Adsorption of Orthophosphate to Humic-Fe-Complexes and to Amorphous Fe-Oxide

The adsorption of orthophosphate to humic surfaces was studied in a model experiment. The adsorption maximum of humic substances greatly increased with higher concentrations of organically complexed Fe (III), indicating that orthophosphate was bound to humic surfaces via metal bridges. The molar ratio P_adsorbed/Fe was nearly 1 for Fe freshly complexed to humic substances, whereas the ratio for amorphous Fe-oxide was a tenfold lower. An increase in pH from 5.2 to 6.2 lead to an increase of P-adsorption of about 30% in the case of humic-Fe-surfaces, which could be explained by an increased accessibility of adsorption sites at pH 6.2. The addition of a 0.01 M CaCl₂-matrix increased orthophosphate adsorption at pH 6.2 but not at pH 5.2. This could be explained by electrostatic interactions caused by the Ca⁺⁺ ion.     

Identification and quantification of caffeoylquinic acids and flavonoids from artichoke (Cynara scolymus L.) heads, juice, and pomace by HPLC-DAD-ESI/MS(n)

A method for the identification and quantification of phenolic compounds from artichoke (Cynara scolymus L.) heads, juice, and pomace by HPLC with diode array and mass spectrometric detection was developed. Among the 22 major compounds, 11 caffeoylquinic acids and 8 flavonoids were detected. Quantification of individual compounds was carried out by external calibration. Apigenin 7-O-glucuronide was found to be the major flavonoid in all samples investigated. 1,5-Di-O-caffeoylquinic acid represented the major hydroxycinnamic acid, with 3890 mg/kg in artichoke heads and 3269 mg/kg in the pomace, whereas in the juice 1,3-di-O-caffeoylquinic acid (cynarin) was predominant, due to the isomerization during processing. Total phenolic contents of approximately 12 g/kg on a dry matter basis revealed that artichoke pomace is a promising source of phenolic compounds that might be recovered and used as natural antioxidants or functional food ingredients.     

Nitrogen release from plant‐derived and industrially processed organic fertilizers used in organic horticulture

As a consequence of the BSE crisis, alternatives for fertilizers derived from animal residues are being sought for use in organic horticulture. Grain legumes (milled seeds of pea, yellow lupine, and faba bean) and organic fertilizers of industrially processed plant and microbial residues (Maltaflor®‐spezial, Phytoperls®, Agrobiosol®, Rizi‐Korn) were investigated as to their suitability as a replacement fertilizer. With four soils, incubation studies were conducted to determine net N mineralization of the organic fertilizers, and pot experiments were used to measure the apparent N utilization by perennial ryegrass. The objectives of this study were (1) to determine simple fertilizer characteristics that describe their N release and (2) to compare the suitability of both experimental setups to predict fertilizer N release. At the end of all experiments, net N mineralization and apparent N utilization from Rizi‐Korn was highest compared to all the other organic fertilizers, while pea performed relatively poor. This differentiation between the fertilizers developed during the first 2 weeks. Nitrogen release from the organic fertilizers as described by net N mineralization or apparent N utilization was significantly related to the N content of the fertilizers. Different soils modified this relationship. Two industrially processed fertilizers (Phytoperls®, Agrobiosol®) could not be included into a generalized relationship because N release from these fertilizers was low compared to their N content. It is discussed that the quality of fertilizer C and N affected the N release from the fertilizers. Both experimental setups, incubation and pot experiments, were suitable to describe the release of plant‐available N from the organic fertilizers. However, N release of fertilizers with a low net N mineralization in the incubation experiments was underestimated compared to plant N uptake of ryegrass in the pot experiments. It is concluded that the N content of organic fertilizers indicates, but not predicts their N release.     

Effect of technological processing on the allergenicity of mangoes (Mangifera indica L.)

In parallel with the rising popularity of exotic fruits in Europe, allergy against mango is of increasing importance. Because mangoes are also consumed as processed products such as chutneys or beverages, the influences of different process conditions on their allergenicity were investigated. Mango purees and nectars were manufactured at small pilot-plant scale, and the allergenic potencies of the resulting intermediate and final products were determined by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting and inhibitive enzyme allergosorbent tests (EAST-inhibition), using a pool serum of 9 individuals with manifest mango allergy. The mango allergens were shown to be very stable during technological processing. Irrespective of enzymatic matrix decomposition, mechanical tissue disintegration and heating during peeling, mash treatment, and pasteurization, significant loss of allergenicity could not be observed in the extracts of mango purees and nectars derived thereof. These results were confirmed by analogous investigation of commercial mango drinks and nectars. Hence, conventional mango processing into pulp-containing products typical for this species obviously does not allow complete elimination of the allergenic potency.     

Identification of betalains from yellow beet (Beta vulgaris L.) and cactus pear [Opuntia ficus-indica (L.) Mill.] by high-performance liquid chromatography-electrospray ionization mass spectrometry

Betaxanthins, the yellow-orange water-soluble pigments from yellow beet (Beta vulgaris ssp. vulgaris cv. Bejo Zaden) and cactus pear (Opuntia ficus-indica cv. Gialla) have been investigated using an HPLC system compatible with mass spectrometry. Five novel betaxanthins were found and characterized as the immonium adducts of betalamic acid with serine, gamma-aminobutyric acid, valine, isoleucine, and phenylalanine. To enable concentration of betalain samples, desalting was performed by solid-phase extraction. With this technique, betacyanins could be separated from the betaxanthins using the pH-dependent retention characteristics of red and yellow betalains. The betaxanthin fraction was taken for the preparation of betalamic acid as a precursor for semisynthetic standards. The HPLC method was applied to yellow beet and cactus pear, revealing a more complex betalain profile than described earlier, thus proving its suitability for screening of betaxanthin-containing plants as potential sources for natural food colors.     

Characterization of sulfur speciation in low molecular weight subunits of glutenin after reoxidation with potassium iodate and potassium bromate at different pH values using x-ray absorption near-edge structure (XANES) spectroscopy

Sulfur speciation in low molecular weight (LMW) subunits of glutenin after reoxidation with potassium iodate and potassium bromate at different pH values, aged subunits of glutenin as well as gluten, and gliadin have been investigated in situ by S K-edge X-ray absorption near-edge structure (XANES) spectroscopy. XANES spectra were analyzed quantitatively using a least-squares fitting routine to provide relative percentage contribution of different sulfur species occurring in the samples. Using potassium iodate and potassium bromate for reoxidation of reduced LMW subunits of glutenin led not only to disulfide states but also to higher oxidation states (sulfoxide state, sulfonic acid state). Strongest oxidation occurred at low pH values. Higher oxidation states were also predominantly detected in the aged subunits of glutenin, whereas the disulfide state was the main sulfur species in gluten and gliadin samples. The results showed that the oxidation state of sulfur prior to oxidation (thiol, disulfide) strongly influences sulfur speciation after oxidation. The choice of the oxidizing reagent seems to be of minor importance.     

Andosols and soils with andic properties in the German soil taxonomy

The presence of soils with andic properties on German territory has been suspected for decades and there are numerous reports of sites where they may potentially occur. Andic properties, however, are not adequately represented by the German soil‐classification system. The German taxonomic category “Lockerbraunerde” has not been revised or reconciled with international taxonomic categories since the year 1957, when it was initially proposed. With this review, we show that there are true Andosols of both the silandic (allophane‐containing) and the aluandic (Al‐Humus‐dominated) type in Germany and that their properties differ substantially from other soils which merely exhibit low bulk density. By (1) comparing soil carbon storage between some German Andosols, Chernozems, and nonandic Cambisols with particularly low bulk density and (2) elucidation of the differential pedogenetic pathways leading to Andosol formation, we further demonstrate that Andosols are important objects of study in research issues of contemporary interest. We propose that appropriate measures be taken to lay the foundations for the protection and conservation of these soils, because they are valuable as archives of natural history and provide opportunities to study unique soil processes.     

Complexation of iron (III) to humic substances of a humic podzol at pH 2.5 - 6.4 - quantification of the organically complexed iron by pyrophosphate extraction

Bonding of Fe(III)-ions to humic substances of a humic podzol are reported with regard to pH (range 2.5 - 6.4). A separation technique is used involving a pyrophosphate extraction, whereby dissolved, precipitated, and organically bound iron can be separated. The necessity of iron speciation results from the fact that the amount of Fe bound to organic matter is overestimated if conventional methods are used. The estimation of formation constants for iron actually bound to organic matter leads to a corrected maximum value of log K'_f(org) = 1.64, whereas for the total eliminated Fe this maximum value is 2 units higher (log K'_f= 3.70).     

Stickstoffverbindungen in Böden und ihre Beziehung zur Humusdynamik. 2. Mitteilung: Zur Bestimmung und Zuordnung des Amidstickstoffs

Nitrogen compounds in soils and their relation to humus dynamics. 2. Communication: On the determination and attachment of amide-nitrogen The amide-nitrogen fraction in soils – so far very insufficiently defined – has been determined in the hydrolysates of 12 different soil samples. The proposed procedure allows to split this amide-nitrogen fraction into two better befined N-fractions, namely: real amide-N (EAN) and pseudo-amide-N (PAN). This splitting is based on. 1.) a detailed N-fractionation, especially a quantitation of aspartic acid + glutamic acid (AG) and ammonia in the hydrolysate, 2.) on the fact, that pure proteins and ?soil proteins”? do not significantly differ in terms of their amino acid composition (average basis per mol protein) and deductive hereupon 3.) on the assumption, that the calculated NH₄/AG- ratio of 0,5 from pure proteins can be transferred to ?soil proteins”?. Methodically the real amide-N (EAN) and the pseudo-amide-N (PAN) are determined as follows: After quantitation of aspartic acid + glutamic acid (AG) in the soil hydrolysate EAN can be calculated by the equation: EAN = (AG) X 0,5. PAN amounts to the difference between Ammonia of the hydrolysate and EAN. For the 12 soil samples the PAN/EAN-ratios are in the range 1,5–11,7.