Retention of oxalates in frozen products of three brassica species depending on the methods of freezing and preparation for consumption

The investigation showed that fresh brassicas: Brussels sprouts, broccoli, green cauliflower and white cauliflower respectively contained 50 mg, 67 mg, 72 mg and 95 mg oxalates in 100 g fresh matter. Soluble oxalates constituted 70%, 40%, 40% and 54% of total oxalates respectively. The cooked product obtained from traditionally prepared frozen vegetables (blanching-freezing-refrigerated storage-cooking) contained 45-66% of soluble oxalates. The product obtained from frozen vegetables produced using the modified method (cooking-freezing-refrigerated storage-defrosting and heating in a microwave oven) contained more oxalates than that obtained using the traditional method. The oxalate: calcium ratio in fresh vegetables varied considerably: 0.63 (Brussels sprouts); 1.10 (broccoli); 1.27 (green cauliflower); and 2.42 (white cauliflower). In products prepared for consumption the ratios were lower. The proportion of calcium bound as calcium oxalate differed between the vegetables investigated, but the treatments applied did not influence this parameter. The apparent retention of oxalate overestimated the true retention.     

Direct shaping of oxides by laser insolation of transition metal oxalates

Films of copper and cobalt-iron oxalates were prepared from suspensions of powders in ethane-1,2-diol deposited on glass or polycarbonate substrates. Two-dimensional structures of oxides, resolved on the scale of less than ten micrometers, were formed by laser insolation of these films, using a photolithography machine. The nature of the constitutive phases of the oxides formed tends to show that the laser heating makes it possible to reach locally, temperatures higher than 1000 °C. The oxides formed are thus sintered. The residual oxalate can be removed by washing or dissolving, leaving the oxide structure on its substrate. In spite of a perfectible sintering, the formed structures could interest different technological applications (electronic or magnetic devices, gas sensors, photovoltaic systems…) requiring the shaping of simple or mixed oxides on a scale close to the micrometer. The process of selective laser decomposition of oxalates, could subsequently be suitable for additive manufacturing of 3D parts.     

草酸盐法制备Y-Ba-Cu-O系超导体

用草酸盐二次共沉淀法制备了 Y-Ba-Cu-O 系超导体。样品的烧结温度低、烧成样品单相均匀,致密性好、密度>6.0g/cm~3。在935～940℃烧成的 YBa_2Cu_3O_(7-δ)超导体,其零电阻温度均>91K,ΔT_c<1K,并且性能稳定。样品制备的总周期约为2d,不多于干法制备所需的时间。     

TEM and SEM studies on the formation of superconducting phases in the Bi-based system

We present the formation mechanism and structure of the superconducting phases in the Bi–Sr–Ca–Cu–O system by TEM and SEM observations. Oxalate coprecipitation was used as preparation method. The average particle size, distribution and the presence of different phases and shapes of the particles were evaluated. All samples were well crystallized, showing grains in submicronic range. After thermal treatments, the complex samples showed mica-like crystals uniform dispersed and also an orientation tendency. The superlattice was composed of building blocks and successive planes. The TEM observations were in agreement with the diffraction patterns that revealed a mixture of 2212 and 2223 superconducting phases. With the building blocks in the system, it is possible to form many incommensurate phases that destroy the symmetry. Careful control of the preparation conditions is essential to produce a well-ordered commensurate phase, suitable for the precise determination of the complete superstructure by X-ray diffraction.     

Synthesis of nanocrystalline Mn-Zn ferrite powders through thermolysis of mixed oxalates

Nanocrystalline Mn-Zn ferrite powders were synthesized by thermal decomposition of an oxalate precursor. Two polymorphs of a mixed Mn-Zn-Fe oxalate dihydrate were obtained by precipitation of metal ions with oxalic acid: monoclinic α-(Mn, Zn, Fe)₃(C₂O₄)₃·6H₂O is obtained after precipitation and ageing at 90 °C, whereas the orthorhombic β-type is formed after precipitation at room temperature. The morphology of the oxalate crystals can be controlled by the precipitation conditions. The α-polymorph of the mixed oxalate consists of prismatic and agglomerated particles. The β-oxalate forms non-agglomerated crystallites of submicron size. Thermal decomposition of the oxalate at 350 °C in air results in an amorphous product. Nanosize Mn-Zn ferrite powders are formed at 500 °C and a mixture of haematite and spinel is observed at 750 °C. The thermal decomposition of the mixed oxalate is monitored by thermal analysis, XRD and IR-spectroscopy. The morphology of the oxalate particles is preserved during thermal decomposition; the oxide particle aggregates display similar size and shape as the oxalates. The primary particles are much smaller; their size increases from 3 nm to 50 nm after decomposition of the oxalates at 350 and 500 °C, respectively. The powder synthesized by decomposition at 500 °C was sintered at 1150 °C to dense and fine-grained Mn-Zn ferrites.     

Determination of oxalates in Japanese taro corms using an in vitro digestion assay

An in vitro assay was used to extract gastric soluble and intestinal soluble oxalates from the corms of four different Japanese taro (Colocasia esculenta (L.) var. Schott) cultivars (Akame, Ishikawa-wase, Yamato-wase and an unnamed cultivar). The oxalate contents were measured in the raw tissue and after boiling and baking the corms.     

Changes in antinutrients,phenolics, antioxidant activities and in vitro α-glucosidase inhibitory activity in pumpkin leaves (Cucurbita moschata) during different domestic cooking methods

Food Science and Biotechnology - Pumpkin leaves (Cucurbita moschata) were subjected to different household cooking methods (boiling, microwaving, steaming, and stir-frying) to evaluate their effect...