Effects of starch types on the properties of baked starch foams

In order to determine how the physicochemical properties of starch foams depend on the type of the starch used in baking process, starch foams were prepared using native starch and selected starch derivatives. The morphology, the density, the water adsorption capacity, the impact strength, and the thermal properties were determined for foams made from native starch, pregelatinized starch, hydroxypropylated starch with different degrees of substitution (DS = 0.015–0.025 and DS = 0.1), low distarch phosphate, medium distarch phosphate, and two cationic starch types (DS = 0.027–0.029 and DS = 0.029–0.033). The modified starch foams exhibited a more expanded structure with thinner cell walls than the foam made from native starch. The density of the native starch was 0.21 g cm^?3 , while the density of the modified starch foams was lower, in the range of 0.14–0.17 g cm^?3 except for the starch foam made from medium distarch phosphate. The thermal and physicochemical properties of the foams made from the other starch derivatives were dependent on the functional groups and the degree of cross-linking. The foam made from medium distarch phosphate had a significantly higher density and impact strength that was accompanied by a somewhat lower water adsorptivity.     

Thermal properties and morphology of cassava starch grafted with different content of polystyrene

The interest in replacing synthetic polymers by biodegradable materials from renewable resources is steadily increasing. In this work, cassava starch grafted with different content of polystyrene (PS) was synthesized via free-radical polymerization using suspension polymerization technique. Thermal data of pure starch and the grafted starch with different content of PS were collected by simultaneous thermogravimetric (TG)–differential scanning calorimetry (DSC) setup in open alumina pans. Separately, typical DSC measurements were conducted in standard aluminum pans with lid. The data obtained by different methods are correlated and discussed. Morphology of cryogenic fracture surface of starch sample was studied by scanning electron microscopy. In order to obtain more reliable data about the processes taking place during the thermal treatment, the changes of surface morphology of starch treated at different temperatures are observed.     

Hyphenation of flow analysis with spectrometric techniques

Quite often one of the biggest problems in analytical methods, including spectrometry, resides in the pre-processing of the sample, which usually must be solved manually. To solve these problems, it can be very useful to request the help of the flow techniques, which will allow to automate the methods, decrease the time of the analysis, decrease the consumption of the samples and reagents, increase the reproducibility, the sample throughput and to work continuously for a long period of time.

Between the advantages of the low separation flow techniques are their very high versatility facing the application of various treatment techniques, such as photo-oxidation, pre-concentration, clean-up, derivatization, gas diffusion, etc. Since the entire process is carried out in a completely closed system, results are obtained in a faster and more reproducible way.

In this contribution, coupling different low-resolution separation flow techniques with several very selective spectrometric instruments, like ICP–AES, ICP–MS, AFS, etc. Hyphenation with different kind of chromatographic and the capillary electrophoretic techniques is also described.     

Conductometric Determination of Sulfur Dioxide in Wine Using a Multipumping System Coupled to a Gas-Diffusion cell

A conductometric system with a multipumping module and a gas-diffusion cell has been developed to determine free and total sulfur dioxide (SO₂) in wine. The developed method has two protocols to determine both types of SO₂ using the same system. For free SO₂, sulfite is converted to H₂SO₄ by acidification and diffusion with H₂O₂ in an acceptor channel. The sample was previously hydrolyzed by mixing the sample with NaOH and heated at 70?°C prior making the determination of total SO₂ in order to break the bonds of the combined SO₂. Free and total SO₂ were determined in the ranges of 2.5–25.4 and 10.2–76.2?mg L^?1 with a sample throughput of 13 and 12?h^?1, respectively. The calibration curves of free and total SO₂ were in the range of ΔG (mS cm^?1)?=?(–1.0242?±?0.2871)?+?(0.6613?±?0.0201) [SO₂, mg L^?1], r² of 0.997 and ΔG (mS cm^?1)?=?(–0.5850?±?0.1678)?+?(0.1236?±?0.0033) [SO₂, mg L^?1], r² of 0.997. The proposed automated method is simple and easy to apply for the determination of SO₂ in wine using simple reagents.