Isolation of Amaranth Starch by Diluted Alkaline-Protease Treatment

Starch was isolated from Amaranthus cruentus seeds by different alkaline treatments and combinations of low alkaline steeping and protease treatments. For low alkaline-protease treatments, amaranth seeds were steeped in a NaOH solution (0.05%, pH 12) for 22 hr to loosen the protein matrix and ground. The pH of the ground slurry was adjusted to 7.5 and subjected to a protease (from Aspergillus sojae) treatment. The slurry was incubated with 1 or 0.5% of the protease (based on total amount of seeds) for 2 hr at 37°C and 50 rpm. The starch was then isolated by screening and centrifugation. This method produced starch with a low protein content (≤0.2%) and a high recovery (≈80%). Amaranth starch isolated by alkaline treatments were also studied by using various concentrations of NaOH steeping solutions and with or without alkaline solution during grinding and washing. The properties of amaranth starch isolated by alkaline and low alkaline-protease treatments were analyzed and compared. The properties of the amaranth starch were also compared with those of normal and waxy maize starches.     

Freeze-Thaw Stability of Amaranth Starch and the Effects of Salt and Sugars

Freeze-thaw stability of amaranth, corn, wheat, and rice starches was determined measuring the percent of syneresis by centrifugation. Thermal properties were calculated by differential scanning calorimetry (DSC). The effects of salt (NaCl at 2 and 5%) and sugars (sucrose, glucose, and fructose at 10, 20, and 30%) on the freeze-thaw stability of amaranth starch were also studied. Based on DSC and centrifugation methods, amaranth starch had better stability after freezing and thawing through four cycles than did corn, wheat, and rice starches. Amaranth starch with added salt showed similar stability as compared with a control when measured by centrifugation and showed increased stability when measured by DSC. Adding sugars to amaranth starch gels had varying results, but for the most part, they showed similar or increased stability when compared with a control.     

Evaluation of Modified Amaranth Starch as Shell Material for Encapsulation of Probiotics

The objective of this study was to develop with thermoplastic extrusion amaranth starch derivatives and to characterize and evaluate their functionality as encapsulating agents of Bifidobacterium breve ATCC 15700 and Lactobacillus casei ATCC 334 during spray drying. The survival of both probiotics during storage at different water activities and at two storage temperatures, their viability in a food model system, and their tolerance to a simulated gastrointestinal tract were determined. Native amaranth starch was chemically modified to obtain phosphorylated, acetylated, and succinylated starch. Starch derivatives were reduced in viscosity, and the solubility in water was increased. In general, the modified amaranth starches and control corn starch did not provide good protection to both probiotics during storage at 25°C. However, there was excellent viability during storage at 4°C for both probiotics. Microcapsules showed a uniform coverage of the cells. Storage for 35 days at 25°C of blends of oat with succinylated amaranth microcapsules with probiotics had a lower reduction. Also, this succinylated amaranth starch containing probiotics showed a higher resistance to simulated gastrointestinal conditions. The results with food model systems supported the applicability of the modified starches.     

Gelatinizing,Pasting, and Gelling Properties of Potato and Amaranth Starch Mixtures

Physicochemical properties of mixtures of native potato and native amaranth (Amaranthus cruentus), heat‐moisture treated (HMT) potato and heat‐moisture treated amaranth, cross‐linked potato and cross‐linked amaranth, native potato and heat‐moisture treated amaranth, and heat‐moisture treated potato, and native amaranth were tested at different ratios. Two peaks were noticed in the pasting curves when large differences of swelling factor and amylose leaching existed between individual components in the mixture. It seems that amylose leaching from one starch in a mixture may affect the swelling and much of the granular break down of the other. The mixtures showed stabilities in hot pastes that were higher than the less stable components in a mixture. Some mixtures such as HMT potato and native amaranth showed very specific nonadditive pasting behavior. Mixing 10% of native amaranth to HMT potato starch caused a large reduction of peak viscosity and cold paste viscosity, resulting in a very soft gel. In the differential scanning calorimeter, each component of a mixture gelatinized independently, showing two peaks corresponding to the individual components. When transition temperatures of both components were similar in DSC, the result was a single endotherm. Dramatic changes of pasting and subsequent gel properties resulted when thermal transition of the two components occurred in the same temperature range. Retrogradation enthalpies as measured by DSC were between the two individual components in all tested mixtures.     

Thermal and Moisture Diffusion Properties of Amaranth Seeds

The physical characteristics, thermodynamic and transport properties of amaranth seeds relevant to the modelling and simulation of the drying processes of these seeds were studied. The water activity as a function of the temperature and moisture content was modelled by means of the Henderson's expression from water activity experimental data. The desorption–vaporisation heat was also calculated. From the solution to Fick's second law for a spherical geometry and assuming equilibrium conditions at the solid–gas interface, an effective diffusion coefficient was evaluated from experimental drying curves obtained in a moisture chamber. The effect of taking into account more than one term in the Fourier series solution was analysed and it is concluded that the diffusion coefficient corresponding to two terms in the series leads to better agreement with the experimental results for short times.     

Measuring and Modeling Grain Sorption Equilibria of Amaranth Grains

Water activity (a_w)of Amaranthus cruentus were measured at 35, 45, and 65°C at different moisture contents by means of an electronic water activity meter. Experimental curves were fitted to one three-parameter equation (GAB equation). The equilibrium values and temperature shifts were modeled with a three-parameter equation in the approximate a_w range of 0.03–0.88. An analytical expression to calculate the isosteric heat of sorption and its moisture content dependence was used, and the results were compared with the isosteric heat calculated from the experimental equilibrium data by means of the Clausius-Clapeyron equation.     

Comparative Effect of Phosphorus Sources for Grain Amaranth Production

Abstract

Phosphorus (P) is expensive to the sub‐Saharan African resource‐poor farmers; therefore, there is a need for investigation of locally available alternative P sources to enhance farmers' productivity. Optimum P rate was determined during the early and late rains of 1999. Using the optimum P rate, influences of three P sources ogun rock phosphate (ORP), sokoto rock phosphate (SRP), single super phosphate (SSP) and a control were evaluated on amaranth varieties in 2000 at the vegetable research plots of the National Horticultural Research Institute (NIHORT), Ibadan, Nigeria. In 1999, three grain amaranth varieties (NH84/452, NH84/445, and NH84/493) were combined factorially with four P rates: 0, 30, 60, and 90 kgP/ha. Application of P significantly increased plant height, number of branches, leaf dry weight, and grain yield (GY) per plant. Significant increase in GY was in the order NH/493>NH/445>NH/452. Optimum P rates across varieties for leaf dry‐matter yield was established at 51.8 kgP/ha and for grain yield production was 48.4 kgP/ha. The experiment in the following year, 2000, was a RCB design using the optimum P determined in 1999. Three P sources (ORP, SRP, SSP) and a control were factorially combined with the three amaranth varieties. In the 2000 experiment, grain yield was 21.3, 16.9, 16.0, and 7.8 g/plant, respectively, for SSP, SRP, ORP, and the control. Growth was ranked in the order SSP>ORP>SRP>control. It was concluded for fertilizer recommendation purposes that 50 kgP/ha is optimum for grain amaranth production and that amaranth productivity indices could be alternatively improved with indigenous P sources.     

Amaranth (Amaranthus hypochondriacus) vicilin subunit structure

The 7S-globulin fraction is a minor component of the amaranth storage proteins. The present work provides new information about this protein. The amaranth 7S-globulin or vicilin presented a sedimentation coefficient of 8.6 ± 0.6 S and was composed of main subunits of 66, 52, 38, and 16 kDa. On the basis of mass spectrometry (MS) analysis of tryptic fragments, the 52, 38, and 16 kDa subunits presented sequence homology with sesame vicilin, whereas the 66 kDa subunit showed sequence similarity with a putative vicilin. Several characteristics of the 66 kDa subunit were similar to members of the convicilin family. Results support the hypothesis that the 7S-globulin molecules are composed of subunits coming from at least two gene families with primary products of 66 and 52 kDa, respectively. According to the present information, amaranth vicilin may be classified into the vicilin group that includes pea, broad bean, and sesame vicilins, among others.     

Amaranth globulin structure modifications induced by enzymatic proteolysis

Globulin-P was partially hydrolyzed with papain under specific conditions to study the resulting structural modifications. Under mild hydrolytic conditions, globulin-P polymers were cleaved to render their unitary constituents (280 kDa molecules). Under stronger hydrolytic conditions these unitary molecules were 13% smaller than those from nonhydrolyzed globulin. Moreover, these molecules remained assembled even though they contained degraded polypeptides. The monomeric (M) subunit and the A chains were preferentially cleaved under mild and intermediate hydrolytic conditions, whereas B chains remained with the same size. These results suggest that the M and A polypeptides might be located at an exposed site of the molecules resembling the structure of the legumins. The M subunit may be participating in the stabilization of globulin-P polymers, on the basis that these two species disappeared under the same hydrolytic conditions. Similar events such as those described in this paper might be taking place on globulin-P during germination of amaranth grain.     

玉米淀粉制备双醛淀粉的试验

双醛淀粉用途广泛，但在国内几乎没有生产和应用。文中对双醛淀粉的制备工艺进行了系统研究，得出了制备双醛淀粉的最佳工艺条件。试验结果表明：在所选参数下，高碘酸钠氧化淀粉时，高碘酸钠应稍过量；NaIO₄/Starch摩尔比=1.1/1；NaIO₄浓度为0.7 M；反应温度35～40℃；反应时间控制在3 h；pH值在1.2～1.5为好；所得产品中淀粉的醛基含量在95%以上。     

籽粒苋不同富钾基因型矿质营养元素含量的研究

采用水培试验,研究了在两种供钾水平(K,0.5mmolL-1和5.0mmolL-1)条件下4个不同籽粒苋品种植株体内矿质营养元素的含量及其变化。同时,还在低钾条件下,测定了不同籽粒苋品种根、茎、叶中矿质营养成分的含量和构成情况,结果表明:(1)籽粒苋各品种氮、钾含量随着供钾水平降低而减少,一般基因型氮钾含量降幅大于富钾基因型;在相同供钾水平条件下,富钾基因型的氮钾含量均高于一般基因型,而相同基因型的不同品种间氮钾含量则相近。籽粒苋各品种氮主要分布在根和叶中,其次是茎;磷大量分布在根,其次是叶,再次是茎;钾主要存在于茎中,根和叶次之。(2)籽粒苋钙、镁、硫含量随着供钾水平的升高而降低,富钾基因型镁、硫含量低于一般基因型。籽粒苋不同品种的钙、镁主要分布在叶片中,其次是茎和根;硫在根中的分布最少,叶中最多。(3)不同品种B、Cu、Fe、Mn、Zn等微量元素含量随着供钾水平的降低而升高,灰分含量则降低。富钾基因型B、Fe、Zn及灰分含量都高于一般基因型,而Cu的含量则是一般基因型高于富钾基因型。4个籽粒苋品种的硼、铜主要存在于叶片中,其次是根,茎含量相对前两者要小;铁、锰、锌在根的含量最高,叶片次之,茎最低,根系中铁的含量分别是叶和茎的7倍左右和10倍以上。     

Starch Characteristics Influencing Resistant Starch Content of Cooked Buckwheat Groats

Cooked buckwheat groats are suggested to contain a greater amount of resistant starch (RS) than cereal grains. High RS content, in addition to dietary fibers present in groats, contributes to the low‐calorie, high‐fiber food status of buckwheat. Six buckwheat genotypes exhibiting high, medium, and low RS content of cooked groats were selected, and starches were isolated to determine their functional properties to explore the possible cause of high RS content of cooked buckwheat groats. Apparent and actual amylose contents were 27.4 and 31.6–34.5% in high, 27.4–28.6 and 32.5–33.7% in medium, and 21.4–25.6 and 24.5–32.0% in low RS genotypes, respectively. Genotypes of high RS content exhibited greater amylose leaching based on total starch content during cooking than genotypes of low RS content, mainly because of higher amylose content in the former than latter. Genotypes of low RS content exhibited a relatively high content of amylose‐lipid complexes, as determined with a differential scanning calorimeter (DSC). Gelatinization enthalpy and degree of amylopectin retrogradation determined with a DSC were not related to RS content. An evident relationship was observed between RS content of cooked groats and amylose retrogradation determined by gel hardness (r = 0.91, P < 0.05), cohesiveness (r = 0.89, P < 0.05), and syneresis (r = 0.88, P < 0.05). Increases in starch amylose content, amylose leaching capacity, and amylose retrogradation, as well as a decrease in the amount of amylose‐lipid complexes all appear to be related to high RS content of cooked buckwheat groats.     

籽粒苋根际土壤及根系分泌物对矿物态钾的活化作用

通过大田和模拟试验等方法 ,研究了籽粒苋根际土壤及根系分泌物对矿物态钾的活化作用 ,研究结果表明 :(1)籽粒苋根际土壤的速效钾含量较非根际土增加了 1.7倍 ,缓效钾 (K)的含量也提高了 5 5 .9% ;(2 )用籽粒苋根际土壤处理后的花岗岩粉末 ,其速效钾和缓效钾含量均较对照有所增加 ,增幅分别为 2 .8%～ 2 4.7%和 15 .7%～ 44 .7% ;用籽粒苋根际土壤处理后的紫色土 ,其速效钾和缓效钾含量较对照分别增加了 18.5 %和 11.1% ;(3 )通过对y值的综合贡献率计算可知 ,不同籽粒苋模拟根系分泌物对花岗岩粉末中矿物态钾的活化能力大小依次为 :草酸 >蔗糖 >核酸 >乳酸 >柠檬酸。     

Consequence of Starch Damage on Rheological Properties of Maize Starch Pastes

Waxy and normal maize starches were damaged to different extents by ball milling, with waxy starch notably more susceptible to damage. Starch damage caused substantial decreases in shear stress or apparent viscosity in both waxy and normal maize starch pastes at a wide range of shear rates (5.6 to 400 1/sec). Shear stress or apparent viscosity decreases were more evident in waxy than in normal maize starch pastes at the same ball milling times. Values of storage moduli were much higher than values of loss moduli, and storage moduli decreased with increase in starch damage in both waxy and normal maize starches, indicating decrease in elastic property. The study showed that starch damage causes substantial rheological changes in gelatinized pastes and that waxy starch undergoes more pronounced changes than normal starch. These results can be used to understand the general behavior of damaged normal and waxy starches in processed foods.     

不同水分条件下氮肥形态配比对苋菜养分与产量的影响

研究了不同水分与氮肥形态配比对苋菜养分和产量的的影响,结果表明:同一水分条件下,苋菜的N,P,Fe含量随NH4 -N比例的增大而增加;K,Ca含量随NH4 -N比例的增大而减小。苋菜的产量随NO3--N比例的增大而增加。同一施肥条件下,苋菜N,P,Fe含量随水分的增加而增加;苋菜的K,Ca含量、产量以中水处理最高。     

籽粒苋不同富钾基因型根际钾营养与根系特性研究

在缺钾土培和水培条件下,研究了籽粒苋不同基因型根际和非根际土壤速效钾、缓效钾和全钾含量的变化,以及根际微生物数量、根系主要分泌物、根系质子分泌量和根系CEC的变化。结果表明,籽粒苋根际土壤速效钾和缓效钾含量明显高于非根际土壤,且在根际形成钾的相对富集区,富钾基因型R104和K12根际钾的富集能力明显高于一般基因型;籽粒苋根际土壤的全钾含量却低于非根际土壤,富钾基因型的降低幅度大于一般基因型。富钾基因型根际微生物数量和根系分泌能力显著高于一般基因型,且根际细菌和真菌数量与主要根系分泌物的分泌量变化基本保持一致。富钾基因型R104和K12根系CEC和H 分泌量高于一般基因型M9和Cr047,而相同基因型内各品种间的变化不显著。     

Effect of Small and Large Wheat Starch Granules on Thermomechanical Behavior of Starch

The physicochemical properties of small‐ and large‐granule wheat starches were investigated to reveal whether gelatinization properties and rheological behavior differ between size classes of wheat starch. All samples contained 60% water (w/w, wb). The starch granule size and shape were examined by scanning electron microscopy in the separated A‐ and B‐type granule populations and in the whole wheat starch granule population. Differential scanning calorimetry (DSC) and electron spin resonance (ESR) analyses were performed in parallel with rheological measurements using dynamic mechanical thermal analysis (DMTA) to relate the viscoelastic changes to modifications in dynamic properties of aqueous solutions and structural disorganization of starch. The small (B‐type) granules had slightly higher gelatinization temperature and lower gelatinization enthalpy than did the large (A‐type) granules. Also, B‐type granules had higher enthalpy for the amylose‐lipid complex transition. Moreover, our results suggested that small granules have higher affinity for water at room temperature. It seems that there is a less ordered arrangement of the polysaccharide chains in the smaller granules when compared with the larger ones. These differences in functional properties of small and large granules suggested that the granule size distribution is an important parameter in the baking process.     

Serum Lipids in Hypercholesterolemic Men and Women Consuming Oat Bran and Amaranth Products

One hundred‐eighty hypercholesterolemic subjects following the National Cholesterol Education Program Step One Diet were randomly divided into six groups (30 ± 2/group). Group 1 served as the control and received no fiber supplements. The fiber supplemented groups received 50 g/day of oat bran or amaranth from various sources: Group 2 (oat bran muffins); Group 3 (amaranth muffins); Group 4 (Oat Bran O's); Group 5 (Oat Bran Flakes); and Group 6 (a variety of oat bran products). Fasting serum total cholesterol (FSTC), low density‐, very low density‐, and high density‐lipoprotein cholesterol (LDL‐C, VLDL‐C, and HDL‐C) and serum triacylglycerols were measured before and after the 28‐day intervention. Three‐day diet records were completed before and after intervention. Subjects reduced (P < 0.05) the mean intake of total and saturated fat, and cholesterol. FSTC dropped more than twice as much (P < 0.05) as was observed with fat modification alone (Group 1 = ‐0.31 mmol/L), when oat bran was provided as flakes (Group 5 = ‐0.86 mmol/L) or in a variety of forms (Group 6 = ‐0.75 mmol/L). If the initial ratio of HDL‐C to FSTC was low, then supplementation did not decrease FSTC to the extent observed when the initial ratio was high. Compliance with the dietary interventions was best when the subjects gave the product a rating of ≤2.0 (on a 1–4 hedonic scale, with 1 being excellent). We can conclude from these data that fiber supplementation to reduce serum cholesterol is most effective in hypercholesterolemic individuals that have a greater proportion of HDL‐C. In addition, not all the oat bran products evaluated were able to lower cholesterol to the same extent, indicating that the ability of soluble fiber to reduce FSTC can be compromised by other dietary factors such as insoluble fiber.     

Influence of pH on Structure and Function of Amaranth (Amaranthus hypochondriacus) Protein Isolates

Structural and functional properties of two amaranth protein isolates as a function of pH were studied. Isolates, A9 and A11, were obtained by alkaline extraction at pH 9 and 11, respectively. Gel filtration chromatograms of A9 and A11 showed similar profiles. The A11 isolate contained mainly albumins and globulins, and a small proportion of globulin‐P aggregates, suggesting the presence of species with a higher degree of denaturation compared to A9. Differential scanning calorimetry (DSC) showed that A9 was characterized by two thermal transitions (65.8 and 98°C); A11 exhibited only a small endotherm (66.6°C) and a second, less defined one. DSC analysis of A9 at pH 2–4 did not show endotherms, but at pH 5, some protein structures were observed. A11 showed a greater degree of denaturation. FPLC results showed that the proteins in A9 are more folded and their conformation is closer to the native state than those in A11, which are more unfolded due to pH‐mediated denaturation, mainly in acid media. The surface hydrophobicity of the isolates in acid media was lower than in alkaline media. The fluorescence emission spectra of the isolates showed differences in acidic pH conditions. As expected, the highest solubility was at alkaline pH. The water‐holding capacity was similar for both isolates. The water‐imbibing capacity and speed of foaming was higher for A11 than for A9. In summary, intense pH treatment of amaranth isolates generated partial or total protein denaturation and differences in the functional properties.