,000 Da (Pd 1.5) and 1,449,000 Da (Pd 2.6), respectively, and their average MW reduced after treatment with protease. The alkali extractable arabinoxylans were elucidated to have a (1,4)-linked beta- d-xylan main chain highly substituted with single arabinose units. The results showed that the alpha- l-arabinofuranosyl residues (Ara f) were attached to the main chain mostly at O-3, followed by both O-2 and O-3 of xylopyranosyl residues (Xyl p).     

Effects of mulch location on banana weevil,soil and plant nutrients,soil water and biomass in banana fields

Major constraints to banana (Musa spp., genome group AAA) production, a dietary staple for over 70 million people in sub-Saharan Africa, are pest infestations, poor nutrition and inadequate water. Although mulch can improve soil water and nutrient status, many farmers believe it also promotes the proliferation of banana weevil (Cosmopolites sordidus), one of the most serious banana pests. In this study, we evaluated the effects of mulch location (mulch to base of banana pseudostem; mulch recessed 1 m from the pseudostem) on banana weevil, soil and plant nutrient status, soil water, and banana growth and development. After 3 years, the fully mulched plots had significantly more soil Ca and Mg than plots that did not receive mulch. Banana foliar K concentration was significantly higher in both mulch treatments (full and recessed) than in the control (no mulch) plots. The mulched plots had greater recharge after rainfall events and higher soil water contents during dry periods due to increased infiltration in the mulched plots. However, the mulched plots also exhibited significantly higher banana weevil densities and greater plant damage than the control plots. There was no difference in weevil damage with mulch location, although weevil density was higher in the fully mulched plots throughout most of the trial. Despite greater weevil damage, the treatments that were mulched yielded significantly heavier bunches. Hence the effects of the mulch on soil water infiltration and banana foliar nutrient status outweighed the detrimental effects of banana weevil damage.     

Relating X-ray absorption and some quality characteristics of mango fruit (Mangifera indica L.).

X-ray absorption was used as an index to detect the quality of mango based on its relationship with density, moisture content, soluble solids, titratable acidity, and pH. A regression equation was obtained between the computed tomography (CT) number and the physicochemical properties based on the principle of X-ray absorption capacities of the fruit. The CT numbers of intact mangoes were positively correlated with density, moisture content, and titratable acidity. The soluble solids and pH were inversely related with CT number. The results suggest that CT number measurements on intact fruit can be used as a nondestructive indicator of the quality of mango.     

Semiempirical molecular modeling into quercetin reactive site: structural, conformational, and electronic features

The conformational behavior, molecular geometry and electronic structure of quercetin were investigated using the semiempirical AM1 and PM3 methods. Results reveal that quercetin has a nonplanar molecular structure, with cross-conjugation occurring at the C ring. Calculations were also performed for quercetin radical species at the OH groups, showing the presence of three radicals in a narrow range of energy. An interpretation of the antioxidative process mechanism, exerted by quercetin as a free radical scavenger, relies on two isoenergetic radicals with extended electronic delocalization between adjacent rings, also having cross-conjugated systems and being affected by the experimental environment influencing their relative order.