Yield and quality of pectins extractable from the peels of thai mango cultivars depending on fruit ripeness

Pectins, recovered from the peels of four mango ( Mangifera indica L.) cultivars by mimicking industrial techniques, were evaluated in terms of yield, composition, macromolecular properties, and technofunctional quality. Freeze-dried peels of mature-green fruits, after major mesocarp softening, and at full ripeness were extracted using hot acid. The pectins were precipitated in propan-2-ol and their crude yields quantified as alcohol-insoluble substance. Like apple pomace, the dried peels provided hardly acetylated (DAc < 6.3%) rapid-set to ultrarapid-set high-methoxyl pectins at starch-adjusted yields of 11-21 g/100 g. However, despite similar high molecular weight fractions and galacturonic acid/rhamnose ratios, their average molecular weight was markedly reduced by a characteristic, almost monodisperse fraction of 16000-19000. Expanded galactans, indicated by galactose/rhamnose ratios of 15-24 mol/mol, probably represented arabinogalactan side-chain fragments withstanding hot-acid extraction at pH 1.5 and 2.0, as implied by arabinose/galactose ratios of 8-15 and 33-56 mol/100 mol, respectively. Limited galacturonic acid contents made the mango peel pectins less valuable than commercial apple pectins with regard to gelling capacity and thickening properties. Whereas starch and matrix glycan fragments almost completely degraded during ripening, depolymerization of pectins and galactans was insignificant. Technofunctional properties, modulated by extraction at different pH values, were ascribed to structural differences influencing macromolecular entanglements.     

Comparison of lipid biomarker and gene abundance characterizing the archaeal ammonia-oxidizing community in flooded soils

In the last years, archaea have been identified as key players in global N cycling, especially in nitrification. Ammonia-oxidizing archaea (AOA) are postulated to belong to the new phylum Thaumarchaeota for which the lipid crenarchaeol should be specific. The ratios between two independent markers for AOA, the ammonia monooxygenase gene and crenarchaeol have been studied in different aerated soils, but so far not in flooded soils. This study investigated ammonia-oxidizing archaea in four paddy soils and a tidal wetland. Ratios were significantly higher in the paddy soils compared to the tidal wetland and in general higher as in upland soils, leading to the assumption that archaeal ammonia oxidizers different from crenarchaeol-containing Thaumarchaeota may play an important role in paddy soils.     

Chromoplast morphology and beta-carotene accumulation during postharvest ripening of Mango Cv. 'Tommy Atkins'

Accumulation of beta-carotene and trans-cis isomerization of ripening mango mesocarp were investigated as to concomitant ultrastructural changes. Proceeding postharvest ripening was shown by relevant starch degradation, tissue softening, and a rising sugar/acid ratio, resulting in a linear decrease (R (2) = 0.89) of a ripening index (RPI(KS)) with increasing ripening time. A modest accumulation of all-trans-beta-carotene and its cis isomers resulted in a slight pigmentation of the mango chromoplasts, because ambient temperatures of 18.2-19.5 degrees C provided suboptimal ripening conditions, affecting color development and beta-carotene biosynthesis. The ultrastructures of chromoplasts from mango mesocarp and carrot roots were comparatively studied by means of light and transmission electron microscopy. Irrespective of the ripening stage, mango chromoplasts showed numerous plastoglobuli varying in size and electron density. They comprised the main part of carotenoids, thus supporting the partial solubilization of the pigments in lipid droplets. However, because different pigment-carrying tubular membrane structures were also observed, mango chromoplasts were assigned to the globular and reticulotubular types, whereas the crystalline type was confirmed for carrot chromoplasts. The large portions of naturally occurring cis-beta-carotene in mango fruits contrasted with the predominance of the all-trans isomer characteristic of carrots, indicating that the nature of the structure where carotenoids are deposited and the physical state of the pigments are crucial for the stability of the all-trans configuration.     

Influence of Soil Type on the Effects of Elevated Atmospheric CO2 and N Deposition on the Water Balance and Growth of a Young Spruce and Beech Forest

Sixteen open-top chambers, each equipped with two non-weighablegravity-drained lysimeter compartments, were used to investigate the impacts of elevated atmospheric carbon dioxide (CO₂) concentration and nitrogen (N) deposition on the water relations and growth of young model forest ecosystems on two different types of soils. The same vegetation of a mixed spruce and beech overstorey and various herbs in the understorey was planted in all treatments on both soils. The soils were repacked on top of a drainage layer. Four combinations of treatments were applied in four replicates each: ambient (370 cm³ m^-3) CO₂ + low (7 kg N ha^-1 a^-1) N deposition, ambient CO₂ + high(70 kg N ha^-1 a^-1) N deposition, elevated (590 cm³ m^-3) CO₂ + low N deposition, and elevated CO₂ + high N deposition. After canopy closure, treatment effects on evapotranspiration and growth during the third year of study were very different for the two soils.On the acidic sandy loam, elevated CO₂ enhanced growth(leaf biomass +21%, roots +27%) at reduced evapotranspiration (–9%). High N deposition increased aboveground growth even more strongly (+50%), but also increased evapotranspiration (+16%). Together, elevated CO₂ and high N had a more than additive fertilizer effect on growth, while their effects on evapotranspirationcompensated. On the calcareous loamy sand, elevated CO₂not only tended to enhance growth (leaf biomass +17%, roots +20%), but also increased evapotranspiration (+5%).On this soil, aboveground growth was stimulated by N only incombination with elevated CO₂, but less than on the acidic soil, while evapotranspiration (–6.5%) and root growth into the subsoil (–54%) were decreased by increased N deposition at both CO₂ concentrations, in contrast to the N treatments on the acidic sandy loam. The influence of the soil on the observed ecosystem responses canbe interpreted in terms of the concept of optimal resource allocation.     

Changes in flavonoids and nonphenolic pigments during on-tree maturation and postharvest pericarp browning of litchi (Litchi chinensis Sonn.) as shown by HPLC-MSn

Polyphenols, chlorophylls, and carotenoids were characterized by HPLC-DAD-MS(n) in the pericarp of unripe to over-ripe 'Hong Huey' and 'Chacapat' litchi fruit at harvest and during subsequent storage (5 °C, 90% RH, 21 days). (-)-Epicatechin and A-type procyanidins always predominated quantitatively. Besides these ortho-diphenolic compounds, minor novel litchi flavonoids included monohydroxylated structures. Chlorophyll degradation by 73-92% and 7-38-fold anthocyanin accumulation affected pericarp color throughout the last 15-20 days of on-tree maturation. Postharvest, anthocyanins and (-)-epicatechin largely degraded within the first 3 days, accompanied by severe pericarp browning. Without packaging of the fruit, desiccation initially accelerated polyphenol oxidase-induced oxidation of (-)-epicatechin, but then hindered its further progress. Constant levels of the monohydroxylated (epi)afzelechin indicated no involvement of peroxidase. Acting as antioxidants, anthocyanins retarded (-)-epicatechin degradation. Hence, pinkish-red fruit with a molar ratio of cyanidin 3-O-rutinoside to (-)-epicatechin of >3:100 retained flavonoids best. However, brown polymers masked remaining red pigments.     

A Review of Sooty Blotch and Flyspeck Disease in German Organic Apple Production

Sooty blotch and flyspeck (SBFS) fungi colonise the surface of a range of fruits, especially apple, without penetrating the cuticle. Economic damage results from the exclusion of severely affected fruit batches from being marketed as table apples. A study of SBFS was conducted in 2007–2012 in the two largest German apple production areas, i.e. the Lake Constance and Lower Elbe regions. The absence of this disease complex from orchards under integrated pest management in both regions in all years was explained by the collateral effects of scab and storage-rot sprays with captan and quinone-outside inhibitors (QoI) such as trifloxystrobin. However, SBFS was economically relevant in organically managed orchards, being generally more severe in Southern Germany than in the North. In both regions, Peltaster cerophilus was the most frequently isolated SBFS fungus and was chiefly responsible for crop losses. Cyphellophora sessilis, Microcyclosporella mali and Schizothyrium pomi also contributed to SBFS in some organic orchards, whereas a diversity of additional species was confined to untreated orchards. Evidence was obtained that P. cerophilus overwinters within orchards, fruit mummies being one of presumably several colonised plant organs. Infections of young apple fruits were initiated at any time following the end of flowering, and P. cerophilus was capable of causing several infection cycles per season by means of conidial inoculum. The colonisation of sheets of waxed paper by P. cerophilus indicated that this species does not require fruit leachates for growth. No further expansion of colonies was observed during cold storage; instead, P. cerophilus was gradually displaced by other fungi. Differences in the susceptibility of apple varieties to P. cerophilus were due to fruit ripening, late-maturing cultivars being most heavily colonised, and to surface properties, varieties with a waxy bloom being conspicuously less strongly colonised than others. This fungus was unable to colonise russeted fruit areas. Repeated spray treatments with lime-sulphur and potassium bicarbonate throughout the season were effective and necessary to control SBFS in organic production. This strategy threatens the fungicide-saving potential offered by scab-resistant apple varieties. Cultural measures against SBFS include summer pruning as well as the manual removal of fruit mummies in winter.     

Manure contaminated with the antibiotic sulfadiazine impairs the abundance of nirK- and nirS-type denitrifiers in the gut of the earthworm Eisenia fetida

The antibiotic sulfadiazine (SDZ) can affect denitrifying bacteria in soil. However, effects on denitrifiers in the gut of earthworms have not been described so far. Therefore, the influence of SDZ-contaminated manure applied to soil on denitrifiers in the gut of the earthworm Eisenia fetida was assessed by quantitative polymerase chain reaction targeting genes coding for nirK- and nirS-type nitrite reductases of denitrifiers. Gut contents of Eisenia fetida contained 2.5 × 10⁶ and 5.1 × 10⁵ gene copies of nirK and nirS, respectively, after 2 weeks in soils amended with manure only. Copy numbers of nirK and nirS in gut contents from manure treatments with SDZ were up to ten times less. Overall, the data indicate a negative impact of SDZ on denitrifiers in the gut of earthworms.     

Influence of different litter quality on the abundance of genes involved in nitrification and denitrification after freezing and thawing of an arable soil

Due to disruption of soil aggregates and cell lysis and the subsequent release of organic C and N, increased microbial N transformation processes can be observed after freeze–thaw cycles. In a microcosm study, we investigated the influence of plant residues with different C/N ratios (lucerne-clover-grass-mix and wheat straw) on N transformations and the abundance pattern of the corresponding functional genes in an arable soil after freezing and thawing. Unfrozen soil samples, continuously incubated at 10°C, served as control. Concentration of soil NH₄⁺, NO₃⁻, and water-extractable organic C (WEOC) as well as genes involved in nitrification and denitrification, quantified by real-time PCR, were determined before freezing and 1, 3, and 7 days after thawing. The amounts of inorganic N and WEOC as well as the investigated gene abundance pattern did hardly differ between control samples and samples subjected to freezing and thawing that have been amended with straw. In contrast, clear alterations of the measured parameters and abundances were observed after freezing and thawing in samples being amended with the lucerne-clover-grass-mix compared to the control samples.     

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.