Food security in Tanzania: the challenge of rapid urbanisation

Urbanisation in Tanzania is proceeding apace. This article seeks to identify the challenge posed by rapid urbanisation for food security in Tanzania to 2030, the Sustainable Development Goals horizon. It is hypothesized that urban food security largely depends on the food supply systems and the rural food production potential. The analysis of these interlinkages is based on secondary macro data and own primary micro data. Tanzania has done well to achieve broad self-sufficiency in basic foodstuffs to date, but rapid urbanisation will pose a severe future challenge as regards food security, particularly for the disadvantaged poorer people of the towns and cities in terms of food affordability, stability and food safety. Whether Tanzania can avoid future deterioration in urban food security will depend on how responsive and resilient the urban food supply systems prove to be in the face of continuing urban growth, changing consumption patterns, weak rural–urban food supply linkages and production constraints in the smallholder farming sector.     

Propylen/Propan‐Trennung im Festbettadsorber und durch Membranpermeation

The metal‐organic framework Mg₂(dhtp) with the linker dihydroxyterephthalate is known as MOF‐74 or CPO‐27. Mg₂(dhtp) has been synthesized as powder to measure breakthrough curves in a fixed‐bed adsorber and adsorption isotherms, and as a supported thin membrane layer for permeation studies. The measurement of the breakthrough curves of the binary propylene/propane mixture shows that separation with the fixed bed adsorber is possible. Propylene shows a higher affinity to Mg₂(dhtp). Although the single gas propane flux is slightly higher than the one of propylene, the binary propane/propylene mixture is not separated.     

Partikelcharakterisierung in hochkonzentrierten Dispersionen – Grundlegende Untersuchungen zu einer neuen Ultraschallmethode

A new method for inline characterization of particles in high concentrated dispersions by ultrasonic backscattering is described, that is sensitive against particle size and concentration. Analyzing the backscattering signal yields the sound attenuation as well as a scattering intensity equivalent. The measurement can be performed without sampling and minimally invasive directly in the process.     

Influence of origin source, different fruit tissue and juice extraction methods on anthocyanin, phenolic acid, hydrolysable tannin and isolariciresinol contents of pomegranate (Punica granatum L.) fruits and juices

To gain more comprehensive knowledge of pomegranate (Punica granatum L.) fruit composition and its impact on juice features, fruits and juices produced from fruits of eleven different provenances were investigated by HPLC–DAD-ESI/MSⁿ for their monomeric phenolic and lignan profiles. Total phenolics and antioxidant capacity were monitored by the Folin-Ciocalteu, ferric reducing antioxidative power and Trolox equivalent antioxidant capacity assays. Peels, mesocarp, seeds and juices obtained from isolated arils (PJAs) as well as from entire fruits were separately analyzed. Ellagitannins were found to be the predominant phenolics in all samples except in PJAs. However, due to the low lignan amounts, only isolariciresinol could be quantitated in peels and mesocarp. The peels and mesocarp revealed highest contents of hydrolyzable tannins (27–172 g/kg and 32–263 g/kg, respectively) and isolariciresinol (4.9–19.8 mg/kg and 5.0–13.6 mg/kg, respectively). To the best of our knowledge, a systematic investigation of monomeric phenolic compounds and isolariciresinol considering diverse pomegranate fruits has been performed for the first time. The study demonstrates that raw material and extraction process have significant impact on juice composition and thus must be carefully selected. Furthermore, pomegranate processors should select juice extraction processes according to the final designation of the product, that is, distinguish between dietary products being rich in phenolic compounds having an astringent taste, and juices for consumption having an appealing taste but lower amounts of phenolics, respectively. This study may further contribute to facilitate authenticity control of diverse pomegranate products and help predict sensory and biofunctional characteristics of pomegranate juices.     

Electron microscopy techniques for the analysis of the polymer electrolyte distribution in proton exchange membrane fuel cells

The polymer electrolyte distribution in PEMFC electrodes plays an important role for the catalyst utilization and various transport processes in the electrode. Moreover, its influence on the transport processes is not only limited to proton transport but it may also affect gas transport, electron conductivity and water management of the cell. However, experimental techniques to study the polymer electrolyte distribution are scarce. In this paper we present various approaches based on scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to characterize the polymer electrolyte distribution. The methods presented include staining of the polymer electrolyte with heavy metal ions, energy dispersive X-ray (EDX) mapping and energy filtered imaging (EFI). Their use for the analysis of the polymer electrolyte distribution and electrode structure will be presented and current limitations of these techniques will be discussed.     

Investigations of peptides and proteases in green coffee beans

Cof. canephora var. robusta. The coffee types were not significantly different in peptide content, but were significantly different in peptide composition. Peptides with weakly acid pI values were mainly found in the Cof. robusta samples. In comparison, peptides from Cof. arabica samples ranged evenly from the weakly acidic up to the weakly basic pH range. The apparent molecular masses of the peptides in the two groups of samples lie between 4 kDa and 10 kDa. The cysteine content of the peptides was relatively high. Model roastings permitted the assumption that peptides make a contribution to coffee flavour. Peptides are already available in freshly harvested coffee. Model tests have suggested that processing after the coffee harvest has an influence on peptide composition but not on the amounts of peptide. All coffee samples contained some extractable proteases. The electrophoretically obtained enzyme patterns of Cof. arabica and Cof. robusta were different. Received: 6 September 1999