Norbert Mundigler

Antioxidative properties of faba bean-, soybean-and oat tempeh

The antioxidative properties of native flours derived from three types of faba beans in different concentrations, as well as flours from dehulled soybeans and oats without husk, were determined using the Schaal oven test. The antioxidative potential was expressed by the protection factor against the oxidation of lard or sunflower oil. All three raw materials showed pronounced antioxidative potential, but native flour from oats had an exceptionally strong antioxidative effect. Although steaming of all three flours reduced their antioxidative potential, it was most detrimental to oat flour. Tempeh fermentation increased the antioxidative effects in all three raw materials, where the highest increase was obtained with flour derived from faba beans. The influence of conditions of fermentation on the antioxidative activity was also tested during the production of tempeh from oats. Fermentation time, as well as the water/oat flour ratio, were found to have a highly significant influence (P < 0.01).

Molecular background of technological properties of selected starches

Selected starches, i.e. waxy maize, amaranth, quinoa, wheat, millet and buckwheat starches, were investigated with respect to their technological properties such as gelatinization, stability to mechanical stress, resistance to conditions and stability in continuous freeze/thaw cycles. Technological properties are correlated with molecular features such as branching characteristics in terms of iodine-complexing potential, molar mass, occupied glucan-coil volume, packing density of glucan coils and rheological properties. Waxy maize and amaranth starches were found to be amylopectin-type short-chain branched (scb) glucans with weight average molar masses M w = 17 × 10 6 g/mol and 12 × 10 6 g/mol, respectively. Waxy maize starch had a high gelatinization potential, high viscosity at 95 °C (340 mPas) low stability at acidic conditions, average stability to shearing and good freeze/thaw stability. For amaranth starch a viscosity of 122 mPas at 95°C, low resistance to acid, but high stability to applied shearing and even high freeze/thaw stability was determined. Investigated quinoa starch was classified as scb-type glucan, however, the branches are significantly longer than those of waxy maize and amaranth. With a M w = 11 × 10 6 g/mol and a viscosity of 187 mPas at 95°C, this sample is comparably resistant to acidic conditions and to shearing, but instable in freeze/thaw experiments. Wheat, millet and buckwheat starches contain significant percentages of amylose-type long-chain branched (lcb) glucans (22.1, 32.1 and 24.3%, respectively) with M w values of 5 × 10 6 g/mol, 12 × 10 6 g/mol and 15 × 10 6 g/mol, respectively. Wheat starch, with a viscosity of 107 mPas at 95°C, shows low stability under acidic conditions, but high stability to shearing. Wheat and millet starches, but not buckwheat starch, form weak gels in the course of subsequent freeze/thaw cycles. Millet starch, with a viscosity of 101 mPas at 95 °C was found to be moderately stable under acidic conditions and to shearing. Buckwheat starch with a viscosity of 230 mPas at 95 °C shows no acid resistance and is instable upon shearing but performs very well in freeze/thaw experiments.

Effect of surface modification of beech wood flour on mechanical and thermal properties of poly (3-hydroxybutyrate)/wood flour composites

Abstract Poly (3-hydroxybutyrate) (PHB), a biodegradable polymer from the polyhydroxyalkanoate biopolyester class, was filled with 20% beech wood flour (WF) to form completely biodegradable films. In the present study, the influence of surface modification of wood flour was investigated on the interfacial adhesion of PHB/WF composites. In addition to a hydrothermal pretreatment, sodium hydroxide and stearic acid were used as surface modifiers. Direct measurement of interfacial adhesion was carried out by mechanical testing and dynamic mechanical analysis. Thermal properties, degree of crystallinity of PHB/WF composites were determined by differential scanning calorimetry. Effects of sodium hydroxide and stearic acid treatment on the adhesion of PHB/WF interface were feeble when no hydrothermal pretreatment was applied. Nevertheless, surface modifiers applied on hydrothermally pretreated WF significantly improved the WF/PHB interface adhesion.

Isolation and Determination of Starch from Amaranth (Amaranthus cruentus) and Quinoa (Chenopodium quinoa)

From the seeds of Amaranthus cruentus and Chenopodium quinoa the starch was gained by the means of mechanical cleaning methods and their starch content was found out by four different methods: by subtractiv determination; polarimetrically with the CaCl 2 -method and with two enzymatic methods. The results of the subtractiv method were used to calculate the Ewers-factor (hydrochloric acid method).

Effects of Long-term Storage on the Mechanical Characteristics of Wood Plastic Composites Produced from Thermally Modified Wood Fibers:

In order to study possible changes in the mechanical properties of wood plastic composites produced from thermally modified wood fibers as reinforcement material (60%) and polypropylene (40%) after long-term storage under constant conditions, tensile and flexural specimens were tested in the years 2004 and 2009 after storage at 20°C and 65% humidity. Increased tensile strength, Young’s modulus (tensile test) as well as modulus of elasticity (flexural test) were observed for the long-term stored samples indicating a positive effect of the storage conditions on the mechanical properties of the samples.

Cyanobacteria Biorefinery — Production of poly(3-hydroxybutyrate) with Synechocystis salina and utilisation of residual biomass

This study evaluates a biorefinery concept for producing poly(3-hydroxybutyrate) (PHB) with the cyanobacterial strain Synechocystis salina. Due to this reason, pigment extraction and cell disruption were investigated as pre-treatment steps for the harvested cyanobacterial biomass. The results demonstrated that at least pigment removal was necessary to obtain PHB with processable quality (weight average molecular weight: 569-988kgmol-1, melting temperature: 177-182°C), which was comparable to heterotrophically produced PHB. The removed pigments could be utilised as additional by-products (chlorophylls 0.27-1.98mgg-1 TS, carotenoids 0.21-1.51mgg-1 TS, phycocyanin 0-127mgg-1 TS), whose concentration depended on the used nutrient source. Since the residual biomass still contained proteins (242mgg-1 TS), carbohydrates (6.1mgg-1 TS) and lipids (14mgg-1 TS), it could be used as animal feed or converted to biomethane (348 mn3 t-1VS) and fertiliser. The obtained results indicate that the combination of photoautotrophic PHB production with pigment extraction and utilisation of residual biomass offer the highest potential, since it contributes to decrease the environmental footprint of the process and because biomass could be used in a cascading way and the nutrient cycle could be closed.

Residual wood polymers facilitate compounding of microfibrillated cellulose with poly(lactic acid) for 3D printer filaments

Microfibrillated cellulose (MFC) is a fascinating material with an obvious potential for composite reinforcement due to its excellent mechanics together with high specific surface area. However, in order to use this potential, commercially viable solutions to important technological challenges have to be found. Notably, the distinct hydrophilicity of MFC prevents efficient drying without loss in specific surface area, necessitating storage and processing in wet condition. This greatly hinders compounding with important technical polymers immiscible with water. Differently from cellulose, the chemistry of the major wood polymers lignin and hemicellulose is much more diverse in terms of functional groups. Specifically, the aromatic moieties present in lignin and acetyl groups in hemicellulose provide distinctly less polar surface-chemical functionality compared to hydroxyl groups which dominate the surface-chemical character of cellulose. It is shown that considerable advantages in the production of MFC-filled poly(lactic acid) filaments for three-dimensional printing can be obtained through the use of MFC containing residual lignin and hemicellulose due to their advantageous surface-chemical characteristics. Specifically, considerably reduced agglomerations of MFC in the filaments in combination with improved printability and improved toughness of printed objects are achieved. This article is part of a discussion meeting issue ‘New horizons for cellulose nanotechnology’.

Unmodified multi-wall carbon nanotubes in polylactic acid for electrically conductive injection-moulded composites:

Tailoring the properties of natural polymers such as electrical conductivity is vital to widen the range of future applications. In this article, the potential of electrically conducting multi-wall carbon nanotube (MWCNT)/polylactic acid (PLA) composites produced by industrially viable melt mixing is assessed simultaneously to MWCNT influence on the composite’s mechanical strength and polymer crystallinity. Atomic force microscopy observations showed that melt mixing achieved an effective distribution and individualization of unmodified nanotubes within the polymer matrix. However, as a trade-off of the poor tube/matrix adhesion, the tensile strength was lowered. With 10 wt% MWCNT loading, the tensile strength was 26% lower than for neat PLA. Differential scanning calorimetric measurements indicated that polymer crystallization after injection moulding was nearly unaffected by the presence of nanotubes and remained at 15%. The resulting composites became conductive below 5 wt% loading and reached conductivities of 51 S m−1 at 10 wt%, which is comparable with conductivities reported for similar nanocomposites obtained at lab scale.