Comparison of the physicochemical properties and pasting characteristics of flour and starch from red and white sweet potato cultivars

This research characterized flour and raw starches isolated from red and white sweet potato cultivars. Their composition, determined by proximate analysis, is typical of sweet potato cultivars. These cultivars have high amylose content (32-34%) and exhibit a Ca-type X-ray diffraction pattern. Similar gelatinization characteristics were detected for both starches with onset temperature of 67 degrees C and enthalpy of 10.5-11.0 J/g. Starches of both red and white cultivars had well-correlated (r (2) = 0.982) and high solubilization and swelling temperatures, starting at 80 degrees C. Pasting properties of the white cultivar exhibit lower tendency for retrogradation. Water and oil absorption capacities were low for both red and white flours. When parboiled, both cultivars showed improved water absorption capacity and decreased least gelation concentration. It is concluded that the white cultivar should be preferred when low retrogradation tendency is required.     

Adsorption and binding of amino acids on homoionic montmorillonite and kaolinite

The adsorption and binding of amino acids (aspartic acid, cysteine, glycine, proline and arginine), ranging in molecular weight from 115 to 174 and in isoelectric point from pH 2.8 to 10.8, to montmorillonite [M] and kaolinite [K] homoionic to H, Na, Ca, Zn, La or Al were studied in unbuffered suspensions. Aspartic acid was adsorbed and bound on M homoionic to Ca or Zn but only adsorbed to K homoionic to Ca or Zn. Cysteine was only adsorbed on M homoionic to Al and adsorbed and bound on M homoionic to Zn and on K homoionic to H or Zn. Proline was adsorbed and bound on M homoionic to H, Ca or Zn and on K homoionic to H; it was adsorbed but not bound on both M and K homoionic to Al. Arginine was adsorbed and bound on M homoionic to H or Al and only adsorbed on K homoionic to Ca or Zn. Glycine was not bound on any of the clays. The amounts of amino acid adsorbed and bound (measured by the loss of amino acid from solution) and the class (Giles et al., 1974a and b) of both the adsorption and binding isotherms (retention against ultimate washing with water) were dependent on the type of amino acid, the type of clay, the type of cation predominant on the clays and the basicity or the additional function moiety (e.g. carboxyl, thiol, guanido) of the amino acid. The relative values of the non-standard free energy of clay-amino acid complexes that had isotherms of the Giles C-class were dependent on the type and molecular weight of the amino acid and on the exchangeable cation on the clay.     

甘薯淀粉接枝共聚高吸水树脂的合成及在种子包衣上的应用研究

以甘薯淀粉为原料,高锰酸钾为引发剂合成高吸水树脂,并研究高吸水树脂作为种子包衣剂对种子发芽率的影响.通过正交试验,探讨了引发剂浓度、催化剂浓度等因素及皂化条件对高吸水树脂吸水率的影响.研究结果表明,接枝共聚的最佳条件是:淀粉1 g,丙烯酰胺7.5 g,糊化水100 mL,催化剂1.54×10-2 mol/L,引发剂1.5×10-3 mol/L.最佳皂化条件为:氢氧化钠用量26 mL/(g单体),100℃水浴,皂化3 h.用制备的高吸水树脂做玉米种子包衣剂,初步试验结果表明可有效提高种子发芽率.     

叶面喷施硫酸锌对马铃薯淀粉合成和积累的影响

"克新13号"马铃薯品种用不同浓度的硫酸锌叶面喷施后,测定叶片与块茎中淀粉、蔗糖和还原糖含量以及相关酶活性。结果表明,适量硫酸锌(2~4 g.L-1)叶面喷施处理后马铃薯叶中蔗糖磷酸合成酶、蔗糖转化酶以及块茎蔗糖转化酶和蔗糖合成酶活性均提高,促进马铃薯叶和块茎中的蔗糖、还原糖的合成,块茎中淀粉合成和积累提高。     

尿素向氨基糖的转化以及对土壤氨基糖库动态的影响

采用13CO(NH2)2为底物进行黑土培养实验,利用气相色谱/质谱技术测定土壤中三种氨基糖含量以及同位素富集比例,根据其微生物标识物作用探讨土壤中不同微生物群落对于尿素碳的同化利用特征及黑土氨基糖库对于尿素添加的响应。研究结果表明,尿素碳可以被土壤微生物同化利用,但是可利用性显著低于葡萄糖。氨基葡萄糖中13C富集比例显著高于胞壁酸,表明真菌对尿素碳的同化能力高于细菌。尿素添加使土壤有机碳含量有所下降,同时土壤氨基糖总量及其与有机碳的相对比例也显著降低,说明在碳源严重受限条件下,氨基糖可被优先分解利用以补充碳源供给。胞壁酸含量虽低,但其调节并平衡碳氮元素供给与需求的能力较强;氨基葡萄糖稳定性高于胞壁酸,但在碳源缺乏时也可部分分解。土壤氨基糖的动态与土壤碳氮的可利用性及其耦合作用密切相关,在平衡土壤碳氮需求方面具有一定的调节作用。     

电喷雾纳米涂膜工艺优化及其对双孢蘑菇保鲜效果

为了使涂膜技术更有效地应用于果蔬采后保鲜,该文通过电喷雾技术将纳米SiO_2/马铃薯淀粉膜液喷涂在新鲜的双孢蘑菇上,研究了在(4±1)℃贮藏期间双孢蘑菇生理品质的变化,筛选出适于电喷雾涂膜的最佳膜液浓度,且对电喷雾形成涂层的性能(透水率、透O_2率、透CO_2率、水溶性、溶胀度、拉伸强度)和微观结构(scanning electron microscopy,SEM、X-ray diffraction,XRD、fourier transform infrared spectroscopy,FTIR)进行一定的研究。结果表明,适合双孢蘑菇电喷雾技术纳米涂膜保鲜的最佳膜液0配比为纳米SiO_2质量分数0.4%、马铃薯淀粉质量分数4%、甘油质量分数3%,其透水率、透O_2率、透CO_2率分别为514.35、126.84、778.06 g/(m2×d)、拉伸强度24.50 MPa、水溶性54.76%、溶胀度85.75%。电喷雾因液滴带同种电荷,形成的涂层比较均匀,纳米SiO_2分散性更好,分子间作用力较强,且涂层的性能更优。在贮藏保鲜期间电喷雾处理的双孢蘑菇相对普通喷雾处理组能保持较好(P0.05)的感官品质及生理品质,研究结果为电喷雾技术在食用菌采后保鲜的应用上提供参考。     

Mango starch degradation. II. The binding of alpha-amylase and beta-amylase to the starch granule

During mango ripening, soluble sugars that account for mango sweetening are accumulated through carbon supplied by both photosynthesis and starch degradation. The cultivar Keitt has a characteristic dependence on sugar accumulation during starch degradation, which takes place during ripening, only a few days after detachment from the tree. Most knowledge about starch degradation is based on seeds and leaves currently used as models. However, information about the mango fruit is scarce. This work presents the evaluation of alpha- and beta-amylases in the starch granule surface during fruit development and ripening. Extractable proteins were assayed for amylase activity and detected by immunofluorescence microscopy and correlated to gene expression. The results suggest that both amylases are involved in starch degradation during mango ripening, probably under the dependence of another signal triggered by the detachment from the mother-plant.     

施肥对土壤腐殖质总碳和氨基酸氮含量的影响

采用盆栽试验研究,对比了不施肥、施化肥、施芝麻饼肥、芝麻饼肥+化肥4个处理对烟草根际土壤腐殖质总碳、酸解性氨基酸氮和微生物C、N含量的影响.结果表明,施用饼肥可使土壤腐殖质含量得到一定的提高.施用饼肥可以明显提高土壤中酸解性氨基酸氮含量,与不施肥相比,增幅最大的是中性氨基酸(增加了830 μg/kg)和碱性氨基酸(增加了300 μg/kg),再次是酸性氨基酸(增加了80 μg/kg),而含硫氨基酸含量基本稳定.饼肥与化肥配施可明显提高根际土壤微生物C、N含量,比单施化肥分别提高79.88%～97.14%和29.73%～74.96%.土壤酸解性氨基酸氮与土壤微生物N含量呈极显著的正相关关系,在烟草不同生育期,根际土壤微生物C、N含量动态变化不同,反映出土壤微生物C、N在协调土壤C、N供应方面的重要作用,适量饼肥与化肥配合施用,有利于平衡烟草C、N营养,改善烟叶品质.     

The effect of pH and metal binding on the transport properties of humic acids

The molecular weight, shape and size of fractionated humic acids and their metal complexes were determined from sedimentation and diffusion measurements made at various pH values. For all the species studied, the molecular weight and size decreased as the pH became more alkaline. However, the shape of the molecule (approximately spherical) was unaffected by pH. The molecular weight and size of the metal humates depended not only on the type of cation but also on the degree of dissociation ofthe humic acid and the hydrolysis ofthe metal ion.     

Changes in free amino acids and sugars in potatoes due to sulfate fertilization and the effect on acrylamide formation

To examine how sulfur deprivation may affect acrylamide formation in cooked potatoes, three varieties of potato were grown under conditions of either severe sulfur deprivation or an adequate supply of sulfur. In all three varieties sulfur deprivation led to a decrease in acrylamide formation, even though the levels of sugars, which are acrylamide precursors, were higher in tubers of the sulfur-deprived plants. In one variety the concentration of free asparagine, the other precursor for acrylamide, was also higher. There was a very close correlation between the concentration of asparagine in the tubers expressed as a proportion of the total free amino acid pool and the formation of acrylamide upon cooking, whereas sugars were poorly correlated with acrylamide. In potatoes, where concentrations of sugars are usually limiting, competition between asparagine and other amino acids participating in the Maillard reaction may be a key determinant of the amount of acrylamide that is formed during processing.     

Effects of amino-acid chemistry and soil properties on the behavior of free amino acids in acidic forest soils

Free amino acids (FAAs) in soil solution are increasingly recognized as a potentially important source of nitrogen (N) for plants, yet we are just beginning to understand the behavior of FAAs in soil. I investigated the effects of amino-acid chemistry and soil properties on mineralization, microbial assimilation and sorption of amino-acid N in soils from three ecosystems representing the two endpoints and mid point of a temperate forest fertility gradient ranging from low mineral N availability/high FAA oak forests to high mineral N availability/low FAA maple-basswood forests. Soils were amended with six ¹⁵N-labeled amino-acid substrates that ranged widely in chemical properties, including molecular weight, C:N ratio, average net charge, hydrophobicity, and polarity: Arginine (Arg), Glutamine (Gln), Glutamate (Glu), Serine (Ser), Glycine (Gly) and Leucine (Leu). Mineralization of amino-acid N accounted for 7-45% (18% avg.) of the added label and was most strongly affected by soil characteristics, with mineralization increasing with increasing soil fertility. Mineralization of amino-acid N was unrelated to amino-acid C:N ratio, rather, I observed greater N mineralization from polar FAAs compared to non-polar ones. Assimilation of amino-acid N into microbial biomass accounted for 6-48% (29% avg.) of the added label, and was poorly predicted by either intrinsic amino-acid properties or soil properties, but instead appeared to be explicable in terms of compound-specific demand by soil micoorganisms. Sorption of amino-acid N to soil solids accounted for 4-15% (7% avg.) of the added label and was largely controlled by charge characteristics of individual amino acids. The fact that both positively- and negatively-charged amino acids were more strongly sorbed than neutral ones suggests that cation and anion exchange sites are an important factor controlling sorption of FAAs in these acid forest soils. Together, the findings from this study suggest that there may be important differences in the behavior of free amino acids in sandy, acidic forest soils compared to generalizations drawn from finer-textured grassland soils, which, in turn, might affect the availability of some FAAs in soil solution.     

Preventive effects of amino acids on the toxicity of copper to Daphnia magna

The protective role of 18 amino acids on the acute toxicity of Cu in a fresh water cladoceran, Daphnia magna is reported. One hundred percent mortality in 48 hr of exposure occured at 0.56 mg L^?1 of Cu or higher. A dose of each tested amino acid (10 mg L^?1 was found to significantly neutralize the toxic effect of Cu as evidenced by a decrease in mortality and a significant increase in the median survival time (LT50) value). The 48 hr LC50 value was 0.093 mg L^?1 for Cu alone, while the LC50s with Cu plus amino acids ranged from 0.438 to 2.516 mg L^?1 of Cu, suggesting a 4.7 to 27 fold decrease in acute toxicity of Cu. A significant difference between LC50 of Cu alone and Cu with amino acids was observed. The role of amino acids for protection against heavy metal pollution stress in aquatic animals is discussed.     

The effect of amino acids and amides on the regulation of nitrate uptake by wheat seedlings

Wheat plants grown hydroponically increased their nitrate uptake rate more than two‐fold after three days of N starvation. Exogenously supplied amino acids and amides had no effect on the nitrate uptake rate of plants well nourished in N. After three days of N starvation, however, some of the amino acids and amides supplied to plants inhibited up to 50% of the nitrate uptake rate. The most effective inhibitor was aspartic acid. Asparagine, glutamine or phenylalanine did not show any inhibitory effect. The percentage of inhibition was not increased by increasing the amino acid concentration, nor did the addition of mixed amino acids and amides increase the inhibition exerted by one amino acid alone. During the three days of N starvation, there was a decrease in the concentration of endogenous amino acids in the roots, but not all amino acids decreased their concentration at the same rate.

It is suggested that the endogenous levels of some amino acids may repress the nitrate uptake system in plants well supplied with N. During the development of the N deficiency, the concentration of these amino acid decreases, de‐repressing the nitrate uptake system.     

The effect of preceding crop on wheat grain zinc concentration and its relationship to total amino acids and dissolved organic carbon in rhizosphere soil solution

The role of cropping systems practices in agronomic biofortification programs with the aim of increasing micronutrient density in food plants has to be clarified. In these field experiments, the effect of four preceding crops, i.e., sunflower (Heliantus annus L. cv. Allstar), Sudan grass (Sorghum bicolor L. cv. Speed Feed), clover (Trifolium pratense L.), and safflower (Carthamus tinctorius L. cv. Koseh-e-Isfahan), on the total amino acids (AA) and dissolved organic carbon (DOC) concentration in rhizosphere soil solution and grain Zn content of successive wheat (Triticum aestivum cvs. Back Cross and Kavir) was investigated during 2009–2010 and 2010–2011 growing seasons. A fallow treatment was also considered as the control. In both growing seasons, preceding crops increased the concentrations of AA and DOC in the soil solution in comparison with the fallow control treatment; although the magnitude of this increase varied upon the preceding crop type and wheat cultivar. In general, clover and sunflower had greater effect on increasing soil solution DOC probably due to higher decomposability of their litter residues in soil. Preceding crops increased the total AA concentration, on average, by 45.9 % for the first year and 10.8 % for the second year. The preceding sorghum and clover had the highest and lowest influence on the concentration of AA in wheat rhizosphere soil solution, respectively. The preceding crops increased grain wheat Zn concentration and content over the fallow control treatment, although this effect was dependent on the crop type. For “Back Cross”, a positive and significant correlation was found between grain Zn concentration and soil solution DOC concentration (r?=?0.60, P?<?0.05) and particularly AA (r?=?0.76, P?<?0.001), while no such correlation was found for “Kavir”. At the second growing season, the concentration of AA in the rhizosphere of Back Cross was greater than that of Kavir, probably due to higher release of these compounds from the roots. According to the results, the preceding crop significantly affect grain Zn density of the successive wheat, that is, at least in part, by releasing soluble organic ligands into soil solution.     

氨基酸硒液体肥在设施桃上的应用效果

以设施栽培的4年生中油4号油桃和春雪毛桃为试材,对氨基酸硒的应用效果进行了研究。结果表明:施用氨基酸硒液体肥显著增加栅栏组织厚度和叶片厚度及比叶重,改善桃树的叶片质量;显著促进叶绿素和类胡萝卜素等光合色素的合成,提高净光合速率,施用氨基酸硒液体肥处理净光合速率是对照的1.22～1.50倍;显著增加产量,施用氨基酸硒液体肥处理比对照高2.836～8.145 t/hm2;显著增加果实可溶性固形物和可溶性糖含量及糖酸比,改善果实品质;显著提高果实的Vc含量、超氧化物歧化酶(SOD)活性和果实硒含量,提高果实的营养与保健品质。与土施相比,叶面喷施效果更佳且经济。     

Ethanol effect on the structure of beta-lactoglobulin b and its ligand binding

The changes of structure and ligand binding properties of beta-LG B have been studied by fluorescence and circular dichroism spectroscopy in ethanolic solutions. Fluorescence measurements of retinol/beta-LG interactions at 480 nm in various ethanol concentrations show that the maximal fluorescence intensity induced by this interaction between retinol and beta-LG is observed around 20% v/v of ethanol. It is reduced to zero at 40% and 50% of ethanol. These results suggest that there are two distinct structural changes in beta-LG occurring between 20% and 30% and around 40% of ethanol. The first transition, which increases affinity and the apparent number of binding sites for retinol, may be related or similar to the Tanford transition. The strong quenching of retinol emission at 480 nm in 40% of ethanol indicates the radical transformation of beta-LG tertiary structure and the release of retinol. CD spectra at the aromatic region show that secondary and tertiary structures of beta-LG are not significantly affected between 0% and 20% of ethanol. In 30% of ethanol, beta-sheet percentage of beta-LG decreases with respect to native beta-LG (from 55% to 46%). beta-Sheet percentage in beta-LG increases in 40% and 50% alcohol (51% and 53%) relative to 30% of ethanol, which also indicates the strong rearrangement of the secondary structure of beta-LG, while its tertiary structure and beta-LG interactions are radically changed.     

超声场对马铃薯淀粉颗粒形貌与结晶结构的影响(简报)

为了深入了解超声场中食品组分结构的变化,采用偏光显微镜、X-射线衍射等现代仪器分析技术研究了超声场中马铃薯淀粉颗粒形貌和结晶结构的变化规律.结果表明:超声场中马铃薯淀粉颗粒形貌受到不同程度的破坏,随着超声波作用时间的延长,淀粉颗粒表面出现的蜂窝状凹陷,小孔的数量增加,部分淀粉颗粒变形甚至消失:偏光十字和X-射线衍射显示马铃薯淀粉的结晶结构没有变化,超声场主要作用在马铃薯淀粉的非结晶区.     

Effects of resistant starch type III polymorphs on human colon microbiota and short chain fatty acids in human gut models

This study probed the possible effects of type III resistant starch (RS) crystalline polymorphism on RS fermentability by human gut microbiota and the short chain fatty acids production in vitro. Human fecal pH-controlled batch cultures showed RS induces an ecological shift in the colonic microbiota with polymorph B inducing Bifidobacterium spp. and polymorph A inducing Atopobium spp. Interestingly, polymorph B also induced higher butyrate production to levels of 0.79 mM. In addition, human gut simulation demonstrated that polymorph B promotes the growth of bifidobacteria in the proximal part of the colon and double their relative proportion in the microbiota in the distal colon. These findings suggest that RS polymorph B may promote large bowel health. While the findings are limited by study constraints, they do raise the possibility of using different thermal processing to delineate differences in the prebiotic capabilities of RS, especially its butryrogenicity in the human colon.     

荞麦、玉米、马铃薯淀粉凝胶特性的试验研究(英)

利用电子万能材料试验机对荞麦、玉米、马铃薯淀粉的力学特性进行了研究。结果表明：在一定范围内，随着淀粉乳浓度的增加，荞麦、玉米、马铃薯的凝胶强度、弹性模量和凝胶弹性呈线性增加，但凝胶弹性变化较小；同一淀粉乳浓度下凝胶强度由高到低顺序为马铃薯淀粉＞玉米淀粉＞荞麦淀粉，弹性模量为马铃薯淀粉＞玉米淀粉＞荞麦淀粉，凝胶弹性为荞麦淀粉＞玉米淀粉＞马铃薯淀粉。在淀粉乳浓度为20％时，随着NaCl浓度增加，3种淀粉的凝胶强度均有一定程度增强。在同一NaCl浓度下，其凝胶强度为马铃薯淀粉＞玉米淀粉＞荞麦淀粉，弹性模量为马铃薯淀粉＞玉米淀粉＞荞麦淀粉，对凝胶弹性的影响不大。     

Effect of heat-induced aggregation on the IgE binding of patatin (Sol t 1) is dominated by other potato proteins

The interaction of the major potato allergen patatin, Sol t 1, with IgE was investigated on a quantitative level as a function of heat treatment at different temperatures. On the basis of a number of publications, potato is considered to be a heat-labile allergen, but the molecular explanation for this behavior was not given. In this work, heat treatment of patatin in the absence and presence of other potato proteins mimicking the proteinaceous environment of the potato was studied. Using far-UV circular dichrosim spectroscopy, tryptophan fluorescence spectroscopy, and differential scanning calorimetry, the molecular transitions during heating of patatin were investigated. It was found that as long as patatin is not aggregated, denaturation of patatin on a secondary or tertiairy folding level is reversible with only a minor effect on the IgE affinity. Aggregation of patatin results in a nonreversible unfolding and a concomitant important decrease in affinity for IgE (25-fold). Aggregation of patatin in the presence of other potato proteins results in a less condensed aggregate compared to the situation of isolated patatin, resulting in a more pronounced decrease of affinity for IgE (110-fold). It is concluded that the heat lability of patatin-IgE interaction is explained by aggregation of patatin with other potato proteins rather than by denaturation of patatin itself.